# Chapter 2 1 Ingestion Toxicity Asses sment

Table of Contents

21.1 Introduction

............ ............ ............ ............ ............ ...... 1 21.2 Hazard I dentification

............ ............ ............ ............ .......... 2 21.3 Predict

ive A pproach for Can cer Effe cts
............ ............ ............ ........ 2 21.3.1 Determining the Point of Dep arture (POD)

............ ............ ........... 2 21.3.2 Deriving the Human Equiv alent Dose

............ ............ ............ ... 2 21.3.3 Extrapolating from POD to Derive the Oral Cancer Slo pe Factor

............ ..... 3 21.4 Dose-response Assessment for D erivation of a Referen ce Dose

............ ............ . 3 21.5 Sources of Hum

an Health Reference Values for Risk Assessm ent
............ ........... 4 References

............ ............ ............ ............ ............ ............ . 5a See ht tp: // www. epa. gov/

tt n/ atw /t oxs ourc e/s ummar y. ht ml for an up-to-date list of dose -response va lues. April 2004 Page 2 1-1 Risk = ƒ (metric of ex

posure, measure of tox

icity) Toxicity Assessment is a Two-Step Process: 1. Hazard Identification–What types of effects does the chemical cause? Under what circumstances? 2. Dose-response Assessmen t – How potent is the chemical as a carcinogen an

d/or for noncancer effects? 21.1 Introduction As des cribed previ ousl y in Chapt er 12, the pu rpose of the tox icit y assessm ent is to wei gh availab le evide

nce regarding

the poten tial for t oxicity in exposed i

ndividual s ( hazard identification ) and to quantify the toxicity by d eriving an appro priate dose-response value ( doseresponse assessm ent ). Toxicity assessment is the second part of the general risk equation. The toxicity assessme nt is accompl ished in two steps: hazard identification and doseresponse assessm ent . Alt hough the toxicity

assessme nt is an inte gral a

nd importa

nt part of the over all air to xics risk as sessment, this is usua

lly a ccomplished prior

to the risk

assessme nt. EPA has

complete d the toxicit

y assessment for all HAPs and has made available the resultingtoxicity information and doseresponse values, which have underg one extensive peer review (see Appendix C). (a) This chapter foc

uses on toxic ity a ssessmen t for the i ngestion (oral)pathway . Dermal toxicity assessme nt is described in d

etail in se veral EPA

guidance docu

ments. (1) The ingestion pathway uses the s ame ge

neral ty pes of stu dies, haza rd and do se-res

ponse inf ormation, and dose -respon se methods to assess toxicity as those used for the inhalation pathway (see Chapter 12). The discussion in this chapter focuses on the unique features of toxicity assessment for the oral pa th wa y. Ingestion Dose-Respo nse Values (a) Oral Can cer S lope

Facto r (CS F) : An upper bound , approximating a 95 percent confidenc e limit, on the incr eased c ancer ri sk fro m a li fetime exposu re to an agent . For i

ngesti on, thi s estim

ate is u sually expressed in units of am

ount of risk per am

ount of intake and

is written as risk p er mg/k g-day or simply (m

g/kg- d) -1

. Reference Dose (RfD) : An estimate (with u ncertain ty spa nning perhap s an ord

er of m agnitu de) of a daily oral exposure to the human population (including sensitive sub- populations) that is likely to be withou t an app reciable risk o f delete

rious ef fects du ring a lifetim e. Generally

used in EPA’s noncancer health assessm ents. RfDs are usu

ally give n in units of intake

per day on a body weig

ht basis (w ritten as mg /kg- d).
(a) The phrase “dose-response” is used generally here and els ewhere in the document. EPA’s values for i ngestion, however, are related to oral i ntake rather t han dose. Consideration of the rel ationship between exposure concen tra ti on, dos e, an d dosi metry (w hat happens to a c hemic al i n th e body on ce i t i s i nges ted) may be considere d, dep ending on data availability in the derivation of these value s.b Note that the corresponding value for i nhalation exposures is the benchmark concentration (BM C).

c A m ode l that estima tes the d ose to a targe t tissue or o rgan b y taking into acco unt the ra te of ab sorp tion into the body, distribution among target organs and tis sues, metabolism, and excretion. April 2004 Page 2 1-2 21.2 Hazard Identification The hazard identification process for the inge stion pathway is identical to that for the inha lation pathway, a

lthough the specific toxic effects of concern a nd details of the toxicity studies are derived from feeding a che mical to animals (either in food or drinking water) ra ther than on having the animals inhale the chemical. As with inhalation, the hazard identifica tion step includes consideration of various ty pes of studies (e.g., feeding, in vitro, etc .) and the resulting weight of evidence with reg ard to potential for carcinogenicity and identification of critical effects. See Part I I, Chapter 12, for information on the ha zard identification step. 21.3 Predictive Approach for Cancer Effects The approach to dose-response assessment for cancer effects is identical to that for the inha lation pathw ay discus sed in Chapt er 12, inclu ding:

• Determination of the point of departure ( POD );

• Duration a djustme nt of the POD to a continuous exposure;

• Extr apola tion of an an imal stud y POD int o its corres pondi ng Human Equiva lent Dose ( POD HED ); and

• Low-dose extrapolation from the POD HED to lower doses for the purposes of deriving the oral cancer risk estimate. As with inhalation, the first three steps are also performed in the de rivation of reference values for ingestion, such as the oral RfD. I n addition to the steps shown above, the derivation of RfDs are followed by

the application of uncertainty factors (see Section 21.4). Additionally , the use of tools such as pharmacokinetic modeling, which go be yond these def

ault approaches, may facilita te the ac complishme

nt of seve ral of the se steps. 21.3.1 Determining the Point of Departure (P OD) The process for determining the POD for ing estion exposures is identical to that for inhalation exposures. The POD may be the no-observed-adverse-eff ect level (NOAEL)

or lowest-observedadverse-effect level (L

OAEL), or it may

be a benchmark dose ( BMD ) for non cancer effects. (b) 21.3.2 Deriving

the Huma n Equivalent D ose The optima

l approa ch for extrapolati

ng from an anima l study to a human

dose-re sponse relationship is to use Physiologically Based Pharmacokinetic (PBPK) (c) modeling. When such a model us used, the duration adjustment step is incorporated into that model. Otherwise, any duration adjustment, if necessary (e.g., when the exposure is not via daily feed), would be accomplished by de

riving an average

daily dose for the e

xposure period (e.g., two y ears in an animal cancer bioassay

).d At the tim e of p ublica tion, an A genc y activity is und erwa y to “harm onize ” the ca ncer a ssessm ent and RfD

devel opment methods wit h reg ard t o the meth od employ ed for int erspe cies scal ing , whi ch mayres ult in t he us e of bod y w ei gh t s ca li ng in

th e de ve lo pme nt

of th e Rf D. April 2004 Page 2 1-3 For pur poses of c ancer a ssessmen t, an animal to huma

n body weight-based s caling

factor is applied to the oral study POD (dur ation-adjusted if applicable) to extrapolate to a human equivalent oral exposure. (2) The def ault sca ling fa ctor is ba sed on the

body mass rais ed to the 3 /4 power of the test animals relative to humans. This step stems from the consideration of var ious studies of the species differences in toxicity of certain compounds, including data collected on chemothe rapeuti c age

nts. (3) These data served as the principal basis for the use of a body sur

face area or metabolic rate scaling as the default method in cancer risk assessments. Empirically , the best estim ate of surface area s caling is BW 2/3 and for metabo lic rate scali ng is BW 3/4

. (4) These findings reflect gener

al expectations of more rapid distribution, clearance, and metabolism by smaller a nimals. In the case of the RfD , a scaling factor is not currently applied. Instead, the interspec ies uncertainty f

actor is intended to account for potential differenc es in sensitivity of humans compared to the test animal, including this consideration. (d) A PBPK model can accommodate adjustments for metabolic rate as well as other species-related dosimetri c varia

bles such as liver p erfusion rates. The mode l theref ore prov ides a mor

e accur ate estimate of steady- state target site concentrations than use of de fault methods. EPA’s preferred approach for calculating a HED for oral exposures is to use a chemical-specific PB PK model parameterized for the animal species and body regions (e.g., of the g astrointestinal tract) involved in th e t ox ic it y. 21.3.3 Extrapolating from POD to Derive the Oral Cancer Slope Factor As with inhalation, extrapolation from the POD HED to lower doses is usually nece ssary and, in the absence of a data set rich e nough to support a biologic ally

based mod

el (e.g ., a PBPK model), is conducte d using li

near extr apolation or a non

linear extrapolati on using a Refer ence Do se approach. The Cancer Slope Factor ( CSF ) for or al exposur

es is der ived in a s imilar wa

y a s the unit r

isk estimate for inhalation (URE) (see Chapter 12). The CSF is der ived using the upper bound estimate of risk. I n other w ords, the

true risk to humans, while not i dentifia ble, is not likely to exceed the upper-bound estimate (the CSF). The CSF is presented a s the risk of cancer per mg of in ta ke of th e s ub st an ce pe r k g b od y we ig ht pe r d ay ( [m g/ kg -d ay] (-1) ). 21.4 Dose-r esponse As sessme nt for Der ivation of a R

eferenc e Dose The ora l reference dose is expressed as a chronic dietary intake level (in units of mg of the substance per kilogram body weight per day , or mg/kg-day ) for the human population (including sensitive sub-popu lations) t hat is like ly to

be withou

t an appr eciable risk of de leteriou s effects during a lifetime. In other word s, exposure s at or be low the Rf D will prob ably

not cause adverse health effects, even to sensitive sub-populations. While the RfD is routinely employed forApril 2004 Page 2 1-4 noncancer effects, it may

be inclusive of cancer for those pollutants for which a nonlinear (e.g., threshol d) mode of

action ha s been de

monstrate d consiste

nt with the

Cancer Guideline s. As with the derivation of an inhalation reference concentration, the reference dose is derived by dividing the POD by one or more uncertainty factors ( UFs ) . EPA includes with each RfD a statement of high, medium, or low confidence based on the c ompleteness of the database for that substance. High confidence RfDs ar e considered less likely

to change substantially

with the collecti on of add

itional inf ormation, while low

confide nce RfDs may be espec ially

vulnera ble to change. (5) The UFs are applied to account for r ecognized uncertainties in the extrapolations from the experimen

tal data c onditions to

an estima

te appro priate to the assumed human s cenari o. As with the deri vation of RfCs, a UF

of 10, 3, or 1 is appl ied for e ach of the followi ng extra polations :

• Animal to human;

• Human to exposed sens itive huma n populati ons;

• Subchronic to chronic;

• LOAEL

to NOAEL; and

• Incomplete to complete databa se. The UFs are ge nerally an order of magn itude (10 ), althou

gh cons ideration of avai lable information on the chemical may result in the use of reduced UFs for RfDs (3 or 1). It is noted that as the

re is cur rently no defau lt dosimetr

ic adjustment for the oral r oute. The uncerta inty factor for extrapolation from animal to human data is usually the full 10, as compared to the reduce d factor

of 3, rout inely used for RfCs which

employs an interspecies

dosimetri c adjustment. Additional discussion on the application of uncertainty factors is provided in Section 12.4.3. 21.5 Sources o f Human Hea lth Refer ence Values for Risk A ssessm ent Appendix C pr

ovides a c urrent li sting of

chronic oral dose -respon se value s (i.e., Rf Ds and CSF s) for HAPs. Chapter 1 2 descri bes addit ional sour ces of hu man heal th refe rence values for risk assessment for the ingestion route.April 2004 Page 2 1-5 1. U.S. Environmental Protection Agency . 2001. Risk Assessment Guidance for Superfund Volume I: Human Health Evaluation Manual (Part E, Supplemental Guidance for De rmal Risk Assessment) Interim Review Draft - For Public Comment , Office of Emergency

and Remedial Response , Washing

ton, D.C. EPA/540/R/99 /005, ava ilable at : http://www .epa.g ov/super fund/pro grams/

risk/rag se/index.h

tm
. U.S. Environmental Protection Agency . 1992. Dermal Exposure Assessment: Principles and Applicat ions. Off ice of He alth and E

nvironme ntal Asse ssment. EPA

/600/6-88 /005C. 2. U.S. Environmental Protection Agency . 1999. Guideline s for Carcin ogen Risk

Assessme

nt. Review D raft . Risk Assessment Forum, Washington, DC. NCEA-F-0644. U.S. Environmental Protection Agency . 1986. Guidelines for Carcinogen Risk Assessment

. Federal Register

51(185):33992-43003. U.S. Environmental Protection Agency . 2003. Draft Final Guideline

s for Carcin ogen Risk Assessme nt (Ext ernal Review Draft) , Risk Asse ssment Forum, Washin gton, DC , NCEA-F-0644A. These do cuments a

re avai lable at http://cf

pub.epa .gov/nc ea/raf

/rafg uid.htm

. 3. Freire ich, E.J., G ehan, E. A., Rall, D .P., et al. 1966. “Qu antitativ e compar

ison of toxic ity anticancer agents in mouse, rat, ha mster, dog, monkey , and man.” Cancer Chemother Report 50:210:244. 4. U.S. Environmental Protection Agency . 1992. Request for Comments on Draft Report of Cross-species Scaling Factor for Cancer Risk Assessment . Federal Register 57:24152. 5. U.S. Environmental Protection Agency . 2002. A Review of the Reference Dose and Referen ce Conce

ntration Pr

ocess . Risk Assessment Forum, Washington, DC. EPA/630/P- 02/002F. Availabl e at: http://cfpub.epa.gov/ncea/raf/rec ordisplay.cfm?deid=55365

. References

# Chapter 2 2 Multip athway Ri sk Charac teriz ation

Table of Contents

22.1 Introduction

............ ............ ............ ............ ............ ...... 1 22.2 Cancer Risk Estimates

............ ............ ............ ............ ......... 2 22.2.1 Characterizing I

ndividual Pollutant I

ngestion Risk

- Scenario Approach

............ 2 22.2.2 Characterizing R isk from E

xposure to Multiple Pollutants - Scenario A pproach

...... 3 22.2.3 Combining

Risk Estim

ates across Multiple I

ngestion Pathways - Scenario Approach

. . 4 22.2.4 Evaluating R

isk Estimates from I

nhalation and I

ngestion Exposures

............ ... 4 22.3 Noncan

cer Hazard

............ ............ ............ ............ ............ . 4 22.3.1 Characterizing I

ndividual Pollutant H azard - Scenario Approach

............ ..... 5 22.3.2 Multiple

Polluta nt Haz ard

............ ............ ............ ............ 6 22.3.3 Evaluating H azard Estimate s From I nhalation and I

ngestion Exposures

............ 6 22.4 Interpretation and Presentation of Risks /Hazards

............ ............ ............ . 7 References

............ ............ ............ ............ ............ ............ . 8April 2004 Page 2 2-1

Steps in a Multipathway Risk Characterization 1. Organize ou

tputs of the ingestion exposure and toxicity assessments. 2. Derive c ancer risk est imates a nd nonc ancer hazard qu otien ts for each pol lutan t in eac h pathw ay. 3. Derive mul tiple pollut ant can cer ri sk esti mates an d nonca ncer ha zard ind ices f or each pathwa y. 4. In co nsideration of target organ, develop targ et organ specific hazard indices, if appropriate. 5. As appropriate, combine inform ation on cancer risk and noncancer haz ard from the ingestion analysis with approp

riate risk informa

tion from the inha

lation analysis to deriv

e a total estimate of cancer risk and noncancer hazard. 6. Identify k

ey features and assu

mptions of expo sure and toxicity asse ssments. 7. Assess and cha

racteriz e key

uncerta inties a ssociate d with the asse ssmen t. 8. Consid

er addit ional re levan

t inform ation (e .g., related

studies ). The risk characterization should be written consisten t with EPA g

uidance and policy , including a risk summary and risk conclusions that are comp lete, informative, and useful for decision-mak ers, and which clearly identify

and discuss the m

ajor uncertainties associated with determ ining the nature and exten t of the risk. 22.1 Introduction The last component of risk assessment, Risk Characterization, integrates the infor mation from the exposure assessment (Chapter 20) and toxicity a ssessment (Chapter 21), using a combination of qu al it at iv e i nf

or ma ti on , q ua nt it at iv e i nf or ma ti on , a nd a d is cu ss io n o f u nc er ta in ty. (1) Risk assessors should pr

esent the risk cha racter ization and

its components so tha

t they are tra nsparen t, clear, and consistent with EPA guidance and policy , and thus components should support the conclusi on that the

analy sis is rea sonably

conservative enough for its inten ded purp ose. The

risk summary and risk conc lusions must be complete, informative, and useful for decision-makers. Major uncertainties associated with determining the natur e and extent of the risk should be identified and discussed. Risk characterization for the multipathway risk assessment is performed using the same approac h as described for the inhalation pathway (Chapter 13), except that risks for both inhalation and ingesti on are c onsidere d. As for inhalation-only

analy ses, most mu

ltipathwa y r isk asses sments for air toxics will focus on estimating individual risk and hazard. This chapter focuses on the unique features of risk character ization for multipathway analy ses. This chapter also assumes that the inhalation risk characterization h as been completed, as described in Chapter 13.

The general process for

characterizing cancer

risks and noncancer hazards for multipathway analy ses can b e thoug

ht of as de

veloping informat ion to fill in

a matrix simi lar to tha

t shown in Exhibit 22-1 (which presents cancer risks for a gr oup of chemicals; a similar matrix can be developed to present noncancer hazards [see Exhibit 22-2]). A table like this would be developed for each of the ty pes of receptors being evalua ted in the study area

(e.g., adult farmer – high-end exposure; adult farmer – central tende ncy exposures; child resident – hig h-end exposure). This type of pre sentation format shows the total risk by che mical, pathway, a

nd across all pathway s. In addition, this format allows one to quickly identify both the individual chemicals and pathways that contribute most to the total risk estimate. The following sections describ e how to de

velop the numbers t

o fill in suc

h a table for both m

ultipathway

cancer risk estimate s (Section 22.2) a nd multipat

hway noncanc er hazar

ds (Secti on 22.3). The foc us of thisApril 2004 Page 2 2-2 chapter is on developing risks and hazards for the ing estion pathways; proce dures for developing inhalation risk estimates have previously been provided in Chapter 13.
Exhibit 22-1. Example Matrix for Estimating Excess C ancer Risks for Multiple Ch emical Expo sure th rough Multiple Ingest ion Path ways for a Pa rticula r Exp osure S cenario Pathwa y 1 (Vegeta ble Ingestion Risk Estimate) (a) Pathway 2

(Fish Ingestion Risk Estimate) (a) Pathway 3

(Egg I ngestion Risk Estimate) (a) Pathwa y 4

(Beef Ingestion Risk Estimate) (a) Agg

regate Chemical Ingestion Risk Estim

ate (a) Chem ical 1 1 × 10 -6 3 × 10 -4 9 × 10 -8 8 × 10 -5 4 × 10 -4 Chem ical 2 4 × 10 -7 4 × 10 -6 4 × 10 -8 4 × 10 -7 5 × 10 -6 Chem ical 3 4 × 10 -9 7 × 10 -7 3 × 10 -8 9 × 10 -9 8 × 10 -7 Chem ical 4 9 × 10 -7 1 × 10 -6 6 × 10 -7 6 × 10 -7 3 × 10 -6 Cumulat ive Ingestion Pathway Risk Estimate (a) 3 × 10 -6 3 × 10 -4 7 × 10 -7 8 × 10 -5 4 × 10 -4

(a) Standa rd rules for rou nding apply which will com

monly lead to an answer of one sign

ificant f igure in both risk and hazard estimate s. For presentation pu rposes, hazard qu

otients (and hazard in

dices) and cancer risk estim

ates are usually reported

as one significant fig

ure. 22.2 Cancer Risk Estimates As discussed in detail in Chapter 13, estimated individual cancer risk is expressed as the probability that a person will deve lop cancer as a result of the estimated exposure over a lifetime. This predicted risk is the increm ental ris k of cancer from the exposure being a nalyzed, which are in addition to other risks due to any other factors (e.g., smoking). D ue to default assumptions in their derivation, cancer slope factors (CSFs) a re generally

considered to be “plausible upperbound” estimates, regardless of whether they are based on statistical upper bounds or best fits. As noted in Chapter 13, risks may be estimated for both the central tendency (average exposure) case and for the high-end (e xposure that is expected to occur in the upper range of the distribution) case, or probabilistic techniques can be used to develop a distribution of estimated risks. 22.2.1 Characterizing Individual Pollutant Ingestion Risk - Scenario Approach The first step in characterizing individual pollutant risk for an exposure scena rio (e.g., a rec rea ti ona l fi she r) i s t o qu ant ify r is k fo r ea ch i nge st io n ex pos ure pat hwa y bei ng e val uat ed. In this step, cancer risks for individual pollutants are estimated by multiplying the estimate of the lifetime a verag e daily

dose (L ADD) for each i

ngestion exposure

pathway by t he appro priate CSF to estimate the potential incremental cancer risk: Risk = LA DD × CSF ( Equation 22- 1)April 2004 Page 2 2-3 where: Risk = Individual cancer r isk (expressed as an upper-bound risk of contracting cancer over a lifetime) for each pollutant via the ingestion pathway

being evaluated (unitless); LADD = Lifetime Averag e Daily Dose f or the pollutant via the ingestion pathway being evaluated (mg/kg-d); and CSF = Cancer Slope Factor for the pollutant via the ingestion pathway being evaluated [(mg/kg-d) -1 ] Estimates of cancer risk are usually expressed as a probability r epresented in scientific notation as a negative exponent of 10. For example, an additional risk of c ontracting cancer of 1 cha nce in 10,000 (or one additional person in 10,000) is written as 1x10 -4 . Beca use CSFs a

re ty pically upper-bound estimates, actual risks may be lower than predicted (see Chapter 12) – note that the true value of the risk is unknown and may be as low as zero. (2) These statistical projections of hypothetical risk are

intended as screening tools for risk manag ers and cannot be used to make realisti c predictions of bio logica l effects. Risks are generally

evaluated initially for individuals within the potentially exposed population. Populati on risks for the e xposed popu

lation may

also be e stimated, which may be usefu l in estimating potential economic costs and benefits from risk reduction. Sensitive subpopulations should also be considered, when possible. Estimates of incidence also a re pos sibl e, alt hough there are some caveats associa ted with these measures (see Chapter 13). For carcinogens being

assessed based on the assumption of nonlinear dose-response, for which a reference dose (RfD) was derived that considers cancer a s well as other effects, the hazard quotient approach will be appropriate for risk char acterization (see Section 22.3). 22.2.2 Characterizing Risk from Exposure to Multiple Pollutants - Scenario Approach For ea ch exposur

e pathwa y of a scena rio, exposu

re may be to multip le chemic als at the same time rather than a single chemical; howeve r, CSFs are usually a

vailable only for individual compound s within a m

ixture. Cons equently

, a component-by

-compone nt approa ch is usua lly employed. (3) The following equation estimates the predicted cumulative incr emental individual cancer risk from multiple su

bstance s for a sin

gle expos ure path way , assuming

additive effects from simul

taneous e xposures to

severa l carcin ogens: Risk T = Risk 1 + Risk 2 + ... . + Risk i ( Equation 22- 2) where: RiskT = Cumulative individual ingestion cancer risk (expressed as an upper- bound risk of contracting cancer ove

r a lifetime); and Riski = Individual ingestion risk estimate for the i th substance. In screening -level assessments of carcinogens for which there is an assumption of a linear doseresponse relation ship, the c ancer r isks pred icted for individual chemic als may be adde d to estimate cumulative cancer risk for eac h pathway. This appr

oach is based on an assumption thatApril 2004 Page 2 2-4 Aggregate vs. Cu mulative Risk Aggregate risk

refers to risk attributed to a single chemic al across multiple pa thways/routes Cumulative risk

refers t o risk attribu ted to simul taneous exposu re to m ultiple chem

icals v ia a single or m

ultiple pathways/routes the risks associated with individual chemicals in the mixture are additive. In mor e refined assessments, the chemicals being assessed may be evaluated to determine whether eff ects from multiple chemicals are sy nergistic (greater

than additive) or antagonistic (less than additive), although sufficient data for this evaluation are usua lly lacking. I

n those cases where CSFs are available for a chemical mixture of concern, r isk characterization can be conducted on the mixture using the same procedures used for a sing le compound. For carcinogens being

assessed based on the assumption of nonlinear dose-response, for which an RfD considering cancer as well as other effects has been derived, the hazard quotient approach will be appropriate (see Section 22.3). 22.2.3 Combining

Risk Estim ates acr oss Multiple Ingestion Pathways - Scenario Approach To evaluate risks

associa ted with the agg

regat e exposure a

cross mult

iple path way s of a gi

ven scen ario, the individua

l pollutant

cancer risk estimates may be summed for each chemical across the multiple ingestion pathwa ys assessed. Additionally, a cumulative multi-pathway risk estimate may be de

rived by summing c

umulative (multiple pollutant)

cancer risk estimates across the mu ltiple ing estion pa

thways. 22.2.4 Evaluating Risk Estimates from Inhalation and Ingestion Exposures Dep end in g on th e in ges ti on s cen ari o, t he i nha lat io n pa th way w il l al so h ave bee n as ses sed . In such cas es, the in

halation exposures

must be pr

esented along w ith the ing estion expo sures to provide a n overal l estimate

of risk a cross the multiple pa

thways. When the

re is a c ompatibili

ty in th e e xp os ur e s ce na ri os , i nh al at io n a nd in ge st io n r is k e st im at es ca n b e c om bi ne d. Es se nt ia ll y, an additional column for inhalation can be added to Exhibit 22-1 to achieve this result. Regardless, when both routes are asse ssed, risk estimates for both routes of exposure should be present ed, along with desc

riptions r egard ing the p opulation s assesse d for all p athway s and rout es, thereby clarify ing any differe nces in po

pulations

. It is important to note, however, that the methods and assumptions used to derive the inhalation and ing estion risks may

not alway

s yi eld compa

tible exposu

re scenarios. Th

is is parti cularly important when population-level (versus individual) risk estimates are being developed. For example, a

scenar io-base d ingest

ion exposur

e assessment will not be easi ly a menable to producing estimates of numbers of people at diffe rent risk levels, while a population-based inhalation assessment may be more appropriate. In addition, it would ge nerally not be appropriate to add an inhalation risk that presumes a 70-y ear exposure duration with an ingestion pathway that pre sumes a 30-yea r exposure duration. Any matc hing of exposure durations among pathways in a multipathway assessment should be carefully considered. 22.3 Noncancer Hazard For noncancer effe cts (as well as carcinogens be ing assessed based on the assumption of nonlinear dose-response), ingestion exposure conce ntrations are compared to RfDs, which are estimate s (with unc ertainty spanning perhaps an order of magn itude) of a daily oral expos

ure toa Alt hough subchroni c RfDs a re not rout inely deve loped by EPA, ATSDR develops MRLs for “interm ediate ” exp osure s and desc ribes the m as b eing re levant to expo sure d uration s on the ord er of we eks to months (i.e. , >14 days to 364 days). April 2004 Page 2 2-5 the human population (including sensitive sub-populations) that is likely to be without an appreciable risk of deleterious noncanc er effects during a lifetime (se e Chapter 21). As with ca

rcinog ens, the d

evelopme nt of haza rd quotie nts (HQs)for ing estion ty pically is performed first for individual air toxics. Then, hazard indices (HI s) may be de veloped for multiple pollutant exposures and summed across pathways to deve lop multiple pathway cumulativ e hazard

estimate s. An addi

tional ste p in the mult

ipathway analy sis is to eva

luate combining

both inge stion and i

nhalation hazard e stimates. These ste ps are de scribed

in separ ate subsections below. 22.3.1 Characterizing Individual Pollutant Hazard - Scenario Approach The first step in characterizing individual pollutant hazard for an exposure sce nario (e.g., a recreational fisher) is to quantify hazard for each pollutant being evaluate d. For ingestion exposures , noncancer haza rds are estimate d by

dividing the estima

te of the Averag e Daily

Dose (ADD) by the chroni c oral Rf D to y ield an HQ

for individual che

micals: HQ = ADD ÷ R fD (Equation 22- 3) where: HQ = Hazard Quotient for the pollutant via each ingestion pathway

being evaluated (unitless); ADD = Estimate of the Average Daily Dose for the pollutant via the ingestion pathway being evaluated (mg/kg -d); and RfD = Corresponding reference dose for the pollutant via the ingestion pathway being evaluated (mg/kg-d). In screening

assessments, the chronic exposure estimate is commonly based on a simplifying assumption of continued similar conditions for a long-term period (for example, that the maximum annual average modeled concentra tion remains constant during the full course of the exposure d

uration) . A more r

efined a ssessmen

t might consider how conce ntration c hange s with time over the exposur

e durati on. I

n both cas es, it is imp ortant to match the typ e of RfD v alue to the spec ific exposu

re scenario. For example, for child hood sce narios ( e.g., a

ges 0-6 ), risk assessors commonly use chr onic RfDs (rather than subchronic). Subchronic RfDs (a) are more commonly used to evaluate e xposure scenarios that last a ye ar or less (e.g., a construction worke r who is exposed for 6 months). For exposure durations of a few y ears, both chronic and subchron ic value s may

be consid

ered, with chron

ic value s commonly

being u sed, par

ticularl y in screen ing asse ssments, w

ith explicit r

ecogn ition of the

decision and its ba sis. Acute

toxicity values are for exposures that are much shorter in dur ation (usually 24 hours or less); howe ver, such exposu

res ge nerally are not e valuate d in a multip athway air toxics r

isk asses sment. Based on the def

inition of t

he RfD, a n HQ less t

han or eq ual to one indicate s that adv erse noncancer effects are not likely to occur . With exposures increasingly g reater than the RfD (i.e.,April 2004 Page 2 2-6 HQs increasingly

greater than one), the potential for adverse effects increases , but we do not know by how much. An HQ of 100 does not mean that the hazard is 10 times greater than a n HQ of 10. Also an HQ of 10 for one substance may not have the same meaning (in terms of hazard) as another substance resulting in the same HQ. 22.3.2 Multiple Pollutant Hazard Noncancer health effec

ts data are usually

available only for

individual compounds within a mixture. I

n these c ases, the

individua

l HQs can be summed

togethe r to calc ulate a mu

ltipol lu tan t HI: HI = HQ 1 + HQ 2 + ...+ HQ i ( Equation 22- 4) where HI = Hazard index; and HQ i = Hazard quotient for the i th air toxic. For screening-level a ssessments, a simple HI may first be calculated for all chemicals of potential concern (COPCs) (Exhibit 22-2). This approach is based on the assumption that even when individua l pollutant

levels a re lower than the c orresponding re ferenc e levels , some poll utants may work tog ether such that their potential for harm is additive and the combined exposure to the group of chemicals poses gre ater likelihood of harm. Some groups of chemicals ca n also behave an ta go ni st ic al ly, su ch th at co mb in ed ex po su re po se s l es s l ik el ih oo d o f h ar m, or syn er gi st ic al ly, such that combined exposure poses harm in a greater than additive manner, although information needed to perform such an analy sis is generally

not available. Where this type of HI exceeds the criterion of interest, a more refined ana lysis is warranted. The assumption of dose additivity is most appropriate to compounds that induce the same effect by similar modes of action. Thus, EPA g uidance for chemical mixtures (3) suggests subgrouping pollutant- specific

HQs by toxicolog ical simila

rity of the pol lutants for subsequ ent calc ulations; that is, calculating a target-organ-specific-hazard index (TOSHI) for each subgrouping of pollutants. This calculation allows for a more appropriate estimate of over all hazard. The HI app roach e ncomp assin g all ch emica ls in a mix ture m ay be appro priat e for a s creeni nglevel study. Howeve

r, it is important to note that applying the HI equation to compounds that may produce

different effects, or that act by different mechanisms, could overestimate the potential for effects. Consequently , in a refined assessment, it is more appropriate to calculate a separate HI f

or each noncancer endpoint of conc ern when target org ans or modes of action are known to be similar. Refined assessments also may employ techniques more complex than the HI de rived usi ng RfDs. (4) 22.3.3 Evaluating Hazard Estimates From Inhalation and Ingestion Exposures As with carcinogenic assessments, inhalation hazards must be combined with ing estion hazards to provide total hazard across all exposure pathways for a receptor. Similar to Exhibit 22-1, inhalation and ingestion risk estimates can be combined either by chemical across pathway s or across chemicals within a pathway . Essentially, an additional column for inhala tion can be added to Exhibit 22- 2 to achie

ve this re sult.April 2004 Page 2 2-7

Estimating Risk for Drinking Water Sources In eval uat ing po ten tia l ri sks as soci ate d wit h dri nkin g wate r sup pli es, r isk a sse ssor s commo nly as sume that the drinking

water undergoes at least a minim um level o f treatment to rem ove solids (i.e., particles in the water which are persistent bioaccum

ulative hazardou s air pollutants [PB- HAPs] or onto which PB-HAPs may be absorbed). Therefore, the risk assessm ent comm only focuses on the dissolved concentrations

of PB-H APs in drinking

water sources. I

n addition, if the drink

ing water source is part o f a publ ic drink ing w ater sy stem, the risk assessm ent may als o assum

e that the water

is treated to meet app licable drinking water standards (i.e., trea ted to maxim

um contam

inant levels or MCLs, unless study-specific inform ation indicates otherwise) for chemicals regu lated under the drinking wate

r program. National Prim ary Drinking

Water Regulations are enforceable standards that apply to pub lic wate

r systems. The MCL s are th e highest level of a s pecific list of c ontam

inants allowed in drinking

water (see htt p:/ /www .epa .gov/ saf ewat er/ mcl.h tml ). Exhibit 22-2. Example Matrix for Characterizing Haz ard for Multiple Chemical Ex posure throug h Multip le Inge stion Pathways for a Particul ar Ex

posure Scenar io Pathwa y 1 (Vegeta ble Ingestion HQ Estimate) (a) Pathway 2

(Fish Ingestion HQ Estimate) (a) Pathway 3

(Egg I ngestion HQ Estimate) (a) Pathwa y 4

(Beef Ingestion HQ Estimate) (a) Agg

regate Chemical Ingestion HQ Est imate (a) Chem ical 1 2 × 10 -1 2 × 10 -1 4 × 10 -2 2 × 10 -1 7 × 10 -1 Chem ical 2 3 × 10 -1 7 × 10 -1 3 × 10 -2 2 × 10 -1 1 Chem ical 3 1 × 10 -1 4 × 10 -1 2 × 10 -1 4 × 10 -1 1 Chem ical 4 9 × 10 -2 1 × 10 -2 1 × 10 -1 2 × 10 -2 3 × 10 -1 Cumulat ive Ingestion Path way HI (a) 7 × 10 -1 1 4 × 10 -1 9 × 10 -1 3

(a) Standa rd rules for rou nding apply which will com

monly lead to an answer of one sign

ificant f igure in both risk and hazard estimate s. For presentation pu rposes, hazard qu

otients (and hazard in

dices) and cancer risk estim

ates are usually reported

as one significant fig

ure. 22.4 Interpre

tation and P resenta

tion of Risks/

Hazards In the final pa rt of the r isk char acteriza tion, estimates of c ancer r isk and non

cancer hazard should be presented in the context of uncertainties and limitations in the data and methodology

. Exposure estimates and assumptions, toxicity estimates and assumptions, and the assessment of uncertainty should be discusse d. Chapter 13 provides more detailed information and examples. Part VI of this refere

nce manual discusses risk communication and other elements of the riskbased de cision-ma

king pro cess.

Note that multipathway air toxics risk assessments are subject to additional sources of uncerta inty as compa red to inhalation r

isk asses sments. The multimed ia modelin

g effort is both more complex and less certain due to many factors. For example: (1) there are many more chemica l-depen dent and c

hemical- independ

ent vari ables involved as i nput value s to the mod

els;April 2004 Page 2 2-8 1. U.S. Environmental Protection Agency . 2002. Framework for Cumulative Risk Assessment (Exte rnal Revi ew Draft) . Risk Asse ssment Forum, Washin gton, DC , April 200 2, availa ble at: http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=29570 U.S. Environmental Protection Agency . 1997. Guidance on Cumulati

ve Risk A ssessmen t, Part 1, Planning and Scoping . Science Policy Council, Wa shington , DC. U.S. Environmental Protection Agency . 1984. Risk Asse ssment an d Manage

ment: Framework for Decision Making , Washington, D.C. EPA 600/9-85-002. 2. U.S. Environmental Protection Agency . 1986. Guidelines for Mutagenicity Risk Assessment

. Risk Assessment Forum, Washington, DC. EPA/630/R-98/003; published in the Federal Registe r 51:(118 5): 34006- 34012, Sept 24, 1986, availab le at: http://cfpub.epa.gov/ncea/raf/pdfs/mutage n2.pdf

. 3. U.S. Environmental Protection Agency . 2000. Supplementary Guidance for Conducting Health Risk Assessment of Chemical Mixtures . Risk Assessment Forum, Washington, D.C. EPA/630/R-00/002, available at http://www.epa.gov/ncea/raf/pdfs/chem_mix/chem_mix_08_2001.pdf

. U.S. Environmental Protection Agency . 1986. Guidelines for the Health Risk Assessment of Chemical Mixtures . EPA/630/R-98/002; published in the Federal Register 51 (185):34014- 34025, Sept 24, 1986, available at http://www.epa.gov/ncea/raf/pdfs/chem_mix/chem_mix_08_2001.pdf. 4. U.S. Environmental Protection Agency . 2002. Guidance on Cumulative Risk Assessment for Pesticide Chemicals that have a Common Mechanism of Action . Office of Pesticides Progra ms, Washing

ton, D.C., January

2002. Ava

ilable at : http://www.epa.gov/pesticides/trac/science/

. U.S. Environmental Protection Agency . 2003. National Center for Environmental Assessment. Developing Approaches to Estimate Cumulative Risks of Drinking Water Contaminan ts . Update d Decem ber 30, 2 003. Avai lable at: http://cf pub.epa .gov/nc ea/cfm/ recordisplay .cfm?deid=18494 . (Last accesse d April, 2004.) (2) the mo dels invol

ve analy sis of the t

ransfe r of air t oxics from t

he air to other me dia (e.g ., soil, sediment, water) , the subse quent move ment of the

air toxics b etween

these me dia (e.g ., soil runoff to surface water), a nd uptake and metabolism by biota; and ( 3) many var iables affect the ingesti on of food , water, and other media by humans an

d wildlife , and the e

xposure an

d risk estimates may diffe

r considerably

as a consequence of the assumptions used to derive intake estimates. Sampling of biota and abiotic media also may be more complex. Additional uncerta inties ar e incorp orated i

n the risk assessme nt when exposure es timates to multiple substances across multiple pathway s are summed. References

# PART IV

ECOLOGI CAL RISK AS SESSMEN T

# Chapter 2 3 Overview and Getting Started : Problem

Formul ation

Table of Contents

23.1 Introduction

............ ............ ............ ............ ............ ...... 1 23.2 Overview o f Air Toxics Ecological Risk Assessm ent
............ ............ ......... 4 23.2.1 Problem Form

ulation

............ ............ ............ ............ .... 6 23.2.2 Analy sis

............ ............ ............ ............ ............ . . 8 23.2.3 Evalu

ation of Ecolog ical Eff ects
............ ............ ............ ....... 9 23.2.4 Ecological Risk

Characterization

............ ............ ............ ...... 9 23.3 Planning and Sc oping

............ ............ ............ ............ .......... 9 23.3.1 What is the Concern?

............ ............ ............ ............ ... 10 23.3.2 Iden

tifyin g The P articipa

nts
............ ............ ............ ......... 11 23.3.3 Determining the Scope of the Risk Assessment

............ ............ ...... 12 23.3.4 Study-S pecific Conceptual Model

............ ............ ............ ..... 12 23.3.4.1 Iden

tifyin g Rec eptors o f Conce

rn ............ ............ .... 13 23.3.4.2 Iden

tifyin g Ass essme

nt Endp oints an

d Measur es of Ef fects

........ 15 23.3.5 Analysis Plan and Quality Assuranc e Program Plan (QAPP)

............ ........ 16 23.4 Tiered Ec ologic al Risk Assessments
............ ............ ............ ......... 21 References

............ ............ ............ ............ ............ ............ 23April 2004 Page 2 3-1 Part IV constitutes

a snapshot of EP

A’s current thinking and approach to th e adaptation of the evolvin g methods

of ecol ogical r isk asse ssment to the con text of Federa l and st ate con trol of air toxics. While inhalation risk assessment has been increa singly used in regulato ry contexts over the last several years, ecologica l risk assessment tools are less we ll developed and field tested in a regulatory cont ext. Part IV should be conside red a living docum ent for review and inp ut. By publishing Part IV

in its current state of development, EPA is soliciting the involvement of persons with experience in this field to help improve these assessment methods for u se in a regulatory context . EPA anticipates rev

isions t o this d raft sec tion of Part IV

on the basis o f this in put.

Trophic Levels and

Biomagnification The trophic level is a way to describe where an organism m

ay be located w

ithin an aquatic or terrestri al food web. The lowes t trophi c leve l consis ts of prim ary pr oducers , the g

reen pla nts that conv ert sunlight into carbohy

drates via photosy

nthesis. The next tro phic lev el generally

consist s of pri

mary consumers, or the organism s that feed directly on green plants. The next level up, often termed secondary consum

ers, represents anim

als that feed on primary con sumers. The hig hest trophic level consists of the top predators in the food web. For some chem

icals, the concentration in b iological tissue can increase as it m

oves up the food

chain, a process called biomagnification

. 23.1 Introduction

Part III of this Reference

Manual discusses how to plan for and conduct a multipathway human health risk assessment when air toxics that persist and may also bioaccumulate (e.g., the persistent bioaccumulative hazardous air pollutant compounds, or PB-HAPs) in media other than air and/ or biomag

nify in food chains are

present in relea ses. For

these compounds, the risk assessment generally

will need to include consideration of exposure pathway s that involve deposition of air toxics onto soil and plants and into water, subsequent uptake by biota, a nd potentia l human expo sures via

consumpti on of con

taminate d soils, se diments, su rface waters, and food s. These

substanc es may

also pose risks to ec ologica

l recep tors from

direct exposure to contaminated media or through indirect exposure via aquatic a nd terrestrial food chains (see Exhibit 23-1). The preliminary list of PB-HAPs was de rived primarily on the ba sis of exposure and risk/ hazard on ce HAPs a

re depos ited onto s oils, into su rface waters, etc. I

ts deriva tion did not consider direct exposures of ecological re ceptors to air toxics while they are in the air (e.g., phytotoxic effects on plants; inhalation by animals). Additional HAPs of potential concern for ecolog ical risk

may be identi fied as EPA gains more fa miliarity with ecol ogical

risk asse ssments for air toxics. Appendix D describes the process by which EPA identified the PB-HAP compound s.April 2004 Page 2 3-2 Exhibit 23-1. Air Toxics E xposure Pathways of Potential Concer n for Ecological Receptors

This gr aphic il lustrate s some of the potenti al mu

ltimed ia pathways of

concer n for ai r toxics exposu re to ecolo gical receptors. Ai r toxics release d from

a sourc e disperse throu

gh the air and event ually fall to the earth (atmosp

heric deposition) via s ettling and/or precipitation. Air toxics deposited to soil may be absorbed or ing ested by plants and soil invertebrates (uptak e). Terrestrial animals m ay be exposed to air toxics via ingestion of contamina ted plants and soil, or by consum ing contam

inated terrestrial animals (for those a

ir toxics that bioaccum

ulate and transfer up the te rrestrial food web). Air toxics deposit ed to w ater m

ay be dissolv

ed in the water

colum n and/or may

settle a nd be a bsorbed into aqua tic sedi ments . Air toxi cs in sedi ments may be a bsor bed o r ing est ed by b ent hic organ isms (uptake); those in sed

iments and the w

ater column m

ay be absorbed by aquatic plants (u ptake). Aquatic organisms (e.g., fish) m ay be exposed directly to air toxics in the water column and/or by consuming contaminated aquatic organisms (for those air toxics that bioacc umulate and transfer up the aquatic food web). Terrestrial animals m ay be exposed to air toxics by eatin g contamin

ated fish or shellfish and/or by d

rinking contam

inated water. Note a

lso that, while in the a

tmosphere, air tox

ics may also ha ve dir ect im pacts on plants (direct exposu

re) and terrestri al anim

als (inhalation)

. This part (Part I V) of this refer ence ma nual intro duces the

basic concepts of

ecolog ical risk assessment and describes their application to air toxics. Several differe nces of particular importanc e are hi ghligh

ted in a text box on pag e 23-3. T he discus sion of ec ologica l risk assessme nt follows

the same gener al frame work as that prese

nted in Par

t II I sinc e the ove

rall concept is the same; namely that certain air toxics may move f rom the air into other media where exposures to orga nisms (in th

is case, non-huma

n orga nisms) ca n occur w ith potenti ally

adverse outcomes . Readers are str ongly encoura ged to b ecome f

amiliar w ith the inf ormation p

rovided i n Part III before re ading this Part. However, although there are many similarit ies betweenApril 2004 Page 2 3-3 Air toxics may have adverse effe cts on ecological receptors through direct expos ures (e.g., inhalation by animals; direct depo sition onto plants). How ever, EPA does n ot have sufficient experience with multipathway a ir toxics risk assessments to identify th e circumstances for which these exposures wou ld represent a potential c oncern. This referen ce manual therefore does not address these additional exposure pathways. The methods for conductin g such an analysis are describ ed in g

reater d etail in EPA’s

Guidel ines for Ecolog ical Ris k Asses sment. (1)

Key Ecological Risk A ssessment Resources

• NCEA’s Ecological Risk Assessm ent webpage http://c fpub.e pa.gov/nce a/cfm

/ecolog ic.cfm

• The Oak Ridg e National Laboratory Ecological Risk

Assessment webpage on tools, guidance, and applications htt p:/ /www .esd .orn l.go v/pr ogra ms/ec ori sk/e cori sk.ht ml

• The Superfund Ecological Risk Assessm ent Program http://e pa.gov/sup erfund/

progr ams/r isk/ec olgc. htm

• Navy Gu

idance for Conducting

Ecological Risk

Assessments http: //web .ead.a nl.gov/e coris k/

• EPA’s Watershed Ecolog ical Risk Assessm

ent program http://c fpub.e

pa.gov/nce a/cfm

/weracs .cfm? ActTyp e=defau lt multimedia human health r isk assess ment and ecol

ogical risk

assessment (

e.g., the y may use the same multim edia monitoring and modelin g tools), professional expertise will always be required t

o apply the

ecologic al risk asse

ssment principles and tool s identifie

d in this document to sp ecific a

ssessment are

as or proble

ms. This document

is not a substit

ute for a working familiarity with ecological principles, their appl ication, and the field of ecological risk asses sment
.

This chapter presents an overview of ec ological risk assessment and discusses the initial planning and scoping activities. The remaining cha pters of this part focus on Characterization of Exposure ( Chapter 2 4), Char acteriza tion of Ec ologica

l Effects (Chapte

r 25), an d Risk Characterization (Chapter 26). The discussion presented her e is based largely

on EPA’s Guidelines for Ecological Risk Assessment (1) and the Residual R isk Repor t to Congres

s. (2) The Guidelines for Ecological Risk Assessment were developed especially for evaluating ecologica

l risk. Readers are also strongly encouraged to become fa miliar with that document for a more complete understanding of EPA’s recommended a pproach to ecological risk assessment. Interested rea

ders are also referre d to EPA’s Ecological Risk and Decision Making W orkshop materials which provide detailed information on the definition of ecological risk assessment, how it relates to human health assessment, the ecosystem protection place-based approach, a nd the bases for ecological protection and r isk assessment at EPA. (3)April 2004 Page 2 3-4

Some Important Differences Between Ecological Risk Assessment and Multipathway Human Health Risk Asse ssment

• Planning and scoping . The ecological risk assessment requires more prelim inary analysis a

nd deliberation regarding

endpoints to be assessed and toxicity reference values to be used because ecological sy stems

are m ore com plex and are not as wel l understood bi ologic ally a s human heal th system s. The p lanning

and sco ping t eam should i

nclude indivi duals w

ith spec ific exp ertise in ecological risk

assessm ent.

• Assessment area . It m ay be necessary

to evaluate additiona

l portions of the assessm

ent area that are not of concern from

a human he alth perspective.

• Potentially exposed po pulations . The fo cus shif ts from potenti ally exposed

indiv idual hu mans to potentially exposed p opulations and species of ecological receptors of concern. I n many cases, the exposu re ass essment may need to a ddres s multip le spec ies and life-st ages, many of which ha ve physiological an

d biochemical pro cesses that differ significantly from hum

ans. (When threatened or endangered spec ies are present, the assessm ent may a lso include an evalu

ation of those organ isms as indiv

iduals).

• Exposure path

ways and exposure ro utes . It may be nece ssary to asses s differ ent exp osure pathways and ro

utes that are not of conce rn for human health.

• Ecological effects assessment . Ecological systems have traits and properties that are differe nt from hum ans and, thus, the ecological effects assessm ent (comparable to hazard assessm ent for human health) m

ay consider a w

ider range of potential causal relationships.

• Risk characterizatio n . While risks m ay be assessed at multiple levels of ecological org anization (i.e., organism , population, com munity, a nd ecosystem

), they gen

erally are assessed at the populat ion level in air

toxics assessm

ents. ( Never theless, when a

ppropri ate, considera

tion sho uld be giv en to as sessments at high l evels of ecolo gical organ ization, such

as at the landsc ape level).

23.2 Overvie

w of Air Toxic s Ecologic al Risk Asse ssment The ecological risk assessment process ha s three main steps that broadly correspond to the four basic steps in human health risk assessment methodology (Exhibit 23-2): (1)

• Problem formulation , which corresponds to the problem formulation step of the human health r isk asses sment methodology (plannin g and sc oping a

ctivities similar to h

uman hea lth risk asse ssment ar

e also inte grate d with this s tep; howe ver, the y a re discu ssed sepa

rately below to ma

intain the operati onal stru

cture of the ecol ogical

risk asse ssment as d

escribe d in EPA’s ecological risk assessment guidelines);

• Analysis , which corresponds to the exposure assessment and toxicity a ssessment steps of the human health risk assessment methodology ; and

• Risk characterization , which corresponds to the risk characterization step of the human he al th ri sk as se ss me nt me th od ol og y.April 2004 Page 2 3-5

Exhibit 23-2. Ecological Risk A ssessment Framework

Source: EPA Guidelin es for Ecological Risk A ssessment (1)April 2004 Page 2 3-6 23.2.1 Problem Formulation Problem formulation provides the foundation for the entire ecologic al risk assessment. This step includes :

• Identify

ing risk management goa ls from an ecological perspective, e cological receptors of concern (e.g., wetlands, fish populations, key stone species that impact the overall ecosy stem), and assessment endpoints (explicit expression of the environmental value that is to be protect ed, oper ationally defined by a n ecological enti

ty a nd its attr ibutes);

• Developing the ecological risk pa rt of the conceptual model as necessary to account for ecological exposure pathway s and receptors; and

• If necessar

y, developing

the Sampling and Analy sis Plan and associated Quality Assura nce Project Plan to collect data on exposures and measures of effe cts that are needed to support the ecological risk assessment. As with human healt

h risk ass essments, problem f ormulation is often

an itera tive proc ess, in which sub stantial r

e-eval uation ma y oc cur as ne

w informa

tion and da

ta become availa

ble. Data collection in subsequent iterations often is triggered by identification of major data gaps and uncerta inties in the risk characte

rization that preve

nt confid ent deci sion-mak

ing by risk manage rs. The problem formulation process for ecologic al risk assessment for air toxics focuses on developi ng a common understanding of what needs to be

done to as sess ecological risks associated with pathway s involving deposition; the transfer of compounds to soil, water, sediment, and biota , and subs equent exposure. Whi le the ec ologica l risk asse ssment may

build on the foundation of the human health multipathway assessment (e.g., using the same emissions data and multimedia models), the problem formulation step is particularly critical for the ecological risk assessment because of the effort needed to understand and identify ecological receptors, exposure pathways, endpoints, and management goals. The e cological risk assessment is not simply an “add-on” to the human he alth multipathway risk assessment. The pr oblem formulation effort will need to consider a wide variety of possible ecological receptors that ar e not similar to humans. For example:

• Different species (and life stag es) may ha ve very dif

ferent responses to the same exposure. Therefore, knowledge of

the exposure-response of many species, including those that may be particularly se

nsitive to the air toxic, is needed.

• Ecosystems may

show adverse effects at lower e xposures than most individual species do because species that are important in terms of ec osystem function (e.g ., energy flow, nutrient recyc ling) may a

lso be sensitive to toxic effects. Ecosystem-le vel metrics such as species diversity indices may

be more sensitive indicators of adverse effe cts than are toxicological studies.

• There may

be many diffe

rent types of e cosystems present in the a ssessment area, and sensitivit y lik ely varies a mong the m. There fore, the partic

ular fe atures o f the ec osy stem(s) that occ ur in are as wher

e high exposures a

re pred icted may be parti cularly

important

.April 2004 Page 2 3-7 An Eco logical

Risk A ssessmen t Case Study: Ozon e Risks To Ag roecosy stems
Th e case study sum mariz ed he re pro vides an exa mple of how EP A ha s assesse d env ironm ental risks from a n air poll utant (oz one) a s par t of EPA’s ef

fort to pr omulg ate Nation al Ambi ent Air Qua li ty Stan dards (NAAQS) for criteri a air pollutant s (see Chapter 2). Note that t his example is f

or ozone, a criteria ai r pollutant; however, the concepts presented here are relevant t o air toxics ri sk assessment. In addition, an agroecosyst em, such as the sys tem di scus sed he re, is more of a human

const ruct tha n a nat

ural ecosy ste m and i s prov ided h ere on ly for illus trati on of general principles . An actual air toxics ecological risk asses sment of a natural system would have to consider sit e-specifi c characterist ics of the system in question.
Problem Formul ation . Pursuant to t he Clean Air Act (CAA), EP A is required to set NAAQS for “any pollut ant which, if present in the air, may reasona bly be anticipated to endang er public hea lth or welfare and wh ose prese nce in th e air resu lts from n ume rous o r diver se mo bile an d/or stationa ry sourc es.” E PA deve lops p ublic health (primary) and welfare (secondary) NAAQ S. According to section 302 of the CAA, the term welfare “includ es ... effects o n soils, wa ter, cro ps, veg etation , manm ade mater ials, anim als, wildlife, w eathe r, visibility, and cl imat e, dama ge t o and det eri orat ion of propert y, and haz ards to t

rans porta ti on, a s wel l as eff ects on economi c val ues . .. .” A s econdar y st andard, as def

ined in s ecti on 109(b) (2) of the CAA, must

“spe cif y a l evel of air qual ity

the at tainment and mai ntenanc e of whi ch in t he judgment

of th e Administ

rator, based on such crit eria, is requisi te to protect t

he public welfare f

rom any known or anticipated adverse effect s associated wit h the prese nce o f such air p ollutant in the am bient a ir.” Th is case stu dy foc uses o n an as sessm ent end poin t for agric ultural cro ps (e.g ., the pre ventio n of an econ omic ally adverse reduction in crop yiel ds). Yield loss i s defined as an impairment of, or decrease in, the value of the int ended us e of t

he pl ant. This c oncept inc ludes a decr ease in t he wei ghtof t

he mar keta

ble pl ant organ , re ducti on in aesthet ic values, changes in crop quality , and/or occurrence of foli ar injury when f oliage is t

he marketable part of t he pl ant. These t

ypes of y iel d los s canbe dir ectly meas ured a s cha nges in c rop gr owth, fol iar inj ury , or pro duc tivity, so they also serve a s the me asure s of effect fo r the asse ssmen t. Exp osur e A naly sis . EPA use d ambien t ozon e moni toring dat a acros s t he U.S. and a Geogr aphic Inf ormat ion System (GIS) model to project national cumulative, seasonal ozone for the maximum three month period during the summer ozone season. This allowed EPA to project ozone concentrations for some rural parts of the country where no moni tori ng dat a were avai labl e butwher e crops were grown, and t o est imat e th e at tai nment of alterna tive N AA QS scena rios. T he U .S. D epa rtmen t of Agr iculture’s (U SD A’s) na tional cr op in vento ry data were used to iden tify where o zon e-sensitive crop spec ies were being grow n and in what q uantities. T his information all owed the Agency to estimate the ext ent of exposure of ozone-sensit ive species under the dif ferent scenarios.
Eco logic al Ef fects A naly sis . Stresso r-respo nse p rofiles d escrib ing the re lationsh ip be tween ozo ne and grow th and productivity f

or 15 crop spec ies representat ive of major production crops in the U.S. (e.g. , crops that are economically val uable t o the U.S., of regi onal i mportance, and represe ntat ive of a number of c rop types ) had alr eady be en deve loped f rom field studies condu cted from 1 980 to 198 6 unde r the Nationa l Crop L oss Asse ssmen t Netw ork (N CLA N) p rogra m. T he N CLA N stud ies also in clude d sec ond ary stresso rs (e.g., low soil moisture and co-exposure with other poll utants l ike sulf ur dioxide), which hel ped EP A interpret the environmen tal eff

ects dat a for ozone.
Risk Charac teri zati on . Under the dif fer ent NAAQS scenari os, the Agency est imat ed th e in creas ed prot ecti on from ozo ne-rela ted effec ts on ve getatio n asso ciated with attainm ent of the differen t NA AQ S sce nario s. M one tized e stimates o f increas ed p rotec tion asso ciated with seve ral altern ative stan dard s for ec ono mica lly impo rtant cro ps we re also deve lope d. T his analysis fo cused on o zon e effects o n vege tation sinc e these pub lic welfare eff

ects are of most concern at ozone concentrations t ypically occurring in t

he U.S. By affecting commercial crops and nat ural v egetat ion, ozone may als o indir ectl y aff ect nat ural e cosyst em components su ch as soil s, wat er, ani mals, and wil dlif e.
Source : U.S. E nviro nme ntal Pr otectio n Age ncy. 19 99. Residu al Risk R eport to C ong ress . Office o f Air Q uality Plann ing and St andards , Res earchTrian gle, NC, March 1999. EPA-453/R- 99-011.April 2004 Page 2 3-8 23.2.2 Analysis Analysis includes two principal steps. Characterization of exposures includes identifying the contaminants of potential ecological concern (COPECs) that may affect ecological rec eptors, characterizing the spatial and/or temporal patter n of stressor concentrations in environmental media (including certain body burden levels), and analy zing the level of contact or co-occurr ence (exposure) between the stressors and the ecological receptors. This often is done using the multimedia models identified in Chapter 18; however, different models or approac hes may be appropriate. Characterization of ecological effects includes identifying the types of ef

fects that different stressors may

have on ecological rece

ptors, along with characterizing the stressorresponse relatio nship (the relationship between the level of exposure to the stressor and the expected biological or ecological re sponse). A common result is the identification of ecological toxicity refere nce value s (TRVs) , which are concentrations of chemica ls in environmental media (including biota such as fish tissues) below which no significa nt ecological effects are anticipated. TRVs are similar, in concept, to RfDs (reference doses) and RfCs (r eference concentrations) for human health noncancer evaluations. TRVs may be screening level (i.e., conservative, generic value s) or more refined values for use in hig her levels of analy sis. They may be point values, ra

nges, or developed using more a dvanced probabilistic methods (such as Monte Carlo techniques). The ecological e xposure characterization also is likely to diffe r significantly f

rom the corresponding multipathway exposure assessment for human health. For example:

• In a ddition to f

ood chain (inges tion) expos

ures, ma ny e cologic al rece

ptors ca n be expose d to air toxics via direct contact with contaminated soils (e.g., earthwor ms) or sediments (e.g., sediment-dwelling invertebrates, bottom-feeding fish); direct exposure to surface water (e.g ., free-swimming invertebrates and f ish); or direct exposure to contaminated air via inhalation (e.g., birds), dermal contact (e .g., amphibians), deposition to plant surfaces, etc.

• Particula

r geog raphic a reas of concer n may differ b ecause

ecolog ical rec eptors ma

y oc cur in areas r arely used by human pop

ulations ( e.g., l arge wetland a reas, ponds wher

e people rarely fish).

• Sampling and analy sis may involve a wider r ange of media (e.g ., sediment) and different typ es of biot

a (e.g ., earth

worms, aq

uatic inv ertebr

ates). E ach ty

pe of sam pling an d analy sis has its own

methods, protocols , and Qua lity Assurance/Qua

lity Control (QA/QC) pro cedure s.

• Quantitative metrics of exposure may include both direct and indirect exposures for ecological receptors. Quantific ation of direct exposure is similar to human health inhalation analyses, in which a

mbient concentrations of COPECs in soil, water, and/or sediment are compare d to corr

esponding

TRVs. Qua

ntificat ion of indi

rect expo sure via

ingesti on is similar to that for human health ingestion analyses, except that different food items may be involved, and the a

ppropria te ecolo gical exposure factors (e.g., diet, body weight) will be different. As with human health analyses, many exposure fac tors can be treated either as constant s or as dis tributions in the expos

ure asse ssment. Ec ologica l exposure

assessme nts for ing estion pa

thways freque

ntly use bioenerget

ic models t

o more expl icitly

relate i ntake to adverse effects. (4)April 2004 Page 2 3-9 23.2.3 Evaluation of Ecological Effects The cha rac ter iz ati on o f ec ol ogi cal eff ect s i s s im il ar t o a t ox ici ty as ses sm ent for hum an h eal th . It consider s the ty pes of ad verse e ffects a ssociate d with che mical expos

ures, str essor-r esponse relation ships, and

related uncerta inties. There ar

e two primary

differe nces:

• Adverse effects of conce rn generally

focus at the population, community, or ec osystem level. With rare exception s (e.g. , threat

ened or e ndange red spec ies), ef

fects to i ndividual organ isms are not t he prima ry concer n. Note, however , that ec ologica l risk asse ssments of

ten use estimates of impacts to individual organisms (e.g., mortality, reproductive effects) to infer impacts a t higher levels of organ ization bec ause expos

ure-re sponse da

ta for po pulations , communities, or ecosystems often a re lacking. Some approaches ar e available, however, for incorpor ating po pulation- level analy sis in eco logica l risk asse ssments. (5)

• A distinction is made between assessment endpoints , which a re the e nvironme ntal values to be protected, and measures of effects , which a re the sp ecific measure s used to e valuate risk to the assessment endpoints (assessment endpoints and measures of effec ts are defined in Section 23.3.4.2). 23.2.4 Ecological Risk Characterization Similar to human health risk characterization, ecological risk cha racterization combines informat ion conce rning exposure to c

hemicals with infor

mation re gardin

g effe cts of chemicals t

o estimate risks. Human health risk assessments consider health effec ts in the bodies of individual people. Ecological risk assessments consider various “ health” issues that can range fr om actual health effects in the bodies of individual ecological r eceptors to something more attuned to the “h ea lt h” of

th e e co sys te m a s m ea su re d b y sp ec ie s r ic hn es s a nd di ve rs it y. 23.3 Planning and

Scoping To ensur e that the ecolog ical risk

assessme nt will provide information useful to the risk managers who will be making the risk management decision s, EPA’s Guideline s for Ecolo

gical Risk Assessme nt recommends a planning and scoping dialogu e occur betwee n the risk assessors, risk managers, and where a

ppropriate, interested stakehol ders at the very

start of t he risk assessment process. The outcome of the planning and scop ing pha se is an a greement on the

basic goals, scope, and timing of the risk assessment. Important goals of the dia logue are the identification of the risk management goa ls and risk management options that the risk assessment will be designed to inform (see accompany ing text box). This ‘kick-off’ dialogue sets the stage for the proble m formulation phase, when the plans for the ecological risk assessment are finalized. Planning and Scoping the Ecological Risk Assessment The planning phase is complete when agreements a

re reached on:

• The managem

ent goals for ecolog

ical values;

• The range of m

anagement options the risk a ssessm

ent is to suppor t;

• Objectives for the risk assessm ent, including criteria for succ ess; and

• The focu s and sc ope of t he asse ssmen

t, and res ource availab ilit y.April 2004 Page 23-10 When actually perf

orming the problem formulation phase of an ecological risk assessment, the five-step planning and scoping proce ss identified for human health risk assessments is a helpful tool to ge t the rig ht people involved a

nd the ris k question s, expecta tions, and plans in pl ace to make the overall assessme nt go smoothly

and in a sc ientific ally

responsi ble manne

r. Similar

to the human health evaluation process, the risk assessment and manag ement team should be assemble d to start i dentify ing the c oncern, identify

ing who needs to be

involved i

n the risk assessment process, determining the scope of the r isk assessment, describing why there may be

a problem, and determining how the concern will be e valuated. 23.3.1 What is the

Concern? In hu man heal th risk ass essment a

nd risk ma

nageme nt, the as sessors a

re deal ing with a

single organ ism (human

beings) and the pr

eceden t and rat ionale f or speci fic risk manage

ment goa ls (such as the 1x10 -6 to 1x10 -4 cancer risk range) are generally

well established. The parallel process for ecosystems, however, is not as easy to study or as straig

htforward to manage. To begin with, it can be difficult to choose which of many organisms in a study a

rea to evaluate. Moreover, there is little agreement on whic h (if any) or

ganisms or ecosy stems are important enough to single out for protection. These fa ctors make planning, evaluation, and manag ement of ecological risks more complicated and time-c onsuming (and often, more controversial). EPA’s Risk Assessment Forum developed draft guidance (6) to help de cision-ma kers wor k with risk asse ssors, sta

keholder s, and othe

r analy sts to plan f

or ecolo gical r

isk asses sments tha

t will effectively

inform the decisions they ne ed to make. Planning for ecologica l risk assessment includes three pr imary steps: 1. Defining the risk management decision to be made, the context in which it will be made, and its purpos e . This includes articulating the decision or problem that the risk manag er faces, understanding the social and legal context for the decision, placing preliminary boundaries on the scope of the risk assessment, and identify ing who needs to be involved. Appropriately f

raming the context will help ensure that management objec tives are relevant to the risk manager’s decision and increa se the likelihood that the information generated by the risk assessment will be useful. 2. Developing objectives . This starts with a clear statement of the problem, issue, or opportuni ty id entified in the first step and ends with a set of s pecific objectiv es which

will guide all of the remaining steps. An important deter mination is the “what to protect” (i.e., the assessment endpoint) question for ecological issues and to descr ibe what is at stake. Key questions include:

– What should

be prote cted? Defi

ne the en tities, ec ologica

l proces ses, and geogra

phic areas to be considered.

– How is “protection” defined? Define the ecologica l objectives.

– What are the most important objectives and how can they be achieved? Review and structur e object ives. In so me case s, there

is a strong

consensu s on “wha

t to protec

t” (e.g ., if a commercia

lly important resource such as a fishery is potentially exposed). I n many other ca ses, it is not always obvious to a risk mana ger or the public what feature s of an ecosy stem are of potential concern or what the broader c onsequences would be from adverse ef fects to those features.April 2004 Page 23-11 Assessm ent En dpoint s According to EP

A’s Guidelines for Ecological Risk Assessment , (1) an assessment e ndpoint is an explicit expression of the en vironmental v

alue that is to be protected, and is operationally defined by an ecological entity

and its attributes. For example, a particu lar area has air toxics releases that may be affecting area salm

on populations that are im portant for location recreation an d comm ercial fishermen as well as an important res ource for a local Nativ e American tribe. In the stu dy area, the salmon population is the valued ecolog ical entity; reproduction and age class structu re of a salmon populat ion are some of their

most important att

ributes. An ap

propria te asses sment

endpoi nt for th is study area m

ight be stated as salmon reproduction an d age class structure . The ecological risk assessment for this study area would be structured to evalu ate whether this specific salm on population is at risk from

air toxics with rega

rd to healthy reprod

uctive ability and

age class structure. Given the div ersity of spec ies and other ec ologic al attrib utes in almos t any study

area, t he asse ssors gener ally e stablish

at least one ass essme

nt endp oint tha

t will, together, pro vide a n assessment of air toxics impacts on the ecosystem as a whole. More than one assessm ent endpoint may

be necessary at the eco system

level

. Developing a consensus on the specific risk mana gement objectives may

be a difficult and time-con suming pa

rt of the p lanning

and scop ing proc ess. 3. Identifying what information is needed to inform the decision . When identifying information needs, planners are encoura ged to think ahead about every thing that will be needed to decide what to do about identified risks. Ecologica l risk is part of the picture, but issues suc h as fea sibility , practi cability , cost, an d acceptability

also nee d to be fa

ctored i nto the decision. They should also c onsider who and what resources are a vailable to perform the ecolog ical risk

assessme nt. The a im of this ste

p is to nar row down

which que stions the r

isk assessment should address and identify those that will be addressed elsewhere. The questions identified at this step will be examined during the remainder of the problem formulation process. Management objectives ar e by definition closely

related to the assessment endpoints evaluated in ecological risk assessment, and it should be possible to chara cterize them using the measures described below.

23.3.2 Identifying The Participants The par ticipants for the e cologic al risk as sessment may include s ome of the

same peo ple as tho se for the human health multipathway risk assessment (e.g., multimedia modelers that understand how to model for both human and ecological rece ptors). However,

• Additional risk managers may be involved, including natural resource mana gement agencies such as the U.S. Fish and Wildlif e Servic e; state, local, or

tribal (S/ L/T)fish and game departments; and

/or priva te-sec tor risk ma

nagers.

• The risk a ssessmen

t technic al team will need si gnific antly differe nt experts ( e.g., a

quatic ecologists, experienced ecologica l risk assessors).April 2004 Page 23-12 • The specific set of interested or affe cted parties may change or be expanded (e.g ., different environmental g

roups may

be more c oncerne d/involve d; local f ishermen may become interested). EPA’s Public Involvement Policy may be helpful in per

forming this task (see http://www .epa.g ov/stake holders/ policy 2003/index.htm ). Part V of this document provides additiona l informa tion on com

munity involveme

nt. 23.3.3 Deter mining the

Scope of the

Risk Asses sment The scope of the human health multipathway risk assessment may expand to include additional exposure pathways and e

xposure routes, and to address ecological rec eptors of concern.

• The spec ific che

micals tha

t will be the

focus of the ecol ogical

risk asse ssment will

gener ally be those that persist, bioaccumulate, and biomagnify (the PB-HAP compounds); however, a differe nt set of PB -HAP comp ounds may be of mor

e conce rn for th e ecolog

ical risk assessme nt than for human he alth risk a ssessmen t. As with h

uman hea lth risk as sessment, additiona l compound s may

need to be

added to t

he analy sis, depe nding on study-area

specific consider ations.

• The spec ific sour

ces incl uded in the

analy sis may be focus ed on the s

ubset tha t releas es most or all of t he identi fied COPEC s.

• The physical bounda

ries of the study ar

ea may ne ed to expand to include geographic ar eas where COPECs may be tr ansported after deposition (e.g., the COPECs may have the potential to be deposited in a watershed and be carr ied out of the geographic a rea defined for the human health multipathway modeling ). 23.3.4 Study-Specific Conceptual Model A study-specific

conceptual model for the ecologica l risk assessment is developed using the fundamental elements of the conceptual model developed f or the human health multipathway assessment as a starting point. Steps to develop the study-specific ecological risk conce ptual model inclu de the follo wing:

• Determine whether the set of potential sources and c hemicals that were identified in the human hea

lth multimed

ia risk as sessment a

re appr opriate for the e cologic al risk as sessment.

• Consider expanding the set of potential sources, chemicals, and exposure pathwa ys to include those identified below (potential exposure pathway s are listed in Exhibit 23-3).

• Identify

ecological receptors of c oncern (see Section 23.3.4.1).

• Formulate a risk hypothe sis that describes possible relationships between emissions of a chemica l, exposure , and asse ssment endpoint re sponse, in cluding the infor mation tha

t sets the problem in perspective, as well as an identification of the propose d relationships that need evaluation.April 2004 Page 23-13 • Identify

assessment endpoints and measures of effects (See Section 23.3.4.2).
Exhibit 23-3. Common Exposu re Pathways Considered for

Ecological Air

Toxi cs Risk

Assess ments Direct exposure pathways: air 6 soil 6 soil- dwellin

g biot a air 6 soil 6 water 6 aquatic biota air 6 water 6 aquatic

biota air 6 water 6 sedim

ent 6 aquatic

biota air 6 soil 6 water 6 sedim ent 6 aquatic

biota air 6 vegetation Indirect exposure

pathways: air 6 vegetation 6 bird/mam mal air 6 soil 6 vegetation 6 bird/mam mal air 6 soil 6 water 6 aquatic biota 6 fish air 6 soil 6 water 6 aquatic biota 6 fish 6 bird/mam mal air 6 water 6 aquatic biota 6 fish air 6 water 6 aquatic biota 6 fish 6 bird/mam mal air 6 soil 6 water 6 sedim ent 6 aquatic biota 6 fish air 6 soil 6 water 6 sedim ent 6 aquatic biota 6 fish 6 bird/mammal Conceptu al model d

iagra ms, such a s the examp le illustra ted in Exhibi

t 23-4, ar e used (a long with the risk hypothesis) to select the pa thways to be eva

luated in the analysis phase of the ecological risk asse ssment, a s well as t o assist in c ommunica

tion with r

isk manag ers. As with human health risk assessments, the conceptual model for an ecolog ical risk assessment must provide both a graphical repre sentation of the important exposure pathway s that are presumed to be occurring along with a written description that outlines each element of the conceptual model. Taken together, these two parts of the conceptual model clearly identify the sources of concern, the COPECs that will be evaluated, the exposure pathwa ys, and the assessment endpoints. Similar to conceptual models for human health analysis, the conceptual model may be modified (pe rhaps a number of times) as more is learned about the study area. 23.3.4.1 Identifying Receptors of Concern Ecological receptors of conc ern are an important part of the conce ptual model. These may be plants, animals, habitats, communities, or larger ecosy stem elements. Specific receptors may be of con cern fo r a vari ety of reas ons, i nclud ing:

• The receptor (or one of it’s life stag es) is particularly vulnerable or sensitive to one or more COPECs;

• The receptor (usually

a species or a community such as a wetland) is listed as endangere d or threate ned or is o therwise

given sp ecial le gal protection by the state or feder al gove rnment;April 2004 Page 23-14 • The receptor plays an important part in the overall structure or function of the ec ological community

or ecosy stem;

• The rec eptor is o f partic ular ec onomic or

cultura l value to stakehol ders.

Exhibit 23-4. Conceptual Model D iagram for Exposure o f Piscivorous Birds to Air Tox ics

Conceptual mod

el diagrams are used, along with the risk hy pothesis, to select the path ways to be evaluated in the ana

lysis phase of the ecological risk a ssessment, as well as to assist in com munication with risk m

anagers. The three risk

hypotheses in this hypothetical exam ple are:

• Risk Hypothesis 1 : Concentrations of che mical X in the surface water column are less than a level known

to cause adverse effects on survival and reproduction in Daphni a

– Mechanism: Chem

ical X causes mortality

and inhibits larval d

evelopment

• Risk Hypothesis 2 : Dietary intake levels of ch emical X in lake trout ar e less than a level known to caus e advers e effe cts on r eprodu ctive ab ilit y

– Mechanism: Du

e to a la ck of enzy

me A in lak e trout, chem

ical X rap idly a

ccum ulates i n lipid tissues and damages reproductive org ans

• Risk Hypothesis 3 : Dietary intak e levels of chem

ical X in kingfisher chicks (passed to them by their parents) is less than a le vel known

to adversely affect their survival

– Mechanism: Chem

ical X accumulating

in egg lipids is a metabolic to xin to the develop ing embryoApril 2004 Page 23-15 For taxonomic, physiologica l, and exposure reasons, it is important to consider a broad range of potentia l ecological rec eptors du

ring pr oblem for mulation. F or example , the ty pes of ad verse effects that may

occur to terrestrial plant communities (e.g., impacts to photosy nthesis, nitrogen fixation, nutrient uptake; foliar damage) are ver y differe nt than the types of adve

rse effects that may occur

to terrestrial mammals. Many ecological receptors (e .g., molds, lichens, many invertebrates) have unique phy siological and biochemical features that may make them particularly se

nsitive to air toxics. Sensitive life stages often are a particular conc ern. In surfac e waters a nd sedime

nts, ear ly li fe stag es (e.g ., egg s, larvae) may be parti cularly

sensitive to contaminants due t

o their sma

ll size (e. g., con

taminants may readily penetra te cell me mbranes ) and developmental processes (e.g., ma jor metamorphosis from one life stage to another). Many ter res tri al o rga ni sm s (e .g. , am phi bi ans , dr ago nfl ies ) ha ve a qua ti c-d wel li ng e arl y lif e st age s. In addition, many

inverte brates that can bi oaccumu late PB- HAPs (e.g ., aquati c dwellin g dragonfly larvae) may

be sources of food for sensitive life stage s of other species (e.g., nestling birds)

. Often it is important to understand the aquatic and terrestrial food webs in the ha bitats of concern because these can be important parts of e cological exposure pathways. Top predators are often of speci al conce

rn for exposure to PB -HAP comp ounds. Ecological receptors for e ach habitat potentially impacted should be identified to ensure (1) plant and animal communities representative of the habitat are r epresented by

the habitat-specific food web, and (2) potentially

complete exposure pathway s are identified. Screening-level e cological assessme nts often focus on t

he most se

nsitive or ganisms within an e cosy stem or on the most sensitive life stages within a species, if these are known. Ecological receptor identifica tion may need to include species both known and expected to be present in a spec ific habitat being evaluat ed, and in clude re sident an

d migra tory populations. Consulta

tion with e cologic al experts is recommended. Potential sources of information include:

• Govern ment Or ganizatio ns . The U.S. Fish and Wildlife Service has biologists and other ecolog ical expe

rts and a lso mainta

ins National Wetland

Inve ntory maps. (7) State Natural Heritage Programs provide ma ps or lists of species based on geogra phic location, and are very helpf

ul in identifying threa

tened or endangered spec ies or areas of special concer n.

• Privat e or Loca

l Organiza

tions . Private or professional organizations that are examples of sources of information include: National Audubon Society , the Nature Conservancy , local wildlife c lubs, and u

niversiti es.

• General Literature . Monographs, field guides, and other litera ture describing the flora and fauna of America and/or a par ticular region or state may be useful sources of information. 23.3.4.2 Identifying Assessment Endpoints and Measures of Effects As previously noted, an assessm ent endpoint is an explicit expression of the environmental value tha t is to be pr

otected or is of c oncern. It inc ludes the identific ation of the ecolog ical enti ty for the analy sis (e.g., a species, ecologic al resource, habitat ty pe, or community) as we ll as the attribute of that entity that is potentially at risk and important to protect (e.g., reproductive success, production per unit area, surfac e area coverag e, biodiversity). The measures of effects are the measure s used to a ssess the se endpo ints. (8)April 2004 Page 23-16 Generally , a manageable subset of the most important assessment endpoints is selected f or the risk assessment, and specific measures of eff ects that address each assessment endpoint are identified. EPA guidance documents discuss additional issues that are important in the identific ation of a ssessmen t endpoint s. (9) Appropriate selection of relevant assessment endpoints is critical so that the r isk assessment provides valuable information for the associated risk manag ement decisions. Assessment endpoints that can be measured directly are most effective, although assessment e ndpoints that cannot be measured directly, but can be represented by measures that are easily

monitored or modeled, may

also be us ed. Addit

ional unc ertainty

is introduc ed depe

nding on the rela tionship between the measurement and the assessment endpoints. Exhibit 23-5 provides examples of assessment endpoints, measures of effect, and other elements of the problem formulation phase. EPA has re cently

releas ed guid

ance tha t describ es a set o f endpoin ts, known a s Gener

ic Ecolog ical Asse ssment End points (GE

AE), tha t can be c onsidere d and ada pted for specific ecolog ical risk

assessme nts. (9) The entit

ies and pr opertie s comprisi

ng the in itial set o f GEAEs is presented in Exhibit 23-6. The EPA Guidance defines GEAE further a nd provides the basis for the terms assessme

nt commun ity

and assessment population , which are used in the definitions. In addition, EPA’s Science Advisory Board recently

published a Framework for Assessing and Reporting on Ecological Condition , (10) which includes a checklist of ecological a ttributes that should be considered when conducting ecolog ical risk assessments and developing ecologic al management objectives (Exhibit 23-7). Note that many of these GEAEs and attributes focus at levels of ecological orga

nization higher than organisms (e.g., spec ies richness) or on ecological processes (e.g., nutrient cy cling) rather than attributes of org anisms (e.g., growth, reproduction). It often is useful to summarize the results of the problem formulation proc ess in a problem formulation summary

that lists management objectives, assessment endpoints, and the structure of the risk assessment from exposure scenarios through risk cha racterization. Exhibit 23-8 pr ov id es an ex am pl e p ro bl em fo rm ul at io n s um ma ry. 23.3.5 Anal ysis Plan a nd Qu ality Assu rance Program Pl an (Q APP) As noted in Parts II

and II I of this refere

nce manual, the Analy sis Plan and QAPP are formulated by c onsideri

ng both the the con

ceptual model and

the data quality require d for the

risk manage ment dec ision. The

Analysis Plan an

d QAPP, inc luding da

ta quality objectiv es, are

just as importa

nt for the ecolog ical risk

assessme nt as they are for the human

health r isk asses sment, and in some cases may

be more complex. The analy sis plan for the ecological risk assessment will need to match each of the elements of the conce ptual model with the analytical a pproach that will be used to develop data about the element, including: sources; exposed populations and exposure pathways; exposure conc entrations of COPEC; exposure conditions; toxicity of COPECs; risk

charac terization; QA/QC; d

ocumenta tion; role s and res

ponsibiliti es; reso

urces; and schedule. Because the focus is on ecological receptors, additional ty pes of monitoring (sampling and analysis) may

need to be conducted. For example, it may be important to measure concentrations of COPECs in the sediments of surface water bodies as part of the a nalysis of direct e

xposures for sedi ment-dwe lling inv ertebr

ates as w ell as bioa

ccumula tion from t

hese inve rtebra tes to predatory fish through the aquatic food web.April 2004 Page 23-17 Exhibit 23-5. Example of Ecologica l Risk Assessment Problem Formulation : EPA’s Wa

ter Qual ity Crit eria A specific examp le of elements of the problem form ulation step in a national- level ecological risk assessment can be

found in the development of Am bient Water Quality Criteria by EPA’s O ffice of Water pu rsuant t o the C lean Water Act ( CWA). (11) Water quality criteria hav e been developed

for the protection of aquatic life from chemical stressors. The following elem ents of problem formulation support subsequent analyses in the risk assessments used to e stablish specific criteria. Regulatory Goal

• CWA Se ction 10 1: Prote ct the chemic al, physical, a nd biol ogica

l integ rity o f the Na

tion’s water. Program Man

agement D ecisions

• Protect

99 perc ent of i

ndivid uals in 95 perc ent of t

he spec ies in a

quatic c omm

unities from acute and chr onic eff ects res ulting from exposu re to a c hemic al stress or. Assessm ent End points

• Survi val of fish, a quatic i nverte brates, and algal speci es unde r acute exposu

re

• Survi val, g rowth, and rep

roducti on of fi sh, aqu

atic inv ertebrat es, and algal species under c hronic exposu re Measures of Effect

• Laboratory LC 50 s for at least eig ht speci es me eting certain requirem ents

• Chroni c no- observed-a dvers e-ef fect- levels

(NOAE Ls) for at least three sp ecies m eeting certain requirem ents Measures of Ecosystem

and Receptor Characteristics

• Water hardness (for som e metals)

• pH The wate r qualit y crite rion is a TRV der

ived f rom a distributional

analy sis of s ingle- species toxicit y data. I t is assu med t hat the species

tested (which represen

t a rang e of tax onom

ic gro ups) ad equatel y repre sent t he compos ition and sens itivit ies of specie s in a nat ural c ommunity.April 2004 Page 23-18

Exhib it 23-6.Gener

ic Ecol ogical Assessmen t Endp oints (a) Entity Attribu te Identifie d EPA Pre cedents Organ ism- level endpoin

ts Organisms (in an assessment popula tion or community) Kill s (mass mor talit y, conspi cuous mor talit y) Vertebrates
Gross anomalies Vertebrat es, she llfish, plants Survi val, f ecundit y, g rowth Endangered species, migratory birds, marine mammals, bald and golden eagles , vertebrates, invert ebrates, plants Popula tion- level endpoin

ts Assessment pop

ulation Extirpation Vertebrates

Abundance Vertebrates, shellfish Production Vertebrates (game/resou rce species ), harv

ested pl ants Comm unity and eco system

-lev el endp oints Assessment com

munities, ass embla ges, a nd ec osys tems Taxa richness Aquatic comm unities, cor al r eefs Abundance Aquatic comm unities Production Plant assemblag es Area Wetlan ds, cor al r eefs , enda nger ed/ rar e eco syst ems Function Wetlands Physi cal stru

cture Aqua tic ecos yste ms Official ly des ignate d endpo ints Critical habitat

for endangered or threatened species Area Quality Special places Ecological properties that relate to the spe cial or l egally protected properties e.g., National Parks, Nation al Wildlife Refuges, Great Lakes

(a) Ge neric e colo gical ass essme nt end poin ts for whic h EP A ha s identified existing p olicies a nd p reced ents (in parti cular, the s pecifi c enti ties lis ted inthe t hird col umn). Bold i ndicat es protection by f ederal s tatute. Source : EPA ’s Generi c Ecologi cal As sess ment Endpoint s ( GEAE) for Ecol

ogical Risk Asses sment (9)April 2004 Page 23-19

Exhibit 23-7. Essential Ecological A ttributes and Reportin g Categories Landscape Condition

• Extent of ecological system/habitat ty pes

• Landscape com

position

• Landsc ape pat

tern and structu re Biotic Condition

• Ecosystems and comm unities

– Commu

nity extent

– Commu

nity compo sition

– Trophic structure

– Commu

nity dynam

ics

– Physi cal stru

cture

• Species and populations

– Popula tion si ze

– Genetic

diver sity

– Popula

tion str ucture

– Population dynam

ics

– Habitat

suitabi lity

• Organism condition

– Physiological status

– Sympto ms of d ise ase o r tr auma

– Signs of disease Chemical and Physical Ch aracteristics (Water, Air, S oil, an d Sedim ent)

• Nutrient concentrations

– Nitrogen

– Phosphorus

– Other n

utrients

• Trace inorganic

and organic ch emica

ls

– Metals

– Other tr

ace elem ents

– Organic com

pounds

• Other chemic al param eters

– pH

– Dissolved oxy

gen

– Salinity

– Organic m

atter

– Other

• Physi cal para

meter s Ecological Processes

• Energy flow

– Primary prod

uction

– Net ecosystem

production

– Growth efficiency

• Material flow

– Organic carbon cy

cling

– Nitrogen and pho sphorus cycling

– Other nutrient cycling Hydrology and Geo mporphology

• Surface and groundwat er flows

– Pattern of surf

ace flows

– Hydrodynam

ics

– Pattern of groundwater flow

– Salinity patterns

– Water stora ge

• Dynamic structural characteristics

– Channe l/shorel ine morpholo gy, comp lexity

– Distribution/e xtent of connected floo dplain

– Aquatic

phys ical hab itat com

plexity

• Sedim

ent and mate rial tran sport

– Sediment supply

/movem ent

– Particle size distribution p atterns

– Other material flux Natural Disturbance Regimes

• Frequency

• Inte nsity

• Extent

• Duration

Source : U.S. EPA. 2002. A Framework for Assessing and Reporting on Ecological Cond

ition (10)April 2004 Page 23-20

Exhibit 23-8. Example Problem Formulation Summary 1. Management Objective

• Bald eagle (entity

), local population siz e (attribute), should be stab le (desired state) 2. Assessm ent En dpoint s

• Bald eagle (entity

), reproduction (m

easurable attribute)

• Bald eagle (entity

), chick surv

ival (measurab le attribute) 3. Expo sure Sc enario

• Sedim

ent –> p ore wat

er –> be nthic in vertebtrates –

> forag e fish –

> bald e agle 4. Risk Hy

pothes is

• Dose of

chem ical X to adult ba

ld eag les from

consum ption o f fish is

less th an a lev

el known to cause a dvers e effect s on rep

roducti ve abi lity

– Mechanism: Chemica l X dam ages r eproductive organs(or inte rferes w ith eg g shel l devel opme

nt)

• Dose of chem

ical X to bald eagle ch

icks (passed to them

by their parents) is less than a level known to adv

ersely affect their surv

ival

– Mechanism: Chem

ical X accumulating

in egg lipids is a metabolic to xin to the develop ing embryo 5. Metrics of Exposure

• Concentration of chem ical X in fish

• Dose of chem

ical X received throug

h consumption of fish 6. Measure of Effect

• TRV for chemical X (NOA EL or LOAEL) where adult reproduction was an endpoint

• TRV for chemical X (NOA EL or LOAEL) where chick surv ival (mortality

) was and endpoint 7. Measure of Characteristics

• Proximity o f bald eagle nest site to potentially contam inated foraging areas

• Proxim

ity of alterna tive (n on-c ontam

inated) foragi

ng are as to th e nest s ite 8. Risk Characteriz ation

• HQ = Oral I

ntake of chem

ical X/TRV (separate calculations for adults an d chicks)April 2004 Page 23-21 23.4 Tiered Ecological Risk Assessments One of the key

elements in the ecological risk assessment process is dec iding if and when further analysis is warra

nted. As with human health risk assessment, EPA recommends a tiered approac h to ecolo gical r

isk asses sment. (1) Each of these tiers follows the basic three steps (proble m formula

tion, ana lys is, and ri sk chara

cterizat ion) but wi

th vary ing leve ls of comp lexity in the assessment and with vary ing requirements for resource s. Examples of the three tiers of ecological risk assessment approache s are described briefly below.

• Screenin g-Level ecological risk assessments provide a g eneral indication of the potential for ecolog ical risk

(or lack thereo f) and ma

y be conducte d for sev eral pur poses inc luding: ( 1) to prioritize COPECs based on their relative environmental behavior (e.g., r elative potential for bioaccumulation or to exhibit chronic toxicity) or determine their re lative contribution to the overall risk estimate; (2) to estimate the likelihood that a particular ecological risk exists; (3) to identify the need f

or additional data collection efforts; or (4) to focus more de tailed ecological risk assessments where wa rranted. Screening assessments often use simplified conservative as sumptions in place of detailed modeling . For exa

mple, con centra tions in aquatic invertebrates or fish might be estimated fr om the modeled or measured water concentrations (obtained as part of a multipathway human health risk assessment) and available bioconcentration factors (B CFs) or bioaccumulation factors (BAF s). Another example is the comparison of maximum sediment and water concentrations to screening le vel TRVs. A screening

level as sessment, while abbreviate d, is nonet heless a complete risk assessme nt. There fore, e ach asse ssment sho uld includ

e docume ntation su pporting the risk charac terization and unc ertainty analy sis. Some examples of s creeni ng leve l TRVs used

in screen ing leve l ecological risk

assessme nts are a vailable from EPA’ s draft E cologic al Soil Screening Le

vel Guidance ( http://www.epa.gov/superfund/programs/risk/ecor isk/ guidance.pdf

) and EPA Region 4 ( http://www .epa.g ov/reg ion4/wast e/ots/ec olbul.htm

).

• More Re fined assessme nts are generally

used to: (1) identify and c haracterize the current and potential threats to the environment from an air toxics release; (2) evalua te the ecological impacts of alternative emissions control or abatement policies; and (3) establish emissions levels that will protect those natural resources at risk. A more r efined assessment may co nt ai n a mo re in te ns iv e e va lu at io n t ha n a sc re en in g l ev el as se ss me nt , a nd us ua ll y em pl oys multipathway analy

sis to estimate if, and to what extent, ecological receptors (e.g ., an oyster fishery, a w

ild duck population, or a unique wetland community) may be exposed. The exposure and potential impact are characterized and e valuated against predetermined assessment endpoints (i.e., edibility of oy sters, sustainability of the duck population, maintenance of the integrity of the wetland community). This tier ma y be iterative. F or example, a

multipathway

analy sis using conservative as sumptions ma y f irst be pe rformed to identify whether any of the COPE Cs emitted f rom the so

urces in an area pose a po tentially significant concern to one or more ec ological receptors. I f so, a more detailed multipathway risk assessment, using more site-specific data, may be performed. From this last stage a detailed characterization of the environmental risks is developed.

• Probabilistic assessments are used to increase the streng th of the predictive evaluation of ecological risks, as well as help better eva luate distributions of observational data for an ecol ogic al ri sk as sessment. Scre ening-le vel a nd mor e ref ined asse ssmen

ts usually utili ze simplified point estimates in the development of a risk characterization, while theApril 2004 Page 23-22 Additio nal Refe rence Ma terials EPA ha s deve loped extensiv e techn ical and policy guida nce on how ec ologic al risk assessm ents should be planned and

performed. These are available at EPA ’s “Tools for Ecological R isk Assessment” we

bsite http://w

ww.ep a.gov

/superfu nd/prog rams/ risk/to oleco.h

tm
.

• EPA’s Guidelines for Ecological Risk Assessment , April 1998. This d ocument expands upon and replaces the earlier 1992 Framework for Eco logical Risk Assessment

.

• EPA’s Ecological Risk Assessm ent Guidance for Sup erfund (ERAGS ): Process for De

signing and Conducting Ecological Risk Assessments, Interim Final , June 1997. This docum ent includes processes and steps for u se in ecological risk assessments at S uperfund sites. This docum ent supersedes the 1989 RAGS, Volume II, Environmental Eva luation Manual, Interim F inal

. Supplements to ERAGS include the Eco Updates (Inte rmitte nt Bull etin Ser

ies, 19 91 to present), which provide brie f recommendations on com mon issues for S uperfund ecological risk assessments. The ap

proaches and m

ethods outlined in the Guidelines and in ERAGS are ge nerally consistent with

each ot her.

• Risk Assessment Guida nce for Superfund ( RAGS): Volum e 1–Human Hea lth Evaluation Manual (Part D, Stand

ardized Planning, Re

porting, and Review of Superfund Risk Asse ssments) , June 2001. This guidan

ce specifies formats that are required to present d ata and results in baseline risk assessments at Sup erfund sites; many of these formats are useful for air toxics ecolo gical risk assessments.

• Policy Memorandum : Guidance on Risk C haracterization for Risk Mana gers and Risk Assessor

s , F. Henry H abicht, Deputy A dministrator, Feb. 26, 1992. This po licy requires baseline risk assessm ents to present

range s of risk

s based on “cen tral tend ency” and “h igh- end” ex

posures with corresponding risk

estimates.

• Policy Memorandum : Role of the Ecological Risk Assessment in the Baseline Risk Assessmen t , Elliott Laws, Assistant A dministrator, Aug

ust 12, 1994. This po licy requires the sam e high level of effort and quality for ecological risk a ssessments as com monly perfo

rmed for hum

an health risk assessments at Sup erfund sites.

• Policy Memorandum : EPA Risk Character ization Program , Carol Browner, Administrator, March 21, 1995. This policy

clarifies the presentation of ha zards and uncertainty

in human he alth and ecolo gical r isk asse ssments , calli ng for cl arity, trans paren cy, reas onabl eness , and con siste ncy.

• Issuance of Final Guid ance: Ecological Risk A ssessment and Risk Mana gement Principles for Superfund Sites . Stephen D. L uftig for Larr

y D. Reed, Octobe

r 7, 19 99. Thi s docum

ent pres ents six key princ iples in ecological risk managem

ent and decision-making

at Superfund sites; these principles are also useful for air toxics ecological risk assessments. probabilistic tier of assessment uses probability distributions as inputs. There fore, this tier generally can yield risk e stimates that allow for a more complete characte rization of variability and unce

rtainty. Although pr

obabilistic assessments generallyare resourceintensive, they may

be especially

valuable in situations when the risks are close to a policy threshold or if the management decisions, if implemented, would require significant expenditur

es.April 2004 Page 23-23 1. U.S. Environmental Protection Agency . 1998. Guidelines for Ecological Risk Assessment

. Risk Asses sment For

um, Washing

ton, D.C., April 1998 . EPA/630/R 095/002F . Availab le at: http://cfpub.epa.gov/ncea/cfm/recordisplay .cfm?deid=12460

. 2. U.S. Environmental Protection Agency . 1999. Residual R isk Repor t to Congres

s . EPA453/R-99- 001. Avai lable at: http://www.epa.gov/ttn/oarpg/t3/reports/risk_rep.pdf

. 3. U.S. Environmental Protection Agency . 1995. Ecological Risk and Decision Making Workshop. December 1995. EPA 230/B96 /004B. 4. Moore, D.W.J., et al. 1999. A probabilistic risk assessment of the effects of methy lmercury and PCBs on mink and kingfishers along East Fork Poplar Cre ek, Oak Ridge, Tennessee, USA. Environm ental Toxi cology an d Chemistr

y8:2941-2953. 5. Suter II , G.W., et al. 2000. Ecological Risk Assessment of Contaminated Sites . Lew is Publishers, Boca Raton, FL. (se e pages 228-231). 6. U.S. Environmental Protection Agency . 2001. Planning fo r Ecologic al Risk Ass essment: Develo ping Manag

ement Ob jective s (Exte rnal Revi ew Draft) . Risk Asse ssment Forum, Washingt on, D.C., June 2001. EPA /630/R01/00 1A. Avail able at: http://cfpub.epa.gov/ncea/cfm/recordisplay .cfm?deid=20683 7. U.S. Fish and Wildlife Service. 2003. National Wetlands Inventory Maps

. Availabl e at: http://nwi.fws.gov

. 8. U.S. Environmental Protection Agency . 1992. Framework for Ecological Risk Assessment

. Risk Assessment Forum, Washington, D.C., February 1992. EPA/630/R92/001. 9. U.S. Environmental Protection Agency . 2003. Generic Ecological Assessm ent Endpo ints (GEAE) for Ecological Risk Assessment . Risk Assessment Forum, Washington, D.C., October 2003. Ava

ilable at : http://cfpub.epa.gov/ncea/raf/rec ordisplay.cfm?deid=55131

. 10. U.S. Environmental Protection Agency . 2002. A Framework for Assessing and Reporting on Ecological Condition . Science AdvisoryBoard, Washington, D.C., September 2002. EPASAB-EPEC -02-009A . Availab le at: http://www.epa.gov/sab/pdf/epec02009a.pdf

. 11. U.S. Environmental Protection Agency . 1985. Guidelines for Deriving Natural Numerical Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses . Office of Water Reg

ulations a nd Standa rds, Washi

ngton, D .C. EPA/822/R85/100. A vailable at: http://yosemite.epa.gov/wa ter/owrccatalog.nsf/0/3fab714d53e9a e5385256b0600723bd3?Ope nDocument References

# Chapter 2 4 Analysi s: Charac teriz ation of E cologi cal

Exposure

Table of Contents

24.1 Introduction

............ ............ ............ ............ ............ ...... 1 24.2 Charact

erizat ion of E xposure ............ ............ ............ ............ .... 1 24.2.1 Quantifying R

eleases

............ ............ ............ ............ .... 3 24.2.2 Estimating Chem ical Fat e and Tra nsport
............ ............ ............ 3 24.2.2.1 Physi cal and Chem ical Par amete rs ............ ............ .... 3 24.2.2.2 Multimedia Modeling

............ ............ ............ . . 3 24.2.2.3 Multimedia Monitoring

............ ............ ............ . 4 24.2.3 Quantif

ying Exposu re ............ ............ ............ ............ ... 5 24.2.3.1 Metrics o f E xposure ........................................ 5 24.2.3.2 Dime

nsions of Expo sure ............ ............ ............ 7 24.2.3.3 Exposu

re Profi le

............ ............ ............ ...... 9 24.2.3.4 Evalu

ating Variabili

ty and Uncert ainty

............ ............ . 9 References

............ ............ ............ ............ ............ ............ 10April 2004 Page 2 4-1 24.1 Introduction As noted in

the prev ious chapter, the

analy sis step of ecological risk

assessme nt include s both characterization of exposures and characte rization of ecological effects. This chapter describes the approaches and methods used for exposure char acterization. Chapter 25 discusses the approac hes and me asures u sed for c haract erization of ecolo gical e ffects. The discu ssion in this chapter is based l argel

y on EPA’s Guidelines for Ecological Risk Assessment

. (1) Readers are refer red to tha t documen

t for a mor

e complete discus sion of av ailable a pproaches and me

thods. 24.2 Characterization of Exposure Ecolo gical e xpos ure ref

ers to the co ntact of an ec ologi cal rec eptor with an air t oxi c thro ugh direct or indirect exposure pathways. As with human health risk assessment, characterization of ecological exposure should initially e valuate (in the problem formulation phase) all exposure pathway s that are potentia lly c omplete. Unlike hu

man heal th exposure , ecological risk assessme nts will g eneral ly id

entify a limited n

umber of specific metrics o f exposure

to actua lly quantify since it is not usually possible to evaluate all exposure pathway s for all the species or other ec osy stem attr

ibutes pr esent in a ny g iven study

area. I nitially the asse ssors will general ly consider all exposur

e pathwa ys broadly, but then i dentify the asse ssment en

dpoints wh

ich will lead to a specific and narrowly defined set of exposure pathways to actually study in depth. Ec ol og ic al ex po su re pa th wa ys t ha t a re ge ne ra ll y im po rt an t f or ai r t ox ic s i nc lu de al l p at hw ays where contaminants are taken up directly from environmental media ( e.g., air, soil, sediment, and surface or rain water) f

or lower trophic level organisms (including plants) a nd ingestion of contaminated plant or animal food items for higher trophic leve l receptors. Pathway s that may be important in specific cases include foliar and root uptake by plants, deposition and dermal exposure pathways, and ing estion via grooming, preening, a nd food consumption. Once the specific set of exposure pathway s to be studied are determined (and the matching assessment endpoints that are to be assessed are deter mined), characterization of ecologica l exposure is based initially on information derived fr om modeling and/or existing monitoring data. Later, additional modeling and/or site-specific empirical information may be obtained. The objective of the exposure characterization is to produce a summary exposure profile that identifie s the expose d ecological enti ty, describ es the co

urse a st ressor ta kes from the sourc e to that entity (i.e., the exposure pathwa y), and desc

ribes the intensity and spatial and te mporal extent of co-occurrence or contac t (see Section 24.2.4.3). The exposure profile also describes the influence of variability

and uncertainty

on exposure estimates and reaches a conclusion about the likelihood that exposure will occur. Exhibit 24-1 provides a list of questions that can help define the specific information needed to charac terize exposure. Exposure c

haract erization includes the follow

ing step s, each o f which is discusse d in a sepa

rate subsection below: (1)

• Quantifying

releases of contaminants of potential ecologic al concern (COPEC);

• Esti mati ng chem ical f ate and trans port v ia mod eling a nd/o r moni torin g;

• Quantifying

exposure (e.g., exposure concentrations and dietary intakes);

• Evaluating uncertainty ; and

• Preparing documentation.April 2004 Page 2 4-2

Exhibit 24-1. Questions to Ask C oncerning Source, Stressor,

Exposure, an d Ecosystem Character istics Source and Stressor

Characteristics

• What is t

he natu re of th e sourc e(s) (e. g., p oint v s. nonp oint v s. mo bile sou rces)?

• What is t

he inten sity o f the str

essor (e .g., the dos e or con centrati on of a chem

ical)?

• What is the chemical form of the stressor and its lability as a fu nction of local phy sical-chem ical conditions?

• What is the mode of action? How do es the stressor impa ct organisms or ecosystem functions?

• How do es the s tressor come into contact with a rec eptor (t ranspor t)? Exposure Ch aracteristics

• With what frequ

ency d oes a st ressor r elease o ccur (e. g., i s it epis odic or continu ous; is it subject

to daily,seasonal, or a

nnual p eriodici

ty)?

• What is the duration of release and exposure? How long does the stressor persist in the enviro nmen t (e.g ., wha

t is its half-l ife)?

• What is the timing

of exposure? When d

oes it occur in relation to critical organism life cycles or ecosy stem event s (e.g ., repr oduction, lak

e over turn)?

• What is t

he spati al scale

of expo sure? I s the ex

tent or influen

ce of th e stress or local , regi onal, global, habitat- specific, or ecosystem -wide?

• What is the distribution? Ho w does the stressor m

ove through the environm ent (e.g., fate a

nd transpo rt)? Ecosystems Potentially at Risk

• What are the geog

raphic boundaries of the study area? How do they relate to functional char act eri sti cs of

the e cosy ste m?

• What a re the key abioti c fact ors inf luenc ing the e cosyst em (e.g., cl imatic facto rs, geol ogy, hydro logy , soil t

ype, water q

uality )?

• Where and how are fun ctional characteristics driving the ecosystem

(e.g., energ

y source and process ing, nutrien

t cycl ing)?

• What are the structural characteristics o f the ecosystem (e.g., species number and ab undance, trophic relation ships)?

• What hab itat ty

pes are present ?

• How do these charac

teristics influence the susceptibility (sensitivity and likelihood of exposu re) of the ecosystem

to the stressor(s)? For example, what p ortion of the receptor’s hom e range is in the area of impact?

• Are there unique features that are particularly v alued (e.g., the

last representative of an

ecosystem type)?

• What is the landscape contex t within which the eco system occu rs? Source: EPA Guidelin es for Ecological Risk A ssessment (1)a EP A’s Sc ience Po licy Co uncil is em bark ing on the de velop men t of an ass essme nt frame work for me tals.

Th e first step in th e pro cess is for mulatio n of an Actio n Pla n that will ide ntify key scien tific issues sp ecific to m etals and metal c omp ound s that nee d to b e add ressed by the fra mew ork, p otentia l app roac hes to c onsid er for inc lusion in the framework (includi ng models and methods), an outline of the f ramework, and the necessary st eps to complete the framework.
April 2004 Page 2 4-3 24.2.1 Quantifying Releases The proc ess used t

o quantif y r elease s of air to xics for pu rposes of ecolog ical risk

assessme nt is identical to that for the human health analyses (see Chapter 7). 24.2.2 Estimating Chemical Fate and Transport The proc ess and me

thods used

to estimat

e chemic al fate a

nd transp ort generally

are simil ar to those used for multipathway huma n health risk assessments. Key differences and special considerations are highlighted in the subsections that follow. 24.2.2.1 Physical and Chemical Parame ters The same phy sical and chemic al para meters id entified in Chapter

17 affe ct the pe

rsistenc e of air toxics in the environment and their potential to accumulate in ecological food webs. Additional consider ations ar e specif ic to eco logica

l risk asse ssment.

• The bioc oncentr

ation fa ctors (B CFs) and

bioaccu mulation f

actors ( BAFs)used to characterize ecologica

l exposure may be diffe

rent than corresponding factors use d for the human health exposure assessment. For example, wildlife may eat different species of fish/shel lfish than humans; t hese may have different BC Fs or BAFs. Also , whole-fis h BCFs or BAF s are use d for ec ologica l exposure

rather than those

specific to the par

ts of the f ish people normally ea

t (e.g., fillets).

• Chemical speciation (e.g., for metals such as mer cury) ma y be an important dete

rminant of ex po su re an d b io av ai la bl it y. (a)

• Fate and transport analy sis may need to examine a wider range of lower-trophic leve l organ isms to asse ss impacts

to the com

munities a

nd ecosy stems of in

terest a s well as t

o develop e xposure es timates f

or ecolo gical f

ood webs. 24.2.2.2 Multim edia Mode ling As with human health exposure assessment, some combination of multimedia modeling and monitoring is generally

used for ecological exposure assessment. The a ppropriate mix of modeling and monitoring will depend on the level of assessment and the r isk management goals. Modeling is relati vely easy and inexpe

nsive to imp lement an

d can be used to evaluate not only risks from current levels of contamination, but also how risks might chang e over time (e.g., concen trations o f persist

ent bioac cumulativ e hazard ous air po llutant [PB -HAP] comp ounds in fish may slowly

increase over time in the presence of a continuous release) or as a result ofApril 2004 Page 2 4-4 potential changes in land use (a chang e in land use might alter a number of habitat fac tors that influence the number and identity of ecological receptors). T he modeling approach, however, has inherent uncertainties, which may lead to either over- or underestimates of exposure. Model cho ices ra

nge fr om simple, s creeni

ng-lev el proce dures tha

t require a minimum of

data to more soph

isticate d methods t

hat describe pro cesses i

n more de tail, but r equire a consider able amount of data. The same multimedia models used for the multipathway human health exposure assessment generally

can be used for at least part of the ec ological exposure assessment (e.g., the same mode ls can be

used to es timate concentra tions in ab iotic medi a at spec ific loca tions, whether for huma n health or ecolog

ical expos

ure asse ssment). H owever , choice of speci fic exposure p oints or a

reas ma y di ffer due to the f

ocus on e cologic al rece

ptors, as will the sp ecific food web s being e

valuate d. Specif

ic models may

also be c onfigur

ed in way s that fac ilitate ec ol og ic al ex po su re as se ss me nt s. Fo r e xa mp le , T RIM (T ot al Ri sk Int eg ra te d M et ho do lo gy) includes a fate, transport, and ecologic al exposure model (TRIM.FaTE) w hich simulates multimedia pollutant transfers and ecological rece ptor exposures in an ecosystem of inter est (see Part III). (2) Howeve

r, other approac hes (e.g ., Multiple

Pathway s of Exposur

e) are not speci fically designed for ecologica

l exposure assessment). 24.2.2.3 Multim edia Monit oring The term monitoring in ecological risk assessment ca n also be more broadly

used to mean collection of any ty

pe of empirical field data for the assessment (e .g., plant counts and spatial distribution in an assessment area). The use of monitoring in ecological risk assessment can serve a number of purposes. For example, if there is a need to reduce uncertainties in the predictive modeling approach, monitoring ca n be performed in various media and biota in the study area . As with human health exposure assessment, monitoring can be used to confirm or calibrate predictive modeling estimates of contaminant c oncentrations in media or biota. For higher-tier risk assessments, monitoring for ecological exposures also mayinclude sitespecific toxicity or bioaccumulation studies, in which test org anisms are exposed to the actual mixtures of contaminants from within the study area to de velop site-specific and chemical-specific toxicological and/or bioaccumulation re lationships (See Chapter 25). However, poorly

designed sampling or toxicological evaluations of environme ntal media from the site may not allow a def initive identification of the cause of adverse response. F or example, receptor abundance and diversity as demographic data refle ct many fac tors (e.g., habitat suitability , availa bility of food, a

nd preda tor-pre y r elationsh ips). I f these f

actors a re not pr operly controlled in the experimental design of the study (e.g., through use of a c omparison site or a gradient design that examines effec ts along a two-dimensional gradient downwind of sourc es), conclusions regarding che mical stressors can be confounded. I n addition, monitoring may not provide sufficient information to develop estimates of potential risks should land use or exposure change in the future. Monitoring techniques for ecological e xposure characterization may differ from those used for multipathway

human hea

lth exposur

e assessment. I

n partic ular, dif ferent species or components of the food web may

be of concern. For example, larg e invertebrates such as drag onfly larvae often are a focus for ecolog ical exposure assessments because they are important components of surface water ecosy

stems as well as key pr

ey items for both aqua

tic (e.g., fish) and terrestrial (e.g., birds) predators.b The TR IM.FATE model (6) can output esti mates of ingest ion intake at user-designat ed time points in a dynamic simulati on, and as an average over a user-designat ed period, as well as est imates for st eady-stat e simulati on. April 2004 Page 2 4-5 Examp le Cons iderati on in Mo nitorin g: Soil Samplin g for Eco logical Risk A ssessmen ts The depth over whic

h surface soils are sam

pled should reflect the ty pe of exposure expected

in the study area, the ty

pe of receptors expected in the study area, the depth of biolog ical activity, and

the dept h of p ote nti al co nta minat ion. For ex ample , if e xpos ures to ep igei c (su rfa ce dw ell ing) eart hwor ms are a concern, concent

rations in the f

irst few inches of soil are most rele vant. On the

other hand, if

a burrowing m

ammal is of concern, concentrations at a depth of two or more feet m ay need to be estimated. Carefu

l consideration of the siz e, shape, and orientation of sampling volume is important since they have an effect on the reported measured contam

inant concentration valu

es. (3) Selection of sampling design and methods can be accompli shed by use of the Data Quali ty Objectives (DQO) process discussed in Chapter 7. Additional so il sampling g uidance that may

be consulted includes EPA’s Preparation of Soil Sam pling Protocols: Sampling Techniques and Stra tegies (4) and Guidance for Data Usability in R isk Assessment

. (5)
24.2.3 Quantifying Exposure Three elements are important components of quantify ing exposure: the specific metrics of exposures that are to be used , the dime

nsions of e

xposure, a

nd the expos

ure prof ile. Each is described in a separate subsection below. These estimates can be produced by some models such as TRIM.FaTE. (6) 24.2.3.1 Metrics of E xposure Depending on the specific rece ptors and pathway s of concern, ecological exposure is quantified gener ally in one of t

hree wa ys. (1)

• Exposures to abiotic media may be eva luated using contaminant media concentrations as the exposure concent rations– that is, concentrations of air toxics in soil, sediment, and/or surfac e water

at the expo sure poin

ts. This is b ecause

the ecol ogical

toxicity refer ence le vels (TRVs) us ed to cha

racter ize risk ar e based o n labora tory studies tha

t directl y r elate environmental concentrations in these media to adverse e cological impacts (e.g., a labor atory study that dissol

ves known

concen trations o f a chem

ical in wa ter and measure s advers e responses in the invertebrates or fish living in that water - the resulting concentration in water that shows no effect is then compared to modeled or monitored conc entrations of the chemical in study ar

ea surface water).

• Exposures via the ingestion route of exposure may be evaluated using the average daily dose (ADD) , generally

expressed as mg of chemical per kg of body weig

ht per day (

mg/kg-d). The gener al formul a (b) for calculating ADD for ec ological receptors is similar to that used for human health ingestion exposure: (1) (Equation 24- 1)April 2004 Page 2 4-6 where ADD pot = Po te nt ia l a ve ra ge da il y do se , e xp re ss ed in un it s o f m g/ kg -d ay. Chemical -related variable : C k = Average contaminant conce ntration in the k th typ e of food , expresse d in units of mg/kg (wet we ight) Variables that describe the e

xposed ecologica l recept

or populati

on (also termed “wi ldlife exposure factors”) : FR k = Fraction of intake of the k th food type that is from the c ontaminated area (unitless). NIR k = Normalized ingestion rate of the k th food ty pe of a w et-weig

ht basis, e xpressed i

n kg fo od /k g b od y-w ei gh t- da y. m = Number of contaminated food ty pes Exposure factors can be found in the EPA Wildlife Exposure Factors Handbook

. (7) Contaminant concentration (C k ) is commonly estimated with the use of multimedia models. In some situations (e.g., a hig her tier of analy sis), C k in food has been measured directly at the point of contact where exposure occurs. An example is the use of food c ollected from the mouths of nestling birds to evaluate exposure to pesticides through contaminated food. Although such measurements can be difficult to obtain, they reduce the need for assumptions about the frequency

and magnitude of contact.

• Expo sures to so me str essor s are ev aluat ed usi ng uptake . Some stre ssors must b e internally absorbe d to exhibit a

dverse e ffects. For examp le, a con taminant t

hat caus es liver t

umors in fish must be absorbed and reach the targ et organ to cause the effe ct. Uptake is evaluated by considering the amount of stressor internally absorbed by a

n organism and is a function of the follo wing:

– Chemical form of the contaminant (speciation);

– Medium (sorptive properties or presence of solvents);

– Biological membrane (e.g ., integrity, pe rmeability); and

– Organism (e.g., sickness, active uptake). Because of interactions among these factors, uptake will vary on a study-specif

ic basis. Uptake is usually assessed by

modifying an e stimate of the exposure concentration indicating the bioavailable fraction (i.e., the propor tion of the

stressor that is ava

ilable for uptake ) actua

lly absorbe d (e.g ., monomer

ic aluminu

m is gene rally bioavail able to c ertain a

quatic r eceptors while polymeric aluminum ge

nerally is not). Absorption fa ctors and bioavailability mea sured for the chemical, ecosy stem, and organism of interest are pref erred. Inter

nal dose can also be evaluated using a physiologically-base d pharmacokinetic (PBPK) model or by measuring biomarkers or residue s in rece

ptors. When using a tiered approach, conserva tive assumptions generally are used at the screening level. Exhibit 24-2 presents examples of conservative assumptions; these are described in more detail in E

PA’s Guidelines for Ecological Risk Assessment

. (1)April 2004 Page 2 4-7 Exhibit 24-2. Examples of Conserv ative Assumptions for Ecolog ical Exposure E stimation Exposure Factor Assumed Value Area-use facto r (fac tor re lated to home ra nge and pop ulati on dens ity) 100 percent (organism lives comp letely within area of highest exposure co

ncentrations) Bioav ailabili

ty 100 percent Life st age most sen sitive life s tage Body weig

ht minim um po ssible Food in gestion rate maxim um po ssible Dietary com

position 100 percent of diet cons ists of the most c ontaminated dietary comp onent The use of conservativ

e assumptions sh

ould be informed

by study- specific information. For example, assum ing 10 0 perce

nt for a rea- use fact

or and d iet wou ld not b e appro

priate if study -spe cific information indicates otherwise (e.g., the receptor is only present in the assessm ent area part of the year). Sim

ilarly, use of the most sens itive l ife stag e would only be appr

opriate if that l ife stag e were reasona bly ex pected to be ex

posed t o the chemica

l.

24.2.3.2 Dimensions of Exposure Three dimensions are considered when quantify ing exposure: intensity, time, and space

.

• Intensity . Intensity

is generally

expressed as the amount of chemical contacted per da y. Intensity may be af

fected by a number of factors, including the conce ntration of the chemical in va ri ou s m ed ia an d b io ta an d c he mi ca l f or m ( e. g. , s pe ci at io n) , w hi ch ma y af fe ct to xi ci ty, bioavailabilty, and/or bioconce ntration.

• Time . The temporal dimension has aspects of duration, frequenc y, and timing. F or air toxics assessments, intensity and time may sometimes be combined by ave raging intensity

over time. Due to the emphasis on persistence and bioaccumulation, the focus of the ecological ex pos ure cha rac ter iz ati on f or a ir t ox ics is gen era ll y on c hro ni c (l ong -te rm) ex pos ure s. In using predictive modeling to estimate exposure concentra tions, an average annual concentration generally

is sufficient, at least for screening-le vel analyses. A

n exception would inc lude situa

tions wher

e the re lease a

nd the pre sence of

ecolog ical rec eptors a

re both periodic (e.g., releases a

re much higher in the spring and summer, w hen ecological receptors are more abundant and active). If using predictive modeling to develop estimates of the average daily

dose (ADD), the duration of time modeled gene rally should be sufficie

nt for concentrations of air toxics in the media and biota of concern to rea ch equilibrium. If the models ind

icate tha t equilibr ium is not re ached, the dura tion of time

modeled g eneral ly should be at least as long as the period of time over which r eleases are likely

to occur (e.g., the design life of a specific fac ility). Timing is particularly important if the exposure coincide s with a se

nsitive lif e stage of the re ceptor o

rganism.April 2004 Page 2 4-8 • Space . Space is important because ecological r isk assessments generally focus at the population level or higher (e.g., community , ecosystem). The

refore, space is a measure of the total fraction of the population, community, or e cosystem that is potentially exposed – a factor that will im

pact the overall risk cha racter ization. Spa

ce is ge nerally expresse d in terms of area s (e.g. , hectar

es, acr es, squar e meters ) that exce ed a par ticular c hemical t hreshold level. However, another important spatial consideration is the fraction of the overall habitat type that is potentially

affected. At larger

spatial scales, the shape or arrang ement of exposure may be an important issue, a nd area alone may

not be the appropriate descriptor. Geographic I

nformation Systems (GI S) have greatly expanded the options for analyzing and presenting the spatial dimension of exposure (see Part VI I of this refere

nce manual for more information about GIS). Several re cent papers discuss ways to incorporate spatial consider ations in e cologic al risk as sessments
. (8) Sometimes, temporal and spacial considerations must both be considered together . For example, in the case of acidic deposition, the andromous fish species in Maryland and other middleAtlantic states ha ve a spec ial risk sc enario. Specific ally , their sp awning run occu rs at the s ame time when the weather pattern chang es in the late winter and early spring from a coastal to a continental pattern. This increases acidic deposition to the headwa ters where the spawning occurs and the eggs a

nd hatchlings are at the most vulnerable part of the ir life cyc le.

Example PAT CH Output. Using Spatial Information in Ecological Expo sure Assessment Many terrestrial organ

isms that m

ight be evalu

ated in an ec ologic al risk

assessm ent are mobil e. Wher

e these populations spend their time depends on the locations of habitats necessary to provide food, breeding sites, and protection from pred ators. Behaviors such as

migration a

lso affect locations of receptor popul ations. Screen ing- level assessm

ents usually assum

e that the ecological receptors of interest reside at the locations o f the highest exposures modeled . In sub sequent tiers of analys is, the asse ssor m

ay spa tially refine t

he expo sure estimate by considering the habitat use and foraging areas of the receptor(s) of intere st. GIS land cover and land use informa

tion can be used to estim ate where an ecologica

l receptor is likely

to reside or breed. For exam

ple, EPA’s Western Eco logy Div ision of the National H ealth and Environm ental Effects Laboratory de

veloped a m

odel called Program

to Assist in Tracking

Critical Habitat (PATCH), which can be used to genera te “patch-by-patch” description s of landscapes, assessm ents of the number, q

uality, and spatial orientation of breeding sites, and map- based estimates of the occupan cy rate. I n the ex ample

output shown here, t he me dium grey

areas d enote significant/acceptable habitat and the lighter g ray (or light g

reen) areas denote areas suitab le for breeding. This inform

ation can be used to id

entify where the ec ological receptors are lik ely to reside or breed, and the m

odeled exposure concentratio ns at those locations can be used in the risk characte rizatio n calcu lations. The PATCH sof tware a nd user ’s gui des are availa ble at: http://w ww.ep a.gov

/wed/pa ges/m odels/p atch/pa

tchma in.htm

.April 2004 Page 2 4-9 Question s Addr essed b y the E xposu re Profile

• How m

ay exp osure o ccur?

• What may b e exposed?

• How m

uch exp osure m

ay occ ur?

• When and where

may exposu re occu r?

• How may expos ure vary?

• How uncertain are the exposure estimates?

• What is t

he lik elihood that ex posure will occ

ur? 24.2.3.3 Exposure P rofile The final product of the ecological exposure assessment is an exposure profile. Exposure is generally described in terms of intensity, space, a nd time, and in units that can be combined with the ecological effects assessment ( see Chapter 25). The exposure profile identifies the receptor and describes eac h exposure pathway a s well as the intensity, spatial extent, and temporal extent of exposure. The exposure profile also describes the impact of variability and unc ertainty on exposure estimates and r eaches a conclusion about the likelihood that exposure will occur. Depending on the risk assessment, the exposure profile may be a written stand alone document or a module of a larger document. In either c ase, the objective is to ensure that the information needed for risk chara cterization has been collected, evaluated, and presented in a clear, concise, a nd transparent way . The exposure profile also provides an opportunity to verify

that all of the important exposure pathway s identified in the conceptual model (i.e., those that support an evaluation of the assessment endpoints) were e valuated. 24.2.3.4 Evaluating Variability and Uncertainty The exposure profile described in the previous section should aid understanding of how exposure can vary depending on receptor attributes (exposure fa ctors) or stressor levels. Variability can be describ ed qualit

atively , by using a d istribution or by

describ ing whe

re a poin t estimate is likely to fall on a distribution. EPA policy recommends the use of both central tendency

and high-end exposure e stimates. (9) The exposure profile also should summarize important uncertainties (e.g., lack of knowledge), inclu ding:

• Identification of key

assumptions and how they wer e addressed;

• Discussion (and quantification, if possible) of the magnitude of modeling, sa mpling, and/or measurement error;

• Identification of the most sensitive variables influenc ing the exposure estimate; and

• Identification of which unce rtainties can be reduced through a dditional data collection, modeling, or analy sis (e.g., in a subsequent tier of analy sis). Professional judgment often is needed to determine the unce rtainty associated w

ith information taken fr om the lite

rature and any extrapola tions used

in develo ping a p aramete

r to estima

te exposures . All assum

ptions use d to estima

te exposur

es should b e stated , includin g some description of the degree of bias possible in ea ch. Where literature values are used, a n indication of the range of values that could be c onsidered appropriate also should be indicated. The uncerta inty and vari ability

associa ted with e cologic al effe cts crite ria must a lso be tak en intoApril 2004 Page 24-10 1. U.S. Environmental Protection Agency . 1998. Guidelines for Ecological Risk Assessment

. Risk Asses sment For

um, Washing

ton, D.C., April 1998 . EPA/630/R 095/002F . Availab le at: http://cfpub.epa.gov/ncea/cfm/recordisplay .cfm?deid=12460

. 2. U. S. Environmental Protection Agency

. Total Risk Integrated Methodology (TRIM). Documen tation is a vailable at: http://www .epa.g ov/ttn/FERA/urban /trim/trimp g.html

. 3. U.S. Environmental Protection Agency . 2000. Draft Ecological Soil Screening Level Guidance . Office of Emergency and Remedial Response, Washington, D.C., July 10, 2000. 4. U.S. Environmental Protection Agency . 1992. Guidance for Data Us eability i

n Risk Assessment (Part A) . Office of Emergency and Remedial Response Publication 9285.7-09A, PB92-963356, Washington, D.C., April 1992. 5. U.S. Environmental Protection Agency . 1992. Preparati on of Soil Sa mpling Pro tocols: Sampling Techniques and Strategies . Office of Research and De velopment, Washington, D.C. EPA/600/R92/128. 6. U. S. Environmental Protection Agency . 2002. Total Risk Integrated Methodology. TRIM.FaTE

Technica l Support D ocument . Volume 1 : Descri

ption of Mo dule . EPA-453 /R02-011a ; Volume 2: Description of Chemical Transport and Transformation Algorithms

. EPA/453/R-02/011b. Evaluation of TRIM.FaTE. Volume 1: Approach and Initial Findings

. EPA/453/R- 02/012; TRIM.FaTE User’s Guide . Office of Air Quality Planning and Standard s, Resea

rch Tria ngle Pa rk, NC. These docu

ments and

informat ion are a vailable at: http://www.epa.gov/ttn/fera/trim_fate.html#current_user

. 7. U.S. Environmental Protection Agency . 1993. Wildlife Exposure Factors Handbook . Office of Resea rch and D evelopme

nt, Washing

ton, D.C. EPA/600/R93/ 187. Avai lable at: http://cf pub.epa .gov/nc ea/cfm/

wefh.c fm?ActTy

pe=def ault

. 8. Freshman, J.S., and Menzie, C.A. 1996. Two wildlife exposure models to assess impacts at the individual and population levels and the efficacy of remedial actions. Human and Ecological Risk Assessment 2:481-498. Hope, B.K. 2001. A case study comparing static and spatially -explicit ecological exposure analysis methods. Risk Analy sis 21:1001-1010. Linkov, I ., Burmistrov, D., Cura, J., and Bridges, T.S. 2002. Risk-based manag ement of contaminated sediments: Consideration of spatial and temporal patterns in exposure modeling. Environmental Science and Technology 36:238-246. 9. U.S. Environmental Protection Agency . 1992. Guidance on Risk Cha racteriza tion for Risk Managers

and Risk A ssessors . Nationa l Center f or Environmental A ssessmen t. Risk Assessment Council, Washington, D.C. February 1992. consideration. A more thorough description of how to deal with var iability and uncertainty

in the risk assessment process is provided in Chapter 31. References

# Chapter 2 5 Analysi s: Charac teriz ation of E cologi cal

Effect s

Table of Contents

25.1 Introduction

............ ............ ............ ............ ............ ...... 1 25.2 Ecological Res

ponse A nalysi s ............ ............ ............ ............ ... 1 25.2.1 Stressor-Re sponse Analy sis

............ ............ ............ ........... 1 25.2.1.1 Ecological Eff ect Lev els

............ ............ ............ 1 25.2.1.2 Selection of TRVs for a Particular Assessment

............ ...... 7 25.2.1.3 Stressor-Respon se Curves

............ ............ .......... 11 25.2.1.4 Species Sensitivity Distribution

............ ............ ...... 11 25.2.2 Linki

ng Mea sures of

Effects to Ass essme

nt Endp oints

............ ............ 12 25.3 Stressor-Re sponse Profile

............ ............ ............ ............ ...... 16 25.4 Evalu

ating Variabili

ty and Uncert ainty

............ ............ ............ ....... 16 References

............ ............ ............ ............ ............ ............ 16April 2004 Page 2 5-1 25.1 Introduction As noted in the previous chapter, the analy sis step of ecological risk assessment includes characterization of exposures and characte rization of ecological effects. Chapter 24 de scribed the approaches and methods used for exposure char acterization. This chapter describes the approac hes and me asures u sed for c haract erization of ecolo gical e ffects. The discu ssion in this chapter is based l argel

y on EPA’s Ecological Risk Assessment Guidelines

. (1) Readers are referr ed to that doc

ument for a more c omplete d

iscussion of avail able approache s and methods. The methodology

used to characterize ecologica l effects is generally

similar to that used for human hea

lth toxicity

assessme nt. One of

the distinc

tive fea tures of ecolog ical eff

ects characterization relates to the more ge neral management goa

l of protecting a receptor population or community rather tha

n a single individual. This has led to the development of water, sediment, and soil quality criteria tha t are designed to protect the communities of org anisms that inhabit surface waters and soils. I t also provides the option of using a distribution or range of values to charac terize chemical to xicity

(an option not ge

nerally availab le in huma

n health r isk assessment). Characterization of ecological eff ects involves describing the potential effects re sulting from exposure to a stressor, linking these effect to the assessment endpoints identified during problem formulation, and evaluating the stresso r-respo nse relat ionship (i.e. , how t he effe cts wi ll cha nge with vary ing stre ssor leve ls). The c haract erization begins by e

valuatin g effe cts infor

mation to specify the r

esulting effects, verify

ing that these effects are c onsistent with the assessment endpoints , and confirming that the c onditions u

nder whi ch the ef

fects oc cur are

consiste nt with the conceptual model. Once this has been done, the ef fects characterization involves two additional steps: (1) performing an ecological response analy sis, and (2) developing a stressorresponse profilewhich als o contain s an anal ysi s of unce

rtainty and vari ability . Each of

these additional steps is discussed in a separate section below. 25.2 Ecologica

l Response

Analysis Ecolog ical res

ponse analy sis examine s three primary elements : identify

ing stre ssor-re sponse relationships, establishing causality , and determining the linkages betwee n measurable ecological effects and assessment endpoints. Each is described in a separate subsection below. 25.2.1 Stressor

-Response

Analysis Stressor -respon se analy

sis for ec ologica

l effects is funct

ionally similar to d

ose-re sponse an

aly sis for huma n health e ffects ( e.g., s ee Chapt er 12). T he speci fic stre ssor-re sponse re lationship (s) used in a g

iven risk assessme nt depend on the sco

pe and na ture of the assessment as de fined in the probl em formul ation and reflected in the

analy sis plan. T

hree ty pes of str essor-r esponse relationships are commonly use d: point estimates, stressor-response curves, and cumulative distribution functions. Each of these is discussed in a separate subsection below. 25.2.1.1 Ecologica

l Effect Lev els Ecological effect levels ar e point estimates of an exposure associated with a given eff ect (e.g., a con cen tra ti on t hat res ul ts in 50 p erc ent mo rta li ty in th e ex pos ed p opu lat io n, o r LC 50 ) used toApril 2004 Page 2 5-2 compare with an en

vironmen tal exposur

e conce ntration. Data on the toxicity of a che mical is usually obtained from laboratory

studies in w

hich gr oups of or

ganisms (e.g. , inverte

brates, benthic organisms, plants, earthworms, laboratory mammals, f

ish) are exposed to vary

ing leve ls of the chemical, and one or more responses ( endpoints such as survival, growth, reproduction) are measured. Various statistical methods are used to e stablish thresholds for adverse ecological effects associated with acute or chronic exposures. Risk assessors often choose no-effect or loweffect levels as screening

values. Stressor-response relationships may be relatively simple (a s illus trated in

Exhibi t 25-1 ) or m ay

be ve ry comp lex.
Exhib it 25-1.Hypoth etical S imple St ressor- Respon se Rela tionshi p

Hypo thetical

relation ship between i

ntensity of stres sor (in this exa

mple, concen

tration of a chemical in water) and ecological respon se (in this example , percent mortality of an exposed population of min

nows). Different points

on the curve rep

resent, respectively , the concentration resulting in 10 percent mo

rtality (LC10 ), 50 percent m ortality (LC50 ), and 90 percent mortality

(LC90 ). Several specific point estimates ar

e commonl

y us ed to cha

racter ize ecolo gical e ffects (

Exhibit 25-2):

• Median effe ct conce ntrations or doses are those levels that result in effects that occur in 50 pe rc en t o f t he te st or ga ni sm s e xp os ed to a s tr es so r. Th e m ed ia n e ff ec t l ev el is al wa ys associated with a time parameter (e.g ., 24 hours, 48 hours). Because the tests used to derive median e ffects l evels se ldom excee d 96 hours , these va lues are used primarily

to assess acute (short-t erm) expo sures.April 2004 Page 2 5-3

Exhibit 25-2. Commonly Used Point E stimates Median effect concentrations or dose s (acute exposur es) LC 50 Conc ent rat ion ( food or wa ter ) res ult ing i n mort ali ty in 50 pe rce nt of the e xpos ed or gani sms LD 50 Dose (usu all y in di eta ry st udie s) re sul tin g in mor tal ity i n 50 p erc ent of th e exp osed organ isms EC 50 Concentration resulting in a non-lethal effect (e.g., g rowth, reproduction) in 50 percent of the expo sed o rgan isms ED 50 Dose resulting in a non-lethal effect (e.g., gro wth, reproduction) in 5 0 percent of the exposed orga nis ms Low- or no-effect concentrations or doses (chronic exposur es ) NOAEL no-observed-adverse -effect- level, the hig hest dose for which ad

verse effects are not statistic ally d

ifferent from control s LOAEL lowest- observed-a dvers e-ef fect lev el, the lowest dose at which a dvers e effect s are statistic ally d

ifferent from control s NOEC no-observed-effect- concentration, the hig hest ambient conc entration for which adv erse effects are not statistic ally d ifferent from control s LOEC lowest-observ ed-effect concentratio

n, the lowest am

bient concentration at which adverse effects are stat

istically differe nt from control s MATC maximum

acceptable toxicant concen tration, the range o f concentrations between the LOEC and NO EC GMAT C geometric m

ean of the MATC, the geometric mean of the LOEC and NOEC

• Low- or no-effect concentrations or doses are derived from experimental data using statistical estimates. The no-effect level is determined by experimental conditions as well as the variability inhere

nt in the experimental data. Thus, depending on experimental conditions (e.g., the range of

concentrations tested), two separate tests using the sa me chemical and the same organism could result in different no-ef fect levels. Low- or no- effect levels are used primaril y to assess chronic ( longer

-term) e xposures.April 2004 Page 2 5-4 Point Estimates, TRVs, and Benchmarks The terms Toxicity Reference V alues (TRVs) and Ecological Benchmarks are used to describe those Point Estimates identified or derived for use in ecological risk

assessments. These part icu lar poin t est imat es may b e der ived from a single study (e .g., an NO EC or EC 50 ) or from the integr ation of mult iple stu dies (e. g., water qua

lity criteria) . When TRVs or benc hmarks are drawn from a sing le study , they

are usu ally s et in consideration of mu

ltiple studies (e.g., from the study most relevant to the purp oses and specifics of the assessment has been selected, or the most sensitive result am

ong the relevant studies) A variety of

different type s of studies can be used to de

velop ec ologica

l stressor -respon se relation ships, inc luding f

ield studie s, laboratory studies, a

nd microcosm studies (Exhibit 25-3). For air toxics, stress-response analysis can include b oth primar

y a nd secondary

effects.

• Primary effects(e.g., lethality , reduced growth , neurolo gical/

behavior al defic its, impaired reproduction) result from exposure of aquatic and terrestrial organisms to air toxics. An example of a chronic effect would be reduce d reprodu ction in a fish spec ies expose d to air toxics i

n a surfa ce wate r body or in a te rrestri al bird e ating c ontamina ted fish f rom a smal l pond. An extreme example of an acute primary effect might be deaths of birds cause d by inhalation of a particular toxin. Toxic effects on survival, growth, development, and reproduction might have population-level consequenc es for a species (e.g., re sult in local population extinction over time) and are widely accepted as endpoints for charac terizing ecolog ical risks. In

recent ye ars, mor

e subtle e ffects have bee

n investig ated, inc luding those pertaining to clinical signs of poisoning, immunotoxicity, a nd even behavioral changes tha t might influence survival, growth, development, or r eproduction.

• Secondary effects (e.g. , loss of pr ey species in the com

munity ) result f rom the a ction of a ir tox ics on suppo rting c ompo nents of the ecosyste m. The se seco ndary effec ts occ ur thr ough biological interaction of one or more species’ populations with individuals or populations that have been primarily

affected. For example, exposure to an air toxic may adversely

affect one or more species of microscopic alg ae, bacteria, or fungus, whic h can adversely

affect an ecosystem’s nutrient c

ycling a nd primary production. This can lead to an alteration in the abundance, distr

ibution, a nd age structur e of a spe cies or p opulation depende nt on these microscopic organisms, which can then lead to cha nges in competition and food web interactions in other species. These ecosy stem effects can be propag ated to still other populations, affe cting their pre sence or repres entation

within the

ecosy stem. A re latively simple example of secondary effects involves the aerial application of pesticides that dramatically r

educed the population of an aquatic insect. This impact to the insect population indirectly aff

ects wild ducklings in the ecosy stem, which depend on the insects as a food su pp ly. (2) Althoug

h it often i s possible

to identif y the potenti al for se condary effects, developi ng stre ssor-re sponse fu

nctions f or secon dary effects (e.g ., in a man

ner ana logous to that illustrated in Exhibit 25-2) is not an easy task. A rece nt paper provides one example of the eval uation of seconda ry effects in ecolo gical r

isk asses sment. (3) The use o f the poin

t estimate approac h has some

potentia l limitation s. The most

important

is that the point estimate established by a g iven study depends on both the ra nge of doses tested and the statistical power of the study ( e.g., the ability to detect an effect if it occurs). F or example, studies wi th low powe

r (e.g ., those with only

a few te st animals

per dose group)tend to y

ield NOAEL or NOEC va

lues that a

re higher than s tudies wit h good power (tho se with ma ny a nimalsApril 2004 Page 2 5-5 per dose group) . In a

ddition, th e choice

of some po int estima

tes (e.g ., NOEC an

d LOE C) is restricted to concentrations that were tested, which ma y or may not be close to the environmentally re levant concentrations, and this uncertainty increases as the interval between doses increases. Finally , it is not always easy to interpret the significance of an exposure that exceeds some particular point estimate, since the severity and incidence of response depends on the shape and slope of the exposure response curve ( information that is not captured in a point estimate).
Exhibit 25-3. Types of Ecological Stre ssor-Response Studies

• Laboratory Studies . Most i nformation on

ecolog ical stre ssor-respons e comes from laborat ory ecotoxicology studies using a g eneric set of species to repres ent different compon ents of terrestrial or aquatic ecosystem

s. For exam

ple, the freshwater crustacean Daphnia, is often used as a surrog ate for a

ll sma ll inv ertebrat

es that inhabit

surface waters , and v

arious s pecies o f min

nows ar e used as surrogates fo

r fish. Laboratory

studies are relatively

easy and inexpe

nsive to conduct, and effects can be d

irectly linke d to exp osure to

a single air to xic. The

re is uncertaint

y, however , in extrapolating the results from standard laboratory species to the wide array of spec ies in the enviro nmen t or from the con trolled laborato

ry con ditions to the c omplex condi tions that occu

r in nature. Additionally , in most cases , laboratory studies are not designed to assess effects on populations, com

munities, and ec osystems.

• Field Studies . Studies of wildlife, populations, com munities, and ec osystems ex posed to air toxics in natural settings can provide valuab le information on stressor-response effe cts. Field data can b e valuable in dem

onstrating the presence or absence of a cause- effect relationship that can prov ide a basis for prioritization or for recognizing the efficacy of a risk

reduction action. These stu dies also can be used to assess stressor-response rela tionships for the site- specific mixtures of c oncern. However, the study organism s may be exposed to num

erous types of stresso

rs (chemical and n

onchemical), and th

e effects of individual air toxics (and som etimes site- specific mixtures) m ay be dif fic ult to is ola te. In a ddit ion, fiel d stu die s are cond uct ed in fre quen tly d ue to the s igni fic ant time and resources required. Comparison of the study area to a control area is necessary to evaluate the potential impact of th

e chemical release.

• Microcosm Studies . Microcosm stud ies use assemblages of several different taxa and environmental media in an en closed experimental system as a surrogate for natural ecosystems. Such st udies ca n contro l for so me of

the unc ertainty

associa ted with mult iple stre ssor exp osure in field studies. These studies also may provide information about food web dynamics a nd the interactions of populations or organisms. As with field studies, microcosm studies are time and resource intensive and, therefore, may be relatively u

ncommon for air toxic studies. A variety of

point estimates are used in ecological risk assessments. Some are developed from acute (short-term) exposures; others are deve loped from chronic (long-term) exposures. Thre e gener al ty pes of poi nt estimat es are a vailable for use i n ecological risk

assessme nts:

• Comm unity-lev el crite ria . EPA has developed ambient water quality criteria (AWQC) and sediment quality criteria f or the protection of aquatic communities. These values are based on consideration of a cumulative distribution function (see Section 25.2.1.4). For example, AWQC are designed to protect 95 percent of all aquatic species in freshwater or mar ine envir onmen ts. C riter ia hav e been d evelo ped fo r both acute a nd chr onic e xpos ures, altho ugh for a limi ted numbe

r of che micals.a No te that so me e colo gical risk a ssessm ent guid ance refers to the po int estima tes of ec olog ical effects

select ed for a gi ven ass essment as Toxicit

y Refer ence Values (TRVs), whil e others use the ter m ecological benchm arks. April 2004 Page 2 5-6 • Effect levels from laboratory toxicity tests . A variety of aquatic species are routinely used in ecological toxicity tests, including f athead minnows (a small fish species) and Daphnia(a tiny freshwa ter cru stacea

n). Effe cts of concern c an includ e acute effects such as

mortality (e. g., LD 50 ) as well

as chron ic effe cts such a s reprod

uction. To xicity

tests also are ava ilable for terrestrial organisms (e.g ., earthworms) and occasionally involve vertebrate species of wildlife ( e.g., t

he effe cts of pol

ychlorinate d bipheny

ls (PCBs)have be en studie d extensive ly in mink).

• Effect levels from field bioassays . In s ome case s, ecolog ical eff ects ar e evalua ted dire ctly by exposing test org anisms to ambient conditions. This most often is done where complex mixtures of chemicals are present (e.g., in soils or sediments). The point e stimates e

mploy ed in eco logica

l risk asse ssments ma

y be gener ally termed to xicity reference values (TRVs). (a) They may be values taken from individual toxicity studies (e.g ., NOECs or EC 50 s)or the result of integration of multiple studies (e.g., wa ter quality criter

ia). TRVs may be deve loped for site-specific ecologica l receptors, depending on the importance of those receptors to the local ecosy stem, or for an endpoint not previously evaluated. For example, while some TRVs may be ba sed on survival, growth, and reproductive succ ess of a population, TRVs protective of a threatened or endangered species, a valuable ga me species (e.g., trout), or an ecolo gicall

y ke y sp ecies ( e.g., wolf) mig ht be base d on an en

dpoint tha

t is relev ant to individual organism health (e.g., a neurolog ical deficit) rather than to population maintenance. On the other hand, TRVs based on higher eff ect levels (e.g., 20 to 50 percent or hig her of the population is affected) might be appropriate f or species for which grea

t functional redundancy exists in the ecosystem (e.g., dif ferent herbaceous plants). (4) Derivation of TRVs for pathways involving wildlife ingestion would require information on food ingestion rates for sensitive and highly exposed animal species and information on the degree of bioaccu mulation in

appropr iate trophic components. Exam ples of th ese der

ivations f or aquat ic sys te ms ca n b e f

ou nd in th e G re at Lak es Wa te r Q ua li ty In it ia ti ve (G LW QI) fo r m er cu ry, dichlorodiphenyltrichloroetha ne (DDT), PCBs, and dioxin (2,3,7,8-TCDD) (5) and for terrestrial sys tems in the

EPA method s of asse ssing expo sures to c ombustor e missions. (6) EPA’s Wildl ife Exposure Factors Handbook (7) also provides data, references, a nd guidance for conducting exposure a ssessmen

ts for wild

life spec ies expose d to toxic ch emicals i n their e nvironme nt. EPA and other organizations have developed a number of types of TRVs base d on data for a chemical’s toxicity to freshwate r or saltwater organisms (see Exhibit 25-4). Toxicity data for longer term or c hronic exposures g eneral ly w ill be more

useful f or an air toxics risk a ssessmen

t; however, short term or acute toxicity data may be

used for chemicals that lack or have incomplete chronic data. EPA has in the past used acute values in c onjunction with conversion factors (i.e., acute-to-chronic r atios) to estimate chronic toxicity values, specific ally for the derivation of chronic Ambient Water Quality Criteria and Great La

kes Water Quality I

nitiative criteria for aquatic life.April 2004 Page 2 5-7 25.2.1.2 Selecti on of TRVs for a Partic ular Asse ssment In re viewing toxicity studies for potentia

l use in ide

ntify ing or de veloping specific TRVs to use in a give n assessment, the f

ollowing questions

should be c onsidere d:

• Wh at ta xa ar e u se d i n t he st ud y?

• Did the stu

dy present a

ny s ignific ant metho dologic al diffic ulties?

• Did th e st udy i den ti fy a LOA EL?

• Were the adverse effects see n possibly related to g

rowth and survival, or reproduction and development?

• Did th e st udy i den ti fy a NO AEL?

• Was the study duration appropriate to assess potential effects of chronic exposure? If the test species ar

e not within the taxonomic group of the ecological rece ptors of concern, the study may

need to be rejected because the test species are too distantly r elated to assume similar phy siologic al responses to a t oxic age nt. Many studies may

be of limited use in selection of TRVs. Potential deficiencies include:

• No control group was analy zed, or there was a high incidence of effects in the control group (applies to laboratory

studies);

• No reference are a was analy zed, or there was a high incidence of effects in the reference

area (applies to field studies);

• No statistical analysis of re sults was conducted;

• In the case of f

ish/shellfish, body burdens were estimated, not measured;

• In the case of f

ish/shellfish, only fillet, carcass (g uts, gills, and scales removed), or other body pa rt co nc en tr at io ns we re me as ur ed , n ot th e w ho le bo dy;

• In the case of wildlife, insuff icient data were provided to calculate the dose to the animal; and

• Multiple c ontamina

nts were present in the expe

rimental studies. Most envir

onmental contamination con

cerns f or air toxic s that persist and bio accumul ate will tend to be long-term and relatively low-level. As such, the most appropriate toxicity studies ar e those eva luating chronic (long- term) toxic ity o

r, if chr onic studi es are n

ot availa ble, subc hronic (medium-term) exposure durations. Although no one definition of “chronic” is accepted by human or e cologic al toxicolog ists, the g eneral

concep t is that the

duration encompa sses a significant portion of the species life span (e.g ., ten weeks for birds and one y ear for mammals). “Subchronic” is commonly de fined as a 90-day or longer study

for mammals and 10 weeks or fewer f or birds. For aqu

atic bioa ssay s, chroni c tests ma y sp an multiple

gener ations an d assess sensi tive gr owth o r repro ducti ve end poin ts. In m ammal ian an d avia n test s, th e term average daily dietary dose (e. g., expr

essed as mg/kg- day

) gene rally implies ch

ronic or subchron ic exposure. (8) In or der to de velop TRV s (sometimes terme d benchma rks) for avian an d mammalia

n receptors, Oak Ridge National La

boratory’s Toxicologic al Benchmarks for Wildlife, (11) and some information from EPA’s Integ rated Risk Information Sy stem (9) can be used (in a more limited fashion). Information provided in these sources has to be modified using allometric information availab le in EPA’ s Wildlife Exposure Factors Handbook (7) to better represent potential wildlife sp ec ie s s en si ti vi ty.April 2004 Page 2 5-8 Exhibit 25-4. Sources of Ecological T RVs or Benchmarks Data Source Available Tox icity Reference Value(s) Overview of Data Source and Va lues
EPA Office of Water Ambi ent Wate

r Qualit y Criteria (AW QC) • AWQC C hronic C riteria

• AWQC Acute Cr

iteria Note: m any st ate water quali

ty standards are based on AWQC EPA has developed national recom mended water q

uality criteria for the protection of aquatic life for ap proximately 1 50 pollutants. These criteria are published pursuant to Section 304(a) of the Clean Water Act (CWA) and provid

e guidance for Sta

tes and Tribes to use in ado pting water quality standards

under Section 303(c) o f the CWA. Source: htt p:/ /www .epa .gov/ wate rsc ien ce/ cri ter ia/ aql ife .html Great L akes W ater Quality Initi ative (GLWQI

) Criter ia Docum ents • GLWQI Tier I Criteri a

• Final Chronic Values (FCVs) GLWQI Tier I criteria and final chronic v alues (FCVs) are calculated under the same guidelines as the S ediment Quality Criteria (SQC). Draft GLWQI

criteria documents were released for public rev iew and were revised as ne cessary before they were published as “fina

l.”

• Tier I Criteria are desig ned to be protective

of aquatic comm

unities

• FCVs are d esi gned t o meas ure c hron ic to xic ity t o aqu ati c orga nis ms Source: Final Water Q

uality Guidance for the Great Lakes System

. Federal Register, Mar. 23, 1995, v ol. 60, no. 56, p. 15365- 15424 EPA So il Scree

ning L evels • Soil scr eening level s EPA ha s deve loped a methodolog

y and initial soil scr

eening level s protective of ecolog

ical receptors. Source: U.S. E

nvironmental Protection Agency . 2000. Ecolog ical Soil Screeni ng Guid ance ( Draft) . Office of Em

ergency and Remedial Response, Washing

ton, D.C., July

2000. http://w ww.ep a.gov

/superfu nd/prog rams/ risk/e corisk

/ecossl. htm

. EPA Region 4 Soil Screening Level s • Soil scr eening level s Source: U.S. E nvironmental Protection Agency . 1995. Supplem ental Guidance to RAG S: Region 4 B ulletins No. 2. Eco logical Risk Assessment. R

egion IV, Waste Managemen t Division. http://w ww.ep a.gov

/region04/wa ste/ots/

ecolbul .htmExhibit 25-4. Sources of Ecological T RVs or Benchmarks Data Source Available Tox icity Reference Value(s) Overview of Data Source and Va lues

April 2004 Page 2 5-9 Ecotox Thresh olds ECO Update and EPA’s Hazar dous Wa ste Identification Rul e (HWIR) docum ents • GLWQI Tier I I Cr

iteria

• Secondary Chron

ic Values (SCVs) The GLWQI Tier I I criteria and S CVs have received some peer re view prior to publication, and 12 of them are included in the HWI R, which unde rwen t pub lic commen t bef ore p romul gati on. T he GL WQI Ti er II methodolog

y calculates SCVs in a similar way to FCVs, but uses statistic ally d

erived “adjustm ent fact ors” and has le ss rig orous d ata requirements.

• Tier II C

riteria are designed to be protective of aqu atic comm

unities

• SCVs are d esi gned t o meas ure c hron ic to xic ity t o aqu ati c orga nis ms Source: Ecotox Thresh olds EC O Upda te (volu

me 3, No. 2 , January 1996, EPA/54 0/F- 95/038 ). ECOTOXicology database (ECOTO X) • Point E stima tes from Chroni c Tests (e.g., EC 50 , EC 10, LC 50, or GMATC)

• Point E stima

tes from Acute Tests (e.g., LC 50 ) ECOTOX is a source for lo cating single chemical toxicity data for aquatic life, terrestrial plants, and wildlife. ECOTOX wa s created and is maintained by

EPA’s Office of R

esearch and Deve lopment and the Nationa l Health and En vironm ental Ef fects Re search L aboratory’s Mid-Continent E cology Div ision. ECOTOX is a so

urce for locating single chem ical toxicity d

ata from three EPA eco logica

l effects databases: AQUI

RE, TERRETOX, and PHYTOTOX. AQUI RE and TERRETOX contain inform ation on lethal, sublethal, and residue effects. AQUI

RE includes toxic effects data on all aquatic species including plants and animals and freshwater and saltwater species. TERRETOX is the terrestrial anim al database. I

t primarily focu ses on wildlife species but the databa se does

include inform ation on dome stic species. PHYTOTOX is a te rrestrial plant database that include s lethal and sub lethal toxic effe cts data . Sour ce: http://www.epa.g ov/ecotox

. Sedim ent Qua lity Criteria • Varies EPA and other ag encies have dev eloped sediment q

uality criteria for the prot ection o f benthi c com

munit ies. The se crite

ria are h ighly specific to regions and bodie s of wa ter in the U.S. Regi onal ex perts ar e the recomm

ended source for approp

riate site-specific criteria.Exhibit 25-4. Sources of Ecological T RVs or Benchmarks Data Source Available Tox icity Reference Value(s) Overview of Data Source and Va lues

April 2004 Page 25-10 Ecological Str

ucture Activity Relationship s (ECOSAR) • Estimated C hron ic GM ATC

• Estimated Acute Data (LC 50 or EC 50 ) ECOSA R is a c ompu

ter prog ram th at uses structur

e-ac tivity relation ships (b ased on

avail able da

ta) to predict the acute and chr onic toxicity of orga

nic chemicals to aq

uatic organism s. ECOSAR provides quantitative estim

ates of chronic value s (e.g., GMA TC), acute LC 50 values, and acute EC 50 values for industrial c hemicals for several aquatic species (e.g. , fish, daphnia, g reen algae, m

ysids). When the estimated aquatic toxic ity value exce eds the water solubility of the comp ound, the esti

mated value is flagged; t

his situation g enerally

is interpreted to mean that the chemical has no toxic effects in a s aturated solution . Sour

ce: http://w

ww.ep a.gov

/oppt/newchem

s/21eco sar.htm Exposu re-R elated E ffects Database (ERED) Tissue-based effects v alues for fish and benthic invertebra

tes The U.S. Arm y Corps of En

gineers Exposure-Related Effects Database (ERED) lists toxicity

information for a large numb er and wide taxonomic rang e of fish and shellfish. ERED is constantly being updated . Sour

ce: http://www.wes.arm

y.mil/el/ered/ Jarvinen and Ank

ley database Fish and shellfish exposu re and effects information The authors assembled a database of fish and shellfish exposure and effect information. Source: Jarvinen and A nkley (1999) (9) Oak Ridg e National Laborat ory (O RNL) S oil Invertebrate toxicity database Acute a nd chronic TRVs f

or soil invertebrates and m

icrobial processes This report focuse s on chemi cals f ound at U.S. Depa rtment o f Energy (DOE) sites; howev

er there are overlaps with air toxics (me tals and organ ics). S ource: E froymson et a l. (199 7); (8) http://www.esd.ornl.gov/programs/ecorisk/docum ents/tm126r21.pdf ORNL Plant to xicity database Acute and chronic TRVs for terrestri al plant s This report prese nts a standard metho d for de riving TRVs, a set of d

ata concerning effects of chemicals in soil or soil solution on plants, and a set of phytotoxicity

TRVs for 38 chem

icals potentiall

y asso ciated w

ith DOE sites. Sourc e: Efroymso n et al. (1997) (8) ORNL Wildlife toxicity database Wildlife NOAEL and LOAELs This report presents both NOAEL- and LOAEL- based TRVs for assessment of effects of 85 chemicals on 9 representative m ammalian wildlife species and 11 av ian wildlife species. Source: Sample et al. (1996) (10)April 2004 Page 25-11 25.2.1.3 Stressor-Response Curves One way to resolve some of the limitations in the TRV approach is to fit a mathematical equation to the available exposure-response data and descr ibe the entire stressor-response curve . Data from individual experiments may be used to deve lop curves and point estimates both with and without associated uncertainty estimates. The advantages of curve -fitting approaches include using al l of the a

vailable experimen

tal data, the abilit

y to interpola te to values other

than the d

ata points measured, and an improved ability to extrapolate to values outside the range of experimen

tal data ( e.g., f

or a low-or no-ef

fect level). Curv e-fittin

g often is used to e

xtrapolate from observed effects levels to develop estimates of N OAELs, NOECs, and/or GMATCs. Stressor -respon se curve s can be d evelope d using a

ny c onvenien

t data fit ting sof tware, b ut EPA has deve loped a so ftware packag e specif

ically designe d for this t

ype of effort. This so ftware

is referred to as the Benc

hmark Dose Software (BMDS). More informa tion on this software can be found on the National Center for Environmental Assessment’s webpag e. (11) A disadvantage of curve fitting is that the number of data points required may not always be a

vailable (e.g., especia lly f or toxicity

tests with w

ildlife sp ecies) 25.2.1.4 Species Sensitivity Distribution In some cases, risk management decisions may a lso consider community-level e ffects as well as population-level

or sub-po

pulation e ffects ( one exampl e is the Am bient Wate

r Quality Criteria for the protection of aquatic life discussed in Section 25.2.1.1). That is, a stressor mig ht be consider ed to be be low a leve l of conc ern for the susta inability of a comm

unity if only a small fraction of the total number of exposed species are af fected. In this case , toxicological responses may be best cha

racterized by

the distribution of toxicity values across species. This is called a Species Sensitivity Distribution (SSD) . The SSD approach is generally used for communities of aquatic receptors, since all of the diffe rent species that make up the community (e.g., all fish, benthic i nvertebrates, a

quatic pl ants, and

amphibia ns that re side in a s tream) w ill be expose d to approximately the same conc entration of contaminant in the water. The proc ess for g enerat

ing an SSD

consists o f the foll owing st eps: (1) Select an appropriate ty pe of endpoint (e.g., lethality , growth, reproduction), and select an appropriate ty

pe of point estimate from the exposure-response curve for e ach species. For ex amp le, th e TR V mi ght be t he LC 50 for lethality or the EC 20 for growth. The key require ment is tha

t the SSD be

composed

of TRVs tha

t are all of the sa me ty pe, not a mixture. (2) Collect all reliable values for that ty pe of TRV from the literature for as many relevant species as possible. When more than one value is available for a pa rticular species, either select the value that is judged to be of highest qua lity and/or highest re levance, or combine the values across studies to derive a single composite value f or each species. I

t is important to have on

ly one value

per spec ies to main

tain equa l weigh ting across spec ies. (3) Characterize the distribution of values across species with an appropr iate SSD. Note that there is no a priori

reason t o expect that an SSD will be wel l chara cterized by a parametric distribution, so both parametric and empirical distributions should be considered.April 2004 Page 25-12 Examples of Extra

polations

• Betwee

n taxa ( e.g., minn

ow to r ainbow trout)

• Betwee

n responses (e. g., m

ortality to gro wth or reproduction)

• From laborat ory to field

• Between geog

raphic areas

• Between spatial scales

• From data co llected over a

short t ime fr ame t o longe r-ter m effe cts Once an SSD has been developed, the frac tion of species in the exposed community that may be affected at some specified conce ntration may be dete

rmined either from the empirical distribution or from the fitted d

istribution. These

distributi ons can h elp ident ify stressor levels tha

t affect a minority or majori ty o f specie s. A limiting factor in the use of SSDs is the amount of data needed as inputs. SSDs also can be derived from models that use Monte Carlo or other methods to gener ate distributions based on measure d or estima

ted vari ation in inp

ut parameters fo

r the mode ls. 25.2.2 Linking Measures of Effects to Assessment Endpoints As noted in

Chapter 2 3, assessment endp oints express the environmental values of concern for the risk assessment; however they cannot always be me asured directly . For example, the as sessm ent en dpoi nt may be m ainta inin g a healthy population of trout in a lake , but measures of effect (e.g ., toxicity tests) were conducted on different species (e.g ., fathead minnows). Where there is a lack of time, monetar y r esource s, or pra

ctical me ans to acquire more data, extrapolations may be the only way to bridge the gap in available data . Two general approache s are used for such extrapola tions:

• Empiric al extra

polations or

process m odels . Empirical extrapolations use experimental or observational data; process-based approa ches rely on some level of understanding of the underly ing ope rations o f the sy

stem of int

erest.

• Profess ional judgm ent . This is not as desir able as e mpirical or proce ss-base d approa

ches, but it is the only option when data are la cking. However, professional judg ment can be credibl e, provid

ed it has a sound scie

ntific ba sis. One of the most common types of e xtrapolations is that of effects observed in the laboratory (e.g., toxicity tests) to those observe d in the field. Exhibit 25-5 highlights the general questions to consider when performing such an e xtrapolation. When conducting field sampling or other monitoring studies, it sometimes is difficult to identify exposure-response

relation ships. How ever, there ar e a numbe

r of reasons why

a relati onship between a chemical and a toxic response in a natura l system may

not be apparent (Exhibit 25-6). Therefore, the lack of an obser ved exposure-response relationship does not disprove that one or more air toxics caused an apparent toxic effect. These sour ces of variation should be considered during planning and scoping, but may not become apparent until field studies have begun.April 2004 Page 25-13

Exhib it 25-5.Questio ns to C onsider When E xtrap olating

from Effects Observe d in th e Labo ratory to Poten tial Effects in Natural Sy stems Exposure Factors

• How will enviro

nmental fate and transformation of the air toxic affect exposure in the field?

• How compa

rable are exposure condition s and the timing of exposure?

• How compa

rable are the routes of exp osure?

• How do abiotic factors influence bioavailability and exposure?

• How likely

are preference and av

oidance behaviors in

the receptors of concern?

• How does life- stage affect exposure? Effects factors

• What is known ab out the biotic and abiotic factors controlling popu lations of the receptors of concern?

• To what degree are c ritical life-stage data available?

• How may expos ure to t he same or other s tress ors in t he fie ld have a ltere d organi sm sensi tivity? Empirical approaches are derive d from experimental data or observations. They commonly are used when adequate effects da ta are available, but the understanding of the underlying mechanisms, action, or ecological principles is limited. Two ty pes of empirical approaches are generally used:

• Uncertainty factors are der ived numbe

rs that ar e divided into measu

re of ef fects va lues to derive an estimated level of stressor that should not cause adve rse effects to the assessment end poi nt . An ex amp le m igh t b e an unc ert ain ty fa cto r of 10 t o co nve rt a n ac ut e LC 50 value into a presumed NOAEL. Unc ertainty fa ctors should be used with caution, especially when used in an overly c onservative fashion, as when chains of factors are multiplied together without sufficient justification.

• Allometric sc aling is used to e xtrapolate the eff ects of a chemica l stressor on one spe cies to another species. Allometry is the study of chang e in the proportions of various parts of an organism as a consequence of g rowth and development. Processes that influence toxicokinetics (e.g., renal clearance , basal metabolic rate, food consumption) tend to vary across species according to a llometric scaling factors that can be expressed a s a nonlinear function of body weight . Allometr

ic scalin g fact ors are commonly

used for human hea

lth toxicity assessme nts (see for examp le Chapte

r 12), but have not b een app lied as extensively to ecolog ical eff ects. When sufficient information on stressors and receptors is available, proc ess-based approaches such as population or ecosy stem process models may be used. Process models allow information on individual effects (e.g., mortality, growth, reproduction) to be extrapolated to potential alterat ions in spe cific po

pulations , communiti es, or ec osy stems. Such models a re part icularly useful in evaluating hy

potheses about the duration and severity of impacts from a stressor on an assessment endpoint (e.g., species diversity ) that cannot be tested readily in a laboratory . Two types of proce ss-based models are commonly used:April 2004 Page 25-14 Exhib it 25-6.Reaso ns Why Contami nant C oncent rations in Amb ient Media May Not Be Corr elated with

Toxi city of T hose Me dia Variati on in b ioavail ability

• Due to variance in

medium characteristics

• Due to varian

ce in contami

nant ag e among loc ations ( contam inants d eposite d to soi l and se dimen ts may beco me less bioav

ailable over tim

e due to sequestration)

• Due to variance in

transformation or s equestration rates amo ng locations Variation in the formof the chemical (e.g., ioniz ation state) Variation in the con centration over time or space (i.e., sam ples for analysis m

ay not be the sa

me as those tested)

• Spatial

heterogeneity

• Temporal va

riability (e.g. , aqueo

us toxic ity tests last f

or sev eral days but ty

pically water f rom only one day is analy

zed) Variation in the compo sition of releases (concentrations of com ponents of releases other th an the individual air toxic that is believed to be the principal toxicant m ay vary over space and time, thereby obscuring the relationsh

ip) Variati on in c o-occur ring co ntamina nts (concentrations of contam inants from upg

radient [background] sources may vary ov er time) Inadeq uate detection

limits (if detection limits are too high, g radients of toxic effect m ay be observed eve

n when the chem

icals are at the “not detected” levels) Variati on in to xicity

tests

• Inherent v

ariation

• Variation due to variance in medium charact eristics (e .g., hardness, organic matter content, pH) Source: Guidelines for E cological Risk Assessmen t (1)

• Single-spe cies populat ion mode ls describ e the dy namics of a finite g roup of in dividuals through time. The

y ha ve been used exten sively

in ecolog y a nd fisher ies mana gement to assess th e impacts

of power plants an d toxic che

micals on s

pecific fish popul ations.

• Comm unity and ec osystem modelsare particularly

useful when the assessment endpoint in vo lv es st ru ct ur al (e .g ., co mm un it y co mp os it io n) or fu nc ti on al (e .g ., pr im ar y pr od uc ti vi ty) elements or when secondary effects are of concer

n. Exhibit 25-7 provides further discussion of process-based models, highlighting a few models that have be en applie d in ecolo gical r isk asses sment.April 2004 Page 25-15 Exhibit 25-7. Process-based Model App lications in Ecological R isk Assessment Process -bas ed mo dels can help the assess or unde

rstand t he pote ntial sig nificanc e of toxicant ef

fects to the pop ulation structu re, and ecosy stem mode ls can help dete rmine whethe r the eff ect may res

ult in seconda ry effe cts on other spe cies in the sy stem that are linke d in the

food w eb or on

overa ll ecosystem fu

nctions. Pastorok

et al

. (12) review a num

ber of population, and commun ity and ecosy stem models, as well as software that im plement these m

odels. Population mode

ls typic ally d

eal with the dy namic s of the

abunda nce or d istribut ion of a singl e species, sometim

es with explicit descriptions o f endpoints in time and space. These m odels can be categorized as scalar abundance, life history , individual- based, and m

etapopulation mod

els. The first two types of m

odels are highlig

hted here:

• Scalar abunda nce mo dels , which represe nt popu lations as a sin

gle sc alar dim

ension withou

t a breakdown of p opulation age structure, are frequently used in screening assessm ents. These models include Malthu sian population grow th models and logistic population g rowth models.

• Life his tory mo dels estimate population characteristics such as surv ival rates and fecund

ity as a function of age or size/morpholog ical state. These models

are important bec ause toxicants can have a differe ntial im pact on differe nt dem ographic sect

ions of the sam

e specie s. These

mode ls include determ inistic a nd stochastic a

ge- or stag e-ba sed m

odels, which a

re imp lemen

ted in software by prog

rams such as RAMAS

-Age ® , -Stage ® , -Metapop ® , or -Ecotoxicology ® ; and ULM

®

. Community a

nd Eco system model

s are intended to describe ecological system s composed of interacting species. These models incorporate species dynam ics and specific biological interactions (predator-prey , competition, dependence) to predict eco system end points such as species rich ness or the productivity of a multi- species assemblag e. Pastorok et al. categorize these models as food

web, aquatic, and terrestrial m odels.

• Food w

eb mod els capture feeding relation ships between all or som e species in an ecolog

ical community, thus de termini ng popul ation dynamics a s well a s ident ifying key ex posur e pathw ays for bioaccumulativ

e chemicals. These m

odels include predator-

prey mode ls and populationdynamic fo od chain mode ls, which are im plemented in software such as RAMAS Ecosystem ® , Populus ® , and Ecotox

. • Aquatic

ecosys tem mo dels are spa tially aggr

egated mode ls that r

epresen t biotic and ab iotic structures in combin

ation with physical, chemical, biolog ical, and ecological processes in rivers, lakes, reservoirs, estuaries, or coastal ecosystems. A n umber of m

odels exist for each ty

pe of aquatic ecosy stem. The stan

dard wa ter colu mn m odel or SWACOM ® require s the us e of lab oratory data to predict chang es in th e param eters of an enti re ecosystem. The ext

rapolati on is accomplished with

knowledg e of toxicological m odes of action, and b

y simulation of the effects of a toxic substance across d ifferent trophic levels according to the relationship between nutrients, phytoplankton , zooplank

ton, and fish. AQUATOX ( http://www.epa.g ov/ost/models/aq uatox/ ) predicts the fate of va

rious pollutants, such as nutrients and organic chemicals, and their effects on the aqu atic e cosyst em, incl uding fi sh, inve rtebr ates, and aqua tic pl ants. The Compr ehensi ve Aquatic Simu lation Mo del ( CASM

) is a bioenergetics-

based food web m

odel that includes phytoplankton , periphyton, m acrophytes, z ooplankton, benth ic invertebrates, fish, bacteria, and cyanobacteria.

• Terrest

rial eco system models

represent biotic and abiotic components in d eserts, forests, grasslands, or other terrestrial environments, and often include physical, chem ical, biological, and ecological pro cesses. The prim ary en dpoints of thes e mod

els incl ude the abunda nce of i ndivid uals within species or g

uilds, biomass, productivity, a nd food-we

b endpoints such as sp ecies richness or trophic structure.April 2004 Page 25-16 1. U.S. Environmental Protection Agency . 1998. Guidelines for Ecological Risk Assessment

. Risk Asses sment For

um, Washing

ton, D.C., April 1998 . EPA/630/R 095/002F . Availab le at: http://cfpub.epa.gov/ncea/cfm/recordisplay .cfm?deid=12460

. 2. Sheehan, P.J., Baril, A., Mineau, P., Smith, D.K., Harfenist, A., and Marshall,W.K. 1987. The Impact of Pesticides on the Ecology of Prairie-nesting Ducks . Techni cal Report Series , No.19. Canadian Wildlife Service, Ottawa. 25.3 Stressor

-Response

Profile The final product of an ecologica l response analy sis is a summary profile in the form of a written document or a comp onent of a

large r proce ss model. T

he stres sor-re sponse pr

ofile sho uld address the follow

ing que stions:

• What ecological entities are affec ted? These may include single spe cies, populations, general trophic le vels, com munities, e cosy stems, or l andscap es.

• What are the nature of the effects? The nature of e ffects should be germane to the assessment endpoints. For example, if a single species is affec ted, the effects should represent parameters (e.g., g

rowth, reproduction) appropriate for that leve l of organization.

• Where ap

propria te, what i s the time s cale for recov ery? Short- and long-ter m effects should be reported as appropriate.

• How do changes in measures of ef fects relate to changes in asse ssment endpoints (see Section 25.2.2 above)?

• What is the uncertainty associa ted with the analysis (see

Section 25.4)? 25.4 Evaluating Variability and Uncertainty The stre ssor-re sponse pr

ofile de scribed

in the pre

vious section should

include a n explicit description of any unc ertainties associated with the ecological re sponse analysis. I f it was necessary to extrapolate from measures of effect to the assessment e ndpoint, both the extrapolation and its basis should be described. Similarly, if a TRV wa s calculated, the extrapolations, assumptions, and uncertainties associated with its development should be described. The discussion also should include any information about known or potential variability in a stressor-r

esponse profile (e.g., among dif ferent species or taxa). Professional judgment often is needed to determine the unce rtainty associated w

ith information taken fr om the lite

rature and any extrapola tions used

in develo ping a p aramete

r to estima

te stressor-response. All assumptions used to develop stressor-response rela tionships and TRVs should be stated, including some description of the degre e of bias possible in each. Where literature values are used, an indication of the ra nge of values that could be considered appropr iate also should be i

ndicate d. A more

thoroug h descri ption of how to deal w

ith variability and unce

rtainty in the risk assessment proc ess is provided in Chapter 31. ReferencesApril 2004 Page 25-17 3. Lohman, K. et. al. 2000. A probabilistic analy sis of regional mercury

impacts on wildlife. Human and Ecological Risk Assessment 6:103-130. 4. Lawton, J.H. and Brown, V.K. 1994. Redundancy in Ecosystems: Biodiversity and Ecosystem Function . Springer-Verlag, B erlin Heidelberg, Germany . pp. 255-270. 5. U.S. Environmental Protection Agency . 1995. Great Lak es Wa ter Qualit

y Initiati ve Criter ia Documents for the Protection of Wildlife: DDT, Mercury, 2,3,6,8- TCDD, PCBs . Office of Water, Washington, D.C. EPA/820/B95/008. U.S. Environmental Protection Agency . 1995. Final Water Quality Guidance for the Great Lakes Sy stem. Fin al Rule

. Federal R egister 60:15366, March 23, 1995. 6. U.S. Environmental Protection Agency . 1993. Addendum to the Methodology for Assessing Health Risks Associated with Indirect Exposure to Combustor Emissions . Office of Research and Development, Washington, DC. EPA/600/AP93/003. 7. U.S. Environmental Protection Agency . 1993. Wildlife Exposure Factors Handbook . Office of Resea rch and D evelopme

nt, Washing

ton, D.C. EPA/600/R93/ 187. Avai lable at: http://cf pub.epa .gov/nc ea/cfm/

wefh.c fm?ActTy

pe=def ault

. 8. Efroymson, R.A., Will, M.E., and Suter I I, G.W. 1997. Toxicological Benchmarks for Contaminants of Potential Concern for Effects on Soil and Litter Invertebrates and Heterotrophic Processes: 1997 Revision. Oak Ridge National La boratory, Oa

k Ridge TN. ES/ER/TM-126/R2. 9. U.S. Environmental Protection Agency . 2003. Integrated Risk Information System. Office of Researc h and Dev elopment , Nationa l Center f or Environmental A ssessmen t. Availa ble at: http://www .epa.g ov/iris/

. 10. Sample, B.E., Opresko, D.M., and Suter II, G.W. 1996. Toxicolog ical Benc hmarks fo r Wildlife: 1996 Revision . June 1996. ES/ER/TM-8 6/R3. Avai lable at: http://www .hsrd.or

nl.gov/e corisk

/tm86r3.pdf

. 12. U.S. Environmental Protection Agency . 2003. Benchmark Dose Software. National Center for Envir onmental Assessme

nt. Availa

ble at: www.epa .gov/nc ea/bmds. htm

. 13. Pastorok, R.A., Bartell, S.M., Ferson, S., Ginzburg, L .R.(eds). 2002 . Ecological Modeling in Risk Assessment: Chemical Effects on Populations, Ecosystems and Landscapes . Lew is Pu bl is her s, B oca Rat on, FL.

# Chapter 2 6 Ecologi cal Ris k Charact eriz ation

Table of Contents

26.1 Introduction

............ ............ ............ ............ ............ ...... 1 26.2 Risk Estim

ation

............ ............ ............ ............ ............ ... 2 26.2.1 Single-P oint Exposure and Effe cts Comparisons

............ ............ ...... 2 26.2.2 Comp arisons

Inv olving the En tire Stre ssor- Respon se Rela tionship

............ .... 3 26.2.3 Comp arisons

Inv olving Variabil ity

............ ............ ............ ..... 4 26.2.4 Process

Models

............ ............ ............ ............ ........ 4 26.3 Risk Description

............ ............ ............ ............ ............ . . 5 26.3.1 Lines of Evidence

............ ............ ............ ............ ...... 5 26.3.2 Signi ficance of the E ffects

............ ............ ............ ............ 6 26.4 Risk Charact

erizat ion Rep ort
............ ............ ............ ............ .... 7 26.5 Evalu

ating Variabili

ty and Uncert ainty

............ ............ ............ ........ 9 References

............ ............ ............ ............ ............ ............ . 9a Consistent with EP A’s Gu ideline s for E colo gica l Risk A ssessm ent, (1) the t erm “lines of e vidence” i ncludes

a “we igh t of

evi dence” in or der t o emphas ize that both qu ali tat ive eval uati on and qu anti tat ive weig hti ng maybe used. April 2004 Page 2 6-1 26.1 Introduction Similar to human health risk characterization, ecological risk cha racterization combines informat ion conce rning exposure to c

hemicals with infor

mation re gardin

g effe cts of chemicals t

o estimate risks. The major difference in ecolog ical risk characterization is the necessity for estimating risks based on individual lines of evidence and then combining them throug h a process of weighing the evide nce. a Another difference is that in human health assessment, we primarily consider he alth effects in the bodies of individual people. I n ecological assessment, we consider various “health” issues that can rang e from actual health effects in the bodies of individual ecological receptors to something more a ttuned to the “health” of the ecosystem as measured by

species richness and diversity . This chapter provides an overview of the appr oaches and metho ds used for ecolog ical risk charac terization. As bef

ore, add itional inf ormation i s provided in EPA’s Guidelines for Ecological Risk Assessment , (1) and readers are ref erred to that document for a mor e comple te discus sion of av ailable a pproaches and me

thods. Risk characterization is the final phase of ecologica l risk assessment and is the culmination of the planning and scop ing, pro

blem form

ulation, a nd analy sis of pre dicted or

observe d advers e ecological effects re lated to the assessment endpoints. It is also based on metrics of e xposure and ecosy stem and r

eceptor charac teristic s that are

used to analy

ze air toxic s source s, their distributi on in the e

nvironme nt, and the

extent and

pattern of conta ct. Risk characte

rization is used to clarify the

relationships between stressors, effects, and ec ological entities, and to reach conclusions regarding the occ urrence of exposure and the likelihood of anticipated eff ects. The results of the anal ysi s phase a

re used t o develop an estima

te of the risk pose d to the ec ologica lly valued e ntities tha t are the focus of the asse ssment endpoints. (2) After e stimating the risk, the risk estimate is described in the context of the significance of any adverse effects and lines of evidence supporting their likelihood. Finally, the uncertainties, assumptions, and qualifiers in the risk asse ssment ar

e identif ied and su

mmarized, and the c onclusion s are re ported to risk manage rs. Conclusion s presen

ted in the risk cha racter ization shou

ld provide

clear information to risk managers in order to be useful for environmental decision making. I f the risks are not sufficie ntly defined to support

a manag ement de cision, r isk manag ers may

elect to p roceed with another iteration of one or more phases of the risk a ssessment process. Re-evaluating the conceptual model (and associated risk hy potheses) or conducting additional studies may improve the risk estimate. Characterization of ecological risk includes risk estimation, (usually a quantitative risk estimate; see Section 26.2), risk description (Section 26.3), and documentation of results (Section 26.4).April 2004 Page 2 6-2 (Equation 26- 1) 26.2 Risk Estimation Several gener al techn iques ar e availa ble for c haract erizing ecolog ical risks associa

ted with a ir toxics that p ersist an

d bioacc umulate. These a

re divide d broadly

into sing le-point c omparisons, comparisons incorporating the entire stressor-r esponse relationship, comparisons involving variabi lity

in exposure

and/or e ffects, and proc ess model s. Each is describ ed in a se

parate subsecti on below. EPA’s Guidelines for Ecological Risk Assessment (1) provides additional discussion and examp les of the se techn iques. 26.2.1 Single-P oint Exposur e and Effects Compar isons The simple st approa

ch for c omparing

exposure a

nd effe cts estima

tes for a ir toxics ec ologica

l risk assessments is the Hazard Quotient (HQ) approach (also re ferred to as the “quotient method”), whi ch i s s im il ar t o t hat use d fo r hu man non can cer hea lt h ri sk a ss ess men ts (se e Ch apt er 1 3). In this approach, modeled or measured concentr ations of the chemical in each environmental medium are divided by the a ppropriate point estimate for ecological ef fects to yield a H Q for an individua l chemica l.

where: HQ = hazard quotient Oral Intake = estimated or measured contaminant intake relevant to the ora l intake-based TR V ( us ua ll y ex pr es se d a s m g/ kg -d ay) TRV = Toxicity

refer ence va lue. This may

be in ter ms of ora l intake, media concentration, or body

burden. As described elsewhere, it may be a result of a single study (e .g., NOAEL) or the result of integration of multiple studies (e.g., water quality

criterion). EEC = estimated or measured environmental media concentr ation at the exposure point (usu

ally expresse d as mg/L

for wate r and mg /kg for soil and se diment) BB = estimate d or meas ured bod y bu rden (us ually expresse d as mg/k

g wet we ight) As with human healt

h assessments, the

measure of oral in take, EE C, or BB must be in the same units as the TRV to which the measure is being compared. As chronic risk will usually “dr ive” an ecological assessment, the HQ a pproach will usually be emplo yed for chr onic e xpos ure sce nario s usi ng chro nic du ratio n TRVs . For i niti al scr eenin g, conservative expo sure fa

ctors may be used ( see Exhibit

24-2). A s in human health risk assessment, an HQ greater than one indicates the potential for adverse ecological effects to occur, but does not predict their occurrence (see Chapter 13).b The HI ap proac h is termed the “qu otient addition ap proac h” in EP A’s Gu idelines for Ec ologica l Risk

Asses sment (1) April 2004 Page 2 6-3 State Water Quality Standa rds Pursuan t to Section 30 3 of the

Clean Water Act, States have de

velop ed num

erical water qua

lity standards for the protection o f aquatic ecosystems. These sta ndards gener

ally a re cons idered r

egula tory requirements that m

ust be met, an

d often are based on EPA’s Am

bient Water Quality Criteria (see Chapte r 25). If pe rsist ent, bi oaccumu lative hazardous air pollutants

(PB-HA Ps) enter surface waters, one way

to assess risk is to compare the EE C to a water quality standard using the HQ approach. State w ater qua

lity st andards can be accesse d via EPA’s national water q

uality standards databas e at http://www.epa.g ov/ost/wqs/

. Wh en e col ogi cal to xi cit y dat a fo r co mp lex mi xt ure s ar e un ava il abl e, t he h az ard in dex (HI) approach

b may sometimes

be used in

screen ing asse ssments, a s scientif ically appropr iate, to assess po tential e cologic al risks a ssociate d with simult aneous exposure to m

ultiple ai r toxics. (1) If the HI approac h is used, t

he assumptions and a ssociate d limitation s should be clearly documented. It may

often be the case that a single che mical is responsible for the HI excee ding one, and the assessment can then focus on the HQ for that chemical. In more re fined as se ss me nt s, an al te rn at iv e a pp ro ac h m ay b e n ec es sa ry. As with human health assessments, a number of limitations restrict application of the HQ approach. While a quotient can be usefu l in answe

ring whether a

dverse effects are likely

to occur or not, it may not be helpful to a risk manager who needs to make a decision requiring an incremental quantification of ecological hazard. For example, it is seldom useful to say that a mitigation approach will reduce the value of a quoti ent from 2 5 to 12, since this reduction cannot, by itself, be clea rly interpre ted in ter ms of eff ects on an asse ssment endpoint. Qu otients also may not be the

most appr

opriate methods f or predi cting se condary

effects (e.g., bioaccumulation, loss of prey species). Finally , in most cases the quotient does not explicitly consider uncertainty , such as extrapolation from the test species to the species or community of concer

n. Some uncertainties, however, can be incorpora ted into single-point estimates to provide a statement of likelihood that the effects point estimate exceeds the exposure point estimate (see Exhibit 26-1). (1) 26.2.2 Compar

isons Involvi ng the Entir e Stress or-Res ponse Rela tionship If a curve r elating the inten sity

or level of the str essor to the magni

tude of r esponse i s availa

ble (for example, see Exhibit 25-1), the risk characterization can examine risks associated with many different levels of exposure. These estimates are pa rticularly usef

ul when the risk management decision is not based on exceeding a pre-deter mined reference value or re gulatory standard (e.g., a state water quality

standard). This approach provides a predictive a bility lacking in the hazard quotient approach, and it may be used in screening level assessments or subseque nt more refined risk ana lys es. Bec ause the

slope of t he effe cts curv e relate s the mag nitude of chang e in eff

ects to incremental changes in exposure, the ability to predict changes in the magnitude a nd likelihood of effects for different exposure sce narios can be used to compare differe nt risk management options. Also, uncertainty can be incorporated by

calculating uncertainty

bounds on the stressorresponse or exposure estimates. Limitations to this approach may include: lack of considerationApril 2004 Page 2 6-4 for sec ondary

effects, assumin

g the expo sure pat

tern use d to deriv e the stre ssor-re sponse cu rve is comparable to the environmental exposure pattern; and failing to consider uncertainties such as extrapolations from tests species to the species or communities of concern.
Exhibit 26-1. Example Compar ison of Point Estimates with Associated Un certainties

26.2.3 Comparisons Involving Variability If the exposure or stressor-r esponse profiles describe the variability in exposure or effects, then many differe nt risk est imates ca n be deve loped. Va

riability in exposure

can be u sed to est

imate risks to mod

erately or highl y exposed memb ers of a

population being

investig ated, wh

ile variability in effe cts can be used to estimate risks to average or sensitive members of populations. As an example, exposure can vary by life-stag e (e.g., exposure may be greater during spawning or migration). L ikewise, effect may

also vary by

life-cyc le (e.g., hatchlings may be more s ensitive t

o a chemi cal than

are adu lts). A ma

jor adva ntage o f this approach is

its ability to predict changes in the magnitude a nd likelihood of effects for different exposure scena rios and thus provide a means for comparing diffe rent risk management options. Limitations include the increa sed data

require ments comp ared wit

h previou sly

describ ed techn

iques and the implic it assumption

that the f ull rang e of var

iability in the expos

ure and e ffects d

ata is ad equatel y repres ented. I

n addition , second

ary effects are no t readily

evaluat ed with thi s approa

ch. This risk estimation technique would likely be used in more refined risk assessments. (A discussion of probabilistic techniques, including Monte Carlo Simulation, is provided in Chapter 31.) 26.2.4 Proce ss Models Process models ar

e mathema

tical expr essions that repr

esent und erstand ing of the mecha

nistic operati on of a sy

stem unde

r evalua tion. They

can be u seful too ls in both a naly sis and risk characterization (process models are discussed br iefly in Chapter 25). A

major advantage of using process models is the ability to c onsider “what if” scenarios and to forec ast beyond the limits of ob served d

ata that c onstrain

approac hes base d solely

on empiric al data. Process modelsApril 2004 Page 2 6-5 also can consider seconda ry effects, and in s ome case s, the com bined ef fects of multiple stressors. Process model outputs may be point estimates, distributions, or corr elations. However, since process models are only as good as the assumptions on which they are based, the outputs from these models should be interpreted with care. The lack of knowledge on basic life histories for many spec ies, and incomplete knowledge about the structure a nd function of natural ecosystems ar

e some of the many

uncertainties that need to be considered. These mode ls are complex an

d, are us ually reserv ed for more ref

ined risk assessme nts.
Risk Assessment Frontiers: I ntegrating Human Health and Ecological Risk A ssessment Many tribal cultures v

iew ecological and human health in an integrated way such that they ca

nnot be easily separated. S imilarly, there is some effort (espec ially in Canada) tow ard an integration of human health and ecological assessment, as well as decision-m aking, in a

field known as strategic environmental assessment

. (3) This ap proach has not

been ap plied widely in the U

nited S tates, a

nd it remains to be see

n how it will develop in the next few y ears. The World Health Organ ization has published approaches to integratin g human health and ecological risk ass essment s to impro ve data q ualit y and unde rstan ding of c umulati ve risks f or deci sion makin g. (4) This approach includes an integ rated framework

(modified from

EPA’s guidan

ce) (1) and case studies. EPA, in its Framework for Cumulative Risk Assessmen t , (5) offers a flexible structure for c onducting and eval uatin g cumulati ve risk as sessmen t. By “cumul ative r isk,” EPA means “th e combine d risks from agg regate exposures to multiple agen ts or stressors.” Ag ents or stressors ma y be chem

icals, but they m ay als o be bio logica

l agen ts or ph ysical agent s, or an

activity th at, dire ctly or indire ctly, alters or caus es the l oss of a

necess ity su

ch as ha bitat. 26.3 Risk Description The results of the risk characterization should be documented in the risk description , which includes an evaluation of the lines of evidence supporting or refuting the risk estimate(s) and an interpre tation of t he signi ficanc e of the o

bserved and/or pr edicted effects. 26.3.1 Lines of Evidence The dev elopm ent of

lines of evi dence p rovid es bot h a pro cess an d a fram ework f or reac hing a conclusi on reg arding

confide nce in the risk estimate. Conf

idence i n the conc lusions of

a risk assessme nt may be incre ased by

using se veral lines of evi dence to interpre t and comp are risk estimates. These lines of evidence may be derived from different sources or by differe

nt techniqu es rele vant to ad verse e ffects o

n the asse ssment en

dpoints (e .g., ha

zard quoti ents, modeling results, o r field ob servational studie s). Ther e are th ree pri ncipal c ategor

ies of fa ctors to consider when evaluating lines of evidenc e: 1. Data adequacy and quality . Data quality direc tly influences conf

idence in the results of a risk assessment and the conclusions that can be drawn from the study . Specific concerns include: whether the experimental design was appropr iate for the questions being evaluated in the risk assessment; whether data quality objectives were clear and adhe red to; and whether the anal yse s were su

fficien tly s ensitive a

nd robust t

o identify stressor -cause d effects in light of natural variability of the attributes of the ecological rec eptors of concern.April 2004 Page 2 6-6 2. Relative uncertainty . One major source of uncertainty comes from extrapolations (e.g., from one species to anothe r; from one tempor

al scale to anothe r; from la borator y to field ef fe ct s) . In ge ne ra l, th e g re at er th e n um be r o f e xt ra po la ti on s, th e g re at er th e u nc er ta in ty. 3. Relations hip to the r isk hypothes is . Finally, the re lative importance of each line of evidence may

be determined by

how directly they

relate to the risk hypothe sis developed during planning and scoping. F or example, lines of evidence based on a definitive mechani sm rather

than asso ciations a

lone are likely to be rel atively

important

. The evaluation of lines of evidence involves more than just listing the evidenc e that supports or refutes the risk estimate. Each factor should be e xamined carefully, a

nd its contribution in the context of the risk assessment should be evaluated. For example, data or study results are often not rep ort ed o r ca rri ed t hro ugh th e ri sk a ss ess men t b eca use th ey are of i nsu ffi cie nt qua li ty. If such data or results are eliminated from the evalua tion process, however, valuable information may be lost with respect to needed improvements in methodologies or recommendations for further studies. When lines

of evide nce do no t point towa

rd the sa me concl usion, it is i

mportant t

o investig ate possible reasons for the disagreements. A star ting point is to distinguish between true inconsistencies and those related to methodology (e.g., statistical powers of detection). For example, if

a model pr

edicts a dverse e ffects t

hat were not obser ved in the field, it i s importan

t to determine whethe

r the mode l predic tions wer e unrea listic, or the exper imental de sign of t

he field study was inadequa

te to detect the predicted effects, or both. 26.3.2 Significance of the Effects In thi s step, the

signific ance of

the obser ved or estimated change s in the as sessment e ndpoints is interpre ted in lig ht of the li

nes of ev idence e valuate d above. In thi s context, s ignific ance re fers to a conclu sion as to w

hether t he obser ved or estimated change s are considere d “adve rse.” A dverse ecological effects re

present changes that are unde sirable because they alter valued structural or functional attributes of the ecological rec eptors of concern (e.g., the loss of a keystone spec ies). This determination is difficult and is frequently based on professional judgment. The assessment of degree of adversity, along with other f actors such as the economic, legal, or soc ial consequences of the ecologica l change, may

be considered in the risk management dec ision. Unless an endangered or thre atened species is at issue, society is generally

not concerned with the death of individual plants or animals, and therefore significa nce is generally

assessed at the population, community, or ecosy stem level(s). The following factors may be used to evaluate the degree of adversity

(see also Exhibit 26-2):

• Nature and intensity of effects . This foc uses on dis tinguish

ing adv erse changes

from those that are within the normal pattern of ecosy stem variability or that result in little or no significant alteration of biota. For example, if survival of offspr ing will be affected, by

what pe rc en ta ge wil l it dim ini sh, an d is

tha t li ke ly to hav e a ma jor imp ac t on

pop ula tion dy na mic s? It is important to consider both ecologica l and statistical information in evaluating the nature and inten sity

of effe cts. For

example, a

small cha

nge in a growth rate may not be sta

tistically distinguishable from natural variation; however, its impact may be more significant for a popul ation of slo wly reprod ucing f ish t han fo r rapi dly repro ducin g algae. W hen pe rform ing a more refined assessment, it is necessary to compare the potentially impac ted ecosystem to aApril 2004 Page 2 6-7 non-impacted ecosy stem (i.e., a “control” site) so there is a basis for statistical compar isons betwee n the two sy

stems.
Exhibit 26-2. Examples of Consid erations for Determining Ecolo gical Significance

• How large is the

area where ecological criteria have been exceeded?

• What proportion of the habitat is affected at local, county , State, and national levels?

• Are the exposure conce ntrations and ecologica

l criteria above back

ground levels for the area of interest ?

• What ty

pes of e colog ical im

pacts ha ve bee n assoc iated with this

polluta nt or si milar polluta

nts in the past?

• Is the criterion o

r stressor-responsiv

e curve based on

high quality data (i.e., is there a h igh degree of conf idence in the criterion

)?

• Spatial and te mporal s cale . The spatial dimension encompasses both the extent and pattern of effect as well as the context of the effe ct within the broader ecosystem or landscape. Factors to consider include the absolute area affected, the percentag e of area affecte d compare d with a la

rger a rea of i nterest, and the r

elative i mportanc e of the a

ffecte d area( s) to the ecological receptors of c oncern (e.g., are they critical breeding or overwintering areas?). For air toxics that p ersist an

d bioacc umulate, the temporal dimen sion of concern g eneral ly will be in the years to de cades range, althoug h effects in other time frames may be important in specif ic case s. Tempor

al responses for

ecosy stems may

involve in

trinsic time lags, so responses to a stressor (or risk mitigation effort) may be delaye d.

• Potential for recovery . Recovery refers to the rate and extent of return of a popula tion or community to some aspect of its condition prior to exposure to the stressor(s) of concern. Because ecosy

stems are dyna

mic, even under natural conditions, it is unrealistic to expect that a system will remain static at some leve l or return to exactly the same state that it was before it was disturbed. Thus, the “attributes” of a re covered population, community, or ecosy stem should

be care fully

defined . In g eneral , chang es that pr eclude r ecover y or result in long recovery

times are more significant than chang es that allow rapid recovery . Note that different components of a community or ecosystem may

recover at different rate s. For example, stream chemistry may recover relatively

rapidly afte

r removal of a stressor, but reestablishment of predatory fish populations may take seve ral yea rs or more. 26.4 Risk Characterization Report The infor mation on e stimates o f ecolog ical risk , the over

all deg ree of c onfidenc e in the r isk estimate s, lines of

evidenc e, and the

interpre tation of t he signi ficanc e of eco logica l effects generally is included in a risk assessment or risk characterization report . Exhibit 26- 3 lists the eleme nts that g eneral ly a

re consi dered in

the risk c haract erization report. A risk characterization report may be brief or extensive, depending on the nature of and resources availab le for the

assessme nt. The re

port nee d not be ov erly

complex or

lengthy; it is most important that the information required to support the risk management dec ision be presented clearly a nd concisely. To fa

cilitate mutual understanding, EPA policy (6) require s that risk characterizations be prepared “in a manner that is clear, transparent, rea sonable, and consistent wit h ot her ris k ch ara cte riz ati ons of s im il ar s cop e pr epa red acr oss pro gra ms in th e Ag enc y.” It describes a philosophy of transparency , clarity, consistency , and reasonableness (TCCR), andApril 2004 Page 2 6-8 provides detailed approaches to achieving TCRR. Exhibit 26-4 provides an overview of the TCRR principles (these are the same principles listed in Chapter 13).

Exhib it 26-3.Possibl e Risk Characteriza tion Report El ements

• Describe risk assessor/risk manager planning results.

• Describ e the sc ope of t he asse ssmen

t.

• Review the con

ceptual model and

the assessment e

ndpoints.

• Describ e the m

easures of effect.

• Discuss the major data sources and analytical procedures used.

• Review the stressor-

response and exposure profiles.

• Assign risks to the assessment endpoints, including risk estimates and adversity evaluations.

• Review and su

mmariz e major areas of uncertain ty (as well as their direction) and the approache s used to ad dres s the m:

– Discus s the de gree of s cient ific c onsens us in key ar eas of u ncert ainty;

– Iden tify m ajor data gaps a

nd, where appropriate , indic ate whe ther g athering

additional data would add significa

ntly to the overall confidence in the assessm ent results;

– Discuss science policy judgments or d

efault assumptions u sed to bridge inform ation gaps and the basis for these assum ptions; and

– Discuss how the elem ents of quantitative un

certainty analysis are embedded in the estimate of risk.

Exhibit 26-4. Transparency, C larity, Consistency, a nd Reasonableness Principles Principl e Definition Criteria for a Good R isk Characterization Transparency Explicitness in the risk

assessment process • Describe assessmen t approach, assum

ptions, extrapo lations, and us e of m odels

• Describe plausible alternative assumptions

• Identify d

ata gaps

• Distinguish science from policy

• Describ e uncer

tainty

• Describe relative streng th of assessment Clarity The asses sment itself i s free f rom obscu re lan guage and is easy to u

nderstand • Empl oy bre vity

• Use plain English

• Avoid tech nic al te rms

• Use simple tables, graphics, and e quations Consistency The conclusions of the risk

assessm ent are characterized in harm

ony with EPA actions • Follow statutes

• Follow Agency

guidance

• Use A genc y inf

ormat ion s yste ms

• Place assess ment in co ntext with si milar ri sks

• Define level of effor

t

• Use rev

iew by peers Reasonableness The risk assessm ent is based on sound judg

ment • Use rev

iew by peers

• Use best available s cientific information

• Use good judg

ment

• Use plausible alternativesApril 2004 Page 2 6-9 1. U.S. Environmental Protection Agency . 1998. Guidelines for Ecological Risk Assessment

. Risk Asses sment For

um, Washing

ton, D.C., April 1998 . EPA/630/R 095/002F . Availab le at: http://cfpub.epa.gov/ncea/cfm/recordisplay .cfm?deid=12460

. 2. U.S. Environmental Protection Agency . 1992. Framework for Ecological Risk Assessment

. Risk Assessment Forum, Washington, D.C., February 1992. EPA/630/R92/001. 3. Bonnell , S., and Storey , K. 2000. Address ing Cumula tive Eff ects Thr ough Str ategic Environmental Assessment: a Case Study of Small Hy dro Development in Newfoundland, Canada. Journal of

Environm ental Asse

ssment Po licy and M

anageme nt 2: 477-499. 4. World Health Organization (WHO). 2001. Approaches to Integrated Risk Assessment

. Inte rnationa l Progra mme on Chem

ical Saf ety , Geneva . WHO/I

PCS/IRA /01/12. Av ailable a

t: http://www .who.int/p cs/emer g_main. html 5. U.S. Environmental Protection Agency . 2002. Framework for Cumulative Risk Assessment

. Office of Research and De velopment, Washington, D.C., October 2002. EPA/630/P-02/001A. 6. U.S. Environmental Protection Agency . 2000. Supplementary Guidance for Conducting Health Risk Assessment of Chemical Mixtures . Risk Asse ssment Forum, Washin gton, DC

. EPA/630/R- 00/002. Available a t: http://cfpub.epa.gov/ncea/raf/rec ordisplay.cfm?deid=20533

. 26.5 Evaluating Variability and Uncertainty An important part of the Risk Characterization Report is a discussion and assessment of variability and unce

rtainty in all aspects of the ecological risk assessment. Note that ecological risk asse ssments ar

e subject to additional sourc es of unc ertainty and vari ability

as compa red to multipathway

human hea

lth risk as sessments . In a ddition to the uncer

tainties a ssociate d with multimedia modeling and sampling, the ecological risk asse ssment involves many decisions regarding choice

of ecological receptors of c oncern and associated assessment and measure s of effect. Some of these may be at levels of organization above individual species (e.g ., communitie s, ecosy

stems), w here str essor-r esponse r elationsh ips are p oorly

understo od. Bec ause many differ

ent species and higher taxonomic groups may be included in the assessment, selection of many par

ameter values such as bioconcentration fac tors, dose-response values, and dietary intake is more complex and uncertain for the ecologica l risk assessment as compared to the human hea

lth multipa

thway risk asse ssment. References

# PART V

RISK-BAS ED DECIS ION MAKING

# Introduc tion to P art V

Part V of this Reference Manual provides an over view of three components of risk-based decis ion m aking.

• Risk Management (Chapter 27) refer s to the regulatory

and other actions taken to limit or control e xposures to

air toxics, including

the role of risk ma

nageme nt in reg ulating hazards.

• Community I

nvolvement (Chapter 28) is an integral part of many risk management strategies because good community involvement helps ensure that the strategy selected will have the highest likelihood of success. Various levels of community involvement are also required by many laws.

• Risk Communication (Chapter 29) describes the process of planning the risk a ssessment (during scoping) and convey ing the results of the risk assessment in a way that meets the information requirements for the risk manageme nt decisions. This chapter discusses the importance of risk communication, and planning and implementing a risk communication st ra te gy.

# Chapter 2 7 Risk Management

Table of Contents

27.1 Introduction

............ ............ ............ ............ ............ ...... 1 27.2 Role of Risk Man agement in Regulating H azards

............ ............ ............ 1 27.3 Types of Risk Management D ecisions Related to Air Toxics

............ ............ ... 4 27.4 Use of Risk E stimates in Decision- Making

............ ............ ............ ..... 5 27.5 Process for Making Risk Manage

ment Decisions

............ ............ ............ 9 27.5.1 Define the Problem and Put it in Context
............ ............ ............ 9 27.5.2 Analyze the Risks Associated w ith the Problem in

Context

............ .......... 9 27.5.3 Examine Option s for Add ressi ng the Ris ks

............ ............ .......... 11 27.5.4 Make Decisions abou t Which Options to I

mplement

............ ............ . . 12 27.5.5 Take Actions to I mplement the Decisions

............ ............ ........... 13 27.5.6 Conduct an Ev

aluation of the A ction’s Results

............ ............ ....... 14 27.6 Informa

tion Dissemination

............ ............ ............ ............ ..... 14 References

............ ............ ............ ............ ............ ............ 15April 2004 Page 2 7-1 27.1 Introduction This chapter intro duces ri sk manag ement, f ocusing on its role

in addre ssing the

risks that air toxics pose . It pr

ovides an overvie w of the ty

pes of ri sk manag ement de cisions re lated to a ir toxics, a discussion of how risks to individuals and populations are presented to the public, and options for implementing decisions (e.g., reg ulation, voluntary risk reduction activities). Sp ec if ic al ly, risk mana gemen t refers to the regulatory and other actions taken to limit or control exposures to a chemical. Risk assess ment , on the other hand, is a tool use d to suppor t risk manage ment dec isions by

providing

quantita tive and q ualitativ e express ions of risk, along with attendant uncertainties. Specifically , the risk assessment convey s a quantitative and qualitative description of the types of impacts that may occur

from exposure to an air toxic, the likelihood that these impacts will occur given existing conditions, and the uncertainties surrounding the analysis. Risk manag ement considers these principle factors along with a variety of

additional information (which may inc lude the cost of reducing emissions or exposures, the statutory authority to take re gulatory actions, and the acceptability of control options) to reach a final decision. 27.2 Role of Risk

Managem ent in Reg ulating Haz ards Risk management may

include implicit or explicit policy and value judgments. Ther efore, one would expe ct there

to be diff erence s of opinion conce

rning w hat repr esents a n appropriate ri sk management action. Even the most basic risk manag ement decision can be highly controversial. A classic example is the decision(s) needed to answer the question how clean is clean? This question refers to a risk management dec ision that must establish a target level to which existing levels of contamination/pollution should be reduced. Establishing this level is not a trivial matter. Working through these issues can be complica ted by the diffe

rent values of the stakeholders and debates over individual perceptions about risk. As discussed be low, many authors a nd orga nizations st

ress the importanc e of unde

rstandin g risk ma nageme nt mandat

es, options, and concerns throughout the risk assessment process, fr om the initial problem formulation steps to the final risk characterization and risk communication. Many of the critical decisions in structuring the technical risk assessment depend on risk mana gement concerns (e.g ., what risk manage ment option s are fe asible, w hat leve l of cer

tainty in the risk

estimate is acceptable). Although the National Academy of Sciences and others stress the distinction betwee n risk assessment and risk management, they also stress the integration of the two efforts (see Exhib it 27-1). Risk assessments are often de signed a

nd conducted with a

warene ss of the r

isk mana gem ent option s ava

ilabl e to decis ion-makers and the so cial , economic , and polit ical context in which those decisions are to be made. L ikewise, periodically reviewing the risk manageme nt options dur

ing the r isk asses sment eff

ort ensur es that the

results of the risk a ssessmen

t will provide meaning ful input in to the dec ision-mak

ing proc ess. The

National Researc h Council (NRC) of the National Academy of Sciences (NAS), in their 1983 study entitled Risk Assessment in the Fed

eral Gov ernment: Managin

g the Proc ess (the “Red Book”), (1) advocated a clear conceptual distinction between risk assessment and risk manage ment, noting, for example, that maintaini ng the d istinction betwee n the two would help t

o preven t the tailoring of

risk assessme nts to the p olitical f

easibilit y of regula ting a chemical s

ubstance . Howeve

r, the NRC also recognized that the choice of risk assessment tec hniques could not be isolated from society ’sApril 2004 Page 2 7-2 risk management goals. Ultimately, the risk assessors should be aware of risk manag ement goals; however, the fundamental scienc e performed in the risk assessment should be impartial and based on the factual base of information, to the extent possible.

Exhibit 27-1. Illustration of the Integration Between Risk Assessment and R isk Management Use of the Term “Safe” Safe: Co ndition

of exp osure u nder whic h there is a pr actical certain ty that no har m will resul t to exposed individuals (as defined in EPA’s Terms of Environment ). Safe: Free

from harm

or risk (as defin ed in th e Merria m-Webste r Colle giate D ictiona ry). During gov

ernment and com

munity interactio

ns and risk com

munication, it is im

portant to be sensitive to perceived meaning s of the term “safe.” Regulators and scientists are often reluctant to use the te rm “safe ,” beca use many peo ple und ersta nd “saf e” to mean “zero ri sk.” Ideall y, one woul d like to elim inate al l risks , but th

is is usu ally not a rea

listic ex pectation. Reg

ulators comm

only w ork to address the m ost im portant risks and de crease t

hem t o the le vel at which they b elieve

the risk s are small er than the benefits of the acti vity causing the pro blem (in this

case, r isk from exp osure to

air toxics). They com

monly refer to this level as “acceptably low risk .” However, com

munity m embers m ay become frustrated with regula tors who are reluctant to use the term “safe,” poten

tially perceiving

the regulators’ choice of words as a dodge of the issue. Therefore, it is important for government representatives to address perceptions of the m eaning of safe durin

g risk c omm

unicatio n and, as appr

opriate, use ris k com

parison s to hel

p in com munic ating the concepts of safe versus acceptably low risk . Inform ation on risk com

munication is prov

ided in Chapter 29, and Section 29.4 prov

ides specific information about risk com

parisons.April 2004 Page 2 7-3 The NRC, in their 1994 report, Science and Judgment in Risk Assessment (the “Blue Book”), (2) noted tha t, while the Red Bo ok emphas ized the distinction be tween ri sk assessment and r isk management, the purpose of separa tion was not to prevent any e xercise of policy judg

ment when evaluating science or to prevent r isk managers from influencing the ty pe of information that assessors would collect, analy ze, or present. The Blue Book concluded further that the sciencepolicy judgments that EPA make s in the course of a risk assessment would be improved if there were more clearly

informed by the Agency’s pr iorities and goals in risk management. Protecting the integ rity of the risk assessment, while building more pro ductive l inkage s to make r isk assessme nt more a ccurat e and re levant to

risk mana

gement , is essen

tial. The integration between risk assessment and risk mana gement also has been emphasized by Presiden tial/Cong ressiona l Commission on Risk Asse ssment and Risk Mana gement . In their Reports Framewor

k for Envi ronmenta l Health Ri

sk Manage

ment and Risk Asse

ssment an d Risk Management In Regulatory Decision-Making (the two-volume “White Book”), (3) the Commission d

evelope d a six-stage integ rated f ramewor k for env ironmenta

l health r isk management that can be applied to most situations (Exhibit 27-2): 1. Define t

he proble m and put it i

n context; 2. Analy ze the risks associa

ted with the proble

m in context; 3. Examine opt

ions for a ddressin g the ri sks; 4. Make dec isions abo

ut which o

ptions to imp lement; 5. Take actions to implement the decisions; and 6. Conduct a

n evalua tion of the

action’ s results.

Exhibit 27-2. The CRARM Framework for Risk ManagementApril 2004 Page 2 7-4 Not All Risk Manag ement Decisions are Regula

tory Some risk managem

ent decisions are m

ade by EPA or state, local an

d tribal (S/L/T) regula

tors pursuan t to spe cific sta

tutory criteria . How ever, gov ernme nt age ncies m ay hav e limi ted auth ority to impact m

any other decisions. For example , some decisions are

made by the individuals w

ho own or operate

the fac ilities t

hat rele ase air toxics, while others ar

e mad e by c itizen s who a

re being impa

cted by em

issions. Risk m

anagement decisions may

need to consider look

ing beyond technological solutions. The Commiss ion noted t

hat the pr ocess of examining

risk mana

gement options doe s not have

to wait until the risk analysis is completed, althoug h a risk analysis often w

ill provide important information for identifying and evaluating risk manageme nt options. In some cases, examining risk management options may help refine a risk analysis. The Commission also recommended that all of these steps involve stakeholders (see Chapter 28). When discussing risk management, it is important to consider where and how changes or interventions may occ

ur in the causal sequence of environmental impacts since interventions may reduce pollutants a number of way s along the critical path of environmental impacts. For example, interventions such as changing manufac turing processes, implementing emissions controls, or influencing worker behaviors tha t actively reduc e exposure may have a positive mitigati ng eff ect on en vironmen tal impacts. In

the discu ssion of r

isk manag ement tha

t follows, it is critic al to kee

p in mind the

range of way s in which e

nvironme ntal risks can be mi

tigate d; it is up to the risk managers to determine the most feasible and c ritical “points of entry”

along the pa th wh en de ve lo pi ng a r is k m an ag em en t s tr at eg y. 27.3 Types of Risk Management Decisions Related to Air Toxics Two general categ ories of risk management decisions are relevant to air toxics: emissions contr ol and siti ng.

• Emissions control . Emissions control decisions may involve “c ommand-andcontrol” decision s (e.g. , emissions limits) or incentives (e.g., tax credits for reduce d emissions) . EPA’s pr

efere nce is to encourage pollution prevention wheneve r feasible (see Exhibit 27-3). Emissions control d ecisions are most l ikely

to involve f ormal risk assessments.

• Siting/loca

ting . These decisions involve where to locate in dustrial f acilitie s, businesse s, waste d

isposal fa cilities, and tran sportation routes. Siting de cisions a re ty pically made by S/L

/T governments through mechanisms such as zoning, de ed restrictions and other property c ontrols, and in some cases regulation. Many of these decision-making processes include public involvement in which citizens may seek to influenc e the final decision. Siting decisions may involve assessment of e nvironmental impacts pursuant to the National Environmental Policy Act, other f ederal statutes, or similar state statutes. Siting decisions may increa singly

involve a ir toxics risk assessments.April 2004 Page 2 7-5

Exhibit 27-3. Pollution Prevention Hierarchy In the Pollution

Prevention Act of 1990, Cong ress established a hierarchy for the handling of pollution (see graphic). The Act established as United S tates policy that pollution should be preve

nted or reduced at the s ource w

henev er feasi

ble, th at pollu

tion tha t canno t be pre

vente d shoul d be rec

ycled in an environm

entally safe m

anner whenever fe asible, and that pollution that cannot be prevented or recycled should be treated in an environ mentally safe manner whenev er feasible. Disposal o

r other release into the environ

ment should be employed only as a last resort and should be conducted in

an enviro nmen tally s afe manner. Pollution prevention is the reduction or elimination of pollutan

ts at the source. As defined in the Po llution Prevention Act, “source reduction” means any practice which (1) reduces the amount of any hazardou s substance, pollutant, o r contaminant entering

any waste stream or otherwise released into the enviro nment (i nclud ing fugit ive emiss ions) pr

ior to re cyclin

g, tre atmen

t, or disposal, and (2) red

uces the hazards to public health and the en vironment as sociated with the relea se of su ch subs tance s, poll utant s, or co ntamina nts. It inc ludes equipmen t or tec hnology modifications, proce ss or procedure m odifications, reformulation or redesign of products, substitution of raw materials, and improvements in housek eeping, m aintenance, training, or inventory control. Examples of the value of pollution p revention for reducing

environme

ntal risks at the com

munity lev

el are demonstrated by EPA’s Env ironmental Justice throug h Pollution Preven

tion (EJP2) grant prog

ram. EPA en cour aged commun ity gr oups , tri bes, and l ocal gover nment s to i dent ify e nvir onmen tal prob lems and generate potential pollution prevention s olutions for their com munities. Source : U.S. Env

ironmental Protection Agency. 2002 . Environmental Ju stice Through Pollution Prevention Program. Update d July 9 , 2002 . Av ailable at: http://w ww.ep a.gov

/opptin tr/ejp2/. (Last accesse d April , 2004 .)

27.4 Use of Risk Es timat es in Dec ision-Maki ng Decision-maker s have a n umber of options wh en decid

ing wha t typ es of risk

estimate s to consider as inputs to

risk mana

gement decision s. Estimate s of human health r isk gene rally fall into two categories, estimated cancer risk and the estimated noncancer hazard magnitude of exposure concentration or dietary intake greater than a pre -established reference exposure leve l), as described in more detail in Chapters 13 and 22. Non-canc er hazard may be considered for both acute (short-term) and chronic (long er-term) exposures. In some c ases, ecologic al risk may be a fact or in d ecisi on-ma king. In some situations, risk managers ma y choose to consider

EPA’s approach for assessing an “ample margin of safety .” For cancer risks, EPA ge nerally conside

rs incremental risk (or pro bab il it y) of

can cer for an i ndi vi dua l p ot ent ial ly ex pos ed t o on e or mo re a ir t ox ics . In protecting public health with an ample margin of sa fety, EPA strives to provide maximum feasible protection against risks to health from HAPs by (1) protecting the grea

test number ofApril 2004 Page 2 7-6 persons possible to an individual lifetime risk level no higher than 1×10 -6 (one in one million) and (2) limiting to no higher than approximately 1×10 -4 (one in te

n thousand

) the esti mated risk that a person living near a source would ha ve if exposed to the maximum pollutant concentrations for 70 y

ears. These goals are de scribed in the preamble to the benzene National Emissions Standards for Hazardous Air Pollutants (NESHAP) rulemaking (54 Federal Register 38044, September 1 4, 1989) a nd are the goals

incorpor ated by Congre ss for EPA ’s residu al risk program under Clean Air Act (CAA) section 112(f). Exhibit 27-4 describes some of the key steps in the development of the 1×10 -4 to 1×10 -6 carcinogenic risk rang e. For non-carcinogenic substanc es, on the other hand, risk managers may consider a reference le

vel that is developed based on data from laboratory animal or human epidemiology studies (see Chapter 12), and to which uncertainty factors are applied. The refe rence level is usually

an exposure level below which there are not likely to be any adve

rse effects from exposure to the chemica l. Exposure s above the refe rence l evel may

have some

potentia l for ca using ad verse effects. This concept ma y a lso be app lied ge

nerally to ecolog ical risks. Risk estima

te options gener ally revolve around e stimates o f individual risk, the number of people at different risk levels (population risk), and occasionally include the expected incidence of disease in the entire population. Risk estimates can be derived for the c urrent population as currently distributed in an a rea or for a population size and geog raphic distribution that might occur in the future; similarly , they may focus on risk estimates for persons currently exposed or possible risks calculated for a hy pothetical individual located where exposures are expected to be relative ly h

igh. I t is importa

nt to note that risk estimates should strive to take in to accou nt both indoor and outdoor exposure to toxics, when possible.

• Risk to a specified individual . Most risk a ssessmen ts focus on estimati

ng indivi dual risk rather than the incidence of adverse effects (e.g., numbers of predicted cancer cases pe r year ) in a population. There are two gener al estimates of individual risk:

– High-end

risk estimates seek to determine a “plausible worst case” situation among all of the individual risks in the population. This estimate is meant to describe an individual who, as a result of where they live and what they do, e

xperiences the highest level of exposure within some reasonable bounds. Reasonable maximum risk estimates are often defined conceptually

as “above the 90th percentile of the population” (4) but not at a higher exposure level than the person exposed at the highest level in the population. When calculated using deterministic methods, the high-end individual is calc ulated by combining

upper-b ound and m

id-rang e exposure

factor s (e.g. , an ave

rage b ody weight , but high- end ing estion ra te) so tha t the resu lt repre sents an e

xposure sc enario t

hat is both protective and reasonable, but not higher tha n the worst possible case.

– Central-tendency

risk estimates seek to determine a reasonable “a verage” or “mid-ra nge” s ituation a

mong all of the ind

ividual ri sks in the p opulation . Many risk management decisions related to exposure to radioactive substances (e.g., in nuclear power pl ants) ar

e based on centra

l-tende ncy risk estimates.April 2004 Page 2 7-7 Exhibit 27-4. Development of the 1×10 -4 to 1×10 -6 Carcinogenic Risk Range The 1970 CAA established Section 112 to de al with hazardous air pollutants. Once the EPA Administrator had identified such a pollutant an d “listed” it, he/she was directed to set emissio n standards for sources em

itting it at levels that would “provide an ample m

argin of safety to protect the publi c healt h.” The regulat ion of b enzene p ursua nt to Se ction 112 ill ustra tes th e evolut ion of r iskbased decision-m

aking for carcin

ogens and the co

nsideration of the “am

ple margin of safety.”

• EPA listed benze

ne as a HAP in June 1977 and indicated that the “relative risk to the public” would be considered in

judging “the deg

ree of control which can

and should be required .”

• In 1980, the first round of benz ene standards followed the proposed procedures in EPA’s 1979 draft airborne carcinogen policy, which reflected a technology -based approac

h to emission standard developm

ent with a limited role for quantitative risk assessment in esta

blishing priorities and e nsur ing that the r esid ual r isk s fol lowi

ng t he ap plic atio n of “bes t av ailab le te chno log y” (BAT) were not unreasonable.

• In 1984, after “weighing all factors,” EPA m

ade several chang es to the proposed ben zene rules, arguin g that the risk s were “ too sm all to w arrant F ederal r

egula tory a ction.” These d ecision s were promptly challenged by the Natural Resources D efense Council, who argued about the uncerta inties in the risk estimates and

the ina ppropri ate con siderati on of co st in reg ulatory decisions made u

nder Section 112. The issues raised were sim ilar to litigation already

pending on amendme nts to the original v

inyl chloride standards.

• On July 28, 1987 , Judge Robert Bo rk, writing for the D.C. Circu it Court of Appeals, remanded the vinyl chloride amendme

nts to EPA, finding

that the Agency

had placed too g

reat an emphasis on technical feasibility and c ost rather than the prov ision of an “amp le margin o f safety” as required by the statute. The opinion also laid out a process for mak ing decisions, con sistent with the requirements of the law. The Bork opinion held that EPA must first determ

ine a “safe” or “acceptable” level cons idering only the potential health im pacts of the pollutant. Once an accepta ble level was i dentifie d, the level could b e reduc ed further, as a ppropri ate and

in consideration of other factors, including cost and technical feasibility to p

rovide the required ample m argin of safety. The Court also held, however, that “sa fe” did not require a findin g of “risk- free” an

d that EPA sho

uld reco gniz e that activiti es such as “dri ving a car o r breath

ing ci ty air” may n

ot be considered “unsafe. ”

• In S eptem

ber of 1 989, af

ter prop osing

sever al options and receiv

ing considera

ble pub lic com

ment, EPA promulgated emission stand ards for several categories of benzene so urces. EPA arg

ued for the consideration of all relev ant health information

and established “presum ptive benchm

arks” for risks that would b e deemed “acceptable.” The goal, w hich came to b e known as the “fuzzy bright line,” is to protect the g

reatest number of persons possible to an in dividual lifetime risk no higher than one in 1,000, 000 and to lim it to no higher than

approximately

one in 10,000 the

estimated maximum

individual risk. The selection of even “fuzzy ” risk targets p laced greater em phasis on the developm

ent and comm

unication of risk chara

cterization results. Source : Nation

al Acad emy of Scie nces’ Science and Judgmen t in Risk Assessment (The Blu e Book ). (2)April 2004 Page 2 7-8 Note that, when calculating deterministic risk estimates, both a hig h end and central tendency estimate of risk give the risk manager some sense of the range of risks in the population. When risks to a population are developed using probabilistic methods, this becomes a moot point, since the result is a distribution of risks across the population, which necessarily includes information about the full variability of risk ac ross the population – including both high and central tendency risks. See

Chapter 3 1 for mor

e informa tion on pro

babilistic approac hes to risk

assessme nt.

• Risk to the total population . Whether or not risk to the total population is considered by EPA may depend on the r egulatory authority provided by

the CAA. For example, Section 112(k) of the CAA re quires EPA

to develo p an Urba n Air Toxics

Strateg y to reduce HAPs from area sources to achieve a 75 percent reduction in cancer incidenc es attributable to such sources. Two general ty

pes of descriptors are used for population risk. One, sometimes termed population at

risk is derived by dete

rmining the number of people in a population with a particular individual risk level (e.g., “1,340,000 people a re exposed at the 1×10 -6 level, and 320 people are exposed at the 1×10 -4 level”) . This is a u seful es timate of the vari ability of risk in a population.

• Incidence , another descriptor used for population risk, is an estimate of the total number (incidence) of adverse ef

fects in a population over a specified time period (e.g ., a period of 70 years) . A screening approach to der iving this estimate for a 70-y ear period involves multiplying the estimate of individual risk (ce ntral tendency

and/or reasonable maximum) by the number of persons for which that risk estimate was predicted. For example, in a population of 200 million persons, an individual cancer risk of 1×10 -4 (i.e., one in ten thousand) for every

one in the population would translate to an incidence of hundreds or thousands of excess cancer cases over a 70-year period (depending on the exposure assumption s). Howe

ver, in a small popu

lation (e .g., a t

own of 200

persons) , the same individua l cance r risk to e very one would

translat e to an exc ess incid

ence of cancer of less than one over a 70-y

ear period.

• Present versus future scenarios . Risks may be chara cterized using present or future scenarios. Use of present scenarios involves pre dicting risks associated with the current exposures to individuals (or populations) that currently re side in areas where exposures are predicted to occur. For example, a curre nt population risk estimate would use the existing population within some specified area. The resultant risk estimates are associated with the presumption that the current exposure conditions exist for the current population over the period of time associated with the assessment (e.g., into the future ). Use of future population scenarios involves estimating risks associated with exposure conditions to individuals that might reside, at some future point, in areas where potential exposures may occur (e.g., if a housing development were built on currently vacant land).

• Potent

ial risk . Risks may be sometimes be char acterized for hy

pothetical exposures. For example, in a screening air toxics modeling application, a potential risk estimate may be derived using the location where the maximum mod eled expos

ure conc entration occurs , regardless of whether ther e is a person there or not. This estimate may be considered along with the pr

edicted individua

l risk asso ciated w

ith a cur rently populate d area, such as the MIR , which reflects risk associated with the maximum exposure concentration at an actua l residence or in a census block with a non-zero population (see Chapter 11).April 2004 Page 2 7-9 27.5 Proce ss for Making Risk Manage ment D ecisions A number of different authors and org anizations have identified key steps or factors to consider in making risk management decisions. The discussion in this section is taken larg ely from the risk mana gement framework deve loped by the Presi dential/C ongre ssional Com mission on Ri sk Assessme nt and Risk M anage

ment. (3) The Commissions’s framework has six stages, each of which is briefly desc

ribed below. The Commission also noted that the framework is conducted:

• In collaboration with stakeholders; and

• Using ite

rations if new information is

develope d that cha

nges the need for or natur e of risk manage ment. 27.5.1 Define the Problem and Put it in Context The pro bl em/ con tex t s tag e is th e mo st im por tan t s tep in th e Ri sk M ana gem ent Fra mew ork . It involves:

• Ide ntify ing and charac terizing an envir onmental health pr oblem, or a potenti al proble

m, caused by chemicals

or other hazardou s agen

ts or situa tions;

• Putting the proble

m into its pub lic healt

h and ec ologica

l context;

• Determi

ning risk manag ement g oals;

• Ide ntify ing risk manage rs with the

authority or responsibility

to take th e neces sary

actions; and

• Implementing a proc ess for engaging stakeholders. These steps are all important, but may be conducted in different orders, depe nding on the particular situation. For example, when a federa l or S/L/T regulatory

agency is mandated by law to take the lead on an air toxics issue, the steps they take often will proceed in the order listed above, with the identity of the r isk managers already

clear, since the agenc

y will have assumed that role from the start. On the other hand, in a community based effort to characterize the cumulative risk posed by multiple sources of air toxics in a neighborhood, stakeholders might have to e ngag e in a col laborat

ive stake holder pr ocess fi rst to iden

tify resourc es as we ll as risk managers with the needed authority to act before the other steps can take plac e. 27.5.2 Analyze the Risks Associated with the Problem in Context The nature, extent, and focus of a risk assessment should be guide d by the risk manag ement goals. The results of a risk assessment – along w ith information about public values, statutory requirements, court decisions, equity considerations, benefits, and costs – all can influence whether and how to

manage the risks. Risk assessment can be controversial, reflecting the important role that both science and judgment play in dra

wing conclusions about the likelihood of effects on human health and theApril 2004 Page 27-10 Some Factors to Consider in Defining the Problem for an Air Toxics Risk A ssessment

• Risk . The specific estimate s of risk to be u sed as inputs to the dec ision should be defined as explicit ly as p ossible . Are a

cute ris ks (e. g., short-term exposure s) the primar y concern, or are exposu res ov er the lo

nger- term m ore im portant ? Are e colog ical risk s a conc ern? H ow cert

ain are we that our ris k estimat es are an accu rate r eflec tion of true ex posur e and ri sk?

• Air toxics of concern . What are the prima ry air toxics o f conce

rn? Are they more preva

lent in indoor or outdoor env

ironments? How many

individual chem

icals contribute to the risk s that need to be manag ed? Do these chem icals exert their effects independe ntly, or are som

e acting in a synergistic (or an

tagonistic) man

ner? Are all equally

important, or w

ill reducing exposures to a subset o f these air toxi cs resul t in ade quate ri sk red

uction?How i

mport ant is it to ma nage e very chemica l of con cern ver sus onl y those t hat pos e the gre atest risk?

• Sources . What are the prim ary sources of the air toxics that need to be managed? Where are these sources located? How

many a re there? Are they

all equally im

portant, or will controlling a subset result in adequate risk reduction?

• Exposure path

way considerations . What exposu re pathways/ro

utes are most important? A

re all equally impo

rtant, or does a subset represent the greatest risk ? Does control of ea

ch pathway require controls over a

ll components of the pathway (e.g ., emissions, exposure), or can the pathway be con

trolled by controlling

a subset of these com

ponents?

• Amount

of emissio ns redu ction d esired/ achieva ble . What is the overall target for emissions/exposure re duction? How doe s this relate to risk red uction by the estim

ates identified above? Will partial redu ctions result in significant risk reduction, or is it more of an all- or-none situation? What technologies are available to ach ieve the desired lev

el of risk reduction? How much do the variou s option s cost?

• Spatial and temporal factors . Are releases of con cern limited to a re latively brief period of time, or do data support the emissions being relatively continu

ous over a longer period of time? Are the released toxics specific to a s ingle location or are there several wide- spread emission p oints? What is the fate and transport of the released chem icals? How does background risk relate to the risk re ducti on stra tegy?

• Data gaps and u ncertainties . What are the m ain sources of uncertainty in the data used in the risk assessm ent? H ow do t

hese uncertaint

ies affe ct the ri sk m

anage ment decisio n? Will more inf ormat ion r educ e the se un cer tai nti es an d can the u ncer tai nty be addr ess ed wi th ava ila ble time and resources? Approa

ches for identifying

and manag

ing uncertainties associated with risk ass ess ment a re di scus sed i n Cha pte rs 13 and P art VII. environment. Ofte

n, the con troversy a rises fr om what we

do not know

and from what risk assessments cannot tell us, because our knowledge of human vulnerability and of environmental impacts is

incomplete, espe cially

at the re latively

low level s of chem

ical expos

ure commonly en co un te re d i n t he ge ne ra l c om mu ni ty.April 2004 Page 27-11 Alterna tive So lutions

to Uni que Prob lems Project XL , which stands for “e Xcellence and Leadership,” is a national pilot program

that allows state and loc al governm ents, businesses, and Federal facilities to develo p with EPA innov

ative strategies to test better or more cost-effective ways of achiev ing environm

ental and public health pr

otection . In

January 2001, EPA s igned

the 50t h XL Final Project Agreem

ent. Although EPA is no long er accepting proposa ls for n ew XL pr

ojects, EPA wil l contin

ue to fu lfill each of its commitm ents under Project XL and will track and m onitor the progress of each XL pilot for the duration of the

project. See www.epa.g ov/projectxl for more inform ation. Supplemental Environm ental Projects (SEPs) are part of enforce ment settlements connected with violations of an environme

ntal statutory or regulatory requirem

ent. As part of the enforcement settlem ent, a violator volun tarily agrees

to und ertake an env ironmentally

benefic ial project in exchange for a red

uction in the penalty . See www.epa.g ov/compliance /civil/program s/seps for more inform ation. 27.5.3 Examine

Options for A ddressing the Risks This stage of the risk management proc ess involves identifying pote ntial risk management options an

d evalua ting the ir effe ctivene ss, feas ibility , costs, be nefits, u nintende d conseq

uences, and cultural or social impacts. This process can begin whenever appropriate after de fining the problem and considering the context. I t does not have to wait until the risk analysis is completed, although a risk analysis often will provide important information for identifying and evaluating risk management options. In some c ases, examining risk management options may help refine a risk analysis. Risk manag ement goals may be redefined after risk manag ers and stakeholders gain some appreciation for what is fea sible, what the costs and benefits are, and what contribution reducing exposures and risks can make toward improving human and ecological health. The Commission noted that stakeholders can play an important role in all facets of identify ing and ana lyzin g options . They

can help risk mana

gers:

• Develop

methods f

or identif yin g risk- reducti on options;

• Develop and analy

ze options; and

• Evaluate

the abilit y of each op tion to red

uce or e liminate r

isk, along with its fe asibility

, costs, benefit s, and legal, socia

l, and cul tural impa

cts. Chapter 28 provides an overview of community involvement and its role in risk assessment and risk mana gement
.April 2004 Page 27-12 27.5.4 Make Decisions about Which Options to Implem ent In most risk management situations, decision-make rs will have a number of options from which to choose. Which option is optimal depends on the particular situation (and in some cases may be driven by statutory

requirements). The following seven ar e fundamental characteristics of sound risk m anageme nt dec isio n maki ng:

• Base the decision on the best available scientific, e conomic, and other technical information;

• Be sure the decision accounts for the pr oblem’s multisource, multimedia, multichemical, and multirisk c ontexts;

• Choose risk manag ement opt ions that a

re fea sible, wit

h benefi ts reasonably

related to their costs;

• Give priority

to preve nting ri sks, not jus t controll ing them ;

• Use alternatives to command-and-control reg ulation, where applicable;

• Be sensitive to political, social, legal, and cultural considera tions; and

• Include incentives for innova tion, evaluation, and research. Options to b e conside

red for air toxics f

all into the

following

gener al cate gories :

• Regulatory approaches . Pursuant to various sections of the CAA, Congress has authorized EPA to reg

ulate air toxics. Man

y S/L /T gove rnments have also

authorize d agen

cies to regulate air toxics. Regulatory approaches include enforcea ble requirements that identified sources must meet (or else be subject to legal a ction, such as fines) as well as emissions- trading

typ e requir

ements tha

t focus on controls over sour

ces in tota

l while allowing flexible emissions among individual sources.

• Voluntary approaches . EPA and other regulatory agencies are looking be

yond reg ulatory approaches to reduce risks from air toxics. Non-reg ulatory (voluntary

) approaches are frequently the

preferred option in a number of cases. D ecision-makers at S/L/T ag encies may not curr ently have spe cific re gulator

y a uthority to addre ss specif

ic air toxic s problem s identified in a risk analysis (pa rticularly in a nove l analysis such as a multi-source , community-based risk asse ssment). The types of pr oblems identified may not lend themselves to regulatory

solutions (e.g., they ma

y require changes in the behavior of the exposed population). Voluntary prog rams may also allow sourc es to significantly r educe overall risk at much lower cost than various reg ulatory options. Various incentives suc h as tax reductions or c onsumer r ebates c an be use d to encou rage voluntary

response s.

• Permits and related authorities . Permits offer opportunities for both regulatory and voluntary risk-mana

gement strategies. Many

sources release air toxics to the atmosphere pursuant to permits and related authorities. Permits generally need to be renewed periodically and/or

modified if conditions at the source change bey ond some specifiedApril 2004 Page 27-13 Example Factors to C onsider When Evalu ating Risk Management Options

• Risk reduction ben efits to be realized . Risk m anagement decisions often focus on the incremental

risk associated with the chemical or other hazard being regulated in the ab sence of background risks. Howev er, backgrou

nd risk m ay be imp ortant in certain situations. For example, if a monitoring

program measures concentration s of air toxics being transported into a given study area that result in risks above an “acceptab le” level, no lev el of emissions control within the study area will be able to redu

ce risk to an “acce

ptable” level, and the comm unity may

wish to address the inc oming air toxics via disc ussio ns beyond the loc al communi ty.

• Level o f uncerta

inty in the an alysis . In the fac e of high ly uncer tain r isks, de cisio n-makers have to carefully weig

h the consequences of two or more o ptions: mak

ing a decision to control emissions or expo sures only to find out later that there was little actual risk (e.g. , incurring unnecessary “cost” to

the comm

unity), or m

aking a dec ision not

to control emission s or exposures only t o find o ut later that the

risks were re al and l arge ( e.g., incurri ng po tentiall

y prev entable harm to the c omm

unity)

.

• Implemen tation c osts , both for volun tary approaches (e.g ., marke ting, process changes, tax incentiv es) as well as to

regul atory agenc ies, the

regul ated co mm

unity, and the

gener al com munit y (consum ers).

• Techni cal feasib ility . Short of shut ting d own the emis sion source alt

ogeth er, is t

here an avail able technology to

reduce or elimina

te emissions?

• Legal fea sibility . Does the decision-mak ing body have legal au

thority to both establish

and enforce requirements?

• Effectiveness/timing . Will the option prov ide effective m

anagement of the problem w ithin a reasonable time- frame?

• Political

feasibili ty . Does the opt ion hav e the ne cessary

politic al supp ort?

• Community Acceptance . Do the stak eholders buy- in to the proposed risk reduction alternatives? Each of these factors m

ay be m ore or less importan

t depending on the context for the risk mana gement dec ision. For ex ample , the ri sk m anage r may be requ ired by statute to weig h economic factors less than technical factors. amount. This may provide an oppor tunity to re-write per

mit conditions so as to reduce highrisk emiss ions. This m

ight be c oupled wi

th volunta

ry measure s or other

flexible so lutions to result in overall r

isk reduc tion (see box). Age

ncies ma y a lso work w

ith emission source s to incorpor ate volun tary measure s or other

flexible so lutions into

the perm it.

27.5.5 Take Acti ons to Implement the Dec isions Traditionally, implementation has been dr iven by reg

ulatory ag encies’ requirements. Businesses and governments (e.g., loca l municipalities) are generally the implementers. However, the chances of success may

be significantly

improved when other stakeholders also play key roles. Dependi ng on the situation, action- takers ma y include pub lic healt

h agencies, other publicApril 2004 Page 27-14 agencies, community

groups, citizens, businesses, industries, unions/workers, and technical experts. These groups can help:

• Develop and implement a plan for taking action;

• Explain to affected communities what decision was made and why and what actions will be taken; and

• Monitor pr

ogress . 27.5.6 Conduct an Evaluation of the Action’s Results At this stage of risk

manage ment, dec ision-mak

ers and other stak

eholders review

what risk management actions have been implemented a nd how effective they

have been. Evaluating effectiveness involves monitoring and measuring , as well as comparing the actual bene fits and costs to e stimates ma

de in the d

ecision- making s tage. T

he effe ctivene ss of the process l eading to implementation should also be evaluated at this stage. Evaluation provides important informat ion about:

• Whether the actions were successful, whether they acc omplished what was intended, and whether the predicted benefits and costs wer e accurate;

• Whether a

ny modifica

tions are needed to the risk

manage ment plan to improve

success ;

• Whether a

ny c ritical information gaps h indered success ;

• Whether a

ny new infor

mation ha s emerg ed that indicates a decisi on or a sta

ge of the proce ss should be revisited;

• Whether the process was effective and how stakeholder involvement contributed to the outcome; and

• What lessons can be learned to guide future risk mana gement decisions or to improve the decision -making

process . 27.6 Information Dissemination The Presidential/Congressional Commission on Risk Assessment and Risk Management noted that effective risk communication is critical to successful implementation of the risk management framework. (3) Risk communication engages both the communicator and the a udience in listening and in expla

ining inf ormation a

nd opinions

about the nature o f risk an

d other to pics that e

xpress concer ns, opinion s, or rea

ctions to r isk messages. (5) The Commission made the following recommendations with respect to risk communication:

• The comp lex and oft

en confu sing pro cess of c ommunica ting inf ormation a

bout risks to diverse affected parties must be improved;April 2004 Page 27-15 1. National Research Council (NRC). 1983. Risk Asse ssment in t

he Fede ral Gove rnment: Managing t

he Proce ss (The “Re d Book”) . Nationa l Acade my Pr ess, Washi

ngton, D .C. 2. National Research Council (NRC). 1994. Science and Judgment in Risk Assessment (The “Blue B ook”). N ational A cademy Press, Washington, D.C. 3. Presidential/Congressional Commission on Risk Assessment and Risk Management.1997. Framewor

k for Envi ronmenta l Health Ri

sk Manage

ment (Final Report, Volume 1). Availabl e at www.riskworld.com/Nreports/1996/risk_rpt

. Presidential/Congressional Commission on Risk Assessment and Risk Management. 1997. Risk Assessment and Risk Management In Regulatory Decision-Mak ing (Final Re port, Volume 2) . Availab le at www.riskworld.com/Nreports/1996/risk_rpt

. 4. U.S. Environmental Protection Agency . 1995. Guidance for Risk Characterization . Science Policy Council, Wa shington , D.C., Fe bruary 1995. Ava

ilable at : epa.g ov/osp/spc

/rcgui de.htm

. 5. National Research Council. 1989. Improving Risk Communication . Nationa l Acade my Pr ess, Washingt on, D.C. • Decision s about how

to alloca te resou rces to r educe r isks can b e made a

nd explaine d partly on the bas is of risk c omparisons;

• The use of “bright lines” which distinguish betwee n contaminant emissions and exposures associa ted with ne gligib le risk le vels and t hose asso ciated w

ith unacc eptable

risk leve ls, needs to be clarified;

• Moving from command-and-control reg ulation to non-regulatory

approaches to risk reduction can increase both efficiency and effectiveness; and

• Criteria for judicial review, a common element in major reg ulatory actions, should be reaffirmed. Chapter 2 9 provide s an over view of r isk commun

ication a nd it’s rol e in risk a ssessmen t and risk manage ment. References

# Chapter 2 8 Community Involvement

Table of Contents

28.1 Introduction

............ ............ ............ ............ ............ ...... 1 28.2 Why is

Com munit y I nvolv emen t Im portant ?

............ ............ ............ .... 1 28.3 When to Inv

olve t he Com munit y ............ ............ ............ ............ . 2 28.4 How to

Inv olve t he Com munit y ............ ............ ............ ............ . . 2 28.4.1 Unders tand Go als, Ob jectives , and R

esponsi bilities for Effe ctive Comm unity Involv ement
............ ............ ............ ............ ........... 4 28.4.2 Identify C ommunity Concerns and I

nterest
............ ............ ........... 5 28.4.3 Plan Comm

unity In volvem ent Strategy an

d Activities

............ ............ . . 5 28.4.4 Identify P ossible Tools and I mplement Commu

nity Inv olvement Activities

......... 6 28.4.5 Provide Opportun ity for Continued Public Interaction

............ ............ . . 7 28.4.6 Release

of Risk Assessment and Risk Mana gement Doc

umen ts
............ ...... 8 References

............ ............ ............ ............ ............ ............ 10April 2004 Page 2 8-1 28.1 Introduction Community involvement can be an important aspec t of the risk assessment and risk management process . Particip ation of lo cal stak eholders, at var

ious leve ls and in va

rious for ms, can he lp ensure a better understanding of the risk assessment results and will promote buy-in to the selecte d risk re duction st

rateg ies. Enco

uragin g and f acilitat ing comm unity involveme

nt also is sometimes required by la

w. This chapter provides a broad overview of c ommunity involvement in air toxics risk assessment and risk management and identifies helpful ref erences on this topic. Also included throughout this chap ter are

descrip tions of su

ccessf ul air toxic s projects and pro grams w here community involveme

nt was a c entral c omponent o f that suc cess. This chapter describes the key tools, resources, and other considerations for an ef fective study area-specific approac

h. It is not, however, intended to provide all the infor mation about conducting community involveme nt activities. If additional information is needed, conta ct the co mm un it y in vo lv em en t s pe ci al is t f or you r a ge nc y. 28.2 Why is Community Involvement Import ant? When performing an air toxics risk assessment in a particular g eographic area, the community is often thought of as the people who live within the area of impact of air toxic sources. However, other parties in the area, such as local industry , also may consider the

mselves part of the community. In a ddition to the people

who actu ally live and work in an a

rea, a n umber of other sta keholder s also may have a st ake in the community ’s conce

rns (e.g ., local o fficial s, health profess ionals, local media). It is often helpful, whe n dealing with a community , to keep in mind that many different people (not just the people who live there) may have an interest in the risk assessment and management work being unde rtaken. As noted above, many

laws recognize and accommodate the ide a that government decisions should be open to citizen input before a decision is finalized. This is realized through the required public meetings and public comment periods associate d with many gove rnment actions. For examp le, the Cle an Air Act (CAA) ha s a number of requi rements t o provide an oppor tunity for the public to review and comment on Agenc y proposals. I

n some cases, the public is brought in at an even earlier stage. When risk assessors and risk managers have the oppor tunity to do so, they

should consider including the public as early as possible in the process. Doing so can lead to some very positive benefits. For example, if the community participates early

on and throughout the process, they will be in a

better p osition to un

derstan d what as sessors a

nd risk ma

nagers are doi

ng, and there is a better chance that they

will believe that the work being done is in their best interest. The process works best when the community appreciates that assessors and manag ers are working with them and respecting their input (keeping the m informed and involved). Ultimately, a community

that is invo lved ear

ly on in the pr

ocess is a community

that may be more w

illing to support the risk as sessment p rocess a nd result s. This may

, in turn, f oster the development of risk reduction strategies the community as a whole can live with and have a stake in.April 2004 Page 2 8-2 In contrast, excluding the public from the pr ocess may re sult in community resentment and rejection of even a sound risk assessment and risk manag ement approach. A “guar dian-like” attitude toward the community that trea ts people as unknowledgeable and incapa ble of meaning ful parti cipation

does not f

oster tru st and ca

n eventua lly u ndermine the proc ess. In addition to fostering the trust and a cceptance of the community , there are many other positive reasons for early

and ongoing involvement. For example, important unrecog nized sources of emissions and exposure pathways may be identified through the community involvement process . Ultimate ly, it is importa nt to rec ognize that commun ity members k

now their community and understand the ty pes of solutions that will be most accepted – after all, they live there! 28.3 When to Involve the Community When appropriate, community involvement should beg in at the earliest possible stage and span the entire risk and assessment and manageme nt process. The level of participation that community members have in some of the more technical phases of the assessment may be tailored to their ba

ckgro und, exper

tise, and interest ; howeve

r, this doe s not mean

the commu

nity cannot serve an important role in the technical phase, a s well. The approach taken, as well as the assumptions and limitations of the analysis, should be clearly explained to the community and their input should be valued in return. For certain CAA requirements, the question of whe n to involve the public is established by law. For examp le, in the

Title V pe

rmitting process the perm itting agency

must provid

e a public notice and an opportunity to comment on a draft new or revised permit when:

• A facili

ty a pplies for its first

Title V pe

rmit;

• A Title V permit is renewed (5 y ears after issuance);

• The permit is reopened because there is a material mistake in the permit or an update to the permit is needed because of new requir ements (review is limited to the part of the permit that is being revised); and

• The fac ility

makes a s ignific ant chan ge in its operati ons and a

pplies for a revi sion to its permit (review is limited to the part of the permit that is being revised). For a community- level effort that may include non-regulatory

aspects, on the other hand, a community involvement plan will need to be tailored to spec ific local needs, particularly if the ultimate risk reduction efforts will likely involve voluntar y action on the par

t of industry and/or citizens. As noted above, involving the community a t the beginning of and throughout the process will greatly

enhance the likelihood that the air toxics risk reduction plan will receive community support (even if the c ommunity does not agre e with all aspects of the analysis). 28.4 How to Involve the Community Many differe nt approa ches have been d

evelope d for invo lving the community

in a risk a

naly sis and mana gement strateg y. E xhibit 28-1 il lustrate s the ge neral f ramewor k used both

by s ome progra ms in EPA an

d by the Age ncy for Toxic Su

bstance s and Dise ase Registry (ATSDR). This framework empha sizes the ne ed for in volving t he commun

ity t hroughout the pr

ocess.April 2004 Page 2 8-3 Exhibit 28-1. ATSDR’s Co mponents of Effective Community Involvement

Source: Community Involvement in ATSD R’s Public Health Asse

ssment Process (see box of additional references at the end of this chapter)

In identify

ing community conc erns and interests, it often is useful to develop a “conceptual map” of the key or

ganizations and decision-making processes in a c ommunity. The map would include information such as who speaks for various parts of the community , who serves in formulating pe rs pe ct iv es , a nd wh at is th e p ro ce ss fo r o bt ai ni ng co ns en su s w it hi n t he co mm un it y.April 2004 Page 2 8-4 TIP: Identify

local associations or g

roups by ask

ing comm unity mem

bers, respected “elders,” o r other associations. This also c an go a long way in dem

onstrating a com

mitment to involving

and mobilizing

all stakeholder g

roups, which helps to

build trust and creates a more successful commun ity-inv olvement p

rocess. But , in seeking

out comm

unity mem

bers, do not rely solely on existing com

munity organizations. Very often comm unity mem

bers are not well org anized or represented by existing

groups. Just becau se there is not an org anization or gro up in the study area does no t mean tha t you can b ypass th at par t of the community.

TIP: Local public health p roviders, such as county health depa

rtments and ho spitals can be a key partner in

the risk analy sis and manag ement proce sses. These organiza tions often h ave resourc es (staf

f and fu nding) that ca

n be us ed in comm unity health a

ctiviti es. Be cause they are locally based, invol

ving them as ke y part ners in the proc ess can

create strong local le aders to promote susta

inable a ctiviti es once

a study is complete. 28.4.1 Understand Goals, Objectives, and Responsibilities for Effective Community Involvem ent At a minimum, goals and objectives for community involvement should include the following items. All study areas ar

e different, however, and this list is just a suggeste d starting point (and may need to be

expanded).

• Earning

trust and credibi lity

through open and respec tful commu

nication s;

• Inc luding the communi ty in the desig n and imple

mentation of risk a ssessmen

t and risk manage ment;

• Helping

community

members u

ndersta nd what th e proce ss involve s;

• Assisting

communitie s in understanding the possib le health

impact of

exposure t

o air toxics ;

• Informing and upda

ting communities about risk management activities; and

• Promoting collaboration between decision-makers, communities, and other agencies and stakehol ders whe

n carry ing out r isk manag ement activities. To reach these goals and objectives, the following key principle s are important:

• Be aware of confidentiality and privacy issues . Any persona

l information that analysts or dec ision-makers receive from community members should be respe cted, as appropriate.

• Be aware of special needs and cultural differences . When conveying information about air toxics and the risk man

ageme nt proce ss, age

ncies sho uld be aw are of n

on-Eng lish speaking community me

mbers and other citizens who may need help in understanding complica ted messa ges. Al so, be sur

e to consi der cult

ural sy mbolism. Th ere ar

e notable examples o f the use

of a sy mbol that is

accept able in one cultur

e but that has an unaccept

able meaning in another.

• Maintain effective communication . As part o f the trust-building process , analy

sts and risk managers should keep community members informed of progress, opportunities for community involvement, how community input will be used, how community members can help to re duce expo sures, a nd upcomin

g issues and eve nts.April 2004 Page 2 8-5 • Respect

comm unity knowledge

and values. It is im

portant to recog nize that c ommunity knowledge can provide valuable infor mation for the deliberative processes of risk assessment and risk manage

ment and p otentiall

y he lp to addr

ess data gaps. I t is partic ularly important

to try to understand people ’s interests (what they care about) during the proce ss (more discussion of this subject is provided in the next section). 28.4.2 Identify Com munity C oncerns a nd Intere st One impor

tant acti vity that risk a ssessors

and risk manage

rs can do at the out set of an

y st udy is simply to listen to the community . Since their concerns may or may not match those of the assessors and managers, the initial phase of c ommunity involvement often involves a fair a mount of listeni ng and d iscussion to help bot

h group s develop

a common u

ndersta nding of what will and will not be studied during the course of the assessment. I n those instances where a community concern is outside the sc ope of what can be studied (e.g., oc casional combined stormwater/sewer overflows that cause odors), a willingness on the part of the assessment team to at least help identify re sources or connect them to agenc ies that can address these concerns will go a long wa y to building trust and credibi lity . Not liste

ning an d not resp onding to community

concer ns at the o

utset may make the process of air toxic s assessme

nt and ris k reducti on more di fficult i n the long run and ma

y se t expecta tions that a

re ultima tely not met. 28.4.3 Plan Community Involvement Str ategy and Activities Planning a communi

ty in volvemen t strateg y a nd activi ties is one of the mos t critica

l compone

nts for effective community

involvement. The type and na ture of communication and involvement activities will depend on (1) the needs and interests expressed by the community during the previous stages, (2) the potential public health issues, and (3) the r esources available for communication and involvement activities. Exhibit 28-2 provides a broad list of issues to be consider ed when d

evelopin g a comm unity involveme

nt strate gy . Not all of

these issu

es must ha ve so lu ti on s i ni ti al ly; ho we ve r, th ey m ay n ee d t o b e a dd re ss ed ev en tu al ly.
Communi

ty Invo lvement Examp le

. Southern Baltimore & Northern Anne Arun del County Comm unity Environmental Partnership (CEP). In 1996 , the residents, businesse s, and organ izations of fi

ve Ba ltimore, MD n

eighb orhood s joined w

ith local, State, and Fede

ral governm

ents in a CEP to b egin a new effort to find ways to improve the local environm ent and economy. This CEP conducted a comprehensiv e screening of the cumulative co

ncentration of air toxics from all the industrial and city facilities in and arou nd the neighborho ods and develope d a first-for-Mary

land survey of cancer incidence at the neigh borhoo d leve l. Bas ed on th is work , the C EP beg an work with local facilities on pollution prevention. The w

ork of the Baltim ore CEP was a l earning

experie nce for all of the peopl e who p art ici pat ed. T he Pa rtn ers hip t rie d a lo t of n ew th ings - some of them work ed and some didn’t. Lesso ns learned from this wo rk were carefully docum

ented. The risk screen

ing method

ology and lessons learned are being translated into a how-

to manual for community use. For m

ore information on this manual and other CEPs, se e http://www.epa.g ov/oppt/cahp

.April 2004 Page 2 8-6 28.4.4 Identify Possible Tools and Implement Community Involvement A ctivities An enormous number

of tools a nd activi ties exist tha

t risk asse ssors and

manage rs can us e to encourage community

involvement – more than can be described here (the additional resources listed at t he end of this chap ter, how ever, should provi de most of any team’s ne eds in this regard). They

range from the simple phone call, to block parties (a t which food may be provided), to the complex mapping of emissions sources and populations. How many and which tools and activities should be used or initiated for a given situation depends on the phase of the risk or public health assessment and management proc ess, the level of community intere st, and the degree of hazard a study area poses. The formation of a partne rship with stakeholders or community-based coa

litions can be an effective way to involve the community, acce ss technical expertise , achiev e consen sus, leve rage r esource s, and obta

in results

. Exhibit 28-2. Issues to Consider When Developing C ommunity Involvement Strategies Community health concern s :

• How many

commu nity mem bers are concerned about the study area?

• What is the level of the comm unity’s concern?

• Is the leve l of com

munit y concern hig

her (or lower) than the

actual risk would su

ggest?

• Are comm

unity concerns unk

nown?

• Would a physician en hance outreach at com

munity m eetings?

• Is informa

tion/ou treach/health ed

ucation avail able now or ca

n this wait unti l report s are generated? Demographics :

• How many

commu nity mem bers are potentially affected ?

• Are there any potentially sensitive p opulations that may be exposed?

• Do socio-de

mographic data suggest need for additional resources, such as translation?

• How do

the com munit y membe rs recei ve inf ormat ion (e. g., newspap er, rad

io, word-o f-m

outh)? Community interest in the r isk assessment and manag ement process :

• How involved in the process wou ld the comm

unity like to be?

• How w ould th e com

munit y lik e to be kept u

pdated and info

rmed (e.g. , news letters, e-m ails)?

• How many communi ty groups or acti vist grou ps are i nvolved? How acti ve are th ey?

• Should the risk as sessment/man agement team

facilitate the creation of a com munity g roup if one has not been form

ed?

• Can information be disseminated at cultural centers? I nformal gathe

rings? Media support :

• What has the comm

unity already heard from the m edia? Are there m

isconceptions that need to be dispelled?

• Will media sup

port req uire m ore com munit y inv olvem ent reso urces than usua

l? Suppo rt of the communit y :

• Are there Native A

merican com

munities affected by

the pollution? Should

a relevant ag ency be involved?

• Does the pollution inv olve an env

ironmental justice issue, air toxics “hot spot,” or other type of special sites?

• What past experiences has the commu nity had with “the

governm ent”? Other agen

cies?

• Is there a hig

her than averag e need for resources, su ch as for more frequent comm unity updates?

• How active w

ill any regional ag ency r

epresen tative s or other age

ncies be in com munit y involvem ent efforts?April 2004 Page 2 8-7 Non-English Speak

ers and Other Special Needs? To ensure the participation of ev eryone in the comm unity, agenc ies ofte

n use o ne or m

ore of the following strate gies:

• Offer tr

anslato rs and s igners

at com munit y meeti ngs, and che ck for

wheelchair acces sibil ity.

• Provide additi onal se ssion s of meeti ngs that are offered exclusively in the comm unity’ s secondary l angua ge(s).

• Seek out adv

ocates f or the s everel

y disabled or others with sp ecial needs.

• Provi de educ ation an

d outrea ch ma terials in both English a

nd secondary lang

uages.

• Devel op unde

rstanda ble and cultura lly appropr iate m essag es and m

aterials

. Exhibit 28-2. Issues to Consider When Developing C ommunity Involvement Strategies (Continued) Public h ealth :

• Is the study

area a designated public health hazard? Is haz ard acute or chronic?

• Are environm

ental health risks larg ely unknow n?

• Is the stud y area cons ide red a high p rio rit y? By who m?

• Is there already

some risk or health outcome results? Are biological data available?

• Is a health co

nnection plausible between contaminant expos ures and comm

unity health concerns ?

• Are data available fo r review now ?

When will they be available?

• Are there toxics reduction steps already in proc ess? Community culture and setting :

• What are the current com munity priorities and projects?

• What are the comm

unity organizations?

• Who are the com

munit y lead ers (une lected)?

• What activities constitute com munity life? Other :

• How many

people on the study

area team? D oes everyone know their role?

• What is the time- frame for report dev elopment and communication?

• Will any special clearances will be required? At w hat levels?

• Will document or g

raphics developm

ent resources be needed?

• Are there schools or loca tions where com

munity m eetings can be held?

28.4.5 Provide Opportunity for Continued Public Interaction While a risk assessment is underway , primary communica tion and involvement goals include updating the community on the status of the assessment, obtaining ongoing feedba ck on the process, obtaining additional information as needed or ava ilable from the community for the assessment, and recommending public health actions, if nee ded, about how community members can red uce exposu

res. Thr oughout this proc ess, the risk a ssessmen

t/manag ement tea

m should continue to listen to community concerns and clearly explain how

they will resp ond to thes e concer ns. Th e team also s houl d leve rage community outreach r

esources whenever possible. For instance, federal ag encies, state health and environmental ag encies, local he alth depa rtments, citizens’ advisory g

roups, and medical advisory groups may have fun ds for involving c ommunity members in the risk assessment/management process. Collaborating with partner org anizations can strengthen community outreach depth and coverage. Generally , community involvement strategies are situation-specific – risk assessment/management teams sho uld deter mine which communityApril 2004 Page 2 8-8 involvement strategies are appropriate given the potential seriousness of the risk, the abilities and involvement of the community, and the re sources available for communication, training, a nd outreach. If r

esources for community

outreach are limited, the team may wish to consider how they can be st prioritize resources for community involveme nt. When resources are limited, the team should look for community outreach opportunities during other community activities, if it would be culturally acceptable. For a deter

mination of cultural acceptability, a sk community leaders or “ trusted elders.” Finally , some com

munity analy ses foste r highly interactive rela

tionships w

ith communi

ty members a

nd other s takehold

ers. For example, the risk a ssessmen t and risk manage ment team s may establish ad hoc working groups to work on specific issues. These groups may

include advisory members f

rom the community or their re presentatives (e.g., community consultants) and may be more or

less formal, as the circumstances require. 28.4.6 Release of Risk Assessment and Risk Management Docume nts At the end of the analy sis phase, the next stage of community involveme nt generally

begins (i.e., after a draft ri sk assessment is wr itten). Sin

ce the pr ocess of data ga thering , analy

sis, and r isk assessment preparation can take many months to years, community interest may have

decreased significantly. H owever, once the risk assessment is ready for release, public interest often peaks again. To help e

nsure a f air and b alance d relea se of inf ormation, the risk assessme nt/manag ement tea

m and thei

r partne rs may consider using a m

ore for mal proc ess to release the risk assessment. For example, the team may release the draft for a per iod of time for people to read and comment. During the re view period, meetings may be held to help describe the results and how the analy sis was done. Once the risk assessment document is finalized, there typically is a need to communicate the key results, limitations, and recommendations through a variety of mater ials inclu ding fa ct sheet s, press r

elease s, public meeting s, and we bsites. The risk management strategy

may be pre sented in a similar fashion, with a draft and final document pr es en te d t o – if

no t a ls o p ar tl y wr it te n b y – t he co mm un it y. If an ag ency or othe

r parties will be conducting any follow-up activities in the area (such as additional environmental sampling or emissions monitoring, cost analyses, health education, health studies), then additional appropriate community involvement may be planne d.April 2004 Page 2 8-9 Additional References Public Health Assessm ent Gui dance Ma nual (2002 Draft Update ) describes the process that AT SDR uses to so rt t hrou gh the many ha zard ous w ast e sit es in the U .S. a nd to dete rmine wher e, an d for whom, public health actions should be undertaken. Chapter 4 addresses c ommunity involvem

ent and commun ication. See www.a tsd r.cd c.gov /HAC /PHA Man ual /co ver. html

. The Annual EPA Community Involveme nt Conference

brings together public participation and commun ity involvement professionals from across all EP A program s, as well as their local, State, Federal , and t

ribal pa rtners. Confe

rence presentat

ions are desig ned to e mpha size the proce ss of pu blic particip ation an

d com munit y inv olvem ent by focusin g on t echniqu es and a pproaches used

in EPA ’s national and regional commun ity involvement prog

rams. See epancic .org

for upcoming

conferences as well as the proceeding s of past conferences. Public Involvement in E

nvironmental Permits: A Reference Guide (2000) at www.e pa.gov/perm

its/publ icguid

e.htm was developed by EPA to help make it easier for state and local agencies to facilitate public participation in env ironmental perm

itting decisions for bus inesses and facilities under yo

ur authority. This g

uide provides basic information about p ublic participation requirem ents and giv es exam

ples under several m

ajor perm its issued by

EPA’s air, w ater, an

d waste programs. This guide also details what public participation activ ities are required under these progr ams, as a m

inimu m, as well as those s ugg ested activitie s that s erve t o aug ment the reg

ulatory requirements. Air Toxics Commu nity Assessment and R isk Reduction Projects D atabase at yose mite .epa .gov/ oar/ Commun ityA sse ssmen t.ns f/W elc ome has been com piled to provide a resource of planned, completed , and ongoing community level air toxics asses sments across the coun try. By sharing inform

ation about efforts at the loc al level to m easure, understand, and

address air toxics emissions, this dat abase will help en sure that communities des igning and implementing their own assessments will be

able to build upon p ast efforts and lessons learned

. Community Involveme

nt in ATSDR’s Pu blic Health Assessment Process (2002) provides an overview of ho w ATS DR wor ks to i nvol ve commu nit ies in th e pub lic heal th as ses sment (PHA) proc ess . It describes how ATSDR

develops com

munity inv

olvement strateg

ies and plans com

munity inv

olvement activities.April 2004 Page 28-10 1. Agenc

y f or Toxic Sub stances

and Dise ase Registry

(ATSDR). 2002. Publi c Health Assessme nt Guidance Manua

l (Update ): Draf

t for Public

Comment.. A

vailable at: http://www .atsdr.c dc.gov /HAC/PHAMa

nual/cov er.html

. Additional References (con tinued) Superfund Commu nity Involvement W eb Site provides com

munities with a ra

nge of tools, inclu

ding guidance docum

ents and other inform

ation to increase their understan ding of Superfund

and the services available to them (e.g ., the Technical Outreach Services for Com munities Prog

ram, Technical Assistance Grants). Se e www.e pa.gov/sup erfund/

action/c omm

unity/ index. htm

. Superfund Commu nity Involvement Handb ook (2002) presents leg al and policy require ments for Superfund comm

unity involv

ement and additional suggestions for involving

the comm

unity in the Superfund process. This h andbook also provides guidanc e for comm unity involv

ement outside of Superfund. See www.epa.g ov/superfund/tools/cag /ci_handbook.pdf

for more inform

ation. Community Culture and the Environment: A Guide to Unders tanding a Sense of P lace (2002) addresses the social and cu ltural aspects of com

munity- based environm

ental protection. The document offers a process and set of tools for defining and un derstanding the hum

an dimension of an environmental issue. The report, published by EPA’s O ffice of Water, is available on the web from EPA’s publication Web site. The report numb er is EPA/842/B- 01/003. Commu nity Air

Screen ing How

To Manu al: A St

ep-by-S tep Gui de to U sing a R isk-bas ed Appr

oach to Identify Priorit ies for Improving Out

door Ai r Quali ty (to be published in 2 003) is being dev eloped by the EPA ’s Com

munit y Ass istance Technica

l Air Tea m to m ake ai r qualit y asse ssmen

t tools m ore accessible to comm

unities. It w

ill present and explain a ste p-wise process

that a comm

unity can follow to form a

partnership, identify and inventory all local sources of air po llutants, review these sources to identify the

hazards and potential risks, and set priorities and develop a plan for mak ing improvem

ents.
References

# Chapter 2 9 Risk Comm unicati on

Table of Contents

29.1 Introduction

............ ............ ............ ............ ............ ...... 1 29.2 Risk Perception

............ ............ ............ ............ ............ ... 2 29.3 Your Ris k Communicat ion Str ategy
............ ............ ............ ........... 2 29.4 Risk Com

parisons

............ ............ ............ ............ ............ . 3 29.5 Implem

enting Risk Commu

nication Strategies

............ ............ ............ . . 5 29.5.1 Present

ation of Risk Result s ............ ............ ............ .......... 5 29.5.2 Workin

g with the Med ia

............ ............ ............ ............ . 8 References

............ ............ ............ ............ ............ ............ 14April 2004 Page 2 9-1 What is Risk Communication? Risk communication is the way in which d ecision-makers commun icate with various interested parties about the nature and level of risk, and abou t the risk reduction strategies to reduce the risk.

Effective Risk Communication:

• Can determine a

nd respond to com

munity con

cerns;

• Can reduce tension between concerned com munities and ag ency staff; and

• Can explain health risk information m

ore effectively to commun ities. 29.1 Introduction The purp ose of an

air toxics risk asses sment is to evaluate the magnitude and extent of exposure to air toxics and the potential effects on humans and the environment. Risk assessments aid the proc ess o f dev elop ing r

isk ma nag emen t alte rnat ives t hat mi nimize risk a nd ma ximize environmental be

nefits.

The purpose of risk communication is to help in the plann ing of the risk as sessment a nd to convey the r

esults of the risk assessment in a way that effectively

supports risk management decisions; this is so that the risk management decisions both meet the goals of the projec t and provide some comfort level for stakeholders. Good risk communication strateg ies are a fundamental aspect of developing trust among various stakeholders and the community and are often considere d an impor tant firs t step that

can begin even be fore conducting the risk assessment. Involving the community , establishing and maintaining relationships, and networking with other partners (e.g ., agencies, organizations, officials, the me dia) are key elements in a risk communication strategy . Tailoring communications to the cultural diversity of the commu

nity is importa

nt becau se it may

help esta blish the tr

ust nece ssary

to complete a risk assessme nt that mee

ts all stak eholder and commu

nity needs. Ri sk manag ement ro oted in voluntary measure s requires effective risk communication to ge t buy-in. The subje ct of risk

communic ation ove

rlaps considera

bly with rela ted topic s discusse d in Chapter 1 3, includi

ng EPA’ s philosoph

y of transpa rency , clarity , consiste ncy , and rea sonableness (TCCR) as d

escribe d in its Policy For Risk Characterization

. (1) This chapter provides an overview of information deve loped by the Ag ency for Toxic Substances and Dise ase Registry

(ATSDR) a

nd other a uthors to a ssist the r

isk asses sment tea

m in communicating the context and results of the risk assessment to the public. Readers are encouraged to consult the refe rences at the end of this chapter for a more complete discussion of this important topic. ATSDR also has an excellent website on risk communication resources (See http://www .atsdr.c dc.gov /HEC/prime

r.html ).

ATSDR has published a handbook on risk communication for its staff. (2) Although focused on agency staff, this handbook clearly and effectively

outlines the detailed steps necessary in order to develo p an eff ective r isk commun

ication p lan, and i s applica ble to all r

isk asses sors and r

isk manage ment team s. The too ls and inf ormation i

n the ATSD R handbook

(and disc ussed in th

is Chapter) will help the risk as sessment t eam:April 2004 Page 2 9-2 Why is R isk Com municat

ion Impo rtant? 1. Provides an oppo

rtunity to com

municate health risk

s in a caring, co

ncerned, and well-planned m

anner 2. Involv es the comm

unity in the risk

managem

ent process 3. Helps a

llevia te fear o r ange r and es tablish trust

Two- way r

isk comm unicatio n work s best. Non- experts

want access to

inform ation an d to g ain knowledge. Technical experts and officials also want to learn m ore about non- experts’ interests, values and concern s. The audience includes governm ent, industry, citiz ens, and both technical and non-technical pe ople. They can all be included in the proce ss as partners. • De ve lo p a co mm un ic at io n s tr at eg y;

• Conduct community outreach a nd evaluation;

• Develop communication messages; and

• Interact eff

ectively with the new s media.

29.2 Risk Perception If people perc eive themselves to be at risk, their perception is unlikely to change even if they

are not being exposed or harmed. Elements that affect risk per ception include experience, culture, level of education, outrage fac tors, who is affected/how they are affected (equa

l treatment), and the level of control exercised on an event or events. People’s pe rceptions of the magnitude of risk also a

re influe nced by factor s other than numer ical data . Accor

ding to Covello (3) and other authors: (4)

• Risks perceived to be voluntary are more accepted than risks per ceived to be imposed.

• Risks perc eived to b e under a n individua

l’s contr ol are more acc epted tha

n risks pe rceive d to be controlled by other

s.

• Risks perceived to have clear benefits ar e more accepted than risks perce ived to have little or no benefit.

• Risks perc eived to b e fairly distribute d are mor

e acce pted than risks per ceived t o be unfa irly distributed.

• Risks perceived to be natural are more ac cepted than risks perceived to be manmade.

• Risks perc eived to b e gene rated by a trusted source a re more accept ed than r isks perc eived to be generated by

an untrusted source.

• Risks perceived to be familiar are more ac cepted than risks perceived to be exotic.

• Risks perceived to affect adults are more a ccepted than risks perceived to affe ct children.

29.3 Your Risk Communication Strategy - The Overall Plan In g eneral , planning

a risk communicati on strate gy includes the follow

ing step s:

• Determi

ne the g oals of th e communi cation e ffort;

• Ide ntify communic ation re straints;

• Identify

the audience(s);

• Ide ntify audienc e conce

rns;April 2004 Page 2 9-3 • Identify

what the audience(s) knows about the issues, both correc t information and misinformation;

• De si gn th e m es sa ge (s ) t o b e s en t o ut to th e c om mu ni ty;

• Design the “channels”/choose the be st methods to reach people;

• Prepare to deliver/present the message ;

• Anticipa

te commun

ication problems;

• Evaluate the program; and

• Modify prog

ram as needed. When working through this process, it is important to know and understand the communication limits and purpose, know your audienc e, and whenever possible, pretest y our message(s). You also shoul d communic ate ear ly, often, a

nd fully and reme mber tha t for many

of the pe ople in your audienc e, perception is reality

. A good communication strategy also will use tested principles of good presentation, such as the use of simplified language to present important conte nt and the ability to be objective (not subjective) and balanced. Presentations also should not be limited to just one form or just one medium. Try to use spokesper

sons who can communicate knowledgeably , honestly, clear

ly, and compassionately and w

ill listen and deal with specific concerns. Finally, it is important to make sure tha t the infor mation provided in the risk communicati on strate gy is convey

ed to all se gments of the audience at a level that they can understand and that the communication materials are honest and up-front about uncertainties. I t is often better to say “ I don’t know” than to hedg e. The ability to establish constructive communica tion will be determined, in large part, by whether or not the audiences perceive the spea ker to be trustworthy a

nd believable. Public assessment of how much we can be

trusted a nd believ ed is base d upon fou r factors: (1)

• Empat hy and cari ng;

• Competence and expertise;

• Honesty and openne ss; and

• Dedica

tion and c ommitment. 29.4 Risk Comparisons Many succe ssful risk communication efforts have had one major thing in common – a portr ayal that puts the calculated exposure risks from an assessment in perspective, with risk ranges the public can easily r

elate to and understand. Risk comparisons can help to put risks into perspective. However, irreleva nt or misleading comparisons can harm trust and credibility . Thus, while risk comparisons are commonly used, they should be used with ca ution, because some kinds of risk comparisons are more likely to be percei ved as pr e-conc eived jud

gments a bout the a ccepta bility of risks. (1) Guideline s for risk comparisons have been published, (5) and provide rank ings of r isk compa

risons in te

rms of the ir acceptability to the c ommunity. The highest-r anking comparisons are those that presume a le vel of trust be

tween the risk commu

nicator and the pu

blic, and that cons ider the

factor s that peo

ple use in the ir perc eption of

risk. Exhibi

t 29-1 des cribes s everal

example ri sk compar

ison rank ings.April 2004 Page 2 9-4 The general rule-of- thumb is to select from the highest-ranking risk comparisons whe never po ss ib le . W he n t he re is no ch oi ce bu t t o u se a l ow -r an ki ng ri sk co mp ar is on , d o s o c au ti ou sl y, being aware that it could backfire . The fifth rank, which risk assessors rarely use, consists of comparisons of unrelated risks (e.g., involuntary vs. voluntary risks). These comparisons have been fou nd to be ve

ry problema

tic. For example, the risk of

driving without a s eat belt i s a voluntar y r isk, while exposure t

o air toxics

is gene rally consider ed involun

tary by c ommunity members. Covello et al. (5) provide specific examples of each of the comparison ra nks, as as so ci at ed wi th a m an uf

ac tu ri ng fa ci li ty ( http://www .psandma n.com/ar ticles/cma-4.htm

). Risk comparison charts are also provided in Appendix B of that document ( http://www .psandma

n.com/ar ticles/cma-appb .htm ), although the authors do not recommend their use in public presenta

tions.
Exhibit 29-1. Relative Acceptability of Risk Comparisons

• First-rank risk comparisons (most acceptable)

– Of the same risk

at two different tim

es

– With a standard

– With different estimates of the same risk

• Second-rank compariso ns (less desirable)

– Of the r

isk of doing some thing versu s not do ing it

– Of al ter nat ive s olut ions to th e same prob lem

– With the same risk

experienced in other plac es

• Third-rank comparison s (even less desirable)

– Of average risk with peak risk at a particular tim

e or location

– Of th e ris k fro m one s ourc e of a n adve rse effe ct wi th th e ris k fro m all s ourc es of the s ame effect

• Fourth-rank comparisons (marg inally acceptable)

– With cos t; or one cost/r isk ra tio with anothe r

– Of risk

with b enefit

– Of occu patio nal ri sk with en vironmen tal ri sk

– With other risks from the same source

– With oth er speci fic caus es of th e same diseas e, illne ss, or i njury

• Fifth-rank comparisons (rarely accep table – use with caution)

– Of risk

s that m ay see m unr elated t o com munit y membe rs (e.g ., sm

oking , driv

ing a car, lightn ing) EPA has included risk comparisons in some air toxics analyse s. For example, the results section of EPA’s National-S

cale Air To

xics Asse ssment ( http://www.epa.gov/ttn/atw/nata/ ) discusses general U.S. backgr

ound risks from air toxics, originating from both mobile sources and other backg round sou rces:

• Mobile Sources . For on-road and non-road mobile sources, EPA e stimates that more than 100 million people live in areas of the U.S. where the combined upper-bound life time cancer risk from all air toxics compounds exceeds 10 in a million. This risk estimate is dominated by the emissions of benzene, for maldehyde, a

cetaldehy de, and 1,3 butadiene. Regarding effects other than cancer, a crolein emissions are estimated to lead to exposures above theApril 2004 Page 2 9-5 reference concentr

ation (i.e., a hazard quotient above 1.0) for approximately 200 million people in the U.S. EP A expects t

hat in 2007 , existing

standar ds affe cting e

missions of

air toxics compounds from new vehicles will reduce exposure from on-road source s by about 50 percent from 1996 levels, and that substantial reductions also will occur for non-road emissions.

• Background Sources . EPA estimates that combined upper-bound cancer risks associate d with air toxics compounds from background sources are less than 100 in 1 million throughout the U.S. However, the entire U.S. population is estimated to exceed an upper-bound c ancer risk level of 10 in a million due to background sources alone (note that in this study backg round concentra

tions inclu

de both uncontrolla

ble emissi ons [e.g. , persiste nt historic emissions, international or global pollutant transport, contributions from natural sources and emissions that can be controlled such as long-rang e pollutant transport within the U.S.]). 29.5 Implementing Risk Comm unication Strategies In or der to impl ement risk communic ation stra tegies , agencies may

need to pl an appro aches to public pr esentat ions and working w

ith the med

ia. The p urpose of communic ation with

the public is to inform, educate, and enhance cooper ative problem solving and conflict resolution. 29.5.1 Presentation of Risk Results Risk communication strategies also consider the meaning of the information (e.g., will the listener understand how to use the information in forming opinions, making dec isions, and taking actions). When risks are calculated for air toxics and the risk results ar e presented to the public, th e co mm uni ty ma y not be f ami li ar w it h qu ant it ati ve r is k da ta a nd w hat it mea ns f or t hem . In order to prevent panic and to encourage participation in and buy- in of risk management decisions, risk communication strategies are develope d that not only reassure the community, but al so ex pl ai n t he po te nt ia l r is ks an d u nc er ta in ti es in an un de rs ta nd ab le , c le ar , a nd ho ne st wa y. Effective communications also provide information in a community -compatible language or form. For example, if the co mmunity speaks Sp anish, the

n the comm

unications could be

in Spanish as well as English. Similarly, if the community includes Native Americans, the communications could be in the appropriate languag e and employ a ppropriate symbolism. The effective communication of risks will allow stakeholders to better participa te in management decisions that weigh the benefits of differe nt alternatives against the costs of achieving “acceptable” levels of risks and the c osts of disruptions associated with implementation. When deve loping me ssages , it is impor tant to consider th e followi ng ques tions:

• What does the community already know?

• Is thi s informa

tion fac tual?

• What does the community want to know?

• What does the community need to know?

• Can the information be misunderstood? When devel opin g a publ ic edu catio n camp aign, i t is gen erall y most eff ectiv e if th e campa ign highlights no more than three primary messages. More than three primary messages may convolute the focus of the education campaig n. Those developing public education campaig nsApril 2004 Page 2 9-6 Audiences may

include:

• Environmen

tal groups;

• Civic organizations;

• Professional and trade organizations;

• Educational and academ ic groups;

• Religious grou

ps;

• Other govern

ment agenc ies;

• Neighborhood/scho ol organizations;

• Industries; and

• Other organiza

tions. may wish to test their risk communication messag es with trusted audience members before releas ing them

to the publ ic. This c an ensur e that the messag es are on-targ et and he lp avoid community

objections that de cision-ma kers may not have a

nticipate d. It a

lso is impor

tant to ensure that the message is culturally attuned and fits the language ne eds of the audience. “Outrage reducer

s” are outlined by

risk communication specialist Peter Sandman ( www.petersandman.com). When developing risk-communication messages, dec ision-makers should (1) review the concerns and worries of their audience; (2) cove r WHO, WHAT, HOW, WHEN, WHERE and WHY; and (3) deve lop messa

ges tha t are consistent with their a ctions. Differ ent messa ges an d channe ls may

be need ed for di ffere

nt audien ces. To c ommunica

te effectively , the risk communicator should try to understand the audience’s values, concerns, a nd perceptions. Cre dibility

is enhanc ed by

the deg ree to wh ich the r isk commun

icator c orrect

ly identifies, anticipates, and empathizes with the specific concerns of his or he r audience(s), which may include:

• Health c oncerns ;

• Safety concer ns;

• Environme

ntal conc erns;

• Economic

concer ns;

• Aestheti c conce

rns;

• Life sty

le/cultur al conce rns;

• Data and informa

tion conc erns;

• Fairne ss/Equity

concer ns;

• Trust and

credibi lity

concer ns;

• Process/value concerns (e.g., w ho makes decisions and how); and

• Risk management concerns. It may be worthwhile to develop audience profiles for ke y audience s. Profiles describe the members of the audience, whom they trust and go to for information (decision-makers ca n seek these people out for advice on communicating with the community ), what their prevailing attitudes and perceptions are, and what conce rns and worries motivate their actions. It i s i mp or ta nt to cl ea rl y co mm un ic at e s ci en ti fi c i nf or ma ti on an d u nc er ta in ty:

• Provide all information possible, as soon as possible;

• Communicate when there is progress being made;

• Ma in ta in you r r el at io ns hi p w it h t he co mm un it y;

• Be honest about what y ou do not know;

• Explain how

you will work t

ogethe r to find the answe

rs;

• Help the a

udience understa nd the pro cess beh

ind y our findi ngs;

• Avoid acronyms a

nd jargon;

• Carefully conside

r what information is necessary ; and

• Use familiar frames of refer ence to which the audience can re late.April 2004 Page 2 9-7 Public interactions may also include a vailability sessions, informal discussions, or poster sessions. Presentations can occur in a variety of venues some of which are better suited than others to different situations. Determining the best channels for your messag e depends on understanding when to use which tool and knowing how the c ommunity prefers to re ceive information. Message delivery channels include: 1. Prese ntations : Speeche s to public groups . Benef

it: offers the audi ence a c hance to ask questions; reaches many

people at one time. Limitations: if poorly presented, can distort community

perception; can

not suffic iently

address individua

l concer ns; can be come argume ntative or confr

ontationa l. 2. Open Houses/

Availabilit

y Sessions : Informal meeting whe re public can talk to staff on a one-to- one basis . Benef

it: allows f

or one-t o-one co nversat ion; helps build trust

and rapp ort. 3. Small Group Meetings : Sharing information with interested community members and gover nment off icials. B enefit: a

llows two- way

interaction with th e communi ty. Limita

tions: may require

more time to reach only

a few people; may

be perceived by

community groups a s an effort to limit attendance; be sure y our information is identical or you may be accused of telling d iffere nt stories to differ ent gro ups. 4. Briefings : Can be he ld with key officia ls, media r

eprese ntatives, and commu

nity leaders; generally not open to the public. Benefit: allows key individuals to question risk assessment staff before release of public infor mation. Limitations: should not be the only for m of community communication; bad feeling s may arise if someone feels that they were left off the invite list. 5. Community mailings : Sends information by mail to key contacts and concerned/involved members o f the com

munity . Benef

it: delive ry of infor mation quic

kly ; may require less planning than a meeting. Limitation: no opportunity for feedbac k. 6. Exhibits : Visual displays to illustrate health issues and proposed a ctions. Benefits: creates visual impa

ct. L imitations: one-wa

y c ommunica

tion tool, no opportun

ity f or commun

ity feedback. 7. Fact Sheets : To introd uce new informat ion. Benefit: bri ef summar y of facts a nd issues; provides background for information discussed during a meeting. Limitations: one-way communication tool; needs to be well-written and understandable. 8. Newsletters : To inform community of ongoing activities and findings. Benefit: explains finding s; provide s backg

round inf ormation. Limita

tions: can

backfir e if commu

nity members d

o not unde

rstand or misinterpret cont

ents. 9. News Rele ase : Statement for the news media to disseminate information to large numbers of community members. Be nefit: reaches large a

udience quickly a

nd inexpensively. Limitations: may

exclude details of possible interest to the public; can focus unneeded attention on a subje ct.April 2004 Page 2 9-8 10. Public Meetings : Large me eting open to the public where experts present information and answer questions

and commu

nity members a sk questions and off er comme nts. Benefit: allows community to express concerns a nd agency

to present information. Limitations: can intensify conflic ts, rathe

r than re solve con

trovers ies. Presentations require a careful balanc ing act between effec tively convey

ing key messages and avoiding a range of pitfalls. I mportant “Dos” and “Don’ts” to avoid presentation pitfalls, are outlined in Exhibit 29-2. 29.5.2 Working with the Media The media

can be a primary source o f informa

tion on risks to the pub lic. Eff ective news media relations have many

benefits, complementing other communication efforts. What people re ad, see, or hear in ne

ws cover age c an lend c

redibilit y to agenc ies assoc iated wit

h air toxics

risk assessment, and can help to make it a familiar topic for public discussion. News c overage can inform pe ople abou

t air toxics

issues an d help the m ask appr

opriate questions . Skill in med

ia relation s can hel

p risk com

munications avoid or

dispel ru mors, re spond to cr

iticism, de fuse controversy, a

nd even turn adversity

to advantage. News coverage is cruc ial to engaging the attention of de cision-makers and earning the support of opinion leaders. Also, because the news media pay distribution costs, helping journalists cover the issues is a cost-effective way to communicate. The best approach to the media, as with the public, is to be open and honest, provide inf ormation tailored to the needs of each ty pe of media, such as graphics and other visual aids, and provide backg round mat

erial. Jour

nalists al so should w elcome s uch mate rials as f act shee ts, press kits, and lists of experts. Establishing an information center also can be an e ffective way to make materials available to the news media (and to the g eneral public). It also is ver y important that the material and discussions you ha ve with the media clearly articulate the messages that y ou want to find their way

into print or onto the TV or radio. Like other communication effor ts, working with the news media is done best when it is based on a strategy and follows a systematic pr ocess. A good strategy

seeks opportunities to match the goals and objectives of the orga nization with the interests of journalists. As in other communic ation stra

tegies , assessi

ng the needs of t

he audie nce – jour nalists – is

important

to re ac hi ng th em ef

fe ct iv el y. After you de

termine that the rules of y our organization concerning contac ts with the media have been met , here a

re a fe w sugg estions on

how to dea

l with new s report

ers:

• When a re

porter c alls, be s

ure to g et a name

and media

affilia tion; if what the re

porter wants is no t c le ar to you , a sk fo r a cl ea r e xp la na ti on ; i f yo u a re un ea sy w it h a re po rt er ’s qu er y, decline in a friendly

way to continue the c onversation.

• Reporters are often under deadline pr essure, but you ca

n take enough time to respond effectively ; don’t get pressured into hasty comments that might backfire.April 2004 Page 2 9-9 • Do not hesitate to ask for more information about a story before responding to a request for an interview. In working with journalists, it is vital to develop good interpe rsonal relationships. How can y ou do that? One rule of thumb followed by experienced pr actitioners is to adhere to the “Five Fs” – Fast, Factual, Frank, Fa

ir, and Friendly

(Exhibit 29-3). (6)

• Inte rvie

ws . Frequently , the best way to g et a message out is through an in-person interview. You should generally

assume that all statements you make are “on the record.” Exhibit 29-4 outlines some techniques to prevent poor transmittal of y our message.

• Press Releases . Press releases may not be an effective way

to transmit a message. However, in some cases, releases that are targeted to particular media outlets and purposes can be useful. For example, the publication of a report on air toxics risk might be newsworthy and of concern to the community , and thus would be sent to local community newspa pers. Remember

that y our pres s relea se should e mphasize, upfront, the messa ges tha t yo u want to get out to the public.

• Other Platf

orms . You m ay have the oppor tuni ty to com muni cate your m essage t hrough other pla tforms suc

h as:

– Letters to the Editor. Keep them short, to the point, and prompt.

– Commentaries. Radio broadcasts and newspapers print a number of opinion pieces each day. Be ar in mind that submissions are numerous, acceptances rare

.

– Talk Radio (and TV). Talk shows may request experts to address various environmental issues.April 2004 Page 29-10 Exhibit 29-2. Presentation D os and D on’ts

• Pitfa ll : Jargon Do : Define all technical terms and acronym s. Don’t : Use la ngua ge that m ay not b e und erstoo d by e ven a p ortion of your audie nce.

• Pitfa ll : Humor Do : Dir ect it

at y ourse lf

, i f us ed. Don’t : Use it in re lation to safety, hea lth, or en viron men tal issues.

• Pitfa ll : Negative Allegat ions Do : Refute the allega tion witho ut repe ating it. Don’t : Rep eat or refer to th em.

• Pitfa ll : Negative Wo rds and Phrases Do : Use po sitive or neutral terms. Don’t : Refer

to nat ional problems (probl ems unrel ated to t he iss ue at hand), i .e., “This i s not Love Canal .”

• Pitfa ll : Reli ance on Words Do : Use vi suals to emphasi ze key poi nts, but be cul tural ly cor rect f or the au dience. Don’t : Rely en tirely on w ord s.

• Pitfa ll : Temper Do : Remain c alm. Use a que sti on or all egati on as a spr ingboard t o say somet hing posi tiv e. Don’t : Let you r feelings in terfere w ith your a bility to co mm unicate positive ly.

• Pitfa ll : Clarity Do : Ask whether you have made yourself clear. Don’t : Assum e you h ave b een un dersto od.

• Pitfa ll : Abstract ions Do : Use examples, stories , and analogies to est ablish a common understanding, but test them out fir st to make sure t hey are clear, make your poi nt, and are cul tural ly ac ceptable.

• Pitfa ll : Nonverbal M essages Do : Be sensiti ve to nonverbal messages you are communicating. Make them consistent wi th what you are saying. Don’t : Allow your body language, y our position in t he room, or your dress to be inconsistent with your message.

• Pitfa ll : Attacks Do : Att ack the iss ue. Don’t : Attack the pe rson o r orga nizatio n.

• Pitfa ll : Promises Do : Promise o nly what you can d eliver. Set and follow strict ord ers. Don’t : Make pr omise s you can’ t ke ep or f

ail to f oll ow up.

• Pitfa ll : Numbers Do : Emph asize perform ance, trends, and achievem ents. Don’t : Focus on or emp hasize large nega tive numbers.April 2004 Page 29-11 Exhibi t 29-2. Present ation Dos and Don’ts (cont inued) Pitfa ll : Guarantees Do : Emph asize achievem ents made and on going efforts. Don’t : Say ther e are n o gua rantee s. Pitfa ll : Specul ation Do : Provide i nformat ion on what is bei ng done. Don’t : Spec ulate ab out wo rst case s. Pitfa ll : M oney Do : Refer to the imp ortan ce you attach to health, sa fety, and e nviro nme ntal issues; yo ur first ob ligation is to public health. Don’t : Refer to the am ount o f mon ey spe nt as a re prese ntation o f your co ncern . Pitfa ll : Orga nizational Identity Do : Use personal pronouns (“I,” “we”). Don’t : Tak e on th e iden tity of a large orga nizatio n. Pitfa ll : Blame Do : Tak e re spon si bil it y f or y our sha re of

th e pro ble m. Don’t : Try to shift blam e or re spo nsibility to o thers.
Pitfa ll : “Off the Rec ord” Do : As sume e very

thi ng y ou say

and do i s par t of

the publi c recor d. Don’t : Ma ke side com men ts or “co nfiden tial” rem arks.
Pitfa ll : Risk/

Benefit /Cost Comparisons Do : Discuss ri sks and benefits carefully (consider putting them in separate communications).
Pitfa ll : Risk Comparison Do : Use th em to help put ris ks inperspective. Don’t : Comp are unrelated risks.
Pitfa ll : Health Risk Numbers Do : Stress tha t true risk is b etwee n zero and th e wo rst-case e stimate. B ase ac tions o n fede ral and state standards, whe n possible, rather than risk num bers. Don’t : State ab solutes o r exp ect the la y pub lic to und erstand risk num bers.
Pitfa ll : Technical Detail s and Debates Do : Focus your remarks on empathy, competence, honesty, and dedication. Don’t : Pro vide to o mu ch de tail or take part in p rotrac ted tec hnical d eba tes. Pitfa ll : Length of

Present ations Do : Limit presentations to 15 minutes. Don’t : Ram ble o r fail to pla n the time well. Source: ATSDR R isk Communication Primer (2)April 2004 Page 29-12

Exhibit 29-3. The “Five Fs” of Media Relation s Fast . Resp ect journalists’ d eadline s. I f a journa

list tele phones for info rmatio n, retu rn the c all immediately , even if it is pa st normal office ho urs. A phone m

essage returned the n

ext day is often to o late. By then, the story already may ha ve been aired or printed. Factual . Be factual, and make the facts interesting. Stories are to be based on facts. Journalists also appreciate a dramatic statement, creative slogan, or pers onal anecdote to help illustra te your point. Give the source o f any facts and statistics provided. Frank . Be c andid. Nev er mis lead jour nalists. Be as open as

possib le and r

espond frank ly to t heir questions. As long

as there is an explanation of the reason, m

ost journalists will understand and respect a sourc e even

if he or she is n ot able to answ er a que stion complet ely or at all. Fair . Organiz ations should be fair to journalists if they expect journalists to b e fair to them. Favoring one news outlet consisten tly, for exam

ple, will lose the confide

nce of the others. Friendly . Like everyone else, journalists appre ciate courtesy. R emember their names; read w hat they write; l isten to

what they say ; know

their in terests; thank

them when t hey cover th e issues

in a factual, unbia sed way.April 2004 Page 29-13 Additional Suggested

References Calow, P. 199 7. H andbook of Environm ental Risk Assessment a nd Management . Black well Publishers. Crawford-Bro

wn, D. 1999

. Risk-based Environme ntal Decisions: Culture a nd Methods . Kluver Academic Pub lishers. Johnson, B.B. , Sand

man, P.M., and Mill er, P. 1992. Testing the Ro le of Technical I

nformation in Public Risk Perception by RI SK. Issues i n Healt h and S afety , Fall 1992:341- 364. Lundgren, R. E. 1994. Risk Communication : A Handbook for Communicating Environmental, Safety, and Health Risks . Battelle Press , Columbus, OH. Langford, I an. 2002. A

n existential approach to risk perception. Risk Analysis 22(1):101-120. U.S. Environ

mental Protection A

gency. 1 992. Air Pollution and the P ublic: A Risk Comm unication Guide for State and L ocal Agencies . EPA 450/3- 90/025. For an additional list of risk commu nication references, see http://w ww.ps andman.com

/articles /cma- bibl.ht m . Exhibit 29-4. Interviewing Techniques

• Always think

carefully before y

ou answer a question. People often ram ble - and sa

y something they wish they

hadn’t if they answer too quickly . Take a m oment to conside

r what you want to say. If you need more tim

e, ask for the q

uestion to be repeated.

• Don’t talk just to k

eep a conversation going with a reporter. Experienced reporters will be silent because often people they interview will talk

to fill awkward voids and then s ay somethin g they don’t mean to sa y.

• Ask the re porte r to make your affil iatio n clear in the s tory.

• Listen carefully to qu

estions and respond clearly . Avoid jargo n. If y ou have a k

ey idea that y

ou want to get across,repeat it several tim es, perhaps using

different words. This is es pecially useful for broa dcast: n o mat ter how the tap e is edi

ted, y ou will mak e you r point.

• Don’t hurry: speak

slowly, and in

short, concise sentences. State your po sition in simple, easy-to- understand language. Use every day exam ples and analogies, when possible.

• Never talk d own to a report

er. Yo u are pa rtners in gettin g yo ur me ssage

across. Arrog ance wi ll come across neg

atively to an audience. An “attitude” can turn an interv

iew into a confrontation.

• Don’t l ose yo

ur tem per! No mat

ter how antag onize d you

feel, r ecogn ize th at this c an be a tactic to get you to say someth

ing you d o not wish to say

.

• If you don’t know the answer to a reporter’s que stion, or cannot answe r, just refrain from answer ing. A lie or bad gue ss will retur n to hau nt you. You will lo se cre dibil ity.

• Some reporters m

ay ask to ta

pe an interview over the telephone. This is a comm on practice for radio reporters to obtain “sou nd bites” and to g et accurate quotes. The repo rter should inform you of the t aping before it beg ins. D o not re peat an alleg ation – it could

be tak en out o f contex

t.April 2004 Page 29-14 1. U.S. Environmental Protection Agency . 1995. Policy for Risk Characterization (“Browner Memoran dum”). Sc ience Pol icy

Council, Wa shington , DC., Mar ch 1995. A

vailable at: http://64.2.134.196/committees/aqph/rcpolicy.pdf 2. Agency

for Toxic Substances and Diseases Registry (ATSDR). 1994. Tools and Techniques for Effective Health Risk Communication . This is an update of the ATSDR Primer onHealth Risk Communication Principles and Practices , Octobe r 1994. Available a

t: http://www.atsdr.cdc.gov/HEC/primer.html#EARNING 3. Covello, V.T., Sandman, P

. 2001. Risk c ommunica tion: Evolu

tion and Re

volution, i

n Wolbarst A. (ed.). Solutions to an Enviro nment in P

eril . John Hopkin s Univers ity Press, Baltimor e, MD: pp. 164-178. Availabl e at: http://www .phli.org

/riskcomm

unication/articl e.htm 4. Fischhoff B, Lic

htenstein S, Slovic P, Keeney D. 1981. Accepta ble Risk . Camb ridge Universi ty Pr ess, Cambr

idge, Ma ssachuse

tts. 5. Covello, V.T., Sandman, P.M., Slovic, P. 1988. Risk Communication, Risk Statistics and Risk Compa risons: A M

anual for Pl

ant Manage

rs . Chemical Manufacturers Association, Washingt on, D.C., 1 988. Avai lable at: http://www .psandma n.com/ar ticles/cma-0.htm 6. Cutlip, S.M., Center, A.H., and Broom, G.M. 1985. Effective Public Relations

. Pr en ti ce -H al l, En gl ew oo d C li ff s, Ne w J er se y. References

# PART VI

SPECIAL TOPICS

# Introduc tion to P art VI

Part VI of this Ref

erence Manual pr

ovides an overvie w of thre e specia

l topics re lated to a

ir toxics risk a ssessmen

t.

• Public He alth Asse ssment (Chapter 30 ) provide s an over view of the proce ss by

which pub lic health a gencie s may

evaluat e the publ ic health

implications posed by the emission s from air toxic sourc es in a community . The publ ic health assessme nt, if per formed, is a compleme

ntary process to risk ass essment.

• Probabili stic Risk As sessment ( Chapter 3 1) discus ses the pr ocess by which pr obability distributi ons are u sed to cha racter ize varia bility or uncer tainty in risk est

imates, a process aimed at d

escribin g risks a s a distrib

ution (or range ) of pote

ntial outc omes.

• Use of Geographical I nformation Systems (GI S) in Risk Assessment (Chapter 32) provides an overview of the software and g eographic data that allow effic ient storage, analysis, and present aiton of s patially explicit an

d geog raphica lly r efere nced inf ormation t

hat can help in the proc ess of conducting risk asse ssments an

d report ing res ults

# Chapter 3 0 Public Health Asse ssment

Table of Contents

30.1 Introduction

............ ............ ............ ............ ............ ...... 1 30.2 History of Public Health Assessme nt
............ ............ ............ .......... 2 30.3 Relationship of Public H ealth Assessment to Risk Assessm ent
............ ............ . . 3 30.4 What I s Publi c Healt h Asses sment?

............ ............ ............ ........... 4 30.5 How Is a Public Health Assessm ent Conducted?

............ ............ ............ . 6 30.5.1 Conduct Scoping

............ ............ ............ ............ ....... 6 30.5.2 Obtain Study A

rea Inform

ation

............ ............ ............ ........ 7 30.5.3 Commu

nity Inv olvement/Ou

treach/Response to Com

munity C oncerns ............ . 7 30.5.4 Exposure Evaluation ............ ............ ............ ............ .... 8 30.5.5 Health Effects Evalu ation

............ ............ ............ ............ 9 30.5.6 Draw Public Health C onclusions

............ ............ ............ ...... 12 30.5.7 Recomm

end Public Health Actions

............ ............ ............ .... 13 30.5.8 Prepare

PHA D ocuments
............ ............ ............ ............ 13 References

............ ............ ............ ............ ............ ............ 14April 2004 Page 3 0-1 30.1 Introduction An adjunct to conducting air toxic risk assessments is public health assessments, which uses public health tools (e.g., health questionnaires, epidemiology ) to investigate the incidence and prevale nce of di sease a

nd to find o

ut the cur rent or p ast heal

th of individuals. Whil e public health methods are not always used for air toxics risk assessments, they ca n provide useful informat ion to answer the qu

estion of whether there is e vidence that ther e is a publ ic health concern, particularly

if disease rates are elevated in the a ssessment area. Air toxics r

isk asses sment, the

main topic

of this man

ual, foc uses on as sessing

the poten tial risk that people have for experiencing adve rse health effects from exposure to air toxics. The outcome o f a risk a ssessmen t is a state ment abou

t the likel ihood that

exposure may

result in disease (e.g., the probability of people developing cancer ). The risk assessment process links the potentia l exposure s to emissions from (o ften) sp ecific s ources t o the like lihood of d

isease occurring. Howeve r, in any community

, conce rns about more tha n just estimates of the likeliho od of risk often come up. For example, communities where risk assessments are being performed often express concern about current health eff ects that may have

resulted from past exposures. Questions like “was my ca ncer caused by

air pollution” are often on the minds of people who live where an air toxics risk assessment is being performed. The risk a ssessmen

t proces s, while a

powerf ul predictive tool f

or evalu ating pu blic hea lth impacts f rom air po llution, is n

ot amena ble to answering

these ty pes of que stions. Ne

verthel ess, questions about dise ase and p ast exposur es will ine

vitably come up a s the air t

oxics risk assessme nt study moves for

ward. The risk as sessment a nd risk ma

nageme nt team wi ll almost always have

to explain that their assessment tool (risk assessment) is not being used to answer questions about existing cases of disease. To help risk assessors and other stakeholders respond to these ty pes of questions, this chapter provides information on a complementary process to risk assessment called Public Health Assessm ent

or PHA . It is

taken la rgely from the A

TSDR Public Health Assessment Guidance Manual

. (1) A PHA for air toxics is an analysis and state ment of the public health implications posed by a source or grou p of sourc es of air

toxics on a g

iven ge ographic are a. I

t usually is conducte d by

a public health ag ency

such as the Agen

cy for Toxics

Substance s and Dise ase Registry or

ATSDR (a federal Agency within the Centers for Disease Control and Prevention) or one of the ir partne

r state or local pub lic healt

h agencies. PHA s are not generally performed by EPA or state, local, or tribal air agencie s since PHAs often rely on specialized medical and epidemiological expertise and due to the difficulty facing these age

ncies in obtaining and reviewing medical information for individuals. PHAs are norma lly performed:

• In re sponse to a

request by c oncerne d community members or phy sicians;

• In re sponse to a

real or percei ved incr ease in a health pr oblem note d during

routine d isease surveillance syste

ms; and/or

• As pa rt of

a b ro ad er pr og ra m s uc h a s a pr oa ct iv e a na lys is of re gi on -s pe ci fi c a ir qu al it y.April 2004 Page 3 0-2 PHAs are perform

ed by ATSDR at each Superfund site on the National Priorities List. ATSDR also perform s PHAs when p etitioned. The term public health assessment ( PHA ) as used here, refers to a b

road range of assessm ent ty pes – fr om screening -lev

el healt h consul tatio ns to co mprehen sive epidem iologi cal asse ssmen

ts – tha t are common ly performed by ATSDR in its work. The PHA process, w

hile comm

only though

t of as a Su perfund -rela ted acti vity , is am

endable to a wide range of exposure scenarios, includi ng the evalu ation of air toxics im

pacts at the c omm

unity level.

The earli

est “bad air ”? The ty pes of ai r toxics ass essments m

ost likely to include a PHA are

those whe

re the po llutants have a clearly

identifiable effect, where the exposure is relatively widespre ad, or where there is a high level of public concern. A

PHA will not nece ssarily

be need ed ever y pl ace an a

ir toxics risk assessment is performed. However, the use of the PHA pr

ocess, in conjunct ion with the risk assessment process, is becoming a more common practice for the purpose of providing holistic evaluations of air toxics impacts on communities. A PHA may involve an a ssessment of relevant environmental data , health outcome data (e.g., cancer statistics), and comm unity conc erns generally associated with a study a rea where air toxics are or have been released. A PHA identifies populations living or working on or near areas f or which more exten sive publi c health actions or studies a

re indic ated and

is gene rally more qua litative, more foc

used on a ctual, me asurabl e harm, a nd past an

d curre nt exposure s. This chapter desc

ribes the history of PHAs, w

hat they are, how they compare to and wor

k in concer t with risk a ssessmen

ts, and how

they are con ducted. S everal

case stu dies are included to help illust rate the diversity of PHAs an

d how they

compare with and a

re used w ith risk assessme nts. 30.2 History o f Public He alth Asses sment PHA as a tool for characterizing and prote cting the health of a society can be traced back thousands of year

s. The ancient Baby

lonians, Egyptians, Gr

eeks, and Romans were among the first known civilizations to describe associations between diseases and sources such a s place, water conditions, climate, eating habits, and housing. One of the first documented public health “assessments” (though later proven incorrect) connected the prese nce of “bad air” around swamps and marshes with the pr

evalenc e of mala

ria, one of the world’s most devastating diseases. (I

t was determined later that the prevalence of malaria was associated not with air, but with mosquitos, the transmission vector for the disease, which breed in standing water associa ted with those plac es.) I

nfectio us diseas es contin

ued to dominate public health concerns until the industrial revolution, although the problems of poor urban air quality from the use of coal were well documented as ear ly as the end of the

16 th ce nt ur y. The mode rn use of PHA for a

ir toxics in the U.S. pro

bably began in the mid- 1900s in re sponse to events su ch as the incapac itating smog epis odes in Los Ange les in the 1 940s, the p olluted a ir inversion that killed 20 people in Donora, Pennsy lvania in 1948, and the atmospheric nuclear weapons tests in Nevada in the 1950s. My riad state and local public health agenc ies shouldered much of the burden of air pollutant health assessment at first. Then, at the fe deral level, the Federal Air Pollution Control Act of 1955 authorized the Public Health Service (PHS) to conductApril 2004 Page 3 0-3 research and technical assistance and work towards a better understanding of the causes and effects of air pollution. In 1980, ATSDR was create d specifically to c onduct PHAs at hazardous waste (Superfund) sites. That role has expanded over time to address additional pollution sources, including air toxics. ATSDR is not

a regu latory agenc y lik e EPA, but r

ather is a public he alth ag ency

that cond ucts assessments and makes recommendations to EPA and others when specific actions at study are as in question are needed to protect the public’s health. ATSDR conducts PHAs when pe titioned by concerned community

members, physicians, state or federal agencies, or

tribal governments. State and local pub lic healt

h agencies also

play an importa

nt role wi th rega rd to PHAs f

or air toxics and o ther haza

rds. 30.3 Relations hip of Public H ealth Asse ssment to Risk Ass essme nt Both the PHA and the quantitative risk assessment address the potential human health ef fects of environmental exposures, but they use diff erent approaches and have diff erent purposes. As illustrate d in Exhibit 30 -1, the PH A tends to b e less qua

ntitative than the r

isk asses sment and

to focus mor

e on actu al past a nd curre nt exposure s. The PHA

evaluat es obser ved hea lth outcome and rela ted data (e.g. , cance

r cluster s, breat hing pro blems, toxic s residue s in biologic sample s) to determine whether rates of disease or death are or could be elevated in a c ommunity and, if so, whether these outcomes are due to a spec ific source. The risk assessment, on the other hand, starts with a specific source and evaluates e stimated potential health outcomes, or risks. The PHA’s subs equent c onclusion s gene rally compleme

nt the risk assessme nt proce ss and hel

p inform the decisions that the state, tribal, or local agency is reaching about a given study area. Similarly, the risk assessment provides considera ble data to the PHA. In a ddition to it s focus on

health ou tcome da ta, such a s cance

r or asth ma incide nce, the PHA also helps put community-provided data a nd information and community conce rns into perspective, which in turns helps both (1) the community better understand whether they have been exposed to hazardous substances and, if so, what that means in terms of possible health outcomes, and (2) the deci sion-mak

er bette r deter mine what

needs to b e done to p

revent or furthe

r study these exposures (e.g., emissions reductions, health education, biologic monitoring ). The PHA ma

y us e similar

techniqu es to those

of the qua

ntitative risk asse ssment, bu

t primari ly as tools e ither to c learly

rule out the existenc e of publi c health hazards, to deter

mine that a clinical disease is really likely in the com

munity , or to ide

ntify areas f or additional study . At a minimum, the PHA helps to identify a baseline in the level of disea se in a community so that later studies will have a basis for comparison.April 2004 Page 3 0-4 ATSDR Definiti on of PHA The evaluation of data a

nd information on the release of hazardo

us substances into the enviro nmen t in ord er to as sess any

[past], current, or future im

pact on public health, develop health adv

isories or other recommen

dations, and identify

studies or actions needed to evaluate and mitig ate or prevent hum

an health effects (42 Code of Federal Regulations , Part 9 0, pub lished i n 55 Federal Register

5136, February

13, 1990). Exhibit 30-1. PHAs and Risk Asses sments: Differences and Similarities

30.4 What Is Public Health Assessment? A PHA is an evaluation of relevant environmental data , health outcome data , and comm unity conc erns associated with a study area where hazardous substances ha ve been released. A PHA identifies populations living or working on or near area s for which more extensive public health actions or studies are indicated. PHAs can range from simple to complex, with the former activity of

ten termed a health consultation rather

than PHA. This more

simple form generally

is conducted in response to aApril 2004 Page 3 0-5 spe cif ic q ues ti on o r re que st for in for mat io n pe rta in in g to a ha za rdo us s ubs tan ce o r fa cil it y. It often contains a time-critical element that necessitates a r apid response. More complex forms of a PHA can involve a wide geog raphical area, many

pollution sources, and take months or ye ars to complete. Understanding and responding to study area-specific community health concerns is an important part of the PHA pro cess. Th ese inve stigations can be conducte d to confi

rm case reports , determine an unusual disease occurrenc e, and explore potential risk factors. One frequently cited concern is the disease cluster – the occurrence of a spec ific disease or condition above the expected number for a given ge ographic location and time period (e.g ., the high incidence of leukemia in a given area). The health agency

needs to learn what people in the area know a bout a source and sourc e-rela

ted exposur

es and what conce

rns they may have ab out its impa

ct on thei r health. Therefore, starting ea rly in the assessment proc ess, the health agency generally gathers information and comments from the people who live or work near the source(s), including area residents, civic leaders, health professionals, and community groups. Throughout the PHA process, the health agency should communicate with the public about the purpose, approach, and results of its public health activities. The PHA pr

ocess is it erative and dy namic an d may lead to a variety of produc

ts or public

health actions. The findi

ngs may be commun

icated in public he alth asse ssment or p ublic hea lth consulta tion documents, whic

h serve a s an aid f

or devel oping a

dditional p

ublic hea lth action s. The audi ence for such pr

oducts of ten inclu des envir onmental and public

health a gencie s, communities, and the public health agency itself. During the course of the PHA process, the public he alth agency may identify

the need to prevent or better define exposures or illnesses in a particular community . The agency ’s response to such a need might include:

• Issuing a public health advisory (if there is an urgent health threa t);

• Initiating an exposure investigation (to better define study area exposures);

• Recommending a health study (to identify eleva

ted illness or disease rates in a community ); and/or

• Cond uctin g health education (for the study area c ommunity

or healt h profes sionals wi

thin the community). The PHA pr

ocess al so can se

rve as a triage mechani sm, enabl ing the p ublic hea lth age ncy to prioritize and identify additional steps neede d to answer public health questions. The science of environmental health is still developing, and sometimes information on the health effects of certain substanc es is not a

vailable . When this o ccurs, r enderin g cert ain quest ions unanswerable by the available

literature, the public health agency will suggest what further resea rch studies and/or health education services are ne eded.April 2004 Page 3 0-6 30.5 How Is a Publi c Health A ssessm ent Conducted? PH As ge ne ra ll y ar e c on du ct ed by p ub li c h ea lt h a ge nc y as se ss or s, of te n s up po rt ed by a multi-disciplinary team of scientists, health communication spec ialists, health educators, and/or medical p rofessionals. The

health a gency solicits a nd evalua tes infor mation fr om other lo cal, state, tribal, and/or federal age ncies; parties responsible for operating sourc es at a particular study area; and the community . All of these stakeholders play an integral role in the PHA process. The public health agency

promotes a team approach to ensures that information used in the assessment is accurate and up-to-date, ensur e that community conce

rns are identified and address ed, and f

osters c ooperat

ive eff orts in impl ementing

recomme ndations a

nd public health activities. Many technica

l resources exist that provide details about conducting a PHA (see Exhibit 30-2), and, thus, only

a broad overview

is provide d here. One of the most compr

ehensive resourc es is the ATSDR Public Health Assessment Guidance Manual

. (1) The ATSDR manual focuses on site-spe cific PHA s such as Su perfund sites; nev erthele ss, it also c an be use d to asses s air emissions within a limited geographical area. As de scribed in detail in the ATSDR manual, the steps of a PHA — whether conducted by ATSDR or a state or local public health agency , and whether comprehensive or limited to a screening assessment – can be multifaceted and interactive. Exhibit 30-3 illustrates this by providing an over view of a typica

l PHA process. The following subsecti ons descr

ibe this pr

ocess in more deta

il. 30.5.1 Conduct Sc oping The first step is to establish an overall understanding of the study area and begin to identify the most pertinent issues. The objective is to quickly g ain some baseline information about the study area and start developing a stra tegy for conducting the PHA. To help ensure a c onsistent approach across study

areas, the following steps are followed dur ing this initial phase:

• Initiate study

area scoping by

performing an initial review of permits and other sour ces of study area information, identifying a ny past health ag ency or pa rtner activities, identifying and commu

nicating with study

area c ontacts, and dete

rmining the need for a stu dy a rea visit to observ e actua

l condition s and spea

k with study

area r eprese ntatives.

• Define roles and responsibilities of team members (internal and e xternal).

• Establish communication mechanisms (internal and external) by developing a schedule for team meetings, thinking about how to present the findings of the assessment, and developing health c ommunica

tion strat egies.

• Develop a study a

rea strategy

for completing the various steps in the PHA process and develop a strategy, identifying the tools and r esources that might be needed to evaluate the study area, c ommunica

te the fin dings, a nd impleme

nt public health actions.

• Based on information obtained during study area scoping, develop an appr oach that focuses on the most

pertine nt public health issu

es.April 2004 Page 3 0-7

Exhibit 30-2. Selected Public Health Assess ment Resources

• Agen cy for Toxic Su bstance s and D isease R

egistr y (ATS DR; www.atsdr.cdc.gov ), which publishes the Public Health Assessm ent Guidance Manual (curren t draft i s avai lable on

line; Guidance for ATSDR Health Studies (1996; available on line), Environ mental Data N eeded f or Publ ic Heal th Assessm ents (1994, available online), and other g uidance.

• Nationa

l Institute o f Environmental H ealth Sc iences ( NIEHS; www.niehs.nih.gov ), which publishes Environmental Health Perspectives and sponsors m ultidisciplinary biom

edical research, prevent ion and inter ventio n effor ts, and communica tion st rategi es that encompas s trai ning, technology tran sfer, and comm unity outreach.

• Amer ican Pu blic He alth As sociation (APH A; www.a

pha.or g ), which publishes the

American Journa l of Pub lic Hea lth and provides m any other resources related to environm ental public health.

• Nationa

l Assoc iation o f Count

y and City Health Official s (NAC CHO; www.n accho. org ), which publishes the Protoco l for As sessing Comm unity E

xcellenc e in En vironm ental H ealth (2000) and Assessm ent to A ction: I

mprovi ng the H ealth of Comm unity A

ffected by Haza rdous W

aste(2002)

.

• Nationa

l Assoc iation o f Local

Boards of Hea lth (NA LBOH)( www.n

alboh. org ), which main

tains an up-to- date database of contact info rmation for all local boards of health, prov ides technical assistance to existing b oards of health, and w ill soon publish the Environmental Health Primer

. 30.5.2 Obtain Study Area Information Throughout the PHA process, various team members will collect infor mation about the study area, although the initial collection of information is ty pically the most intensive. I nformation sources typ ically include i ntervie ws (in-pe rson or vi a telephone); stu dy a rea-sp ecific investig ation re

ports pre pared by federa l, state, a nd local e nvironme ntal and health de

partmen ts; and study are a visits. Gathering pertinent study area information requires a series of iterative steps, including gaining a basic under standing of the study a

rea, identify

ing data needs and sources, conducting a study area visit, communicating with community members and other stakeholders, critically

reviewing study

area documentation, identify ing data gaps, and compiling and org anizing r

elevant data to su

pport the assessme nt. 30.5.3 Comm unity Involve ment/O utreach /Response

to Com munity C oncerns The community associated w ith a study area

is both an important resource for and a key audience in the PHA process. Community involvement activities should be developed a nd implemented with the following objectives in mind:

• Earning

trust and credibi lity

through open, compassiona

te, and r espectf ul communic ations.

• Helping community membe rs understand what the PHA process involves and what it can and cannot do.

• Providing

opportuni

ties for c ommunities

to become

involved i

n the PHA a

ctivities

. • Promoting

collabor ation bet ween the public he alth ag ency , communiti es, and o ther ag encies.

• Informing and upda

ting communities about the health agency ’s work.

• Assisting communities in understanding the possible health impact of exposures to hazardous substanc es.April 2004 Page 3 0-8

Exhibit 30-3. Overview of a Typical Public Health Assessmen t Process

Chapter 2 8 of this re ferenc e manual provides a more de

tailed dis cussion of

community involvement and outreach. 30.5.4 Exposure Evaluation For the exposure evaluation, public health assessors review e nvironmental data to determine the sources of pollutants and exposure pathway s/routes. The conceptual model described in Chapter 6 should be

a reasonable sta

rting po int for the

PHA exposur

e evalua tion. Generally

, the publi c health agency

involved does not collect its own environmental sampling data, at least at first, but rather reviews informat ion provid

ed by federa l, state, a nd local governme

nt agen cies and /or their contractors, businesses, and the public. Assessors can indicate wha t further environmental sampling may be

needed and may

collect environmental and biologic samples when appropr iate. This step i

nvolves two key

substeps:April 2004 Page 3 0-9 Exposure Inv estigations When a PHA expos

ure evaluation conclu

des that add itional exposu

re infor mation is needed, an exp osure in

vestigation g enerally

is conducted. An ex

posure investiga

tion is the collecti on and analy sis of s tudy area- specific information to determ

ine if human populations have b een exposed to air toxics. This information m

ay include env

ironmental sampling, exposure-dose reconstruction, biologic or biom

edical testing, and/or evaluation of m

edical information. • Evaluate Environmental Contamination Data . This step involves determining what pollutants people ma

y be exposed to a

nd in what concentrations. This evaluation involves assessing the quality a nd representativeness of available monitoring data and measurements or modeled estimates of exposure point concentrations. This is an important way to ensure that any public he alth conclusions and recommendations for the study area are based on appropriate and reliable data. Both sampling data and modeling techniques described in Chapters 9, 10, 18, an d 19 are s ometimes u sed to ge nerate data for PHAs. Evaluation of environmental contamination data ty pically proce eds simultaneously with the exposure pathway evaluation.

• Characterize Exposure Pathways . During the exposure pathway characterization, the asses sor ev aluat es who may be or ha s been expo sed to stud y area cont amina nts, for ho w long, and under what conditions. This involves identifying and studying the f

ollowing five components of a “complete” exposure pathway : a source of air toxics; a mechanism for release into the air and, in some cases, transfe r between media (i.e., the fate and tra nsport of environmental contamination); an exposure point or area; an exposure route (e .g., ingestion, dermal c ontact, i

nhalation); and a

potentia lly e xposed popu

lation. The overa

ll purpose of this evaluat ion is to und

erstand how peopl e might b ecome exposed to stu dy a rea con taminants and to identify and cha

racterize the size and susceptibility of the potentially exposed populations. If no complete or potentially complete exposure pathway s are identified, no public health hazards exist and there is no need to perform further scientific e valuation. When complete environmental or biologic data are lac king for a study

area, an exposure investigation may be

recommended to better assess possible impacts to public health. 30.5.5 Health Effects Evaluation If the exposure evaluation shows that people ha ve been or could be exposed to pollutants such as air toxics, the public

health a ssessor w

ill evalua te whethe r this con tact cou ld have r esulted in harmful effects. Assessors use existing scientific information to determine the health effects that may result from e

xposures. Public health agencies recognize that childre n, because of their play activities and their growing bodies, may be particularly

vulnerable to exposures to air toxics. Developing fetuses also may be more vulnerable to such exposures. Thus, the impact to children and developing fetuses is considered first when e valuating the health threat to a community . The health effects evaluation is composed of two basic substeps: a scr eening analysis and a more indepth ana lys is.

• Screenin g Analysis . Screening is a first step in understanding whe ther the detected concen trations t o which pe ople may

be exposed

are har mful. The

screen ing ana lys is is a fairly standar

d process developed to help health assessors sort through the large volumes of environmental data for a study area. It ena

bles the assessor to safely rule out substances that are not at levels of health concern and to identify substances and pathway s that need to beApril 2004 Page 30-10 examined more closely. F or complete or potential exposure pathways identified in the exposure p athway

evaluat ion, the sc

reening analy sis may involve c omparing

media concen trations a t points of e

xposure to “ screen

ing” va lues (ba sed on protective d efault exposure assumptions) and estimating exposure doses based on study area-specific exposure condition s. The as sessor th en compa res estimated dose s with hea lth-base d guide lines to identify substances re quiring further evaluation. Exhibit 30-4 describes several of the ATSDR-derived comparison values available. See Chapter 12 f or how these values are used in an air toxics risk a ssessmen

t.
Exhibit 30-4. Definitions of ATSDR-Der ived Comparison Va

lues Environmen

tal Media Evaluation G

uides (EMEGs) . EMEGs are estim ated contaminant concentrations that are not ex pected to result in adverse noncarcinogenic health effects based on ATSDR evaluation. EMEGs are based on ATSDR MRLs an d conservative assumptions abou t exposu re, such as int

ake ra te, exp osure fr

equency and du ration, and bo dy we ight. Minimal Risk Levels (MRLs) . An MR L is an estimate of d

aily h uman exposu re to a s ubstanc e (in mg/kg/d ay for oral expo sur es an d par ts pe r mill ion [ ppm] for inhalation exposures) that is likely to be without noncarcinog enic health effec ts during a specifi ed duration of exp osure based on ATSDR evaluations. Cancer Risk Ev

aluation Guides (CRE Gs) . CREGs are estimated contam inant concentrations that would be expected to cause no more than one excess cancer in a million (10 -6 ) persons exposed during their lifetime (70 y

ears). ATSDR’s CR

EGs are calculated from

EPA’s cancer slope factors (CSFs) for oral exposures or unit risk values for inhalation exposures. These va lues are based on EPA evaluations and assu

mptions about h

ypothetical cancer risk

s at low levels of exposure. Reference Media Evalu

ation Guides (RMEGs) . ATSDR derives RMEGs from EPA’s oral reference doses, which are dev

eloped based on EPA evaluations. RMEGs represent the con centration in water or soil at which daily

human expo sure is unlikely to result in adverse n oncarcinogenic effects.

• In-depth Ana

lysis . For those pathway s and substances that were identified in the screening analy sis as req uiring more car

eful con siderati on, the as sessor wi ll examine a host of fa

ctors to help dete rmine whe

ther stud y a rea-sp ecific e

xposures a

re expected to re sult in illne ss. In this in-depth analysis, exposures are studied in conjunction with substance-specific toxicologic, medical, and epidemiologic data. Throug h this analysis, the assessor will be answe ring the following question: Based on available exposure, toxicologic, epidemiologic , medical, and study area-specific health outcome data , are adverse health effe cts expected in the co mm un it y? Answering this last question can be very challenging. For example, evalua ting epidemiological data involves addressing a number of criter ia to assist in judging the causal significance of associations revealed in studies (epidemiology is described in more detail in Exhibit 30-5). Individual criteria, if met, support a c ausal relationship but do not prove it. The more criteria that are met, the more likely

it is that an observed health effect is causally related to the exposure under study. The c

riteria for evaluating causation ar e:

• Time sequence . Exposure must precede the onset of the disease. A logica l sequence of events must be demonstrated.April 2004 Page 30-11 Exhibit 30-5. What Are Epidemiolog ic Data and How Might They Be Used in an In-Depth Analysis? Epidemi ologic data ar e one of the key dis tingui shing fe ature s of PHAs compared to most qu antit ative risk a ssessm

ents. U ndersta nding the stre ngths and we aknes ses of t

he var ious ty pes of e pidem iologi c studies will help determ

ine the suitability of a particular study in sup porting and drawin

g study area and substance- specific public health conclusio ns. Because of the inherent limitations and uncertainties associated with en vironmental e

pidemiologic evaluations (gen erally due to the lack

of adequate exposure data o r sample size ), however, epidemiologic data shou ld be used with cautio n . The health assessor should call upon an epidem iologist to assist in ev

aluating the applicability

and usabilit y of li terature -bas ed or st

udy a rea- specific

epidem iologi c data. The ty

pes of e pidem iologi c data that may

be available and how they m ay be used are briefly summ arized below, in order of greate st pote ntial utili ty:

• Analytical studies , such as case- control or coho rt studi es, evaluate t

he role of var

ious ris k fact

ors in causi ng ill ness or disease

by re lying

on com parison s betwe en gro

ups. D ependin

g on t he qual ity of the study, it m

ay provide in sight to the study area-specific exp osure situation under ev aluation. Study area- specific

analy tical stu dies tha t meet certain

desig n criter ia exam ine stud y area-spe cific exposures and health ou

tcomes in com

munity m embers. When available, these studies are the most relevant to the PH

A. These data are rarely

initially available, but the PHA pro cess may lead to a recom mend ation to collect such d ata. D ependin

g on t he indiv idual st udy d esign and hea

lth outcome studied,results may provide som

e insight on the p

resence or absence of a particular illness of concern in the c ommunity . Unfortunately, establishing a definitiv e link with a stud

y area-related exposu

re is generally difficult if not impossib le.

• Descriptive (or ecological) studies examine differences in disease rates am

ong populations over time or in different g

eographical locations an

d may b e helpful in identifying plausible associations between a particular substan ce and disease. Ho

wever, descriptive studies provide lim ited inform ation on causal relation ships (i .e., the degr ee of ex posure or caus al age

nt).

• Case re

ports that describe an effect in an individual or sm all group can be considered in the indepth analysis, bu

t may hav e limited usefulness due to the generally small size of the affected population and som

etimes anecdotal natu

re of the reports.

• Strength of association . The stronger the association, the more likely it is causal. The relative magnitu de of the incidenc e of dise ase in tho se exposed compare d to the inc idence i n those who are not exposed can be a valuable measure of the strength of the association.

• Dose-r esponse r elationshi p . The pro

bability and/or se verity of the ef fect sho uld incre ase with increasing intensity

and duration of exposure.

• Specificity of association . If the effe ct is unusual or is specific to the studied exposure, a causal relationship is more easily demonstrated.

• Consistency . A relationship should be reproducible (i.e., observed in other studies or analyses).April 2004 Page 30-12 • Biologic pla usibility (o r coher ent explan ation) . The link between the “cause” and the effect should make sense biologically , by what is known about the disea se and the exposure under stu dy. The findi

ngs shou ld be vali dated by

what is known about a

nimal mode ls. Similarly, biologic sampling re sults (biomarkers) need to be interpreted with caution. Specific ally , issues to

consider include: (1) as wi

th environmental sa

mpling da

ta, biolog ic data need to be

collecte d by

trained profess ionals an

d analy zed in a sta

ndard wa y; (2) detected leve ls may not be the re sult of study area-related exposures (e.g., blood lead levels resultingfrom nonair toxics sources such as flaking paint); (3) results will likely only repre sent a snapshot of conditions in time; (4) the association between detected levels and clinical e ffects may not be understo od based

on scient ific know ledge; (5) “nor

mal” ran ges, pa rticular ly f or trac e eleme

nts, may not be known; and (6) the people tested may

not be fully repre sentative of the exposed population, resulting from a small sample size and variations in exposures across the exposed population due to dif

ferent activity pattern s. 30.5.6 Draw Publi c Health C onclusions Upon completing the exposure and health effects eva luations, the assessor will draw conclusions regarding the deg

ree of hazard posed by

a study are a - that is, they will conclude either that the study area do es not pose

a public health ha

zard, tha t the study

area do es pose a

public he alth hazard, or that insufficient data are available to de termine whether any

public health hazards exist. The process also involves assigning a hazard conclusion categoryfor the study ar ea or for an individual exposure pathway (Exhibit 30-6).
Exhibit 30-6. Summary of ATSDR C onclusion Categories Category Definition 1. Urgen

t Public Health Hazar

d Applies to study areas that have certain physical hazards or evidence of short-term

(less than 1 year), study area- related exposure to hazardous substances that could resu lt in adverse health effects a nd require quick intervention to stop people from being exposed

. 2. Public Health Hazard Applies to study areas that have certain physical hazards or evidence of

chronic, study area-

related exposur

e to haz ardous substa nces tha t could result i n adver se healt h effect s . 3. Inde termin ate Public Health Hazar d Applies to study areas where critical information is lacking (missing or has not ye t been gathered

) to sup port a jud gme nt reg arding

the lev el of pu blic health hazard. 4. No Apparent Public Health Hazar d Applies to study areas where exposure to study area-related chemicals m ight have occurred in the past or is still occurring , but the exposures are not at levels e xpected to caus e adver

se healt h effect s . 5. No Pub lic Hea

lth Hazar d Applies

to stud y area s where

no exposure

to study area-

related hazardous substances exists.April 2004 Page 30-13 30.5.7 Recom mend P ublic Health Actions After drawing conclusions, the public health assessor – usually in coopera

tion with other team members and stakeholders – will develop recommendations for ac tions, if any, to prevent harmful e xposures, o

btain more

informat ion, or conduct othe

r public health actions. The se actions generally

will be detailed in a public health action plan, which will ultimately be part of the PHA document (or possibly the public he alth consultation document) developed for the study area. Note that some public health actions may be recommended earlier in the proce ss. See Exhibit 30-7 for an ov erview o f the con clusions a nd recom mendations proce ss. 30.5.8 Prepare PHA Docum ents The public

health a ssessor ma

y de velop var ious mater

ials durin g the PHA

process to communicate information about the assessment, including outreach mate rials, health advisories that aler t the public

and appr opriate officia ls to the exis tence of

an imminen

t public he alth thre at, and, at the end of t

he asses sment pro cess, a r eport tha t summarize s the appr

oach, re sults, conclusions, and recommendations. This report gener ally is either a public health assessm ent (PHA) document or a public health consultation (PHC).

Exhibit 30-7. Overview of Typical PHA Conclusion an d Recommendation ProcessApril 2004 Page 30-14 1. Agenc

y f or Toxic Sub stances

and Dise ase Registry

(ATSDR). 2002. Publi c Health Assessme nt Guidance Manua

l (Update ): Draf

t for Public

Comment.. A

vailable at: http://www .atsdr.c dc.gov /HAC/PHAMa

nual/cov er.html

. References

# Chapter 3 1 Probabilistic Risk Assessment

Table of Contents

31.1 Introduction

............ ............ ............ ............ ............ ...... 1 31.2 Tiered Approach for Risk Assessment

............ ............ ............ ......... 2 31.3 Methods for Probabilistic Risk Assessment

............ ............ ............ ..... 4 31.4 Presenting Results for Probabilistic Risk A ssessment
............ ............ ......... 6 References

............ ............ ............ ............ ............ ............ 10April 2004 Page 3 1-1 A detailed discussion of PRA is beyond the scope of this document. Two documents provide more det ailed intr oductory informat ion and g uidance and should

be revie wed if a P RA is contempl ated: U.S. EPA. 2001. Risk Assessment Guidance for Superfund (RAGS) , Volume III - Part A, Process for Conducting Probabilistic Risk Assessment . Office of Solid Waste and Emergency Response . Decem

ber. EPA 5 40-R-02- 002, OSWER 92 85.7-45, PB2002 96 3302, ava ilable at: http://www .epa.g ov/super fund/pro grams/

risk/rag s3a/index.htm. National Council on Radiation Protection and Measurements (NCRP). 1996. A Guide for Uncertainty Analysis in Dose and Risk Assessments Related to Environmental Contamination

. NCRP Commentary No. 14, May 1996. 31.1 Introduction Probabilistic risk assessment (PRA) uses probability distributions to characte rize variability or uncerta inty in risk est

imates. I n a PRA, one

or more v ariable s in the risk equation is defined as a probability distribution rather than a single number. Similarly, the output of a PRA is a rang e or probabil ity d

istribution of risks

experienced by

the rec eptors. N ote that the ability to perform a PRA often is limited by the availability of distributional data that adequately describe one or more of the input parameters. For example, data often a re insufficient to assess toxicity in a probabil istic manner (and theref ore, dose -respon se value s such as i nhalation unit risks

(IU Rs) and ref erence concen trations ( RfCs) are included in a PRA ana

lys is as point values). This gener al lack o f data imp acts both human hea

lth and ec ologica

l recep tors. The primary a

dvantage of PRA is that it can provide a quantitative description of the de gree of variabi lity

or uncer tainty (or both) in risk est

imates for both ca

ncer an d noncancer hea

lth effe cts and ecological hazards. The quantitative ana lysis of uncertainty

and variability ca

n provide a more comprehensive character ization of risk than is possible in the point estimate approach. Another signific ant adva

ntage o f PRA is the

additiona l informa tion and potential f

lexibility it affords the risk manager. Risk manag ement decisions are often based on an evaluation of highend risk to an individual – for deterministic analy ses, this is generally developed by the combination of a mix of central tendency and high-end point values for various exposure parameters (se e Part I

I, Cha pters 9 a nd 13). Whe

n using PRA , the risk

manage r can se lect a specific upper-bound level from the high-e nd range of percentiles of r isk, generally

between the 90 th and 99.9 th percen

tiles. PRA may not be app

ropriate for eve ry analy sis. The pr

imary disadvan tages o f PRA are

that it generally requires more time, resources, and expertise on the par t of the assessor, reviewer, and risk mana ger tha n a point e stimate a

pproach . The chi ef obsta cle to usin

g PRA in a

ir toxics risk assessments is usually the lack of well-documented frequency distributions for many input variabl es.April 2004 Page 3 1-2 Thi s ch apt er p rov id es a gen era l o ver vi ew o f PR A as it app li es t o ai r to xi cs r is k as ses sm ent . It revisits the tiered approach to risk assessment, introduces calcula tion algorithms, and identifies advanc ed statist

ical methods curr

ently availab le to support risk pol icy decision s. 31.2 Tiered App roach for R isk Assessm ent The tiered approach is a process for a systematic, informe d progression to increasingly more complex risk assessment metho ds includi ng PRA. Exhi

bit 31-1 pr

esents a schemat ic representation of the tiered approac h. Higher tiers reflect incre asing complexity and, in many cases, will require more time and resource s. Higher tiers also reflect incre asing characterization of varia bility and/or un

certain ty in the risk e stimate, w

hich may be importa

nt for mak

ing risk management decisions. Central to the concept of a systematic, informed prog ression is an iterative process of evaluation, deliberation, data c ollection, work planning, and communication. All of these steps should focus on deciding: (1) whether or not the r isk assessment, in its current state, is s ufficie nt to suppor

t risk mana

gement decision s (a cle ar path t

o exiting the tiered

process is available at each tier), and (2) if the a ssessment is determined to be insufficient, whether or not progression to a higher tier of c omplexity (or refinement of the c urrent tier) would provide a sufficie nt benef it to warr ant the a dditional e ffort.

• The problem formulation step precedes Tier 1 and include s scoping and refinement of the conceptual site model, including exposure pathway s/routes, and identifying

chemicals of potential concern (COPCs).

• In Ti er 1, det

erministic (point es timate) r

isk asses sment is the

n perfor med using

the basic methodology de scribed in Part II (inhalation) and/or Part II I (multipathway

) of this Reference Manual. In deciding

whether the results of a deterministic risk assessment are suff icient for decision-making or whether more re fined analyse s should be implemented, two factors generally are considered: (1) the magnitude of the estimates of risk (i.e., the value of hazard indices [HIs] or cancer risks for COPCs), and (2) the level of confidence in these estimates. In a Tier I deterministic risk assessment, quantitative risk estimates can be easily calculated, but the level of confidence associated with these ca lculations can be difficult to assess. For example, variability in exposure levels among individual members of the population can generally only be assessed se

mi-quantitatively by

considering central tendency and high-end exposure e stimates. Uncerta inty can ofte n be eva luated on ly a s confide

nce limits on certa in point estimates (e.g., the concentration term). In some cases, the re sults of a Tier 1 risk analy sis may be sufficient f or decision-making. For ex amp le, a de ter mi ni st ic a nal ysis may i ndi cat e ve ry lo w le vel s of ris k fo r so me a ir t ox ics . If the asse ssment is c onsidere d to be ove rly conservative (e

ven in lig ht of unce rtaintie s), this may be suffic ient for a “no action” decision for those chemica ls. The same analy sis may indicate a very

high potential for risk for other air toxics. EPA genera lly recommends that the risk manager proceed to hig her tiers only whe

n site decision-making would benefit from additional analysis bey

ond the point-estimate risk assessment (i.e., when the risk manager needs more complete or certain information to complete the r isk management process).April 2004 Page 3 1-3 Thus, only the combinations of COPC-exposure pathway -receptors of highest potential concern are gene

rally analy

zed using higher level techniques such as PRA.
Exhibit 31-1. Example of a Tiered Approach for Risk Assessment

Adapted from V olume III of EPA’s Risk Assessment Guidance for Superfund (1)

• Tier 2 is represented as an intermediate-le vel analysis using mor

e realistic exposure assumptions (e.g., use of actual receptor locations) and more detailed modeling (e.g ., a model that req uires ad ditional si te-spec ific input s). Althou gh not de picted, T ier 2 cou

ld incorp orate a sensitiv ity a naly sis to ident

ify the most imp ortant pa

rameter s that are driving the risk estimate for specific receptors or population g roups. Tier 2 also could incorporate limited (one-di mensiona l) Monte Ca

rlo tech niques.

• Tier 3 is represented as an advance d analysis using probabilistic techniques such as twodimensional Monte Carlo analysis. Results of sensitivity analyses (T ier 2 or Tier 3) could beused to assess risk distributions for the high-end individuals within the population. The onedimensional Monte-Carlo simulation does not separate variability and uncertainty

associated with the risk estimates. If necessa ry, separ ate analy ses of uncertainty and variability ca

n be performed in Tier 3. Techniques such as two-dimensional Monte Car lo simulation can be used to es timate the

relative impact of

natural variabi lity

and lack of data on the over

all uncerta inty in the risk

estimate , and ca

n be used to direc t additiona

l data g atherin

g or to support mitigation decisions. The deliberation cy

cle provides an opportunity to e valuate the direction and goals of the assessme nt as new informat ion becomes avail able. I

t may include e valuations of both s cientifi c and polic y information. (Also note that, while a th ree-tie red appr oach wa s provide d in ExhibitApril 2004 Page 3 1-4 31-1, the tiered approach is really more of a continuum from a point where the analy sis is done with little data and conservative assumptions to a point where there is an extensive data set and fewer assumptions. In betwe en, there can be a wide varie ty of tiers of incre asing complexity, or, as discussed in Chapter 3, there may only be a fe

w reasonable choices between sc reening methods and highly r

efined analy ses. The three tiered approach is only provided here as an illustration of the concept, not a prescriptive, fixed methodology .) 31.3 Methods for

Probabil istic Risk Assessm ent As discussed in previous chapters, there are a number of approaches available for analyzing uncertainty in risk asse ssments. For simple screening level analy ses, or analyse s where there are only a few ma jor sourc es of unc ertainty , sensitivi ty a naly ses may

be used to

estimate the impacts of likely variations in the ke

y pa rameter values. Where sce

nario unc ertainty

is importa

nt (that is , there are multiple sequences of events that could c ontribute to risk), decision tree or Bay esian statistica l analy sis are c ommonly

used. The

most common

numeric al techn

ique for PRA (analyse s in which a large number of variable s need to be evaluated simultaneously) in largescale air risk assessments is Monte Carlo simulation. Monte Carlo simulation integrates vary ing assumption s, usually

about expos

ure, to c ome up with

possible d

istributions (or ra

nges) o f risk instead o f point es timates. A continuou s probabi lity

distributi on can be

display ed in a g raph in the form of either probability density funct

ions (PDFs ) or cor respo ndin g cumulative distributio n functions (CDFs); however, for clarity , it is recommended that both representations be prese nted in ad jacent ( rather than over

laid) plot s. Exhibit 31-2 illustrates a PDF and CDF for a normal probability distribution for adult body weight. Both display s represent the same distribution, but are useful for convey ing different information. PDFs are most useful for display ing (1) the relative probability of values; (2) the most likely

values ( e.g., modes); a

nd (3) the shape of the distri bution (e .g., ske

wness, ku rtosis, multimodality). CDFs can be used to display (1) percentiles, including the median; (2) hig h-end risk range (e.g., 90 th to 99 th percentiles); (3) confidence interva ls for selected percentiles; and (4) stochastic dominance (i.e., for any percentile, the value for one variable exceeds that of any

other variable). Note that it is helpful to include a text box with summary statistics relevant to the distribution (e.g., mean, standard deviation). These results expressed as probability distributions help risk managers decide whether and w hat actions are necessary

to reduce risk. Monte Carlo simulation has been widely used to explore problems in many disciplines of scienc e as well as engineering , finance, and insurance. (1) The process for a Mon

te Carlo s imulation i s illustra ted in Exhibi

t 31-3. I n its general form, the ri sk equation can be expressed a s a funct ion of a to xicity

term (as a point va

lue) and multiple exposure variables (Vn ) represented as distributions (not point values):



### Risk = f(V 1 

### , V 2 

### , V 3, 

### ...V n 

### ) × To xici ty Equation 31-4 The first decision(s) the risk assessor has to make is which of the “V s” are going to be eva luated probabil istically . Ide ally , every model inpu

t that is va

riable or uncer

tain shoul d be eva

luated to provide a comprehensive characterization of uncertainty in exposure estimates. I n practice, theApril 2004 Page 3 1-5 number of

variabl es that c an be ad

dressed sys tematica

lly i s severe ly li

mited by lack of d ata related to variability, unc ertainty, or both. Sensitivity analyses c an often be used to focus the analy sis on the v ariable s that con tribute mo st to the ov erall uncertain ty in risks.

Exhibit 31-2. Examples of Probability D ensity and Cumulative Distribution Functions

Example of a normal distribution tha t characterizes variab ility in adult body weight (m

ales and females com

bined). The arithmetic mean = 71.7kg, and standard deviation = 15.9 kg . Body weight may be considered a continuous random va riable. The left panel show s a bell-shaped curve and represen ts the P DF, w

hile the right panel shows an

S-shaped c

urve a nd repr esents t he CDF . Both displays represent the same distribution (inclu ding summ

ary statistics), but are u seful for convey ing different information. Source: Finley and Pau stenbach (2) Solutions f

or equat ions with PD Fs are t

ypi cally too comple

x for even

an expert mathemat

ician to calcula te the risk distribut

ion analy tically . Howeve

r, numer ical tec hniques a pplied wit

h the aid of computers can provide very close approximations of the solution. This is illustrated here for the simplified case in which the assessment variables are statistically independent, that is, the value of one variable has no relationship to the value of a ny other var

iable. In this case, the computer selects a value for each va riable (V n ) at random from a specified PDF and ca lculates the corresponding risk. This process is repea ted many times (e.g ., 10,000), each time saving the set of input values and corresponding estimate of risk. F or example, the first risk estimate might represent a hy

pothetical individual who drinks 2 L/day of water and weighs 65 kg, the second estimate might represent someone who drinks 1 L /day and we ighs 72 kg, and so forth. Each calculation is referred to as an iteration , and a set of iterations is called a simulation

. Each iteration of a Monte Carlo simulation should represent a plausible combination of input values (i.e., exposure or ecotoxicity var iables), which may

require using bounded or truncated probability distributions. However, risk estimates ar e not intended to correspond to any one person. T

he “indiv iduals” r eprese nted by Monte Car

lo iterat ions are “virtua l,” and the risk distributions derived from a PRA allow for inferences to be made a bout the likelihood or probability of risks occur ring within a specified range for an exposed human or ecologicalApril 2004 Page 3 1-6 population. A simulation yields a set of risk estimates that can be summarized with selected statistics (e.g., arithmetic mean, percentiles) a nd displayed g

raphically using

PDF and CDF for the estimated risk distribution.

Exhib it 31-3.Conce ptual Mo del of Monte Carl o Anal ysis

Random varia bles (V 1 , V 2 , ...V n ) refe r to exp osure variabl es (e.g. , body wei ght, exp osure freque ncy, ingestion rate) that are c

haracterized by probability distributions. A unique risk estimate is calculated by sampling

each set of the random

values and calculatin

g a result. Re

peated sampling

results in a frequency distribution o f risk can be desc ribed by a probab ility density function. In h uman health risk assessments, the to xicity term is usually expressed as a point estimate. In ecolog ical risk assessm

ents, the toxicity term

may be expressed as a point e stimate or as a pro bability distribution.

31.4 Prese nting Resul ts for Pr obabilistic

Risk Asses sment The complexity of risk evaluation, and pa rticularly of pr

obabilistic methods, may pose a significant barrier to understanding a mong the affected and intereste d parties (and thus to the utility of the analy

sis). In the past, reg

ulatory decisions have

been evaluated primarily in terms of point estimates of r

isk and simp le dichot

omous dec ision rule s (e.g. , “I f the poin t estimate of riskApril 2004 Page 3 1-7 is above a certain level, take a ce rtain action. If not, take anothe r action.”). In contr

ast, it may not be intuitively obvious, even to relatively sophisticated audiences, how to relate the outputs of quantitative uncertainty e valuation to a particular decision. For example, important aspects of a regulatory

decision may re st on relatively subtle statistical distinctions (e.g., the difference between a 95 th percentile risk estimate and a 95 th percen t upper c onfidenc e limit on a risk estimate), and the challenges in presenting such information can be formidable. I n its recent guidance, EPA has beg

un to defi ne concrete ap

proache s to prese

nting ri sks and uncertain

ty informat ion to dec ision-mak

ers and s takehold

ers. (5) The key f actors for successful communication of PRA include early and continuous involvement of affected and interested par ties, a well-developed communication plan, good g raphics, a working knowledge of the fa ctors that may influenc e perceptions of risk and uncertainty, and a foundati on of trus t and cre dibility . A certa in amount o f trainin

g for in tereste d stakeho lders wil l likely be nece ssary

to help the

m underst and the c omplexities

of not only

risk asse ssment in general, but the intricacies of hig her levels of analy sis. Part II I of this Reference Manual provides guidance on community involvement and risk communication. When summarizing results of PRA, graphs and tables should genera lly also include the results of the point estimates of risk (e.g., central tendency and high-end). Consistent with EPA’s guidance on risk characterization, (3) the central tendency and high-end cancer risks and noncancer ha zards, along with decision points, should be highlighted on graphics. The discussions accompany ing the graph should emphasize that these values re present risks to the

average and hig

h-end ind ividuals, respectively , and ser ve as a po int of ref

erence to EPA’s decision point. The distribution of risks should be characterized as representing variability among

the population based on differences in exposure. Similarly , graphics that show uncertainty in risk estimates c an be described using terms such as “c onfidence interval,” “credi ble inter val,” or “plausib le rang e,” as a

ppropria te. The g raphics need not h

ighlig ht all percentiles. Instead, se lected percentiles that may inform risk management decisions (such as the 5 th , 50 th , 90 th , 95 th , and 99 th percentiles) should be the focus. Exhibit 31-4 presents an example of a PDF for variabi lity

in risk with

an assoc iated text b ox for iden tify ing key risk desc riptors. By under standing the assumptions regarding the inputs and modeling approaches used to derive point estimates and

probabil istic estimates of r isk, a risk communic ator will b e better prepar ed to explain the

signific ant diffe

rences in risk est

imates tha

t have be en deve loped. Spe cial emphasis should be g

iven to the

model and

parameter assu

mptions tha

t have the most influe

nce on the

risk estimate s, as dete

rmined fr om the sen sitivity

analy sis.April 2004 Page 3 1-8 Exhibit 31-4. Example of Presenting th e Results of a Probabilistic Risk Assessment

Hypothetical PRA

results showing a

PDF (top panel) for cancer risk with selected summ ary statistics for central tendency a

nd high- end percentiles. This v iew of a distribution is us eful for illustrating the shape of the distribution (e. g., slightly right-sk ewed) and explaining

the concept of probab ility as the area under a curve (e.g., m ost of the area is below

1x10 -6 , but there is a sm

all chance of 2x10 -6 ). Althou gh pe rcentile s can al so be o verlay ed on th is gra phic, a CDF ( bottom panel) may

be pref erable for explaining the co

ncept of a percentile.April 2004 Page 3 1-9

Additio nal Refe rences on Unc ertaint y Anal ysis Burmaster, D .E. an

d Ande rson, P .D. 1 994. Principle s of g ood pra ctice for the us e of Mon

te Carlo techniques in hum

an health and ecological risk assessm ents. Risk An alysis

14: 477-48 1. Cullen, A.C. an

d Frey, H.C . 1999. Probabilistic Techniques in Exposure Assessment . New York: Plenum Press. Fayerweather, W.E ., Collins, J.J., Schnatter, A.R., Hearne, F.T., Menning, R.A., and Re yner, D.P. 1999. Quantify

ing uncertainty in a risk assessm ent using hum

an data. Risk An alysis

19: 1077-1 090 Finkel, A.M. a

nd Evans, J.S. 1987. Eva luating the benefits of uncertainty reduction in environme

ntal health risk m

anagement. Journal of the Air Po llution Control Association. 37: 1164-1 171. Frey, H.C. 1992. Quantitativ e analysis of uncertain

ty and variab ility in environm ental policy m

aking. Pitts burgh: C arnegi e Mell on Univer sity. Hattis, D. and B urmaster, D.E . 1994. Asses sment of variability and uncertainty distributions for practical risk assessm

ents. Risk An alysis

14: 713-73 0. Hope, B. K. 19 99. Assessm ent of risk to terrestrial rec eptors using uncertainty analysis -

A case study. Humanand Ec ologica l Risk A ssessme nt 5(1): 145-170

. Moore, D.R.J., Sam

ple, B.E., Sute

r, G.W., Park

hurst, B.R., an

d Teed, R.S. 19 99. A probabilistic risk assessment of the effects of methy lmercury and

PCBs on m

ink and kin

gfishers along East Fork Poplar Creek, Oak

Ridge, Tennessee, USA. Environmental Toxicolog y and Chemistry 18: 2941-29 53. National Research Cou

ncil (NRC). 1991

. HumanExposu re Asse ssment for Airb orne Po llutants

. Washington DC: National Academy Press. Roberts , S.M. 1999. Practi cal issues in th e use of probab ilistic r

isk as sessment and

its app lication s to hazardous waste sites

. Human and Ecolo gical Risk Assessment . 5(4): 729- 868. Special I ssue. Smith, R.L .. 1994. U se of Monte Carlo sim ulation for human

exposure assessm

ent at a Superfund site. Risk Analysis 14(4): 433-43 9. U.S. Environ

mental Protection A

gency. 1 985. Methodo logy for Chara cterizat

ion of U ncertai nty in Exposu re Asse

ssments . Washin

gton D C, EPA -600

/8-8 5-00 9).April 2004 Page 31-10 1. Rugen, P. and B. Callahan. 1996. An overview of Monte Car lo: A fifty y

ear perspective. Human Health and Ecological Risk Assessment 2(4): 671-680. 2. Finley

, B. and D . Paustenb ach. 199 4. The be nefits of probabil istic exposu

re asse ssment: Three case studies involving contaminated air, wa ter, and soil. Risk Analy

sis 14(1): 53-73. 3. U.S. Environmental Protection Agency . 1992. Guidance on Risk Cha racteriza tion for Risk Managers

and Risk A ssessors . Risk Assessment Council, Washington, DC, February 26, 1992. References

# Chapter 3 2 Use of Geographic Information Systems

(GIS) in Risk Assessme nt

Table of Contents

32.1 Introduction

............ ............ ............ ............ ............ ...... 1 32.2 Sele cti ng a GIS

............ ............ ............ ............ ............ ... 2 32.3 Acquiri

ng and Using

Demographic Dat

a ............ ............ ............ ....... 4 32.3.1 U.S. C ensus D ata
............ ............ ............ ............ ....... 5 32.3.2 Current and Sm

all-Area Dem

ographic Estim

ates
............ ............ ...... 5 32.3.3 Public Health Applications

............ ............ ............ ........... 7 32.3.4 Data Access and D istribution

............ ............ ............ ......... 7 32.4 Cartog

raphic C oncepts
............ ............ ............ ............ ......... 7 32.4.1 Generalization, Sim plification, and Abstraction

............ ............ ...... 10 32.4.2 Map Projections

............ ............ ............ ............ ....... 10 32.5 Using the I

nternet as a GI S Tool

............ ............ ............ ............ . 10 32.6 Current GIS Applications at EPA

............ ............ ............ ............ 11 32.6.1 ORD/ESD

............ ............ ............ ............ ........... 12 32.6.2 ATtILA

............ ............ ............ ............ ............ . 12 32.6.3 ReVA

............ ............ ............ ............ ............ ... 12 32.7 GPS Tec hnology

............ ............ ............ ............ ............ . 13 References

............ ............ ............ ............ ............ ............ 15April 2004 Page 3 2-1 32.1 Introduction A geographi c inform ation syst em (G IS) can be defined as an orga nized collection of software and ge ographic data

that allow

efficie nt storag e, analy

sis, and pr

esentat ion of spa tially explicit and geographically

referenced information. Traditional methods of proc essing such data have been extremely labor

intensive, such as manually dig itizing a map from an aerial photograph and then adding information about chemical contaminants. A GI S provides a powerful analy tical tool that can be used to create and link spatial and desc riptive data for problem solving, spatial modeling and presentation of results in tables or maps. For a ir toxics risk assessment, GIS can be a powerful tool for display ing and analy

zing data during the planning, scoping , and problem formulation phases, during the exposure assessment, and display ing and evaluating the results of the risk c haract erization . It is

also a ve ry helpful me ans for c ommunica ting inf ormation t

o risk manage rs and other stake

holders. GIS data gene

rally consist of two components: (1) g raphical data about geog

raphic features (e.g., rivers, land use, political boundaries), and (2) tabular da ta about features in the geog raphy (e .g., population, eleva

tion, mode led ambie

nt conce ntrations of air toxic s). GI S combines these different type s of data using a “lay ering” technique that refer ences each ty

pe of data to a uniform geographic coordina

te system (usually

a grid such as latitude and longitude coordina tes). Lay ered da ta can then be analy

zed using special softwar e to cre ate new

layers of da

ta (see Exhibit 32-1). Over the last several y

ears, GIS applications have evolved from very

specialized and expensive analyses that re quired specialized computers (e.g., supercomputers and workstations) to userfriendly desktop applica

tions utilized by every

day users to do such munda ne tasks as print maps or driving directions. Libra ries of geographica

l information developed for general use (e.g., topographical maps, infrastructures, natura l resources), and for use by EPA and other regulatory agencies, can be ea sily downloaded from diffe rent servers and used in air toxics risk assessments. One example of a GIS Web-based a pplication is EPA’s Envirofacts system (1) which provides website access to several EPA databases tha t provide information about environmental activities that may affect air, wa

ter, and land any where in the Unite d States (

with much o f the dat

a available in GIS format). This chapter provides an overview of GI S and its application to air toxics risk assessment. More detailed information is provided in the Agency for Toxic Substances and Disease Registry (ATSDR)/Southern Appalachian Assessment GI S (SAAGIS) publication Introduc tion to ArcView a nd Spatial A nalysis Techniques for Public

Health Pr

ofessiona ls

. (2)April 2004 Page 3 2-2

Exhibit 32-1. Example Conc eptual Model Using G IS

Example of lay

ering within a G

IS. The location of monitoring wells, industries, and potential receptors (homes) are all referenced to the sam e geographic coordinates. This allows spa tial analysis of the ov

erlap of sources, contam

inant plumes, an

d receptors, as well as a visual means to com

municate com

plex data sets.

32.2 Selecti ng a GIS Aft er r is k as ses sor s de cid e to use a GIS , t hey m ust cho ose a so ftw are syst em. A va rie ty of GIS softw are is avail able fr om com merci al ven dors. A key featu re in s elect ing a GIS i s iden tifying a minimal set of capa

bilities ne eded. I

mportant f

unctiona l capabi lities to c onsider i nclude: d ata ca pt ur e, da ta st or ag e, da ta ma na ge me nt , d at a r et ri ev al , d at a a na lys is , a nd da ta di sp la y. (3)

• Data Capture . All data used in a G

IS must have a sp atial com

ponent. T

his means that all informat ion broug ht into the syst

em must be geo-ref

erence d (i.e., c orrespond to some phy sical loc ation). D ata capture is the process of incor porating map and a

ttribute d ata into the GIS. Geocod ing , which is t he conve rsion of a nalog d ata to g eo-ref

erence d digita

l format, is a common way for

GIS users to bring map and a ttribute data into their GIS analy ses. Two common methods of geocoding are sc anning and digitizing. Both involve taking non-digital informat ion (e.g ., a hard

-copy map), an d conver ting it int o a digit al forma t. In a ddition to paper files, GIS users of

ten import files from common formats such as AutoCAD DXF. TheApril 2004 Page 3 2-3 newly imported digital information (e.g., the boundary of a state), is geo-refer

enced by coordinates so that it corresponds to a phy sical location. In a ddition to g

raphica l data, GI S incorpor

ates tab ular dat a for obj ects inc luded in a data layer. F or example, the graphical data associated w ith a home could consist of its size and location. The tabular data associated with that home consists of attributes such as who lives there, when it was built, where its water supply comes from, and what ty pe of heating system it uses. These attributes would be listed in a table that is linked to the phy sical location of the house by the GI S. While obta

ining g eogra

phical ba se lay

ers that show bound

aries is essential, data capture also involves attribute data, which nec essitates that the GIS software package have some level of database manager assoc iated with the program. A useful program will generally

have features that allow it to import common database files such as those fr om dBASE ® , Acces s ® , Excel ® , and Paradox ® . The diff erent so ftware

packag es will vary in their a

bility to check the cha

racteristics of the databases.

• Data Storage . A GI S can incorporate a tremen dous amoun

t of data into a map . Space is

a key issue rela

ted to data storage in a GI S. With the decrease in cost of disk storage, the development of high-density storage media (e.g., CD-ROM) , and the incorporation of compression methods, space is not as critical an issue as it has been in the past. Howe ver, GIS is still relatively

memory-intensive. GI S microcomputer software can take up tens of megaby tes of space without data, and a more complete worksta tion version may use hundre ds of mega byt es of spa ce. Add t o this the d

atasets w ith very high re solution (t

hat can m ove into the gigaby

te range in size), and there is a the potential for a significant storage problem. Some storage problems can be resolved by establishing data sets on a common server, access ible to mult

iple users.

• Data Mana gemen t . A powerful GIS is one which ha s the ability to manage both map and attribute data. Every

GIS is built around the software ca pabilities of a database management system (DBMS). A D BMS is software that is capable of storing, selecting, retrieving, and reorganizing attribute information. I t allows data entry, da

ta editing, and supports several different type s of output. Functions include the ability to select records based on their value. Several databas e functi ons can work indep endently of the GI S function s.

• Data Retrieval . A GI S will suppor t the retr ieval of featur es by their att ributes or by

their spatial characteristics. A basic retrieva l based on spatial characteristics is used to show the position of a single feature. I n addition, a GIS is capable of allowing the operator to use the map as a query

vehicle. A simple way

of doing this is to point to a feature and retrieve the list of attributes for that feature. The database mana gement function also is important for the data retrieval capacity

because it allows for the selection and retrieva l based on an attribute. Buffering

is one retrieval operation that defines a GI S. Buffering allows the user to retrieve features within a specified distance of a point, line, or a rea. Overlayis another spatial retrieval operation in which non-overlapping r egions are joined to create a ne w area. More sophisticated retrieval operations also are available

. (2)April 2004 Page 3 2-4 • Data Analy sis . GIS systems vary a g reat deal in their data analy sis capabilities. Basic tasks that should be included in a GIS are: spre adsheet and database analy sis, computing new attributes, generating summary statistics, creating reports, statistics such as mean and varianc e, signi ficanc e testing , and plott ing res iduals. I

n addition , select

ed geometric te sts should be included (e.g., point-in-poly gon analy sis, surface partitioning).

• Data Display . GIS software display s information visually as data lay ers of a map. GIS users must select the correct map projection to make sure that their ma ps are not distorted. For example, large areas, such as continents, must be proje cted with the earth’s curvature taken into consideration. Small areas can be projected essentially as flat. GIS software g

ives users as wide variety

of map projection options to ensure that maps are as accur ate as possible. Section 32.4.2 discusses map projections in further detail. Different data sources and ag encies provide digital data that has been proc essed using different coordinate systems and map projections. Risk assessors may want to use data laye rs from many diffe

rent sources to create a single map. For example, a topography layer f rom the U.S. Geologic Survey might be combined with a lay er showing census blocks from the U.S. Censu s and a la

ye r showing lead sme lters fr

om EPA. Soft

ware tha t can han dle a var iety of coordinate sy stems and map projections is essential to GIS capability to overlay lay

ers create d from man

y di ffere nt source s. 32.3 Acquiring and Using Demographic Data Demography

is the study of the size, composition, distribution, and change in population. Geographers focused on population studies ar e also interested in the spatial distribution of demogr aphic characte

ristics. (4) Data from the U.S. Bureau of the Census dec ennial census is the most common source of residential population information for states, the District of Columbia, and many U.S. terr

itories (e.g., Puerto Rico, U.S. Virgin I slands, American Samoa, and Guam). These da ta also pr ovide the base for curren t ye ar popula

tion estima

tes and pr ojection s. Risk assessors are often interested in using demog raphic data because it allows them to identify sensitive sub-populations, such as children or the elderly . A GIS lets risk assessors combine demogr aphic da ta with da ta on the l ocation o f source s (or esti mated amb ient air c oncentr ations) to visualize where human health is potentially at r isk (see Exhibit 32-2). Within a GI S, politica

l and stati stical g eogra

phic are a bounda

ry files ar e linked t o the attr ibute data (e.g., age, r

ace, housing value) describing residents and housing units in that area using Federal I nformation Processing Standard (FI PS) codes. These codes provide unique identifiers for various geographic

areas. When analy

zing census data that is nested within the data hierarchy (e.g., census blocks within census tracts), it is best to include the FI PS codes for the larger geographic are as in that hierarchy to ensure that you a

re using a unique identifier. For example, connec ting the

FIPS c odes for

block 201 , census t

ract 12, Fulton co

unty , state of

Georg ia, resu

lts in the unique identifier “13089001200201” for that block. Beca use the codes are nominal num era ls , i t i s be st to tre at t hem as c har act er d ata (or st rin gs) rat her th an n um ber s i n t he G IS database (although this may not be consistent across data sources).April 2004 Page 3 2-5

Ex hib it 3 2-2 . I llu str ati on o f th e Us e of GIS to I den tify Sensitive Receptors C lose to Emissions Sources

In this m ap, the squares represent hazardous waste sites , and the flagg ed symbols re prese nt scho ols. Sch ools an d other locat ions wh ere se nsiti ve subpopulations m

ay occur that are c lose to air toxics em issions sources may be of pa rticular interes t in a ri sk ass essme nt.

32.3.1 U.S. Census Data U.S. cens us data de scribing

the resid ential po pulation a nd housing

in the U.S. provide t

he most complete picture of our na tion and its

subarea s, which ma

kes them v ery

valuable demogr aphic data. Exhibit 32-3 shows the type of information collecte d in the 2000 census. Many of the Census 200 0 data fi les are availab le for us e in GI S. 32.3.2 Current and Small-Area Demogr aphic Estimates An issue with census data is that the information represents a “snapshot” in time (g enerally ba sed on April 1 of the census year). As one moves forward in time, such data ma y be less ref

lective of the actu al demog raphic c onditions in

the study area. T his proble m is more pr

onounce d for sma

llarea da ta (e.g ., censu s tracts a

nd block g

roups). Wh

ile the ce nsus data typ ically are app ropriate for screening-level assessments (e .g., some air quality models include the 2000 census data), more refined assessments may require more current information, which is available from several commerc ial sourc es.April 2004 Page 3 2-6

Exhibit 32-3. Information Collected in the 2000 Census During census y

ears, households receiv

ed and were ask

ed to respond to one of two census forms – the “short f orm, ” which

giv es the “ 100-

percent comp onent, ” or the

“long form ,” whic

h gives the “ sampl e comp onent. ” Ques tions on the short form

were al so foun

d on th e long

form and thu s, were (theoret ically ) aske d of every ho

usehold in the n ation. Basic p opulati on and housing data w ere gathered in this wa

y. More detailed p opulation information was obtained from the long form

sent to a sample of househ

olds. On average, approxim ately one in six h

ouseholds received the long form . The rate v aried fr

om on e in two households in some small er areas , to one in eig ht hous eholds for more densely populated a

reas. 100 Percent Component from the Short Form Population

• Name

• Househ

old rela tionship

• Sex

• Age

• Hispan

ic or La tino ori gin

• Race Housing

• Tenure – owned or rented

Sample Component from the L ong Form Population Social characteristics

• Marital status

• Place of birth, citizen ship, year of entry to the U.S.

• School

enrollm ent and attainm ent

• Ancestr

y

• Residency fiv

e years ago (migration)

• Language s

poken at hom

e and ability to spe ak English

• Veteran status

• Disabil ity

• Grandp arents a s care g ivers Economic characteristics

• Labor force status

• Place o f work

and jour ney to work

• Occupation, industry , and class of work er

• Work status in 1999

• Incom e in 1999 Housing

• Units in

structu re

• Year st

ructure built

• Numbe r of r ooms a nd nu mber o f bed rooms

• Year moved into residence

• Plumbing and kitchen facilities

• Telephone service

• Vehicles availa

ble

• Heating fuel

• Farm residence Financial Characteristics

• Value of home

or mo nthly rent pai d

• Utilities, mortg age, taxes, insuran ce, and fuel costs

Source: U.S. C ensus. Census 2000 Basics . Ava ilable a t: http://www.census.gov/mso/ww w/c2000basics/00Basics.p dfApril 2004 Page 3 2-7 A number of commercial entities provide annual small-are a population and housing estimates and projections. Estimates are calculated using the most re cent decennial census as the population base and incorporating other, often propr ietary, data

sources to refine the estimates. In addition to providing updated demog raphics, some vendors have developed seg mentation systems that classify

the U.S. population into distinct lifestyle segments or clusters depending on residen tial loca tion (“g eodemog

raphics ”). The

idea of c lustering

is based on the notion that, more ofte n than not, people will choose to live ne ar others like them selves. T his is impor

tant to public health because assessors can be more efficient in identifying

and understanding where potentia l hazards are con centra ted, as w ell as de

veloping messag es that re ach peo

ple living in those areas. 32.3.3 Public He alth Applica tions The us e of cen sus d ata is centra l for p ubli c healt h comm unica tion plann ing, p rogram plann ing, implement

ation and informat ion dissemi

nation. F or example , the Georgia D ivision of P ublic Health used demographic information to targ et mammography programs in factory

towns classified as “Mines & Mills” because women in those communities wer e found to have higher rates of breast cancer. (5) As another example, the Centers for Disease Control (CDC) Office of Communica

tion has c ollabora

ted with a number of

centers on proje cts that in tegra te epidemiological and other data for communication planning including HIV status awa reness and hantavirus prevention. (6) Because exposure to air toxics is often influenced significantly by proximity to source s, spatia

l informa tion is esse

ntial to ide

ntify ing are as wher

e human he alth might be adversely

impacted. 32.3.4 Data Access and Distribution There are numerous sources for acquiring U.S. census data. I n addition to the Census Bureau’s data ac cess tool s, includi

ng Fac tfinder, its Web-ba sed data dissemina

tion system, many

public and pri vat e or gan iz ati ons are in clu di ng c ens us d ata wit h GIS or m app in g so ftw are (e. g., ES RI, EPA La ndView, H

UD Communit

y 20 20, Geoly

tics, Clar itas, CACI

). State governme

nts, universi ties, and non-governmen

tal org anizations

(e.g. , CIES IN)are als o source s for dat a. Costs as so ci at ed wi th ob ta in in g t he da ta va ry. 32.4 Cartographic Concepts While spati al information and GIS c an be extr

emely useful, p eople mus t have as sistance in observing and study

ing the great amount and varie ty of information that is repre sented on maps. Geogr aphic da ta are e xtensive a

nd volumino

us, so car tography, a techni que that i s fundame ntally concerned with reducing the spatial c haracteristics of a large

area, makes maps readable a nd meaning ful. A map

is more tha

n a reduc tion of inf

ormation t

o an unde rstanda ble leve l. If

it is well made , it is a ca

refully designe d instrume

nt for re cording , calcul ating, a naly zing, and in general, understanding the inter relation of things in their spatial relationship. This section provides an overview of cartogr aphy. A more c omplete discussion can be found in The Geographer’s Craft Project

. (7)April 2004 Page 3 2-8 One of the most useful approaches to the study of cartography

is to view maps as a form of visual communic ation – a s

pecial p urpose la nguag e for de scribing

spatial r elationsh ips. Carto graph

y is related to, but different from other forms of visual communication. Cartog raphers must pay special attention to coordinate sy stems, map projections, and issues of scale and direction that are in most cas es of re latively little concern to o ther gr

aphic de signers or artis ts. But, b ecause cartography

is a type of g

raphical communication, some insights to the demands of cartog raphy can be gleaned from the literat ure of graphical co mmunicati on and stat istical graph ics. By stressing cartography

as a form of communication, it is easier to make the point that maps are really sym bolic abs traction s – or representa tions – of r

eal worl d phenome

na. I n most cas es, this means tha

t the worl d repre sented on a map has

been g reatly simplified , or ge

neralize d, with symbols being used like wor ds to stand for real things. Some of the most important decisions cartog raphers make in the proce ss of car tographic desig

n revolve around: ( 1) how muc

h to simplify the situation being depicted; a nd (2) how to symbolize the relationships being represented. I

n order to make good choices, car tographers often ask themselves the following questions :

• What is the motive, intent, or goal of the map?

• Who will read the map?

• Where will the map be used?

• What data is available for the composition of the map?

• What reso

urces a re avai lable in te

rms of both

time and e quipment? By identify ing the most importa

nt points to b e conve

ye d by the map a

long with the map’ s main audience, cartographe

rs can prioritize where to direct the audience’ s attention with larger symbols or brighter

colors.April 2004 Page 3 2-9 Basic MapElemen ts A leg end and

sym bols tha t inform the viewer o f distance, sca le, and directio n, are b asic ele

ments to any map. The USGS (

http://e dc.usg s.gov

/earthsh ots/slow /Help- GardenCity/l egend stext) provides examples of com

mon m ap legends. Example U.S.Geological Survey (USGS) Topogra phic Map Legend

Example Legend

for Universal Transverse Mercator (UTM) Projection ZonesApril 2004 Page 32-10 Map Making Tips

• Experim

ent with differe nt layouts

• Think carefully abou

t every elem

ent on your map and whether it has an essential function

• Less is more 32.4.1 Genera

lization, Simplifica

tion, and Abstraction As noted above, cartography is a process of abstraction in whic

h featur es of the real wor ld are generalized or simplified to meet the demands o f the the

me and au

dience. Not all elements or details have a bearing on the pattern or proce ss being

studied a nd so some are eliminated to draw the reader’ s attention to those facts that are relevant. Too much detail can even hide or disguise the messag e of a map. The amount of detail that can be included is very much depe

ndent on the scale at which the map will be produced (see Exhibit 32-4). 32.4.2 Map Pro

jectio ns As section 32.2 notes, the projection used to create a map influenc es the representation of area, distance , direct

ion, and shape. Thi s is read ily a pparent when look

ing at a flat map o f the wor

ld versus looking at a spherical map of the world (i.e ., a globe). Maps that ignore the na tural shape of the ea rth distor t the plac es they

are try ing to re present . It should be no ted when these characteristics (e.g., ar

ea, distance, direction, and shape), are of prime importance to the interpre tation of a

ny m ap. Some w

idely used loca tional re ferenc e sy stems such as the U. S. State Plane Coordinate system and Unive rsal Transverse Mercator sy stem are based on predefined pro jec ti ve g eom etr ies th at a re i mp li cit in th e us e of th e co ord in ate syst ems th ems elv es. GIS software packages make

it easy for use

rs to choose an appropriate map projection. 32.5 Using the Internet as a GIS Tool The internet can be a valuable resour ce for GIS users looking

for data. Many

federal agencies provide digital data free for download tha t can be used with GIS. The Census B ureau, EPA, and the United States Geological Survey are all good sources of GI S data. For example, in addition to demographic data, the Census bureau distributes what a re called T op ol og ic al ly I ntegrated G eographic E ncoding and R eferencing (TIGER) files. The TIGER/L ine files are a digital database of geogr

aphic features, such as roads, lakes, political boundar ies, and census statistical boundaries, available for the entire United States. The da tabase contains tabular information about these features such as their location in latitude and longitude, the name, the type of feature, and other important attributes. GIS clear inghouses, universities, and data supply companies are also goo d places

to look for

data. A We

b search engine can he lp users lo cate site s that con tain the ty pe of dat a neede d for a given proj ect. Once users locate relevant data, the y must then get the da

ta onto their computer. GIS cover ages can take up a lot of computer memory, so choosing the right file transfer method is ver y important. Many websites allow dire ct downloads. This type of tra nsfer involves clicking a link and specify

ing a target directory . Other data providers require users to g o through a file transfer protocol(FTP) sit

e. FTP sit

es allow p eople to e

xchange large data file s more re adily

than with other pr otocols.April 2004 Page 32-11

Exhibit 32-4. Effect of Scale on Detail and Abstraction

Finally, the interne

t can serve as a resource f or users looking for technical support or advice

. Most user s will find t

hat GI S softwar

e manufa cturer s offer

online sup

port. Some

companie s even ha ve online courses . 32.6 Curren t GIS A ppli catio ns at EPA EPA is an excellent source of GIS data a nd information for risk assessors. Several offices and branche s can ser

ve as re sources

for those interest ed in lea rning more about

GIS a nd its uses , especially in the a

reas of landscape, land cover, a nd land use. GIS helps EPA integrate geospatial data on a region (e.g ., landscape, elevation, climate, slope) with information about potential exposures to give risk assessors a comprehensive picture of that region’s hazards. Because projected land use may be an important input to air models, risk assessors may want more information on landscape change models. For an overview on this subject, see EPA’s Projecti ng Land-Us e Change: A Summary of Models

for Assess ing the Eff

ects of Com munity Growth and C

hange on La nd-Use P

atterns. (8)April 2004 Page 32-12 32.6.1 ORD/ESD EPA’s Office of Research and De velopment/Environmental Sciences Division (ORD/ESD) conducts research, development, and tec hnology tra

nsfer programs on environmental exposures to ecological and human receptors. GI S is an important tool for the type of che mical and physical stressors cha

racterization conducted, especially with ESD’s emphasis on ecological exposure. The Divis ion devel ops landsc ape and regional asses sment ca

pabilitie s throug

h the use of advanced spatial monitoring and analy sis techniques, such as remote sensing and GI S. For more information, go to http://www.epa.gov/nerlesd1/

. 32.6.2 ATtILA Another EPA resource is the L andscape Ecology Branch’s ATtILA progra m, which stands for Analytical Tools Int

erface f or Landsca

pe Assessments . The Br

anch use s ATtILA, w

hich is a GIS, to conducts multiple-stressor regional assessments based largely on geo-spatial landscape data. As part of these assessments, ATtI LA gener ates complicated landscape metrics, which are quantitative measurements of the environmental condition or vulnerability of an area (e.g., ecological region). ATtI

LA provides an interfac e that allows users to easily c alculate many common landscape metrics regardle ss of their level of GIS knowledg e, despite the complexity of developing the metrics. Four metric g roups are currently

included in the package (e.g ., Landscape Chara

cteristics, Riparian Characteristics, Phy sical Characteristics, and Human Stresses). ATtIL

A runs within ArcView ® , and is de signed t o be flexib le enoug

h to accommodate spatial da ta from a variety of sourc es. More

informat ion is ava ilable at : http://www .epa.g ov/nerle sd1/land- sci/northern_ca lifornia /attila/ba ckgro und.html

. 32.6.3 ReVA Also from

EPA’s ORDis the Regional Vulnerabilit y A ssessmen

t (ReVA)progra

m. This program is an approach to reg ional scale, priority- setting assessment meant to expand cooperation among the laboratories and c enters of ORD, by integrating researc

h on human and environmental he alth, ec orestor ation, la ndscape analy sis, regional expos

ure and p rocess modeling , problem

formulat ion, and e cologic al risk g uideline s. Curren

tly, ReVA is working in the Mi d-At

lanti c reg ion to pred ict f uture envi ronme ntal r isk. T his wi ll hel

p EPA prior

itize efforts to protect and restore environmental quality efficiently a

nd effectively . ReVA is being develope d to identif

y those ecosyst

ems most vul

nerable to being lost or pe rmanent ly harmed in the next 5 to 25 years and to deter mine which stressors are likely to cause the greatest risk. The goal of ReVA is not exact predictions, but identification of the undesirable environme ntal chang es expect

ed over t he coming

ye ars. Many function s work tog ether to provide R

eVA’s r egiona l assessme

nt capab ility . GIS p

uts into a spatia l context da

ta on stre ssors and

effects from ma

ny s ources. Researc

h guide s how to ap

ply this data a

t the land scape a

nd reg ional sca

le and he lps EPA unde

rstand how socioe conomic drivers affect environmental condition. The transfe r of data and analy

tical tools to regional manage rs is also c

ritical f or this tool

to be usef

ul. ReVA is

consider ed a GI S becaus e it is designed to analy

ze the spatial distribution of sensitive ecosystems by analyzing knownApril 2004 Page 32-13 distributions of plant and animal populations or communities within ecosystems. Modern methods in landscape ecology and characterization help further identify the locations of ecosystems that ar

e vulnerable to future stress through fea tures such as topography

(i.e. increased erosion potential) and habitat patch configurations. Multimedia assessments ac ross water, air, terrestrial, and demographic var iables are possible at various scales with this tool. For more information on ReVA, see http://www .epa.g ov/reva /approa ch.htm

. 32.7 GPS Technology Globa l Pos itio ning S ystem (GP S) tec hnol ogy can be in tegrat ed wit h GIS. GP S tech nolo gy allows use

rs with the

appropr iate tec hnology to obtain a

lmost the exact loca

tion of an y G PS receiver. This means that cars can get driving directions while moving, hikers can alwa ys know their exact position for navigating in and out of the wilderness, and the military can trac

k movements of troops or vehicles. For risk assessments, the location of specific sources (i.e., vents) or receptor locations can be ac curately de termined with GPS. GPS is funded and controlle d by

the U.S. D epartme

nt of Def ense (D OD). While

there a re many thousands

of civil users of GPS world-wide, the sy stem was designed for, and is operated by the U.S. military. The system works throug h specia lly c oded sate llite sig

nals that c an be pro cessed i n a GPS receiver, enabling the re ceiver to compute position, velocity, a nd time (see Exhibit 32-5). Four GPS satellite signals are used to compute positions in three dimensions and the time offset in the receiver clock (see Exhibit 32-6). The GPS pr

ovides two

levels of service – a Standa

rd Position

ing Serv ice (SPS), and a Pre cise Positioning Service (PPS). Access to the PPS is restricted to U.S. Armed Forces, U.S. Feder al agencies, and selected a

llied armed forces and governme nts. The SPS is available to all users on a continu ous, worl dwide ba sis, free of any direct u ser cha

rge. A nationwid

e diffe rential G PS service (NDGPS) is being established pursuant to the authority of Section 346 of the Department of Trans portation and Rela ted Age ncies Ap propria tion Act. When comple

te, this se rvice wi ll provide uniform differential GPS coverage of the continental U.S. and selected portions of Hawaii a nd Alaska

regar dless of te

rrain, ma n-made, and other

surfac e obstructions. NDG PS accuracy is specified to be 10 meters or better. Ty pical system perf

ormance is better than 1 meter in the vicinity of the broadc ast site. Achievable accuracy degrades at an approximate rate of 1 meter for each 150 km distance from the broa dcast site. (9) Receiver costs vary

depending on capabilities. Small civil SPS receivers can be purcha sed for under $200. Receivers that can store files for post-pr ocessing cost more ($2,000 to 5,000). Receivers that can act as DGPS refer ence receivers (computing and providing correction data) and carrier phase tracking receivers (and two are ofte n required) can cost many thousands of dollars ($5,000 to $40,000). Receivers are important because they are the intermediary

part of the system that c onnect real world data to GIS. Satellites send signals to the re ceiver and users and store the information. Sometimes, the user

will have to manual ly r

ecord po sition and

time rea dings an d then ty pe thoseApril 2004 Page 32-14 into a computer later. Other times the user can plug the receiver into a special port on her co mp ut er an d d ow nl oa d t he di gi ta l d at a d ir ec tl y.

Exhibit 32-5. Global Positioning System (GPS) Satellites

GPS sa tellites orbit th e Earth

every 12 hou rs, sending s ignals

to rece ivers around the wor

ld

Exhibit 32-6. Positioning and Time from Four G PS Satellites

Measurements of cod

e-phase arrival times from at least four satellites are used to estimate four quantit ies: po sition i

n three dimen sions (X, Y, and Z) an d GPS time ( T).April 2004 Page 32-15 1. U.S. Environmental Protection Agency . 2004. Envirofac ts Data W arehouse . Availab le at: http://www .epa.g ov/envir o/index.html

(Last accesse d March 2004). 2. Agency

for Toxic Substances and Disease Registry . 2004. Introduction to ArcView and Spatial Ana lysis Techniques fo r Public H ealth Prof

essionals

. An A TS DR/ SA AGIS publication (in press). 3. Clarke, K.C. 1997. Getting St arted with G

eographic

Informati

on System s. Prentice

Hall, Upp er S add

le R iver, NJ. 4. Plane, D.A., and Rogerson, P.A. 1994. The Geographical Analysis of Population. John Wiley & Sons, Inc, New Yor

k, NY. 5. Weiss, M.J. 2000. The Clustered World. Little, Brown and Company , Boston, MA. 6. Pollard, W., and Kirby, S. 1999. Geograph ical Infor mation Sy stems ( GIS), Public He

alth Data, and Syndicated Market Research Data Bases in Health Communication. Presented at the National Confe

rence on Health S tatistics, Washingt on, D.C. 7. Ke nn et h E .F . a nd Cr um , S . T he Ge og ra ph er 's Cr af t P ro je ct . D ep ar tm en t o f G eo gr ap hy, University of Texas at Austin. 8. U.S. Environmental Protection Agency . 2000. Projecti ng Land-Us e Change: A Summary of Models for Assessing the Effects of Community Growth and Change on Land-Use Patterns

. Office of Research and De velopment, Cincinnati, OH. EPA/600/R00/098. 9. U.S. Department of Defense and U.S. Depar tment of Transportation. 2001. 2001 Federal Radionavigation Plan , DOT/VN TSC/RSPA-01/3; DOD-4 650.5. Av ailable a t: http://www.navcen.uscg.gov/pubs/frp2001/FRP2001.pdf. (Last accesse d March 2004.) References

# Glossary
This list of glossary terms was compiled from existing EPA definitions and supplemented, where necessary, by additional terms and definitions. The wording of selected items may have been modified from the original in order to assist readers who are new to risk assessment more readily comprehend the underlying concept of the glossary entry. As such, these glossary definitions constitute neither official EPA policy nor preempt or in any way replace any existing legal definition required by statute or regulation.April 2004 Page 1 

# A
Absorbed Dose – the amount of a substance that has penetrated the absorption barriers (e.g., skin, lung tissue, gastrointestinal tract) of an organism through either physical or biological processes. Absorption - The process of taking in, as when a sponge takes up water. Chemicals can be absorbed through the skin into the bloodstream and then transported to other organs. Chemicals can also be absorbed into the bloodstream after breathing in or swallowing. Absorption Barrier - Exchange barriers of the body that allow differential diffusion of various substances across a boundary. Examples of absorption barriers are the skin, lung tissue, and gastrointestinal tract wall. Abiotic Degradation - Degradation via purely physical or chemical mechanisms. Examples include hydrolysis and photolysis. Acceptable Risk - The likelihood of suffering disease or injury that will be tolerated by an individual, group, or society. The level of risk that is determined to be acceptable may depend on a variety of issues, including scientific data, social, economic, legal, and political factors, and on the perceived benefits arising from a chemical or process. Accuracy - The measure of the correctness of data, as given by the difference between the measured value and the true or standard value. Active Monitor - A type of personal exposure monitoring device that uses a small air pump to draw air through a filter, packed tube, or similar device. Activity Patterns - A series of discrete events of varying time intervals describing information about an individual’s lifestyle and routine. This information typically includes the locations visited, the amount of time spent in the locations, and a description of what the individual was doing in each location. Acute Effect- Any toxic effect produced with a short period of time following an exposure, for example, minutes to a few days Acute Exposure Limits - A variety of short-term exposure limits to hazardous substances, designed to be protective of human health. Published by different organizations, each limit has a different purpose and definition. Acute Exposure - One dose (or exposure) or multiple doses (or exposures) occurring within a short time relative to the life of a person or other organism (e.g., approximately 24 hours or less for humans). Actual Risk - The damage to life, health, property, and/or the environment that may occur as a result of exposure to a given hazard. Risk assessment attempts to estimate the likelihood of actual risk.April 2004 Page 2 Additive Effect- The overall result of exposure to two or more chemicals, in which the resulting effect is equal to the sum of the independent e ffects of the chemicals. “Effects” or “Response Addition” is a method employed in EPA risk assessments of mixtures in which the components act or are presumed to act independently (without interaction). Additive Dose - The overall result of exposure to two or more chemicals, when each chemical behaves as a concentration or dilution of the other chemicals in the mixture. The response of the combination is the response expected from the equivalent dose of an index chemical. The equivalent dose is the sum of component doses scaled by their toxic potency relative to the index chemical. Adjusted Exposure Concentration - Also called a refined exposure concentration, an estimate of exposure concentration that has been refined, usually by application of an exposure model, to better understand how people in a particular location interact with contaminated media. Administered Dose - The amount of a substance received by a test subject (human or animal) in determining dose-response relationships, especially through ingestion or inhalation. Advection - In meteorology, the transfer of a property, such as heat or humidity, by motion within the atmosphere, usually in a predominantly horizontal direction. Thermal advection, for example, is the transport of heat by the wind. Advection is most often used to signify horizontal transport but can also apply to vertical movement . Large-scale horizontal advection of air is a characteristic of middle-latitude zones and leads to marked changes in temperature and humidity across boundaries separating air masses of differing origins. Adverse Environmental Effect- Defined in the CAA section 112(a)(7) as “any significant and widespread adverse effect, which may reasonably be anticipated, to wildlife, aquatic life, or other natural resource, including adverse impacts on populations of endangered or threatened species or significant degradation of environmental quality over broad areas.” Adverse Health Effect- A health effect from exposure to air contaminants that may range from relatively mild and temporary (e.g., eye or throat irritation, shortness of breath, or headaches) to permanent and serious conditions (e.g., birth defects, cancer or damage to lungs, nerves, liver, heart, or other organs), and which negatively affects an individual’s health or well-being, or reduces an individual’s ability to respond to an additional environmental challenge. Affected (or Interested) Parties - Individuals and organizations potentially acted upon or affected by chemicals, radiation, or microbes in the environment or influenced favorably or adversely by proposed risk management actions and decisions. Agent- A chemical, physical, or biological entity th at may cause deleterious, beneficial, or no effects to an organism after the organism is exposed to it. Aggregate exposure - The combined exposure of an individual (or defined population) to a specific agent or stressor via relevant routes, pathways, and sources. Aggregate risk - The risk resulting from aggregate exposure to a single agent or stressor.April 2004 Page 3 AirData - An EPA website ( http://www.epa.gov/air/data/info.html ) that provides access to yearly summaries of United States air pollution data, taken from EPA’s air pollution databases. The data include all fifty states plus District of Columbia, Puerto Rico, and the U. S. Virgin Islands. AirData has information about where air pollution comes from (emissions) and how much pollution is in the air outside our homes and work places (monitoring). Air Emissions - The release or discharge of a pollutant into the air. Air Pressure (Atmospheric Pressure, Barometric Pressure) - The pressure experienced above the Earth’s surface at a specific point as a result of the weight of the air column, extending to the outer limit or top of the atmosphere. Consequently, pressure declines exponentially with height, the rate of decrease being a function of the temperature of the atmosphere. Atmospheric pressure is generally measured, in meteorology, either in the SI unit hectopascals (hPa) or in the c.g.s. unit of the same size, the millibar (mb) using a mercury or aneroid barometer, or a barograph. In the U.S., surface atmosphere pressure is measured in inches of mercury (Hg). Air Mass - A large volume of air with certain meteorological or polluted characteristics (e.g., a heat inversion or smogginess) while in one location. The characteristics can change as the air mass moves away. Air Toxic - Any air pollutant that causes or may cause cancer, respiratory, cardiovascular, or developmental effects, reproductive dysfuncti ons, neurological disorders, heritable gene mutations, or other serious or irreversible chronic or acute health effects in humans. See hazardous air pollutant

. Ambient Medium (e.g., Ambient Air) - Material surrounding or contacting an organism (e.g., outdoor air, indoor air, water, or soil), through which chemicals can reach an organism. Ambient Water Quality Criteria (AWQC) - A ecological benchmark level for aquatic contaminants, published by EPA Office of Water, which is designed to protect 95 percent of all aquatic species in freshwater or marine envir onments. Criteria have been developed for both acute and chronic exposures, although for a limited number of chemicals. Ample Margin of Safety - This term has regulatory significance in EPA’s air toxics program. It was interpreted by the Agency in the 1989 notice of final benzene NESHAP (FR54:38044- 38072), and reiterated in the 1990 amendments to the Clean Air Act (sections 112(f) and 112(c)). AMTIC - Ambient Monitoring Technology Information Center. An EPA website that contains information and files on ambient air quality monitoring programs, details on monitoring methods, monitoring-related documents and articles, information on air quality trends and nonattainment areas, and federal regulations related to ambient air quality monitoring. [ http://www.epa.gov/ttn/amtic/ , 2003]April 2004 Page 4 Analysis - The systematic application of specific theories and methods, including those from natural science, social science, engineering, decision science, logic, mathematics, and law, for the purpose of collecting and interpreting data and drawing conclusions about phenomena. It may be qualitative or quantitative. Its competence is typically judged by criteria developed within the fields of expertise from which the theories and methods come. Analysis Plan - A plan that provides all the details of exactly how each part of the risk assessment will be performed. It usually describes in detail what analyses will be performed, how they will be performed, who will perform the work, schedules, resources, quality assurance/quality control requirements, and documentation requirements. Animal Studies - Toxicity investigations using animals. Such studies may employ animals as surrogates for humans with the expectation that the results are pertinent to humans or for investigation of effects pertinent to animals (e.g., for ecological risk assessment). Antagonistic Effect- The situation where exposure to two chemicals together has less effect than the sum of their independent effects. AP-42 - A compilation of air pollutant emission factors. Volume I of the fifth edition addresses stationary point and area source emission factor s. AP-42 is accessible on the Air CHIEF website ( http://www.epa.gov/ttn/chief/ap42/ ) and is also included on the Air CHIEF CD-ROM. Applied Dose - The amount of a substance in contact with an absorption boundary of an organism (e.g., skin, lung, gastrointestinal tract) and is available for absorption. Area of Impact – The geographic area affected by a facility’s emissions (also known as the zone of impact). Area Source (legal sense) - A stationary source that emits less than 10 tons per year of a single hazardous air pollutant (HAP) or 25 tons per year of all HAPs combined. Area Source (modeling sense) - An emission source in which releases are modeled as coming from a 2-dimensional surface. Emissions from the surface of a wastewater pond are, for example, often modeled as an area source. Area Use Factor - For an animal, the ratio of its home range, breeding range, or feeding/foraging range to the area of contamination or the site area under investigation. Assessment Endpoint- An explicit expression of the environmental value to be protected. An assessment endpoint includes both an ecological entity and specific attributes of that entity. For example, salmon are a valued ecological entity; reproduction and population maintenance (i.e., the attribute) form an assessment endpoint. Assessment Questions - The questions asked during the planning/scoping phase of the risk assessment process to determine what the risk assessment will evaluate. Atmospheric Stability (Stability) - the degree of resistance of a layer of air to vertical motion.April 2004 Page 5 ATSDR (Agency for Toxic Substances and Disease Registry) - An Agency of the U.S. Department of Health and Human Services, whose goal is to serve the public by using the best science, taking responsive public health actions, and providing health information to prevent harmful exposures and diseases to toxic substances. Its website ( www.atsdr.cdc.gov ) includes information on hazardous substances [e.g., toxicol ogical profiles, minimal risk levels (MRLs)], emergency response, measuring health effects, hazardous waste sites, education and training, publications, and special issues (e.g., Children Health). Averaging Time - The time period over which something is averaged (e.g., exposure, measured concentration). 

# B Background Levels - The concentration of a chemical already present in an environmental medium due to sources other than those under study. Two types of background levels may exist for chemical substances: (a) Naturally occurring levels of substances present in the environment, and (b) Anthropogenic concentrations of substances present in the environment due to human associated activities (e.g., automobiles, industries). Background Source - Any source from which pollutants are released and contribute to the background level of a pollutant, such as volcano eruptions, windblown dust, or manmade source upwind of the study area. Benchmark Dose - An exposure due to a dose of a substance associated with a specified low incidence of risk, generally in the range of 1% to 10%, of a health effect; or the dose associated with a specified measure or change of a biological effect. Benthic Burial Rate ( k b ) - Rate of the deposition of the sediment suspended in a surface water body column to the benthic sediment surface that becomes no longer available for resuspension in the water column, effectively becoming part of the sediment “sink.” Best Available Control Technology (BACT) - An emission limitation based on the maximum degree of emission reduction (considering energy, environmental, and economic impacts) achievable through application of production processes and available methods, systems, and techniques. BACT does not permit emissions in excess of those allowed under any applicable Clean Air Act provisions. Use of the BACT concept is allowable on a case by case basis for major new or modified emissions sources in attainment areas and applies to each regulated pollutant. Best Professional Judgement- Utilizing knowledge based on education and experience to determine the best course of action during the course of performing a risk assessment project. Bias - systematic error introduced into sampling or analysis by selecting or encouraging one outcome or answer over others. Binational Toxics Strategy - A Canada-United States jointly-sponsored program that provides a framework for actions to reduce or eliminate persistent toxic substances, especially those which bioaccumulate, from the Great Lakes Basin.April 2004 Page 6 Bioaccumulation - The net accumulation of a substance by an organism as a result of uptake from and or all routes of exposure (e.g., inges tion of food, intake of drinking water, direct contact, or inhalation). Bioavailability - The ability to be absorbed and available to interact with the metabolic processes of an organism. Bioaccumulation Factor (BAF) - The concentration of a substance in tissue of an organism divided by its concentration in an environmental medium in situations where the organism and its food are exposed (i.e., accounting for food chain exposure as well as direct chemical uptake). [EPA, 1999: Residual Risk Report to Congress. EPA453R99001.] Bioassay - A test conducted in living organisms ( in vivo ) or with living cells ( in vitro ) to determine the hazard or potency of a chemical by its effect on animals, isolated tissues, or microorganisms. [Based on Air Risk Information Support Center, OAQPS, March 1989: Glossary of Terms Related to Health, E xposure, and Risk Assessment. EPA/450/3-88/016.] Bioavailability - A measure of the degree to which a dose of a substance becomes physiologically available to the body tissues depending upon adsorption, distribution, metabolism and excretion rates. [Air Risk Information Support Center, OAQPS, March 1989: Glossary of Terms Related to Health, E xposure, and Risk Assessment. EPA/450/3-88/016.] Bioconcentration - The net accumulation of a substance by an organism as a result of uptake directly from an environmental medium (e.g., net accumulation by an aquatic organism as a result of uptake directly from ambient water, through gill membranes or other external body surfaces). Bioconcentration Factor (BCF) - The concentration of a substance in tissue of an organism divided by the concentration in an environmental medium (e.g., the concentration of a substance in an aquatic organism divided by the concentration in the ambient water, in situations where the organism is exposed through the water only). Biological Medium - Any one of the major categories of material within an organism (blood, adipose tissue, breath), through which chemical s can move, be stored, or be biologically, physically, or chemically transformed. Biological Monitoring - The measurement of chemicals in biological media (e.g., blood, urine, exhaled breath) to determine whether chemical exposure in humans, animals, or plants has occurred. Biologically Effective Dose - The amount of chemical that reaches the cells or target site where an adverse effect may occur. Biomagnification or Biological Magnification - The process whereby certain substances, such as pesticides or heavy metals, transfer up the food chain and increase in concentration. For example, a biomagnifying chemical deposited in rivers or lakes absorbs to algae, which are ingested by aquatic organisms, such as small fish, which are in turn eaten by larger fish, fish-April 2004 Page 7 eating birds, terrestrial wildlife, or humans. The chemical tends to accumulates to higher concentration levels with each successive food chain level. Biotic Degradation (Biodegredation) - Decomposition or metabolism of a substance into more elementary compounds by the action of organisms (e.g., bacteria, fungi). Bounding Estimate - An estimate of exposure or risk that is higher or lower than that incurred by any person in the population. Bounding estimates are useful in developing statements that exposures or risks are within an estimated range. Blue Book - The 1994 National Research Council (NRC) report entitled Science and Judgement in Risk Assessment

. Body Weight (Mass) - The weight or mass of an individual’s body. It can apply to a human or an ecological receptor. Breathing Zone - Air in the vicinity of an organism from which respired air is drawn. Personal monitors are often used to measure pollutants in the breathing zone. Bright Line - Specific levels of risk or of exposure that are meant to provide a practical distinction between what is considered “safe” and what is not. Building Downwash (Plume Downwash) - The interaction of a plume with a structure, such as a building, which causes the plume to fall to ground. 

# C CalEPA (California Environmental Protection Agency) - An Agency within the California State government whose goal is to protect human health and the environment and to assure the coordinated deployment of State resources against the most serious environmental risks. There are six boards that address environmental issues, including air quality, pesticides, toxic substances, waste management, water control, and the Office of Environmental Health Hazard Assessment (OEHHA). Note that OEHHA is res ponsible for developing and providing state and local government agencies with toxicological and medical information relevant to decisions involving public health and is a good resource for such information. Cancer - A group of related diseases characterized by group of diseases characterized by the uncontrolled growth of abnormal cells. Cancer Incidence - The number of new cases of a disease diagnosed each year. Cancer Risk Estimates - The probability of developing cancer from exposure to a chemical agent or a mixture of chemicals over a specified period of time. In quantitative terms, risk is expressed in values ranging from zero (representing an estimate that harm certainly will not occur) to one (representing an estimate that harm certainly will occur). The following are examples of how risk is commonly expressed: 1.E-04 or 1×10 -4 = a risk of 1 additional cancer in an exposed population of 10,000 people (i.e., 1/10,000); 1.E-5 or 1×10 -5 = 1/100,000; 1.E-6 or 1×10 -6 = 1/1,000,000.April 2004 Page 8 Cancer Risk Evaluation Guides (CREGs) - Developed by ATSDR, the concentration of a chemical in air, soil or water that is expected to cause no more than one excess cancer in a million persons exposed over a lifetime. The CREG is a comparison value used to select contaminants of potential health concern and is based on the cancer slope factor (CSF). Cancer Slope Factor (CSF) - An upper bound (approximating a 95% confidence limit) on the increased cancer risk from a lifetime exposure to an agent. This estimate, usually expressed in units of proportion (of a population) affected per mg/kg/day, is generally reserved for use in the low-dose region of the dose-response relationship; that is, for exposures corresponding to risks less than 1 in 100. This term is usually used to refer to oral slope factors (i.e., slope factors used for assessing ingestion exposure). Carcinogen(ic) - An agent capable of inducing cancer. Carcinogenesis - The origin or production of a benign or malignant tumor. The carcinogenic event modifies the genome and/or other molecular control mechanisms of the target cells, giving rise to a population of altered cells. Census Bureau (Bureau of the Census) - A Bureau within the Department of Commerce, this is the country’s preeminent statistical collection and dissemination agency of national demographic information. It publishes a wide vari ety of statistical data about people, housing, and the economy of the nation. The Census Bureau conducts approximately 200 annual surveys and conducts the decennial census of the United States population and housing and the quinquennial economic census and census of governments. Census Block - An area bounded by visible and/or invi sible features shown on Census Bureau maps. A block is the smallest geographic entity for which the Census Bureau collects and tabulates 100-percent decennial census data. Census Tract- A small, relatively permanent statistical subdivision of a county or statistically equivalent entity, delineated for data presentation purposes by a local group of census data users or the geographic staff of a regional census center in accordance with Census Bureau guidelines. Designed to be relatively homogeneous units with respect to population characteristics, economic status, and living conditions at the time they are established, census tracts generally contain between 1,000 and 8,000 people, with an optimum size of 4,000 people. Census tract boundaries are delineated with the intention of being stable over many decades, so they generally follow relatively permanent visible features. However, they may follow governmental unit boundaries and other invisible features in some instances; the boundary of a state or county (or statistically equivalent entity) is always a census tract boundary. Census Tract (or Census Block) Internal Point- A set of geographic coordinates (latitude and longitude) that is located within a specified geographic entity such as a Census Tract or Census Block. For many Census Tracts or Blocks, this point represents the approximate center of the Census Tract or Block; for some, the shape of the entity or the presence of a body of water causes the central location to fall outside the Census Tract or Block or in water, in which case the point is relocated to land area within the Census Tract or Block. The geographic coordinates are shown in degrees to six decimal places in census products.April 2004 Page 9 Chemical Abstracts Service Registry Number (CASRN) - A unique, chemical-specific number used in identifying a substance. The registry numbers are assigned by the Chemical Abstract Service, a division of the American Ch emical Society. (Note that some mixtures of substances, such as mixtures of various forms of xylene, are also given CAS numbers.) Chemicals of Potential Concern - Chemicals that may pose a threat to the populations within the study area. These are the chemicals which are carried through the risk assessment process. Chemical Speciation - Detailed identification of the specific identities and forms of chemicals in a mixture. Chemical Transformation - The change of one chemical into another. Chronic Exposure - Continuous exposure, or multiple exposures, occurring over an extended period of time or a significant fraction of the animal’s or the individual’s lifetime. Chronic Health Effects - An effect which occurs as a result of repeated or long term (chronic) exposures. Coefficient of Variation (CV) - A dimensionless measure of dispersion, equal to the standard deviation divided by the mean, often expressed as a percentage. Cohort- A group of people within a population that can be aggregated because the variation in a characteristic of interest (e.g., exposure, age, education level) within the group is much less than the group-to-group variation across the population. Community - The persons associated with an area who may be directly affected by area pollution because they currently live in or near the area, or have lived in or near the area in the past (i.e., current or past residents), member s of local action groups, local officials, tribal governments, health professionals, and local media. Other entities, such as local industry, may also consider themselves part of the community. Comparative Risk Assessment- The process of comparing and ranking various types of risks to identify priorities and influence resource allocations. Conceptual Model - A written description and/or a visual representation of actual or predicted relationships between humans or ecological entities and the chemicals or other stressors to which they may be exposed. Conductivity (Conductance) - The ability of a material to carry and electrical current. Confidence Interval - A range of values that has a specified probability (e.g., 95 percent) of containing the statistical parameter (i.e., a quantity such as a mean or variance that describes a statistical population) in question. The confidence limit refers to the upper or lower value of the range. Coning - In pollution studies, emissions from a chimney stack under atmospheric conditions of near neutral stability such that concentrations of a pollutant at a given distance downwind fromApril 2004 Page 10 the stack may be described by a normal or Gaussian distribution, being the same for both vertical and horizontal cross-sections perpendicular to the flow. Consumption Rate - The average quantity of an item consumed or expended during a given time interval, expressed in quantities by the most appropriate unit of measurement per applicable stated basis. Continuous Monitoring - The measurement of the air or water concentration of a specific contaminant on an uninterrupted, real-time basis by instrumental methods. Control Technology/Measures - Equipment, processes or actions used to reduce air pollution at the source. Convection - The transfer and mixing of heat by mass movement through a fluid (e.g., air or water). It is one of the major mechanisms for th e transfer of heat within the atmosphere, together with conduction and radiation. The convection process is of major importance in the troposphere, transferring sensible heat and latent heat from the Earth’s surface into the boundary layer, and by promoting the vertical exchange of air-mass properties (e.g., heat, water vapor, and momentum) throughout the depth of the troposphere. Convection is generally accepted to be vertical circulation, whereas advection is usually horizontal. Cost-Benefit Analysis - An evaluation of the costs which would be incurred versus the overall benefits of a proposed action, such as the esta blishment of an acceptable exposure level of a pollutant. Criteria Air Pollutant- One of six common air pollutants determined to be hazardous to human health and regulated under EPA’s National Ambient Air Quality Standards (NAAQS). The six criteria air pollutants are carbon monoxide, lead, nitrogen dioxide, ozone, sulfur dioxide, and particulate matter. The term “criteria pollutants” derives from the requirement that EPA must describe the characteristics and potential health a nd welfare effects of these pollutants. It is on the basis of these criteria that standards are set or revised. Critical Effect- The first adverse effect, or its known precursor, that occurs to the most sensitive species as the dose rate of an agent increases. Cumulative Risk - The combined risk from aggregate exposures to multiple agents or stressors. Cumulative Risk Assessment- An analysis, characterization, and possible quantification of the combined risks to health or the environment from multiple agents or stressors. Cumulative Distribution Function (CDF) - The CDF is alternatively referred to in the literature as the distribution function, cumulative frequency function, or the cumulative probability function. The cumulative distribution function, F(x), expresses the probability the random variable X assumes a value less than or equal to some value x, F(x) = Prob (X 

### # x). For continuous random variables, the cumulative distribution function is obtained from the probability density function by integration, or by summation in the case of discrete random variables.April 2004 Page 11 Cumulative Risk Assessment- An analysis, characterization, and possible quantification of the combined risks to health or the environment from multiple agents or stressors. 

# D Data Integrity - Refers to security (i.e., the protection of information from unauthorized access or revision) to ensure that the information is not compromised through corruption or falsification. Data integrity is one of the constituents of data quality. Data Objectivity - A characteristic indicating whether information is being presented in an accurate, clear, complete, and unbiased manner, and as a matter of substance, is accurate, reliable, and unbiased. Data objectivity is one of the constituents of data quality. Data Quality - The encompassing term regarding the quality of information used for analysis and/or dissemination. Utility, objectivity, and integrity are constituents of data quality. Data Quality Objectives (DQOs ) - Qualitative and quantitative statements derived from the DQO process that clarify study objectives, define the appropriate type of data, and specify tolerable levels of potential decision errors that will be used as the basis for establishing the quality and quantity of data needed to support the decisions. Data Quality Objectives Process - A systematic planning tool to facilitate the planning of environmental data collection activities. Data quality objectives are the qualitative and quantitative outputs from the DQO Process. Data Utility - Refers to the usefulness of the information to the intended users. Data utility is one of the constituents of data quality. Delivered Dose - The amount of the chemical available for interaction by any particular organ or cell. Deposition (Wet and Dry) - The removal of airborne substances to available surfaces that occurs as a result of gravitational settling and diffusion, as well as electrophoresis and thermophoresis in the absence of active preci pitation (Dry) or in the presence of active precipitation (Wet). Deposition (Flux) - The removal of airborne substances from the air to available surfaces that occurs as a result of gravitational settling and diffusion, as well as electrophoresis and thermophoresis. Dermal - Referring to the skin. Dermal absorption means absorption through the skin. Dermal Exposure - Contact between a chemical and the skin. [EPA, 1997: Terms of Environment, http://www.epa.gov/OCEPAterms/.] Detection Limit- The lowest concentration of a chemical that can reliably with analytical methods be distinguished from a zero concentration.April 2004 Page 12 Deterministic - A methodology relying on point (i.e., exact) values as inputs to estimate risk; this obviates quantitative estimates of uncertainty and variability. Results are also presented as point values. Uncertainty and variability may be discussed qualitatively, or semi-quantitatively by multiple deterministic risk estimates. Developmental Toxicity - The potential of an agent to cause abnormal development. Developmental toxicity generally occurs in a dose-related manner, may result from short-term exposure (including single exposure situations) or from longer term low-level exposure, may be produced by various routes of exposure, and th e types of effects may vary depending on the timing of exposure because of a number of critical periods of development for various organs and functional systems. The four major manife stations of developmental toxicity are death, structural abnormality, altered growth, and functional deficit. Dietary Composition - The fractions of different foods that constitute a given diet. Differential Heating - The property of different surfaces which causes them to heat and cool at different rates. Direct Exposure - Contact between a receptor and a chemical where the chemical is still in the medium to which it was originally released. For example, direct exposure occurs when a pollutant is released to the air and a person breathes that air. Direct-read Monitor - Using a pump to draw the air sample through the detector, this type of air toxics monitoring device provides a direct reading of the pollutant measurement. The monitor may be designed as a table-top unit, for example, or it may be rack-mounted such as for use in an ambient air monitoring station. Dispersion - Pollutant or concentration mixing due to turbulent physical processes. Disease Cluster - An unusual number, real or perceived, of health events (i.e., reports of cancer) grouped together in time and location.April 2004 Page 13 Dose - The amount of substance available for interaction with metabolic processes or biologically significant receptors after crossing th e outer boundary of an organism. The potential dose is the amount ingested, inhaled, or applied to the skin. The applied dose is the amount of a substance presented to an absorption barrier and available for absorption (although not necessarily having yet crossed the outer boundary of the organism). The absorbed does is the amount crossing a specific absorption barrier (e.g., the exchange boundaries of skin, lung, and digestive tract) through uptake processes. Internal dose is a more general term denoting the amount absorbed without respect to specific absorption barriers or exchange boundaries. The amount of the chemical available for interaction by any particular organ or cell is termed the delivered dose for that organ or cell. Dose-Response Assessment- A determination of the relationship between the magnitude of an administered, applied, or internal dose and a specific biological response. Response can be expressed as measured or observed incidence, percent response in groups of subjects (or populations), or as the probability of occurrence within a population. Dose-Response Curve - A graphical representation of the quantitative relationship between administered, applied, or internal dose of a chem ical or agent, and a specific biological response to that chemical or agent. Dust Resuspension - Involves the deposition of dust from the air and its subsequent resuspension or re-entrainment into the atmosphere. 

# E Ecological Risk Assessment- The process that evaluates the likelihood that adverse ecological effects may occur or are occurring as a result of exposure to one or more stressors. Eddy - In the atmosphere, a distinct mass within a turbulent fluid that retains its identity and behaves differently for a short period within the general larger volume flow. An eddy thus ranges in size from microscale turbulence (1 cm for example) to many hundreds of kilometers in the form of frontal cyclones and anticyclones. The smallest scale eddies are critical in the process of, for example, heat and water vapor tran sfer from the Earth’s surface into the air, while frontal cyclones transport heat toward the poles. Emission Factor - The relationship between the amount of pollution produced and the amount of raw material processed or product produced. For example, an emission factor for a blast furnace making iron could be the number of pounds of particulates released per ton of raw materials used. Emission Inventory - A listing, by source, of the amount of air pollutants discharged into the atmosphere in a particular place. Two of the more important publicly available emissions inventories for air toxics studies are the Na tional Emissions Inventory (NEI) and the Toxics Release Inventory (TRI). Emission Rate - The amount of a given substance discharged to the air per unit time, expressed as a fixed ratio (e.g., tons/yr).April 2004 Page 14 Emissions Inventory Improvement Program (EIIP) - A jointly sponsored effort of the State and Territorial Air Pollution Program Administra tors/Association of Local Air Pollution Control Officials (STAPPA/ALAPCO) and EPA, and is an outgrowth of the Standing Air Emissions Work Group (SAEWG). The goal of EIIP is to provide cost-effective, reliable inventories by: (1) Improving the quality of emissions information, and (2) Developing system(s) for collecting, calculating, and reporting emissions data. The goal is achieved by developing a set of “preferred and alternative methods” for all inventory associated tasks. This standardization improves the consistency of collected data and results in increased usefulness of emissions information. Emissions Monitoring - The periodic or continuous physical surveillance or testing to determine the pollutant levels discharged into the atmosphere from sources such as smokestacks at industrial facilities and exhaust from motor vehicles, locomotives, or aircraft. Emissions Tracking System (ETS) - This EPA system contains all emissions data submitted under various clean air market programs. Data from Continuous Emissions Monitoring Systems at utilities sends the emission data to the utility’s computer system, which then compiles the data for submission to EPA on a quarterly basis. At the end of each calendar year, EPA compares tons of emissions emitted with the allowance holdings of the utility unit to ensure that it is in compliance with the relevant program. Endocrine Disruptor - Substances which interfere with endocrine system function. Environmental Data - Any measurements or information that describe environmental processes, location, or conditions; ecological or health effects and consequences; or the performance of environmental technology. Environmental data include information collected directly from measurements, produced from models, and compiled from other sources such as data bases or the literature. Environmental Media Evaluation Guides - Environmental Media Evaluation Guides (EMEGs) are concentrations of a contaminant in water, soil, or air that are unlikely to be associated with any appreciable risk of delete rious noncancer effects over a specified duration of exposure. EMEGs are derived from ATSDR mini mal risk levels by factoring in default body weights and ingestion rates. Separate EMEGS are computed for acute (14 days), intermediate (15-364 days), and chronic (365 days) exposures. Environmental Medium - Any one of the major categories of material found in the physical environment (e.g., surface water, ground water, soil, or air), and through which chemicals or pollutants can move. Epidemiology - The study of disease patterns in human populations. Epidemiologic Study, Case Study - A medical or epidemiologic evaluation of one person or a small group of people to gather information about specific health conditions and past exposures. Epidemiologic Study, Descriptive - An evaluation of the amount and distribution of a disease in a specified population by person, place, and time.April 2004 Page 15 Epidemiologic Study, Analytical - An evaluation of the association between exposure to hazardous substances and disease by testing scientific hypotheses. Exposure - Contact made between a chemical, physical, or biological agent and the outer boundary of an organism. Exposure Assessment- An identification and evaluation of a population exposed to a toxic agent, describing its composition and size, as well as the type, magnitude, frequency, route and duration of exposure. Exposure Concentration - The concentration of a chemical in its transport or carrier medium (i.e., an environmental medium or contam inated food) at the point of contact. Exposure Duration - The total time an individual is exposed to the chemical being evaluated or the length of time over which contact with the contaminant lasts. Exposure Factors - Any of a variety of factors that rela te to how an organism interacts with or is otherwise exposed to environmental pollutants (e.g., ingestion rate of contaminated fish). Such factors are used in the calculation of exposure to toxic chemicals. Exposure Frequency - The number of occurrences in a given time frame (e.g., a lifetime) of contact or co-occurrence of a stressor with a receptor. Exposure Investigation (in Public Health Assessment) - The collection and analysis of site-specific information and biologic tests (when appropriate) to determine whether people have been exposed to hazardous substances. Exposure Modeling - The mathematical equations simulating how people interact with chemicals in their environment. Exposure Pathway - The course a chemical or physical agent takes from a source to an exposed organism. An exposure pathway includes a source and release from a source, an exposure point, and an exposure route. If the exposure point differs from the source, a transport/exposure medium (e.g., air) or media (in cases of intermedia transfer) also is included. Exposure Profile - The exposure profile (ecological) identifies the receptors and describes the exposure pathways and intensity and spatial and temporal extent of exposure. It also describes the impact of variability and uncertainty on exposure estimates and reaches a conclusion about the likelihood that exposure will occur. The profile may be a written document or a module of a larger process model. Exposure Route - The way a chemical enters an organism after contact (e.g., by ingestion, inhalation, dermal absorption). Exposure Scenario - A set of conditions or assumptions about sources, exposure pathways, concentrations of toxic chemicals, and populations (numbers, characteristics and habits) which aid the investigator in evaluating and quantifying exposure in a given situation.April 2004 Page 16 Exposure Unit (in Geographical Information System applications) - The geographical area in which a receptor moves and contacts the contaminated medium during the period of exposure. 

# F Factor Information Retrieval System (FIRE) - A database management system containing EPA’s recommended emission estimation factors for criteria and hazardous air pollutants. FIRE includes information about industries and their emitting processes, the chemicals emitted, and the emission factors themselves. FIRE allows easy access to criteria and hazardous air pollutant emission factors obtained from the Compilation of Air Pollutant Emission Factors (AP-42), Locating and Estimating (L&E) documents, and the retired AFSEF and XATEF documents. Fate and Transport- A description of how a chemical is carried through and changes in the environment. Fate and Transport Analysis - The general process used to assess and predict the movement and behavior of chemicals in the environment. Fate and Transport Modeling - The mathematical equations simulating a physical system which are used to assess and predict the movement and behavior of chemicals in the environment. Fence Line - Delineated property boundary of a facility. Field Study - Scientific study made in the ambient air to collect information that can not be obtained in a laboratory. Food Chain - A sequence of organisms, each of which uses the next lower member of the sequence as a food source. Forage - (1) Edible parts of plants, other than separated grain, that can provide feed for grazing animals or can be harvested for feeding, including browse, and herbage. (2) To search for or to consume forage (of animals). Fugitive Release - Emission of a chemical to the air that does not occur from a stack, vent, duct, pipe or other confined air stream (e.g., leaks from joints). Fumigation - (1) The use of a chemical compound in a gaseous state, often to kill pests such as insects, nematodes, arachnids, rodents, weeds, and fungi in confined or inaccessible locations or in the field. (2) a pattern of plume dispersion produced when a convective boundary layer grows upward into a plume trapped in a stable layer. The elevated plume is suddenly brought downward to the ground, producing high surface concentrations. Future Scenario - A scenario used in risk assessment to anticipate potential future exposures of individuals (e.g., a housing development could be built on currently vacant land).April 2004 Page 17 

# G Geographic Information Systems (GIS) - A computer program that allows layering of different types of spatial information (i.e., on a map) to provide a better understanding of the characteristics of a certain place. Generally Available Control Technology (GACT) Standard - These standards are less stringent standards than the Maximum Available Control Technology (MACT) standards, and are allowed at the Administrator’s discretion for area sources according to the 1990 Clean Air Act Amendments for area sources. Grab Sample -A single sample collected at a particular time and place that represents the composition of the water, air, or soil only at that time and place. Great Waters Pollutants of Concern - The toxic pollutants of concern to the Great Waters program are mercury; cadmium and lead (and their compounds); dioxins; furans; polycyclic organic matter; polychlorinated biphenyls (PCBs); and the pesticides chlordane, DDT/DDE, dieldrin, hexachlorobenzene, alpha-hexachloro cyclohexane, lindane and toxaphene. Nitrogen compounds such as nitrogen oxides and ammonia are also pollutants of concern. Greenhouse Effect - Trapping and build-up of heat in the atmosphere (troposphere) near the earth’s surface. Some of the heat flowing back toward space from the earth’s surface is absorbedby water vapor, carbon dioxide, ozone, and several other gases in the atmosphere and then reradiated back toward the earth’s surface. If the atmospheric concentrations of these greenhouse gases rise, the average temperature of the lower atmosphere will gradually increase. Greenhouse Gas (GHG) - Any gas that absorbs infrared radiation in the atmosphere. Greenhouse gases include, but are not limited to, water vapor, carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O), hydrochlorofluorocarbons (HCFCs), ozone (O 3 ), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF 6 ). Guidelines (human health and ecological risk assessment) - Official documentation stating current U.S. EPA methodology in assessing risk of harm from environmental pollutants to human populations and ecological receptors. 

# H
Half-Life - The time required for a reaction or process to proceed such that half of the original amount of the substance of interest has reacted or undergone the process. Examples include: (1) the time required for a pollutant to degrade to one-half of its original concentration; (2) the time required for half of the atoms of a radioactive element to undergo self-transmutation or decay (half-life of radium is 1620 years); (3) the time required for elimination from the body to half a total dose. Hazard - In a general sense, “hazard” is anything that has a potential to cause harm. In risk assessment, the likelihood of experiencing a noncancer health effect is called hazard (not risk).April 2004 Page 18 Hazard Identification - The process of determining whether exposure to an agent can cause a particular adverse health effect (e.g., cancer, birth defect) and whether the adverse health effect is likely to occur in humans at environmentally relevant doses. Hazard Index (HI) -The sum of more than one hazard quotient for multiple substances and/or multiple exposure pathways. The HI is calculated separately for chronic, subchronic, and shorter-term duration exposures. Hazardous Air Pollutants (HAP) - Defined under the Clean Air Act as pollutants that cause or may cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental and ecological effects. Currently, the Clean Air Act regulates 188 chemicals and chemical categories as HAPs. Hazard Quotient (HQ) - The ratio of a single substance exposure level over a specified time period (e.g., chronic) to a reference value (e.g., an RfC) for that substance derived from a similar exposure period. Health Effects Assessment Tables (HEAST) - An older listing of (usually) interim toxicity values for chemicals of interest to Superfund, the Resource Conservation and Recovery Act (RCRA), and the EPA in general. HEAST values are generally placed low on the hierarchy of Agency recommended toxicity data sources and the compilation will eventually be phased out altogether. Health Endpoint- An observable or measurable biological event used as an index to determine when a deviation in the normal function of the human body occurs. Health Outcome Data (in Public Health Assessment) - Community-specific health information such as morbidity and mortality data, birth statistics, medical records, tumor and disease registries, surveillance data, and previously conducted health studies that may be collected at the local, state, and national levels by governments, private health care organizations, and professional institutions and associations. Health Outcomes Study (in Public Health Assessment) - An investigation of exposed persons designed to assist in identifying exposure or eff ects on public health. Health studies also define the health problems that require further inquiry by means of, for example, a health surveillance or epidemiologic study. Health Education (in Public Health Assessment) - Programs designed with a community to help it know about health risks and how to reduce these risks. Health Consultation (in Public Health Assessment) - A review of available information or collection of new data to respond to a specific health question or request for information about a potential environmental hazard. Health consultations are focused on a specific exposure issue. Health consultations are therefore more limited than a public health assessment, which reviews the exposure potential of each pathway and chemical. Henry’s Law Constant- The ratio at equilibrium of the gas phase concentration to the liquid phase concentration of the gas.April 2004 Page 19 High-End Exposure Estimate - A plausible estimate of individual exposure or dose for those persons at the upper end of an exposure or dose distribution, conceptually above the 90th percentile, but not higher than the individual in the population who has the highest exposure or dose. Human Exposure Model (HEM) - An EPA model combining the Industrial Source Complex Short Term air dispersion model (ISCST) with a national set of meteorology files, U.S. census data, and a risk calculation component that can be used to estimate individual and population risks. Hydrolysis - The decomposition of organic compounds by interaction with water. 

# I Impervious Surface - A surface that cannot be penetrated by water (e.g., pavement). Indirect Exposure Pathway - An indirect exposure pathway is one in which a receptor contacts a chemical in a medium that is different from the one to which the chemical was originally released (an example occurs with dioxin, which is emitted into the air, deposited on soil and accumulated in plants and animals which are then consumed by humans). Individual Risk or Hazard - The risk or hazard to an individual in a population rather than to the population as a whole. Indoor Source - Objects or places within buildings or other enclosed spaces that emit air pollutants. Industrial Source Complex (ISC) Model - A steady-state Gaussian plume model which can be used to assess pollutant concentrations from a wide variety of sources associated with an industrial complex. This model can account for the following: settling and dry deposition of particles; downwash; point, area, line, and volume sources; plume rise as a function of downwind distance; separation of point sources; and limited terrain adjustment. ISC3 operates in both long-term (ISCLT) and short-term (ISCST) modes. Influential Information - Scientific, financial, or statistical information that will have or does have a clear and substantial impact on important public policies or important private sector decisions. Ingestion - Swallowing (such as eating or drinking). Ingestion Exposure - Exposure to a chemical by swallowing it (such as eating or drinking). Inhalation - Breathing. Inhalation Exposure - Exposure to a chemical by breathing it in.April 2004 Page 20 Inhalation Unit Risk (IUR) - The upper-bound excess lifetime cancer risk estimated to result from continuous exposure to an agent at a concentration of 1 μg/m 3 in air. The interpretation of unit risk would be as follows: if unit risk = 2 × 10 -6 μg/m 3 , 2 excess tumors may develop per 1,000,000 people if exposed daily for a lifetime to a c oncentration of 1 μg of the chemical in 1 m 3 of air. Intake - The process by which a substance crosses the outer boundary of an organism without passing an absorption barrier, e.g., through ingestion or inhalation. Intake Rate - Rate of inhalation, ingestion, and dermal contact depending on the route of exposure. Integrated Risk Information System (IRIS) - An EPA database which contains information on human health effects that may result from exposure to various chemicals in the environment. IRIS was initially developed for EPA staff in response to a growing demand for consistent information on chemical substances for use in risk assessments, decision-making and regulatory activities. The information in IRIS is intended for those without extensive training in toxicology, but with some knowledge of health sciences. Internal Dose - In exposure assessment, the amount of a substance penetrating the absorption barriers (e.g., skin, lung tissue, gastrointestinal tract) of an organism through either physical or biological processes. Inversion - Subsidence Inversion - A temperature inversion that develops aloft as a result of air gradually sinking over a wide area and being warmed by adiabatic compression, usually associated with subtropical high pressure areas. Inversion - Advection Inversion - Associated with the horizontal flow of warm air. Warm air moves over a cold surface, and the air near est the surface cools, causing a surface-based inversion. Inversion - Radiation Inversion - A thermally produced, surface-based inversion formed by rapid radiational cooling of the Earth’s surface at night. It does not usually extend above the lower few hundred feet. Conditions which are fa vorable for this type of inversion are long nights, clear skies, dry air, little or no wind, and a co ld or snow covered surface. It is also called a Nocturnal Inversion. Iterative Process - Replication of a series of actions to produce successively better results, or to accommodate new and different critical information or scientific inferences. Isopleths - A delineated line or area on a map that represent equal values of a variable.April 2004 Page 21 

# L Laboratory Studies - Research carried out in a laboratory (e.g., testing chemical substances, growing tissues in cultures, or performi ng microbiological, biochemical, hematological, microscopical, immunological, parasitological tests). Leaching - The process by which soluble constituents are dissolved and filtered through the soil by a percolating fluid (usually rainwater). Life Stage - A phase in the life cycle of an organism. Line Source - A theoretical one-dimensional source from which releases may occur (e.g., roadways are often modeled as a one-dimensional line). Lofting - In pollution studies, a pattern of flow that occurs when the top of a plume from a chimney stack disperses into slightly turbulent or neutral airflow conditions, while the lower part of the plume is prevented from dispersing down toward the surface by a stable boundary layer, especially at night. [Smith, J. [ed], 2001: The F acts on File Dictionary of Weather and Climate.] Low-dose Extrapolation - An estimation of the dose-response relationship at doses less than the lowest dose studied experimentally. Lowest Observed Adverse Effect Level (LOAEL) - The lowest exposure level in a study or group of studies at which there are statistically or biologically significant increases in frequency or severity of adverse effects between the exposed population and its appropriate control group. Also referred to as lowest-effect level (LEL). 

# M Major Source - Under the Clean Air Act, a stationary source that emits more than 10 tons or more per year of a single hazardous air pollutant (HAP) or 25 or more tons per year of all HAPs. Margin of exposure (MOE) - The point of departure divided by the actual or projected environmental exposure of interest. Mass-Balance Estimate - An estimate of release of a chemical based on, generally, a comparison of the amount of chemical in raw materials entering a process versus the amount of chemical going out in products. Maximum Achievable Control Technology (MACT) - Under the Clean Air Act, a group of technology based standards, applicable to both major and some area sources of air toxics, that are aimed at reducing releases of air toxics to the environment. MACT standards are established on a source category by source category basis. Maximum Exposed Individual (MEI) - The MEI represents the highest estimated risk to an exposed individual, regardless of whether people are expected to occupy that area.April 2004 Page 22 Maximum Individual Risk (MIR) - An MIR represents the highest estimated risk to an exposed individual in areas that people are believed to occupy. Metric (or Measure) of Exposure - The quantitative outcome of the exposure assessment. For air toxics risk assessments, personal air concentration (or adjusted exposure concentration) is the metric of exposure for the inhalation route of exposure and intake rate is the metric of exposure for the ingestion route of exposure. Measurement- In air toxics assessment, a physical assessment (usually of the concentration of a pollutant) taken in an environmental or biological medium, normally with the intent of relating the measured value to the exposure of an organism. Measurement Endpoint - A measurable ecological characteristic that is related to the valued characteristic chosen as the assessment endpoint. Also known as “measure of effect.” Mechanical Turbulence - Random irregularities of fluid motion in air caused by buildings or other nonthermal, processes. Mechanistic Model - A model that uses information about a chemical or other agent’smechanism(s) of action – how it interacts with and harms the target organs – to predict the doseresponse curve or other applications. Media Concentrations - The amount of a given substance in a specific amount of environmental medium. For air, the concentration is usually given as micrograms (μg) of substance per cubic meter (m 3 ) of air; in water as μg of substance per L of water; and in soil as mg of substance per kg of soil. Metabolism - Generally, the biochemical reactions by which energy is made available for the use of an organism. Metabolism includes all chemical transformations occurring in an organism from the time a substance enters, until it has been utilized and the waste products eliminated. In toxicology, metabolism of a toxicant consists of a series of chemical transformations that take place within an organism. A wide range of enzymes act on toxicants, that may increase water solubility, and facilitate elimination from the organism. In some cases, however, metabolites may be more toxic than their parent compound. Meteorology - The science of the atmosphere, including weather. Microcosm Studies - Studies of the effects of stressors on multiple species found in multiple media which are conducted in enclosed experimental systems. Microscale Assessment- An air monitoring network designed to assess concentrations in air volumes associated with area dimensions ranging from several meters up to about 100 meters. Microenvironment- A small 3-dimensional space (e.g., an office, a room in a home) that can be treated as homogeneous (or well characterized) with regard to exposure concentration of a chemical.April 2004 Page 23 Middle Scale Assessment- An air monitoring network designed to assess concentrations typical of areas up to several city blocks in size with dimensions ranging from about 100 meters to 0.5 kilometer. Minimal Risk Levels (MRL) - Derived by ATSDR, an MRL is defined as an estimate of daily human exposure to a substance that is likely to be without an appreciable risk of adverse effects (noncancer) over a specified duration of exposure. MRLs can be derived for acute, intermediate, and chronic duration exposures by the inhalation and oral routes. Mixed (Mixing) Layer - In the atmosphere, that part of the turbulent boundary layer that is dominated by turbulent diffusion caused by eddies generated by friction with the surface and thermals arising from surface heat sources. Surface heating during the day and the absence of temperature inversions allow components of the air within the planetary boundary layer to exhibit mainly random vertical movements. Such movements may become more organized into gusts of wind and dust devils during the afternoon. Despite being random, the turbulent movements allow the transfer of atmospheric properties, such as heat, water vapor, momentum, and air pollutants, from the near surface up through the planetary boundary layer. Mixing Height- The depth through which atmospheric pollutants are typically mixed by dispersive processes. Mixtures - Any set of multiple chemical substances occurring together in an environmental medium. Mobile Source Air Toxics - Air toxics that are emitted from non-stationary objects that release pollution. Mobile sources include cars, trucks, buses, planes, trains, motorcycles and gasoline-powered lawn mowers. Another example is a portable generator. Model - A mathematical representation of a natural system intended to mimic the behavior of the real system, allowing description of empirical da ta, and predictions about untested states of the system. Model Uncertainty - Uncertainty due to necessary simplification of real-world processes, misspecification of the model structure, model misuse, or use of inappropriate surrogate variables or inputs. Modeling - An investigative technique using a mathematical or physical representation of a system or theory that accounts for all or some of its known properties. Modeling Node - In air quality modeling, the location where impacts are predicted. Monitoring - Periodic or continuous physical surveillance or testing to determine pollutant levels in various environmental media or in humans, plants, and animals. Monte Carlo Technique - A repeated random sampling from the distribution of values for each of the parameters in a generic exposure or risk equation to derive an estimate of the distribution of exposures or risks in the population.April 2004 Page 24 

# ( ) Pd e q qd q d q d k k 

### ( ) ... 

### = − − + + ++ 

### 1 01 2 2 Multipathway Assessment - An assessment that considers more than one exposure pathway. For example, evaluation of exposure through both inhalation and ingestion would be a multipathway assessment. Another example would be evaluation of ingestion of contaminated soil and ingestion of contaminated food. Multipathway Exposure - When an organism is exposed to pollutants through more than one exposure pathway. One example would be e xposure through both inhalation and ingestion. Another example would be ingestion of contamin ated soil and ingestion of contaminated food. Multipathway Risk - The risk resulting from exposure to pollutants through more than one pathway. Multistage Model - A mathematical function used to extrapolate the probability of cancer from animal bioassay data, using the form:

where: P(d) = probability of cancer from a continuous, lifetime exposure rate d; q i = fitted dose coefficients of model; i = 0, 1, . . ., k; and k = number of stages selected through best fit of the model, no greater than one less than the number of available dose groups. Mutagen - A chemical that causes a permanent genetic change in a cell other than that which occurs during normal growth. Mutagenicity - The capacity of a chemical or physical agent to cause permanent genetic change in a cell other than that which occurs during normal growth. 

# N National Ambient Air Quality Standards (NAAQS) - Maximum air pollutant standards that EPA has set under the Clean Air Act for attainment by each state. Standards are set for each of the criteria pollutants. National Air Toxics Assessment (NATA) - EPA’s ongoing comprehensive evaluation of air toxics in the U.S. Activities include expansion of air toxics monitoring, improving and periodically updating emission inventories, im proving national- and local-scale modeling and risk characterization, continued research on health effects and exposures to both ambient and indoor air, and improvement of assessment tools. National Emissions Inventory (NEI) - EPA’s primary emissions inventory of HAPs. National Emissions Standards for Hazardous Air Pollutants (NESHAPs) - Emissions standards set by EPA for hazardous air pollutants. Also commonly referred to as the MACT standards.April 2004 Page 25 National Emissions Trends (NET) Database - The NET database is an emission inventory that contains data on stationary and mobile sources that emit criteria air pollutants and their precursors. The database also includes estimates of annual emissions of these pollutants from point, area, and mobile sources. The NET is developed every three years (e.g., 1996 and 1999) by EPA, and includes emission estimates for all 50 States, the District of Columbia, Puerto Rico, and the Virgin Islands. Natural Source - Non-manmade emission sources, including biological (biogenic sources such as plants) and geological sources (such as volcanoes), and windblown dust. Neighborhood Scale Assessment- An air monitoring network designed to assess concentrations within some extended area of the city that has relatively uniform land use with dimensions in the 0.5 to 4.0 kilometers range. Neurotoxicity - Ability to damage nervous system tissue or adversely effect nervous system function. New Source Review - A Clean Air Act requirement that State Implementation Plans must include a permit review that applies to the construction and operation of new and modified stationary sources in nonattainment areas to ensure attainment of national ambient air quality standards. New Source Performance Standards - Uniform national EPA air emission standards which limit the amount of pollution allowed from new sources or from modified existing sources. Noncarcinogenic Effect- Any health effect other than cancer. Note that, while not all noncancer toxicants cause cancer, all carcinogens exhibit noncarcinogenic effects. No Observable Adverse Effect Level (NOAEL) - An highest exposure level at which there are no statistically or biologically significant increases in the frequency or severity of adverse effect between the exposed population and its appropriate control; some effects may be produced at this level, but they are not considered adverse, nor precursors to adverse effects. Nonpoint Source (NEI sense) - Diffuse pollution sources that are not assigned a single point of origin (e.g., multiple dry cleaners in a county which are only described in an inventory in the aggregate). Nonroad Mobile Sources - Sources such as farm and construction equipment, gasoline-powered lawn and garden equipment, and power boats and outdoor motors that emit pollutants. Non-Threshold Effect- An effect (usually an adverse health effect) for which there is no exposure level below which the effect is not expected to occur. Non-Threshold Toxicant - A chemical for which there is no exposure level below which an adverse health outcome is not expected to occur. Such substances are considered to pose some risk of harm at any level of exposure.April 2004 Page 26 Non Steady-state Model - A dynamic model; a mathematical formulation describing and simulating the physical behavior of a system or a process and its temporal variability. North American Industry Classi fication System (NAICS) - NAICS replaced the Standard Industrial Classification (SIC) beginning in 1997. This industry-wide classification system has been designed as the index for statistical reporting of all economic activities of the U.S., Canada, and Mexico. NAICS industries are identified by a 6-digit code. The international NAICS agreement fixes only the first five digits of the code. The sixth digit, where used, identifies subdivisions of NAICS industries that accomm odate user needs in individual countries. 

# O Octanol/Water Partition Coefficient (K ow ) - The ratio of a chemical’s solubility in n-octanol to its solubility in water at equilibrium. This measure is often used as an indication of a chemical’s ability to bioconcentrate in organisms. Office of Air and Radiation (OAR) - EPA’s Office responsible for providing information about air pollution, clean air, air quality and radiation. OAR develops national programs, technical policies, and regulations for controlling air pollution and radiation exposure. OAR is concerned with pollution prevention, indoor and outdoor ai r quality, industrial air pollution, pollution from vehicles and engines, radon, acid rain, stratos pheric ozone depletion, and radiation protection. Office of Air Quality, Planning, and Standards (OAQPS) - An EPA Office within OAR whose primary mission is to preserve and improve air quality in the United States. As part of this goal, OAQPS monitors and reports on air quality, air toxics, and emissions. They also respond to visibility issues, as they relate to the level of air pollution. In addition, OAQPS is tasked by the EPA with providing technical information for professionals involved with monitoring and controlling air pollution, creating governmental policies, rules, and guidance (especially for stationary sources), and educating the public about air pollution and what can be done to control and prevent it. OAQPS Toxicity Table - The EPA Office of Air and Radiation recommended default chronic toxicity values for hazardous air pollutants. They are generally appropriate for screening-level risk assessments, including assessments of select contaminants, exposure routes, or emission sources of potential concern, or to help set priorities for further research. For more complex, refined risk assessments developed to support regulatory decisions for single sources or substances, dose-response data may be evaluated in detail for each “risk driver” to incorporate appropriate new toxicological data. ( http://www.epa.gov/ttn/atw/toxsource/summary.html )April 2004 Page 27 Office of Radiation and Indoor Air (ORIA) - An EPA Office within OAR whose mission is to protect the public and the environment from the risks of radiation and indoor air pollution. The Office develops protection criteria, standards, and policies; works with other programs within EPA and other agencies to control radiation and indoor air pollution exposures; provides technical assistance to states through EPA’s re gional offices, and to other agencies having radiation and indoor air protection programs; di rects an environmental radiation monitoring program; responds to radiological emergencies; and evaluates and assesses the overall risk and impact of radiation and indoor air pollution. Office of Transportation and Air Quality (OTAQ) - An EPA Office within OAR whose mission is to reconcile the transportation sector with the environment by advancing clean fuels and technology, and working to promote more liveable communities. OTAQ is responsible for carrying out laws to control air pollution from motor vehicles, engines, and their fuels. Mobile sources include: cars and light trucks, large trucks and buses, farm and construction equipment, lawn and garden equipment, marine engines, aircraft, and locomotives. Onroad Mobile Source - Any mobile source of air pollution such as cars, trucks, motorcycles, and buses that travels on roads and highways. Open Pit Source - Large, open pits, such as surface coal mines and rock quarries. Operating Permit Program - A program required by the Clean Air Act; requires existing industrial sources to obtain an"operating permit". The operating permit program is a national permitting system that consolidates all of the air pollution control requirements into a single, comprehensive “operating permit” that covers all aspects of a source’s year-to-year air pollution activities. 

# P
Particle-bound - Reversibly absorbed or condensed onto the surface of particles. Particulates/Particulate Matter (PM) - Solid particles or liquid droplets suspended or carried in the air. Partitioning - The separation or division of a substance into two or more compartments. Environmental partitioning refers to the distribution of a chemical into various media (soil, air, water, and biota). Partitioning Model - Models consisting of mathematical equations that estimate how chemicals will divide (i.e., partition) among abiotic and biotic media in a given environment based on chemical- and site- specific characteristics. Passive Monitor - A type of air toxics monitor that collects airborne pollutants by absorption onto a reactive material (for example, sorbent tube, filter) for subsequent laboratory analysis. No pump is used to draw the air across the reactive material. This type of monitor is usually used for personal exposure monitoring or work space monitoring.April 2004 Page 28 Pathway Specific Risk - The risk associated with exposure to a chemical agent or a mixture of chemicals via a specific pathway (e.g., inhalation of outdoor air). Persistent, Bioaccumulative, and Toxic (PBT) Chemicals - Highly toxic, long-lasting substances that can build up in the food chain to levels that are harmful to human and ecosystem health. They are associated with a range of adverse health effects, including effects on the nervous system, reproductive and developmental problems, cancer, and genetic impacts. Percentile - Any one of the points dividing a distribution of values into parts each of which contain 1/100 of the values. For example, the 75th percentile is a value such that 75 percent of the values are less than or equal to it. Persistence - Refers to the length of time a compound stays in the environment, once introduced. A compound may persist for very short amounts of time (e.g., fractions of a second) or for long periods of time (e.g., hundreds of years). Persistent Organic Pollutants (POPs) - Highly stable organic compounds used as pesticides or in industry. They are also generated unintentionally as the byproduct of combustion and industrial processes. POPs are a special problem because they persist in the environment, accumulate in the tissues of living organisms, a nd are toxic to humans and wildlife. POPs with these characteristics are typically semi-volatile, enabling them to move long distances and condense over colder regions of the earth. These properties lead to increased concern for the toxic effects that they can exert on a range of biota, in particular on top-of-the-food chain species, even at extremely low levels in the ambient environment. Personal Air Monitoring Device - Unlike a passive air toxics monitor, this device uses a pump to draw the air sample through to measure exposure in the immediate vicinity of an individual. The air sample can be drawn across a reactive material (to be analayzed in a laboratory), or it can be drawn through a direct-read detector. Personal Monitoring - A measurement collected from an individual’s immediate environment using active or passive devices to collect the samples. Pervious Surface - A surface that can be penetrated (usually in reference to water; e.g., crop land). Pharmacodynamics - Process of interaction of pharmacologically active substances with target sites, and the biochemical and physiological consequences leading to therapeutic or adverse effects. Pharmacokinetics - The study of the absorption, distribution, metabolism, and excretion of chemicals in living organisms and the genetic, nutritional, behavioral, and environmental factors that modify these parameters. Photolysis - The breakdown of a material by sunlight; an important mechanism for the degradation of contaminants in air, surface water, and the terrestrial environment.April 2004 Page 29 Physical Factors - Manmade and/or natural characteristics or features that influence the movement of pollutants in the environment (e.g., settling velocity, terrain effects). Physiologically Based Pharmacokinetic (PBPK) Model - A computer model that describes what happens to a chemical in the body of a human or laboratory animal. It describes how the chemical gets into the body, where it goes in the body, how it is changed by the body, and how it leaves the body. Piscivorous - A species feeding preferably on fish. Planning and Scoping - The process of determining the purpose, scope, players, expected outcomes, analytical approach, schedule, deliverables, QA/QC, resources, and document requirements for the risk assessment. Plume - The visible or measurable presence of a contaminant in the atmosphere, once released from a given point of origin (e.g., a plume of smoke from a forest fire). Plume Height- The elevation to which a plume travels (i.e., the sum of the release height and plume rise). Plume Rise - The height to which a plume rises in the atmosphere from the point of release. Plume Transport- The movement of a plume through the atmosphere and across land and water features. Plume Washout- The removal of a substance from the atmosphere via a precipitation event. PM-10/PM-2.5 . PM-10 or PM 10 refers to particles in the atmosphere with a diameter of less than ten or equal to 10 micrometers. PM-2.5 or PM 2.5 refers to smaller particles in the air (i.e., less than or equal to 2.5 micrometers in diameter). Point of Departure (PoD) - The dose-response point that marks the beginning of a low-dose extrapolation. This point can be the lower bound on dose for an estimated incidence or a change in response level from a dose-response model (BMD), or a NOAEL or LOAEL for an observed incidence, or change in level of response. Point of Exposure - The location of potential contact between an organism and a chemical or physical agent. Point of Release - Location of release to the environment. Point Source (NEI sense) - A source of air pollution which can be physically located on a map. Point Source (non-NEI sense) - A stack, vent, duct, pipe or other confined air stream from which chemicals may be released to the air. Pollutant Release and Transfer Registries (PRTRs) - The international equivalent to the Toxics Release Inventory (TRI). PRTRs are data banks of recorded information of the releasesApril 2004 Page 30 and transfers of toxic chemicals from industr ies, such as manufacturers, mining facilities, processors, or government-owned and operated facilities. Population Risk or Hazard - Population risk refers to an estimate of the extent of harm for the population or population segment being addressed. It often refers to an analysis of the number of people living at a particular risk or hazard level. Potential Risk - Estimated likelihood, or probability, of injury, disease, or death resulting from exposure to a potential environmental hazard. Potential Dose - The amount of a compound contained in material swallowed, breathed, or applied to the skin. Practical Quantitation Limit- The lowest level of quantitation that can be reliably achieved within specified limits of precision and accuracy during routine laboratory operating conditions. Precision - A measure of the reproducibility of a measured value under a given set of circumstances. Present Scenario - Risk characterizations using present scenarios to estimate risks to individuals (or populations) that currently reside in areas where potential exposures may occur (e.g., using an existing population within some specified area). Prevailing Wind - Direction from which the wind blows most frequently. Prevention of Significant Deterioration (PSD) - An EPA program in which state and/or federal permits are required in order to restrict emissions from new or modified sources in places where air quality already meets or exceeds primary and secondary ambient air quality standards. Primary Standard - A pollution limit based on health effects. Primary standards are set for criteria air pollutants. Probabilistic - A type of statistical modeling approach used to assess the expected frequency and magnitude of a parameter by running repetitive simulations using statistically selected inputs for the determinants of that parameter (e.g., rainfall, pollutants, flows, temperature). Probabilistic Risk Assessment/Analysis - Calculation and expression of health risks using multiple risk descriptors to provide the likelihood of various risk levels. Probabilistic risk results approximate a full range of possible outcomes and the likelihood of each, which often is presented as a frequency distribution graph, thus allowing uncertainty or variability to be expressed quantitatively.April 2004 Page 31 Probability Density Function (PDF) - The PDF is alternatively referred to in the literature as the probability function or the frequency function. For continuous random variables, that is, the random variables which can assume any value within some defined range (either finite or infinite), the probability density function expresses the probability that the random variable falls within some very small interval. For discrete random variables, that is, random variables which can only assume certain isolated or fixed values, the term probability mass function (PMF) is preferred over the term probability density function. PMF expresses the probability that the random variable takes on a specific value. Problem Formulation (in Ecological Risk Assessment) - The initial stage of a risk assessment where the purpose of the assessment is articulated, assessment endpoints and a conceptual model are developed, and a plan for analyzing and characterizing risk is determined. Problem Statement- A statement of the perceived problem to be studied by the risk assessment. Problem statements often also include statements about how the problem is going to be studied. Public Health Consultation (Public Health Assessment) - See health consultation. Public Health Assessment (PHA) - An evaluation of hazardous substances, health outcomes, and community concerns at a hazardous waste site or other potential source of pollutants to determine whether people could be harmed from coming into contact with those substances. The PHA also lists actions that need to be taken to protect public health. Public Health Advisory (in Public Health Assessment) - A statement made by a regulatory agency that a release of hazardous substances or contamination by microbial pathogens poses an immediate threat to human health. The advisory includes recommended measures to reduce exposure and reduce the threat to human health. Public Health Hazard Category (in Public Health Assessment) - Statements about whether people could be harmed by conditions present at the site in the past, present, or future. One or more hazard categories might be appropriate for each site. ATSDR’s five public health hazard categories are no public health hazard, no apparent public health hazard, indeterminate public health hazard, public health hazard, and urgent public health hazard. 

# Q Qualitative Uncertainty Estimate - A detailed examination, using qualitative information, of the systematic and random errors of a measurement or estimate. Quality Assurance Project Plan - A document describing in comprehensive detail the necessary quality assurance, quality control, and other technical activities that must be implemented to ensure that the results of the work performed will satisfy the stated performance criteria. Quality Assurance - An integrated system of activities involving planning, quality control, quality assessment, reporting and quality improvement to ensure that a product or service meets defined standards of quality with a stated level of confidence.April 2004 Page 32 Quality Control - The overall system of technical activities whose purpose is to measure and control the quality of a product or service so that it meets the needs of its users. The aim is to provide data quality that is satisfactory, adequate, and dependable. 

# R
Random Variable - A quantity which can take on any number of values but whose exact value cannot be known before a direct observation is made. For example, the outcome of the toss of a pair of dice is a random variable, as is the heightor weight of a person selected at random from a city phone book. Receptor (modeling sense) - In fate/transport modeling, the location where impacts are predicted. Receptor (non-modeling sense) - The entity which is exposed to an environmental stressor. Red Book - 1983 NRC publication entitled Risk Assessment in the Federal Government: Managing the Process

. Reference Concentration (RfC) - An estimate (with uncertainty spanning perhaps an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. Reference Dose (RfD) - An estimate (with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. Reference Media Evaluation Guides (RMEG) - A type of comparison value derived by ATSDR to protect the most sensitive populations . They do not consider carcinogenic effects, chemical interactions, multiple route exposure, or other media-specific routes of exposure, and are very conservative concentration values designed to protect sensitive members of the population. Regional/National Scale Assessment - An air monitoring network designed to assess from tens to hundreds of kilometers, up to the entire nation. Relative Potency Factor - The ratio of the toxic potency of a given chemical to that of an index chemical. Release Parameters - The specific physical characteristics of the release (e.g., stack diameter, stack height, release flow rate, temperature). Representativeness - The degree to which one or a few samples are characteristic of a larger population about which the analyst is attempting to make an inference.April 2004 Page 33 Reproductive Toxicity - The occurrence of biologically adverse effects on the reproductive systems of females or males that may result from exposure to environmental agents. The toxicity may be expressed as alterations to the female or male reproductive organs, the related endocrine system, or pregnancy outcomes. The manifesta tion of such toxicity may include, but not be limited to, adverse effects on onset of puberty, gamete production and transport, reproductive cycle normality, sexual behavior, fertility, gest ation, parturition, lactation, developmental toxicity, premature reproductive senescence, or modifications in other functions that are dependent on the integrity of the reproductive systems. Residual Risk - The extent of health risk from air pollutants remaining after application of the Maximum Achievable Control Technology (MACT). Resources - Money, time, equipment, and personnel available to perform the assessment. Risk (in the context of human health) - The probability of injury, disease, or death from exposure to a chemical agent or a mixture of chemicals. In quantitative terms, risk is expressed in values ranging from zero (representing the certainty that harm will not occur) to one (representing the certainty that harm will occur). (Compare with hazard.) Risk Assessor(s) - The person or group of people responsible for conducting a qualitative and quantitative evaluation of the risk posed to human health and/or the environment by environmental pollutants. Risk Assessment- For air toxics, the scientific activity of evaluating the toxic properties of a chemical and the conditions of human or ecological exposure to it in order both to ascertain the likelihood that exposed humans or ecological receptors will be adversely affected, and to characterize the nature of the effects they may experience. Risk Assessment Forum - A standing committee of senior EPA scientists which was established to promote Agency-wide consensus on difficult and controversial risk assessment issues and to ensure that this consensus is incorporated into appropriate Agency risk assessment guidance. Risk Assessment Work Plan - A document that outlines the specific methods to be used to assess risk, and the protocol for presenting risk results. The risk assessment workplan may consist of one document or the compilation of several workplans that, together, constitute the overall risk assessment workplan. Risk Characterization - The last phase of the risk assessment process in which the information from the toxicity and exposure assessment steps are integrated and an overall conclusion about risk is synthesized that is complete, informative and useful for decision-makers. In all cases, major issues and uncertainty and variability associated with determining the nature and extent of the risk should be identified and discussed. The risk characterization should be prepared in a manner that is clear, transparent, reasonable and consistent. Risk Communication - The exchange of information about health or environmental risks among risk assessors and managers, the general public, news media, and other stakeholders.April 2004 Page 34 Risk Management - The decision-making process that uses the results of risk assessment to produce a decision about environmental action. Risk management includes consideration of technical, scientific, social, economic, and political information. Risk Manager(s) - The person or group responsible for evaluating and selecting alternative regulatory and non-regulatory responses to risk. Root Uptake - The uptake of compounds available in the soil and their transfer to the above ground portions of the plant. Route-to-Route Extrapolation - Calculations to estimate the dose-response relationship of an exposure route for which experimental data do not exist or are inadequate, and which are based on existing experimental data for other route(s) of exposure. Runoff - That part of precipitation, snow melt, or irrigation water that runs off the land into streams or other surface water. It can carry pollutants from the air and land into receiving waters. 

# S Sample - A small portion of something designed to evaluate the nature or quality of the whole (for example, one or several samples of air used to evaluate air quality generally). Sampling and Analysis Plan - An established set of procedures specifying how a sample is to be collected, handled, analyzed, and the data validated and reported. Sampling Frequency - The time interval between the collection of successive samples. Science Advisory Board (SAB) - A group of recognized, non-EPA experts who advise EPA on science and science policy. Scenario Uncertainty - Uncertainty due to descriptive errors, aggregation errors, errors in professional judgment, or incomplete analysis. SCREEN3 - An air dispersion model developed to obtain conservative estimates of air concentration for use in screening level assessments through the use of conservative algorithms and meteorology. Screening-level Risk Assessment- A risk assessment performed with few data and many conservative assumptions to identify exposures that should be evaluated more carefully for potential risk. Secondary Production/Pollutant- Formation of pollutants in the atmosphere by chemical transformation of precursor compounds. Secondary Standard - A pollution limit based on environmental effects (e.g., damage to property, plants, visibility). Secondary standards are set for criteria air pollutants.April 2004 Page 35 Sensitive Subgroups - Identifiable subsets of the general population that, due to differential exposure or susceptibility, are at greater risk than the general population to the toxic effects of a specific air pollutant (e.g., depending on the pollutant and the exposure circumstances, these may be groups such as subsistence fishers, infants, asthmatics, or the elderly). Settling Velocity/Rate - The maximum speed at which a particle will fall in still air. It is a function of its size, density, and shape. Silage - Stored vegetation used as feed for cattle. Simulation - A representation of a problem, situation in mathematical terms, especially using a computer. Soil Volumetric Water Content - The soil-water content expressed as the volume of water per unit bulk volume of soil. Soil Dry Bulk Density - The mass of dry soil per unit bulk volume. Soil Erosion - Detachment and movement of topsoil or soil material from the upper part of the soil profile, by the action of wind or running water, especially as a result of changes brought about by human activity, such as unsuitable or mismanaged agriculture. Solar Radiation - Energy from the sun. Of importance to the climate system, solar radiation includes ultra-violet radiation, visibl e radiation, and infrared radiation. Solubility - The amount of mass of a compound that will dissolve in a unit volume of solution. Aqueous solubility is the maximum concentration of a chemical that will dissolve in pure water at a reference temperature. Source - Any place or object from which pollutants are released. Source Category - A group of similar industrial processes or industries that are contributors to releases of hazardous air pollutants. The 1990 amendments to the Clean Air Act (CAA) requires that the EPA publish and regularly update a listing of all categories and subcategories of major and area sources that emit hazardous air pollutants. Source Characterization - The detailed description of the source (e.g., location, source of pollutant releases, pollutants released, release parameters). Spatial Variability - The magnitude of difference in contaminant concentrations in samples separated by a known distance. SPECIATE - EPA’s repository of Total Organic Compound (TOC) and Particulate Matter (PM) speciated profiles for a variety of sources for use in source apportionment studies. The profiles in the system are provided as a library of available profiles for source-receptor and source apportionment type models, such as Chemical Mass Balance 8 (CMB8).April 2004 Page 36 Stable Conditions (in the Atmosphere) - Air with little or no tendency to rise, that is usually accompanied by clear dry weather. Stable air hol ds, instead of dispersing, pollutants. [National Weather Service, Southern Region Headquarters’ Jetstream Weather School, http://www.srh.weather.gov/jetstream/append/glossary.htm and EPA, 1997: Terms of Environment, http://www.epa.gov/OCEPAterms/ .] Stack - A chimney, smokestack, or vertical pipe that discharges used air. Stack Release - The release of a chemical through a stack. Stack Testing - The monitoring, by testing, of chemicals released from a stack. Stakeholder(s) - Any organization, governmental entity, or individual that has a stake in or may be impacted by a given approach to environmental regulation, pollution prevention, energy conservation, etc. Standard Industrial Classification (SIC) - A method of grouping industries with similar products or services and assigning codes to these groups. Standard Operating Procedure (SOP) - A established set of written procedures adopted and used to guide the work of for a specific project. For example, an air monitoring study would include SOPs on sample collection and handling and SOPs on analytical requirements and data validation and reporting. Standing Crop - The quantity of plant biomass in a given area, usually expressed as density (dry mass per unit area) or energy content per unit area. Stationary Source - A source of pollution that is fixed in space. Steady-state Model - Mathematical model of fate and transport that uses constant values of input variables to predict constant values of receiving media concentrations. Stochastic - Involving or containing a random variable; involving probability or chance. Stressor - Any physical, chemical, or biological entity that can induce adverse effects on ecosystems or human health. Stressor-response Profile or Relationship (in Ecological Risk Assessment] - The product of characterization of ecological effects in the anal ysis phase of ecological risk assessment. The stressor-response profile/relationship summarizes the data on the effects of a stressor and the relationship of the data to the assessment endpoint.April 2004 Page 37 Structure-activity Relationship (SAR) - Mathematical or qualitative expression of the relationships between biological activity or toxicity of a chemical to its chemical structure or substructure. Ideally, such relationships can be formulated as Quantitative Structure Activity Relationships (QSARs), in which some degree of predictive capability is present. [Air Risk Information Support Center, OAQPS, March 1989: Glossary of Terms Related to Health, Exposure, and Risk Assessment. EPA/450/3-88/016.] Support Center for Regulatory Models (SCRAM) - An EPA website that is a source of information on atmospheric dispersion models (e.g., ISCST3, SCREEN 3, and ASPEN) that support regulatory programs required by the Clean Air Act. Documentation and guidance for these computerized models are a major feature of this website. This site also contains computer code, data, and technical documents that deal with mathematical modeling for the dispersion of air pollutants. Synergistic Effect- A situation in which the overall effect of two chemicals acting together is greater than the simple sum of their individual effects. 

# T Target Organ - The biological organ(s) most adversely affected by exposure to a chemical substance (e.g., the site of the critical effect). Target Organ Specific Hazard Index (TOSHI) - The sum of hazard quotients for individual air toxics that affect the same organ/organ system or act by similar toxicologic processes Temporal Variability - The difference in contaminant concentrations observed in samples taken at different times. Teratogenesis - The introduction of nonhereditary birth defects in a developing fetus by exogenous factors such as physical or chemical agents acting in the womb to interfere with normal embryonic development. Terrain Effects - The impact on the airflow as it passes over complex land features such as mountains. Terrestrial Radiation - The total infrared radiation emitted by the earth and its atmosphere in the temperature range of approximately 200 to 300 Kelvin. Terrestrial radiation provides a major part of the potential energy changes necessary to drive the atmospheric wind system and is responsible for maintaining the surface ai r temperature within limits of livability. Thermal Turbulence - Turbulent vertical motions that result from surface heating and the subsequent rising and sinking of air. Threshold Dose/Threshold - The lowest dose of a chemical at which a specified measurable effect is observed and below which it is not observed.April 2004 Page 38 Threshold Effect- An effect (usually an adverse health effect) for which there is an exposure level below which the effect is not expected to occur. Threshold Toxicant- A chemical for which there is an exposure level below which an adverse health outcome is not expected to occur. Tiered Analysis - An analysis arranged in layers/steps. Risk assessments/analyses are often conducted in consecutive layers/steps that begin with a reliance on conservative assumptions andlittle data (resulting in less certain, but generally conservative answers) and move to more studyarea specific data and less reliance on assumptions (resulting in more realistic answers). The level of effort and resources also increases with the development of more realistic data. Time-integrated Sample - Samples are collected over a period of time. Only the total pollutant collected is measured, and so only the average concentration during the sampling period can be determined. Time-trend Study - Samples spaced in time to capture systematic temporal trends (e.g., a facility might change its production methods or products over time). Time-weighted Sum of Exposures - Used in inhalation exposure modeling. Provides a total exposure from all different microenvironments in which a person spends time. Toxic Air Pollutants - see hazardous air pollutant. Toxicity - The degree to which a substance or mixture of substances can harm humans or environmental receptors. Toxicity Assessment- Characterization of the toxicological properties and effects of a chemical, with special emphasis on establishment of dose-response characteristics. Toxicity Test- Biological testing (usually with an cell system, invertebrate, fish, or small mammal) to determine the adverse effects of a compound. Toxicology - The study of harmful interactions between chemicals and biological systems. Toxic Release Inventory (TRI) - Annual database of releases to air, land, and water, and information on waste management in the United States of over 650 chemicals and chemical compounds. This data is collected under Section 313 of the Emergency Planning and Community Right to Know Act. Trajectory - The track taken by a parcel of air as it moves within the atmosphere over a given period. Transformation - The change of a chemical from one form to another. Transparency - Conducting a risk assessment in such a manner that all of the scientific analyses, uncertainties, assumptions, and science policies which underlie the decisions made throughout the risk assessment are clearly stated (i.e., made readily apparent).April 2004 Page 39 Turbulence - Irregular motion of the atmosphere, as indicated by gusts and lulls in the wind. 

# U Uncertainty - Uncertainty represents a lack of knowledge about factors affecting exposure/toxicity assessments and risk characterization and can lead to inaccurate or biased estimates of risk and hazard. Some of the type s of uncertainty include scenario uncertainty, parameter uncertainty, and model uncertainty. Uncertainty analysis - A detailed examination of the systematic and random errors of a measurement or estimate (in this case a risk or hazard estimate); an analytical process to provide information regarding the uncertainty. Uncertainty Factor (UF) - One of several, generally 10-fold factors, used in operationally deriving the RfD and RfC from experimental data. UFs are intended to account for (1) the variation in sensitivity among the members of the human population; (2) the uncertainty in extrapolating animal data to humans, i.e., interspecies variability; (3) the uncertainty in extrapolating from data obtained in a study with less-than-lifetime exposure to lifetime exposure, i.e., extrapolating from subchronic to chronic e xposure; (4) the uncertainty in extrapolating from a LOAEL rather than from a NOAEL; and (5) the uncertainty associated with extrapolation from animal data when the data base is incomplete. Universal Soil Loss Equation - An equation used to predict the average annual soil loss per unit area per year. Unit Risk Estimate (URE) - The upper-bound excess lifetime cancer risk estimated to result from continuous exposure to an agent at a concentration of 1μ g/L in water, or 1 μg/m 3 in air. The interpretation of unit risk would be as follows: if the water unit risk = 2 x 10 -6 μg/L, 2 excess tumors may develop per 1,000,000 people if exposed daily for a lifetime to 1 μg of the chemical in 1 liter of drinking water. Unstable Conditions (in the Atmosphere) - An atmospheric state in which warm air is below cold air. Since warm air naturally rises above cold air (due to warm air being less dense than cold air), vertical movement and mixing of air layers can occur. Uptake - The process by which a substance crosses an absorption barrier and is absorbed into the body. Urban Scale Assessment- An air monitoring network designed to assess the overall, citywide conditions with dimensions on the order of 4 to 50 kilometers. This scale would usually require more than one site for definition.April 2004 Page 40 

# V Vapor - The gas given off by substances that are solids or liquids at ordinary atmospheric pressure and temperatures. Variability - Refers to the observed differences attributable to true heterogeneity or diversity in a population or exposure parameter. Examples include human physiological variation (e.g., natural variation in body weight, height, breathi ng rate, drinking water intake rate), weather variability, variation in soil types and differences in contaminant concentrations in the environment. Variability is usually not reducible by further measurement of study, but it can be better characterized. Volatilization/Vapor Release - The conversion of a liquid or solid into vapors. Volume Source - In air dispersion modeling, a three dimensional volume from which a release may occur (e.g., a gas station modeled as a box from which chemicals are emitted). 

# W
Watershed - The land area that drains into a stream; the watershed for a major river may encompass a number of smaller watersheds that ultimately combine at a common point. Weight-of-Evidence (WOE) - A system for characterizing the extent to which the available data support the hypothesis that an agent causes an adverse health effect in humans. For example, under EPA’s 1986 cancer risk assessment guidelines, the WOE was described by categories “A through E,” Group A for known human carcinogens through Group E for agents with evidence of noncarcinogenicity. The approach outlined in EPA’s proposed guidelines for carcinogen risk assessment (1996 and updates) considers all scientific information in determining whether and under what conditions an agent may cause cancer in humans, and provides a narrative approach to characterize carcinogenicity rather than categories. White Book - 1996 Presidential Commission on Risk Assessment and Risk Management (CRARM) publication entitled Risk Assessment and Risk Management in Regulatory DecisionMaking

. Wind Rose - A graphical display showing the freque ncy and strength of winds from different directions over some period of time.