# Chapter 4 Air Toxi cs: Chemical s, So urces, and

Emissions Inventori es

Table of Contents 4.1 Introducti on ................. ................. ................. ............... 1 4.2 Air Toxics

................. ................. ................. ................ 1 4.2. 1 Introd uctio n to A ir To xics Ch em ical L ists

................. ................. . . 1 4.2. 2 Hazard ous A ir Pollutants (HA Ps)

................. ................. ........ 4 4.2. 3 Crite ria A ir Po llutan ts
................. ................. ................. 5 4.2. 4 To xics Re lease In ven tory (T RI) C hem icals

................. ................. . 6 4.2. 5 To xic C hem icals T hat P ersist an d W hich Als o M ay Bio accu mu late

................ 6 4.2. 6 Oth er C hem icals

................. ................. ................. .... 11 4.3 Sources of Air Toxics

................. ................. ................. ...... 11 4.3.1 Point Sources

................. ................. ................. ...... 12 4.3.2 Nonp oint Sources

................. ................. ................. ... 13 4.3.3 On-Road and Non road Mobile Sources

................. ................. ... 14 4.3.4 Sou rc es Not

I nc lu de d i n the NEI or TRI

................. ................. . . 15 4.3. 4.1 Indoor Sources

................. ................. ............... 15 4.3. 4.2 Natural Sources

................. ................. ............... 18 4.3. 4.3 Fo rma tion o f Sec ond ary Po llutan ts
................. ................. 19 4.3. 4.4 Oth er

Sou rc es Not

I nc lu de d i n NEI or

TRI

................. ........... 20 4.4 Emissions Inventor ies

................. ................. ................. ...... 20 4.4.1 N atio na l Em issio ns Inv en tory (N EI)

................. ................. ..... 21 4.4.2 To xic s R elea se In ven tory (T RI)

................. ................. ......... 25 References

................. ................. ................. ................. .... 29a CAS (C hemical Abstracts Service) is a divis ion of the American Chemical Society. A CAS Registry

Number (CAS number

or CASRN) is ass ig ned i n se quen ti al orde r t o uni que, new sub st ance s i dent if iedby CAS scientists fo r inclusio n in the C AS R EG IST RY datab ase. E ach C AS R egistry N umb er is a uniq ue num eric identifier; d esigna tes only o ne sub stance ; and h as no chem ical significa nce. A CA S Re gistry N umb er is a num eric April 2004 Page 4 -1 Th e exh au stive lists o

f air toxic s disc usse d in this sec ti on do not includeall of the hazardous chemic als of pu blic h ealth con cern . No te also tha t oth er for ms of a ir pollution (e.g., od ors) are no t ad dre ssed in th is Reference Library. 4.1 Introduction This chapter iden

tifies the set of chemicals broadly, and most commonly, considered “ air toxics.” This section also describes the general ca

tegori es of air

toxics sourc es that e

mit these chemicals as well as the primary places where air toxics emissions information (e.g., databases that contain information on the location and nature of emissions released from var ious types of source s) used in air toxics risk assessments can be found. Se ction 4.2 d

iscusses air toxics; Section 4. 3 descri bes air toxics sources; and Section 4.4 describes air toxics emissions data sour ces. 4.2 Air Toxics Chapter 2of this Vol

ume introd

uced Ha zardous Air Pollutan

ts (HAPs) , criter

ia air po llutants, Toxic Release Inventory

(TRI) chemicals, and pe

rsistent, bioaccumulative, and toxic (PBT) chemica ls and disc

ussed the relation ships amon

g these various g rouping s. This sec

tion will revisit each of these groups to provide more de tailed information related to the chemicals on each of those lists. A thorough understanding of the different type s of chemicals that may be of interest for an a ssessmen

t, as well as the nua

nces of t he vario us ways chemic als are

written in

to those lists, will be important for the risk assessment team to comprehend before the assessment begins in earnest. The term “air toxics” is a generic term that could c onceivably e ncompass literally any

thing in the air that p oses har

m to people

or the en vironmen t. This Volu

me uses the term “a

ir toxics” i

n this general sense. Thus, while the focus of most air toxics risk assessments will be on the 188 chemicals and chemical compounds listed as HAPs in the Clean Air Act (CAA) se ction 112(b), some asse ssment tea

ms may wish to have a broa

der foc us. The us e of the t

erm “air toxics” in this general sense is meant to provide for this flexibility . Ultimately, the scope of a ny assessme nt must clearly identify the chem icals tha t will be e valuate d and the r

eason for their inclusion or exclusion in the evaluation. 4.2.1 Introduction to Air Toxics Chemical Lists The var ious lists that are the focus o f this volume were all derived directly f

rom the Cle an Air Act, the Emergency

Planning and Community Right to Know Act, or a specific EPA initiative (e .g ., th e P BT in it ia ti ve li st of ch em ic al s) . It is im po rt an t t o u nd er st an d t ha t t he re is no t a lw ays consistency among

these various lists in either the naming of chemicals or the meaning of the names. F or example , as noted in Chapter

2, “gly col ethe rs” are defined differe ntly for the TRI and as HAPs (see box in Section 2.4.4). Lists of toxic chemicals commonly provide the chemical identity by both a name a

nd a unique identifying number, called a Chemical Abstracts Registry Number

. (a) Howeve r, mostidenti fier that can contain up to ni ne digi ts, someti mes divi ded by hyphens int o three par ts. See ht tp: // www. cas .or g/ fa q.h tmlfor more information. April 2004 Page 4 -2 chemicals have multiple synony ms (sometime dozens). Fortunately, e very unique c

hemical has only one unique CAS number and one can alway s refer to this unique number to identify the compound

in question. For example, tolu ene and methy lbenzene are sy nony ms for the

same compound (which is normally re ferred to as toluene). However, the re is only one CAS number for the compound: 108-88-3. No matter where one is in the world or w hat name is attached to a chemical, there is unanimity of identity through the

CAS numbering system. When ther

e is any question a

bout what a partic ular che mical name means, it is alway s advisab le to try to pinpoint the identity through use of the CAS number. For example, a risk assessment team may ask f

or air sampling analysis for the HAP acetaldehy de (CAS number 75-07-0); however, when they

receive the analy

tical lab report, acetaldehy de is not reported. A quick scan of the CAS n

umbers r eported by t he lab list s the CAS num

ber 75-0 7-0 next to the name “ethanal.” Ethanal is a sy nonym for ac etaldehyde

and, hence, has the same CAS number. EPA’s Handbook for Air Toxics Emission Inventory Development includes a list (Ap pendix C) of synony ms and CAS numbers for HAPs that is helpful in overcoming the nomenclature obstacle. (1) (Note, however, that there are nua nces even bey

ond this simplistic description. For example, some chemicals have one CAS number for their pure for m and a different CAS number for a technical grade. A

knowledgeable chemist can usually identify and clar

ify these issues.) Some of the

entries on chemic al lists ar e for la rge g roups of c ompounds a

nd not just one singl e substanc e. For e

xample, one

of the HA

Ps is listed i

n the CAA a s “poly

chlorina ted biphe nyl s (arocl ors)” a

nd is most commonly

refer red to as PCBs. This

listing is not for one single substance but, rather, for any one or a mixture of any of the 209 possible chemicals that are themselves PCBs. As another example, the pesticide “2,4-D” is written into the list of HAPs as “2,4-D (salts and esters).” This listing includes any possible salt of 2,4-D and any possible ester of 2,4-D. In our ea

rlier lead example, the lead compound listing includes any compound known to exist in or be emitted to the environment that contains a lead molecule as part of the compound’s molecular structure (a potentially huge number of possibilities). Another important group o f chemic als is cal led “POM” for poly cyclic organic matt

er. This i ncludes organic compounds with more than one benzene ring, and which have a boiling point greater than or equal to 100 o C (e.g., poly cyclic a romatic hydroc arbons (PAHs) such as benzo(a)py rene). In re ality , most risk assessmen ts will dea

l with a re latively

small numbe

r of che micals be cause either the source s in a given place are re leasing

only a limited n

umber of chemica ls or the a bility to model or monitor the numerous chemicals present is limited by the available inventories or monitoring/analytica

l methods, respectively. In the initial sta ges of t he asses sment, ris

k assessors often

sort the c hemicals of intere st into groups that, generally

, have similar physical a

nd/or chemical properties. This is a helpful thing to do as a way of

making some educated guesses a bout how chemicals are likely to behave in the environment. The groupings also help an asse ssment team to plan for the type s of sampling and analysis methods that will be neede d, because the sampling and analy tical methods tend to be broken out along these same lines. I n general, all air toxics can be broadly categorized into three main gr oups, organic che

micals, in organ ic chemic als, and organometallic compound s as follow s:b The regu lat ory de fi nit ion of VOC does not i denti fyvapor pr essu re as a cons ider ati on. Se e 40 CFR 51.100(s).

c “VOC” ref

ers to vol ati le or gani c compounds tha t con tri bute to ozon e for

mati on as de fi ned by 40 CFR 50.10 0(s) as ozo ne precu rsors. VO C is a subset of V OC s. VOC emissi ons inv entory inf ormation i s someti mes used to der ive est imat es f

or spe cif ic c hemic als ; wh en this is done, the VOC number is sai d to ha ve beenspeci ated. April 2004 Page 4 -3 Organic C hemica

ls Organic chemical compounds are composed of carbon in combination with other elements such as hydrog en, oxygen, nitrogen, phosphorous, chlorine, and sulfur (not including carbonic a cid or ammonium c arbonat

e). Organic com

pounds ca

n gene rally be split int

o two diff erent g roups, based on their propensity to evaporate. The following such groupings ar e commonly employ

ed by analy tical chemistry labora

tories for purposes of sample analysis.

• Volatile

Organic C ompounds (

VOCs) . These are organic c hemicals that have a high vapor pr es su re an d t en d t o h av e l ow wa te r s ol ub il it y. (b) Simply put, VOCs have a hig

h propen sity to evaporate and remain airborne. Many VOCs are human-made chemicals that are used and produced in the manufacture of paints, pharmac euticals, and refrigerants, a s industrial solvents, such as trichloroethyle ne, or produced as by

-products, such as chloroform produced by chlorination in water

treatment. VOCs are often also components of petroleum fue ls (e.g., benzene) , hy

draulic fluids, pa int thinner

s, and dry cleanin g age nts. (c) A subgroup of VOCs is termed Carbonyl C ompoundsand includes chemicals such as formalde hyd e and ac etaldeh

yde . While such chemic als are themselve s VOCs due

to their high vapor pressure, they are often grouped as a se parate class from the VOCs because of the special sampling and analy tical methods necessary

to measure them in air.

• Semivol atile Org anic Compounds (SVOCs ) . SVOCs are organic chemicals that have a lower vapor pressure than VOCs and, thus, have a lowe r propensity to evapor

ate from the liquid or solid form. Once airborne, they also tend to more readily condense out of the gas phase. E xamples of S VOCs inclu

de most or

ganic p esticide s (e.g. , chlorda ne), and certain components of petroleum, such as poly cyclic a romatic hydroc arbons. Note that the demarc ation bet

ween SVO Cs and VOCs

is not exact. For exa

mple, the two sepa rate air sampling and analy

tical methods for VOCs and SVOCs will both usually detect na phthalene when pre sent, indi cating

that this chemical i s on the lower end of the VOC sc ale of vo latility and on the

higher end of the

SVOC scal e of vola

tility . In general , as chem icals inc rease i n molecular weight and/or polarity, they become more SVOC-like. Inorganic

Chemic als This group includes all substances that do not contain carbon and include s a wide array of substanc es such a s:

• Metals (e.g., mercury , lead, and cadmium) and their various salts (e.g., me rcury c hloride);

• Halogens (e.g, chlorine a nd bromine);

• Inorganic

bases (e.g., ammonia); and

• Inorganic

acids (e.g., hy

drogen chloride, sulfuric acid).April 2004 Page 4 -4 Organom etallic C ompounds Th is gr ou p i s c om pr is ed of co mp ou nd s t ha t a re bo th or ga ni c a nd me ta ll ic in na tu re . T he al kyl lead compounds that were added to gasoline to enha nce its properties can be used for illustration. “Alkyl” re fers to the organic portion of a compound which is attac hed to the inorganic metal lead. The result is a so-called “orga nometallic” material, a hy brid of both metallic and organic. (Note that salts, such as sodium benzoate, are usually classified as an organic chemica l, rather than an organometallic compound.) An understanding of the gener al characteristics of orga

nic chemicals, inorganic chemicals and organometallic

compound s will aid in

planning a risk as sessment a

nd develo ping an appropr iate analy sis strate gy . For exa

mple, most VOCs tend to remain a irborne and also d

o not tend t

o bioaccumulate to the same extent as some of the non-volatile chemicals. Thus, if an asse ssment were be ing plan

ned to eva

luate the impact of

a source from whic

h only VOCs wer

e relea sed, it becomes less likely that a multipathway risk analysis will be nece ssary (since VOCs do not tend to migrate into soil or water and do not tend to bioaccumulate as strongly in living tissue). In addition, the sampling and ana lytical methods available to test for chemicals in environmental media are generally

broken out along the same chemical g roupings noted above. Thus, if one were int ereste d in testing

for airb orne chl ordane ( an SVOC), a VOC monit oring me thod would not be used. Detailed information on available monitoring methods and the che micals for which they have be en validated is provided in Chapter 10. In air toxics studies, both individual substances and mixtures of substances are of interest. Particulate matter (PM), for example, is almost never comprised of just one substance; instead, PM is usually

made up of

numerous

individua

l substanc es (sometimes in the hundred s). Both the physical and c

hemical nature of a mixture will influence the fate and transpor t of the chemicals in the environment as well as the potential for the mixture to cause harm. F or example, a toxic chemical adsorbed onto the surface of a re latively larg e particle (> 10 microns in diameter) will usually be tra pped in the upper portion of the respiratory system and either coughe d/sneeze d out of the body or swallowed. The

same che mical ads orbed on

to a very small particle (< 2.5 microns in diameter) has a much hig her likelihood of being inhaled into the deep lung. As we will see in later chapters, both the route of exposure (in this example, ingestion or inhalation) as we ll as the to xic proper ties of the chemica l in questio

n are imp ortant de

terminan ts of potent ial harm. 4.2.2 Hazardous

Air Pol lutants (HA

Ps) The HAPs a

re a gr oup of 188 specific

chemica ls and che mical com

pounds an

d are ide ntified in Section 112(b) of the CAA. The Agency provides additional information on the HAPs online. (2) HAPs are pollutants known to cause or suspected of causing cancer or other serious human health effects or ecosy

stem damage. They

include individual organic and inorganic c ompounds and pollutant groups closely related by c

hemical structure (e.g., arse nic compounds, cyanide compounds, glyc ol ethers, polycy clic organic matter) or emission sources ( e.g., coke oven emissions). EPA may add or re move pollutants from the HAP list as new information becomes available. A full list of the HAPs is provided in Appendix A. When people talk about “air toxics risk assessment,” they generally mean assessments of risks associated with one or more of the HAPs. This is largely because of the CAA listing of 188April 2004 Page 4 -5 HAPs and its requirement under Section 112(f)(2) (Residual Risk) that EPA assess the risks associated with HAPs that remain after the application of the Maximum Achievable Control Technol ogy

(MACT) st

andards (Section 112(d) of the Act) . Howeve

r, give n that this i s a relatively short list of chemica ls, many communities may want to go bey

ond this list when assessin g risk. I t is for thi s reason , that ass essors a nd other stakehold

ers must clearly ide

ntify why they are conducting an “air toxics” risk assessment and wha t they want to include in that assessme nt. In its Inte grated Urban Air Toxics Strategy , EPA identified a subset of 33 HAPs as those posing the greatest risk in urban area s (see Section 2.2.1). These 33 HAPs were selecte d based on a number of

factors, includi

ng toxicity

-weig hted emiss ions, monitoring da ta, past a ir quality modeling analy sis, and a review of existing risk assessment literature. The national-scale assessment for 1996 (see Sec tion 2.3.2) focused on 32 of these 33 Urban HAPs (dioxin

was omitte d) and al so include s diesel p articula te matter, which is u sed as a surrogate measure of diesel e xhaust. EPA recently concluded tha t diesel exhaust is likely to be carcinogenic

to humans by in

halation at envir onmental levels of exposure. Diesel exhaust is addressed in several regula tory actions and diese l particulate matter plus diesel organic g ases are listed by EPA as a mobile source a ir toxic (see Section 4.3.3 below). 4.2.3 Criteria Air Pollutants The “criteria air pollutants” are six substances reg ulated pursuant to Title I of the CAA, for which “criteria documents” are de veloped by the Agency prior to national standard setting decisions. There are already national ambient air quality standa rds (NAAQS) in place for each of these pollutants as well as established regulatory programs and activities in place to meet those standards. However, they are discussed here because the re is some crossover between the realm of HAPs and criteria pollutants. The more important crossover issues a re discussed below.

• Particulate matte r . NAAQS ha ve been established for pa

rticles w ith an ae rody namic diameter less than or equal to 10 microns (calle d PM 10 ) and particulate matter with an aerody namic dia meter le ss than or

equal to 2 .5 micron s (calle d PM 2.5 ). As noted above, however, PM can be made up of as little as one or a f ew, or many hundr

eds of individual chemicals. In many

cases (and depending on the source of the PM), any number

of specifically listed HAPs may be a part of the PM mix. It is for this reason that risk assessors may opt to eva

luate the composition of PM and

to include

the ident ified chemicals i

n risk calculations. For examp le, it is pos sible to co llect sam ples of PM 10 for purposes of determining the ty pes and amoun

ts of indivi dual subst

ances c ontained

in the par

ticles. T he risks p osed by

those individua l chemica ls may then be e stimated f

or the inhalation r

oute of exposure. B ecause particle s with diameters g reater than 10 mic

rons are not general ly r

espirab le, anal

yst s usually select a PM 10 monitor to capture samples for risk assessment purposes rather than a total suspended particulate (TSP) sampler, because TSP would capture larger particles that do not penetra te very far into t he respi ratory tract (t hus leadi ng to an overest imate in in

halation riskassociated with the specific pollutants studied). Note that this would not be true for particlebound che

micals tha

t exert the ir toxic ef

fects on the nasa l passag es.April 2004 Page 4 -6 • Ozone and other criteria pollutants . Certain other cr iteria po llutants a

re not spe cifical ly listed as HAPs, but HAPs may lead to their forma tion or they may

lead to HAP formation. For example, ozone is produced by the interaction of certain VOCs, oxides of nitrogen (called NO x ), and sunlight. As noted previously , many of the HAPs ar e VOCs and may pla

y a role in ozone formation. In contrast, sulfur dioxide is a criter ia pollutant that can be transformed in the environment into sulfuric acid which, in turn, may become part of a listed HAP (e.g., cadmium sulfate). I n general, the criteria pollutants ozone, nitroge n dioxide, sulfur dioxide, car

bon monoxide

are not u sually

consider ed in air toxics risk assessmen

ts. 4.2.4 Toxics Release Inve ntory (TR I) Chemicals Data on TRI chemicals a

re reported pursuant to Section 313 of the Emerg ency Planning and Community Right-To-Know Act (EPCRA) of 1986 a nd Section 6607 of the Pollution Prevention Act of 1990 (PPA). EPCRA and the PPA are intended to inform communities and citizens about chemical hazards in their areas. EPA and states are required to collect data annually on releases (to each environ

mental me dium) and

waste ma nageme nt methods

(e.g. , recy

cling)of cert

ain toxic chemicals from industrial facilities, and to make the data available to the public in the TR I. (3) EPCRA Section 313(d) permits EPA to list or delist chemicals based on certain criteria. In a 1994 rule

making, EPA adde d 286 che mical ca tegori es to the TRI chemical li st. The TRI chemicals are listed in 40 CFR Section 372.65, and information about the 667 currently -listed TRI chemicals is provided online. (4) The current TRI c

hemical list contains 582 individually listed chemicals and 30 che mical categories (including three delimited categories containing 58 che micals), for a total of 612 separa te chemic als. I f the memb ers of the three delimited

categ ories ar

e counte d as sepa

rate chemicals then the total number of chemicals and chemica l categories is 667 (i.e., 582 + 27 + 58). The TRI list of toxic chemicals includes most (180) of the HAPs. Similar to the HAPs, the TRI chemicals include VOCs, SVOCs, inorga nic compounds, and organometallic compounds. The utility of the TRI

for air toxics risk assessment is two fold. First, it provides a broader perspec tive of ind

ustrial e missions tha

n the HAP li st becau se it inclu des infor mation on a

ir releas es of man

y hu ndreds of additiona l chemica ls. Second , acces sing TRI informat ion is extremely quick and easy. Using the TRI Explorer search engine ( http://www .epa.g ov/tri/ tridata/ index.htm

), one ma y qu ickly identify the loca tion of emi ssions sour

ces and t he identi ty and quan tity of chemi cals re leased t

o the air . The dat

a is also u pdated a nnually (as oppos ed to the National Emissions Inventory (NEI), a nationwide inve ntory of emissions developed by EPA, which is only updated triennially ). However, other characteristics of the TRI data may limit their use for risk assessments (see Section 4.4.2). 4.2.5 Toxic Chemicals That Persist and Which Also May Bioaccumulate Some toxic c ompounds have the a bility to persist in the env

ironment f

or long p eriods of

time and may also have

the ability to build up in the food chain to levels that are harmful to human health and the environment. For example, releases of me tals from a source may

deposit out of the air onto the ground where they remain in surface soils for long periods of time. Children playing in the a

rea may ingest this contaminated dirt through hand-to-mouth behaviors. The chemica ls in the dir

t may also be ta

ken up into

plants thr

ough the roots and accumul ate in foraging animals.d Bio mag nification is the pro cess wh ereb y certain substa nces tra nsfer up the foo d cha in and increa se in

concentration. Chemicals t hat biomagnify t end to accumulates to higher concentrat ion levels wi th each successive food chain le vel. B ioma gnificatio n is a pa rticular c onc ern for ecolo gical risk a ssessm ent. April 2004 Page 4 -7 EPA’s cha

llenge in reduc ing risks from this categ ory of toxic air

pollutants

stems from this ability to transf er from a ir, to sed iments, wa

ter, land, and fo od; to ling er for lo ng per iods of time in the environment; and for some substances, their ability to travel long distances. Many of these chemicals (e.g., DDT) ha ve been banned for use in the U.S. As such, there should be no active air emissions of these chemicals (although re leases into the air are still possible, e.g., by resuspe nsion of pr

eviously contaminated soil) . Howeve r some, su

ch as mer cury, are stil l in use today. A number of

lists of these persistent and bioaccumulative chemicals have bee n developed through international and internal EPA efforts (see Exhibit 4-1). A number of the HAPs appear on one or more of these lists. Exposure to persistent and bioaccumulative air toxics through a pathway other than inhalation of contaminated air is termed an indirect exposure pathway because contact with the chemical occurs in a medium that is not the original medium to which the chemical was re leased (i.e., air). In contrast, a direct exposure pathway is one in which contact occurs with the chemical in the medium to which it was originally r eleased. When exposure of a person to a chemical (or chemicals) occurs through more than one pathway, a multipathway analysismay be consider ed. In air toxics risk assessment, the inhalation pathway is commonly assessed (i.e., the r elease of a chemical to air and human exposure through breathing that air). However, indirect exposure pathways ar

e usually assessed f

or a limited set of chemicals released to the air. EPA has identifie d a preli

minary set of HA

Ps for whic

h indirect exposure

pathway analy ses should generally be conducted for situations involving significant emissions of these chemica ls in a study area . This new list of chemicals is termed Persis tent Bioac cumulat ive HAP Compounds (PB-HA P Compounds) (Exhibit 4-2); however, all of the PB-HAP compounds occur on one or more of EPA’s existin

g lists of PBT che micals. T he desig nation “PB -HAP” was develop ed to distingu ish this list f

rom the existing lists

of PBT chemicals (Exhibit 4-1)and spec ifically to clarify tha

t chemicals on this new list are:

• HAPs;

• Relatively persistent in the environment; and

• Fo r s om e c he mi ca ls , h av e a st ro ng pr op en si ty t o b io ac cu mu la te an d/ or bi om ag ni fy. (d) This preliminary list of PB-HAPs was de rived primarily on the basis of human health concerns. It does not consider direct conta ct by plants or inhalation by animals. Additional HAPs may be identified as EPA gains more familiarity with ecological risk assessments for air toxics. Appendix D d

escribe s the proc ess by

which EPA

identifie d the list of

PB-HAPs.April 2004 Page 4 -8 Exh ibit 4-1 . “L ists” of To xic C hem icals tha t Persist a nd W hich Also M ay B ioacc um ulate LR TA P c hem icals – The Unit ed States si gned pr oto col s on Pe rsi st ent Organi c Pol lut ants (POPs) and hea vy m etals p ursu ant to the C onv entio n on Lon g-R ang e T rans bou nd ary A ir Po llution (LR TA P) in June 199 8 at a minist erialmeeting in Aarhus, Denmark. Sixteen POP s and three metal s are r egulated ( http ://ww w.e pa.g ov/o pp fead 1/in terna tiona l/lrtap2 pg. htm ):

• aldrin

• cadmi um

• chlo rdane

• dield rin

• end rin

• he xa bro mo bip he nyl

• kepone (chlordecone)

• mirex

• toxa phene

• hexachl orobe nzene • heptachlor

• lead

• mercu ry

• polychlorinated biph enyls (PCB s)

• di chl or odi phe ny lt

ri chl or oe th ane (DDT)

• lindanediox ins (polychlorinated dibenzo -p-dioxins)

• furans (polychlorinated diben zofurans)

• hexachl orobe nzene

• poly cy cli c ar omati c hy droc arbo ns
PB T C hem icals – E PA has id entifie d th e follow ing p riority pe rsisten t, bioa ccu mu lative, a nd toxic (PB T) c hem icals an d h as de velop ed th e PB T p rogra m to add ress th e cros s-me dia iss ues assoc iated with these chem icals ( http ://ww w.e pa.g ov/o pp tintr/p bt/ ):

• aldrin /dield rin

• mercur

y and it s co mpounds

• benzo( a)py

rene

• mirex

• chlo rdane

• oct achl oros ty

rene

• DDT • dichlo rodip hen yldichloroe thane (DD D)

• di chl or odi phe ny ld ic hl or oe th yl ene (DDE)

• PCBs

• hexachl orobe nzene

• dioxins and f

urans

• alkyl -lea d

• toxa phene Great La kes Priority Substances . In kee pin g w ith th e ob ligation s of th e G reat L akes W ater Q uality Agreement, Canada and the United States on April 7, 1997, signed the “Great Lakes Binational Toxics Stra tegy: C ana da-U nited State s Stra tegy for th e V irtual E limin ation of P ersisten t To xic S ub stan ces in the Great Lakes” ( ht tp :/ /ww w.e pa. gov/g ln po/

p2/ bns .h tml ). This Str ate gy see ks pe rce ntag e re ducti ons in targe ted persis tent t oxic substances s o as to prot ect and ensure the heal th and integri ty of the Great Lakes ecosystem. Th e list of “Level 1” su bstances is identical to EPA ’s priority PB T pollutants. Great W aters Pollutants of Con cern . The 1990 Cl ean Air Act Amendment s es tabl is hed re sea rch and reporti ng requirements rel ated to t he deposition of hazardous air poll utants to the Great Lakes, Lake Champlai n, Ches apeak e Bay , and c ert ain othe r “Gre at Water s.” The Prog ram ha s i denti fi ed t he fol lowi ng pol lut ants of c oncer n ( ht tp :/ /ww w.e pa. gov/a ir

pro gm/ oa r/ oa qps /g r8w at er /i nde x. ht ml ):

• cadmi um and cadmi um compounds

• chlo rdane

• DDT/ DDE

• dield rin

• hexachl orobe nzene

• " -he xachl oroc yc lohe xane

• lindane ( ( -hexachlorocy clohexane)

• lea d and l ead c ompounds • mercur y and merc ury

compounds

• PCBs

• polycy clic organic matter

• tetrachlorodibenzo-p-dioxin (d ioxins)

• tetrachlorodibenzofuran (furans)

• toxa phene

• nit roge n compoundsApril 2004 Page 4 -9 Exhib it4-1 ( cont inue d) TR I PB T c hem icals . EP A h as pu blished two fina l rules that low ered th e To xics R elease Inve ntory (TRI) reporting thresholds for certain persist ent bioaccumulative and toxic (PBT) chemicals and added certain other PBT chemicals to the TR I lis t of toxic chemicals ( http:/ /www.epa.gov/tri /lawsandregs /pb t/pb trule.h tm ). The following P BT chemicals are subject to reporting at lowered thresh olds:

• dioxi n and di oxin- li ke co mpounds

• lea d compounds

• mercur

y c ompounds

• poly cy cli c ar omati c compounds

• aldrin

• benzo( g,h, i) pery lene

• chlo rdane

• heptachlor

• hexachl orobe nzene

• isod rin • lead

• mercu ry

• methoxychlor

• oct achl oros ty

rene

• pen dim etha lin

• penta chlo robe nzene

• PCBs

• tetrab rom obis ph eno l A

• toxa phene

• triflura lin W aste M inim izatio n P rior ity C hem icals . EPA’s N ational Waste M inimizati on Partnership Program focu ses on redu cing or elim inatin g the gen eration of ha zard ous was te con tainin g an y of 30 W aste Minimization Priori ty Chemicals ( WM PCs). This list replaces the li st of 53 chemicals EPA identif ied in 1998 ( Notic e of

Avail abil it y: Draf t RCRA Waste Minimizati on Pers is tent , Bi oaccumulativeand Toxic (PB T) Ch emical L ist , Fed eral R egiste r 63 (21 6): 6 03 32 -60 34 3, N ovem ber 9 , 19 98 ). Tw enty six of t he che mica ls in t

he cur rent li stwere al so i n the draf t l is t publ is hed i n 1998. The r emai ning f our chemicals on the curr ent li st were added in res ponse to comments and new information EPA receive d from the p ub lic rega rdin g the Ag enc y’s m etho dolo gy for se lectin g the 53 che mic als in th e dra ft list ( http ://ww w.e pa.g ov/ep aosw er/ha zw aste/m inim ize/ch em list.htm ).

• 1,2, 4-t

ri chlo robe nzene

• 1,2, 4,5- tet

rac hlor obenze ne

• 2,4,5-tr ichlorophenol

• 4-bromophenyl phenyl ether

• acena

phthene

• acena

phthy lene

• anthr acene

• benzo( g,h, i) pery lene

• dibenzofuran

• dioxi ns/ fur ans

• end osu lfan, alph a an d en dos ulfan , beta

• fl uore ne

• hepta chlo r and he ptac hlor epoxi de

• hexachl orobe nzene

• hexachl orobut adie ne • hexachlorocycl ohexane, gamma-

• hexachl oroe thane

• methoxychlor

• naphtha lene

• PA H gro up (as d efin ed in T RI)

• pen dim etha lin

• penta chlo robe nzene

• penta chlo roni tr obenze ne

• pentachlorophenol

• phenant

hrene

• pyr ene

• triflura lin

• cadmi um and cadmi um compounds

• lea d and l ead c ompounds

• mercur

y and merc ury

compoundsApril 2004 Page 4-10 Exhib it4-2. PB-HAP Compounds
PB-HAP Com pound Poll uti on Prevent ion Pri or it y PBTs Great W aters

Poll utants of Con cern TRI P BT

Ch em icals Cadmium compounds X Chlor dane X X X Chlor inat ed di benzodi oxins and fur ans X (a) X X (b) DDE X X Heptachlor X Hexachl orobe nzene X X X Hex achlorocyclohexane (all i somers) X Lead c ompounds X (c) X X Mercury c ompounds X X X Methoxychlor X Po lychlo rinate d b iph enyls X X X Polycy clic organic matter X (d) X X (e) Toxaphene X X X Triflu ralin X
(a) “Dio xins and furans” (“” de notes the ph raseo logy o f the sou rce list) (b) “Dioxin and dioxin-like com pound s” (c) Alkyllead (d) Benzo[a]pyrene (e) “Polycy clic aromati c compounds” and benzo[g, h,i] peryle neApril 2004 Page 4-11 Th e HP V Ch al l e ng e Pr og r am EPA , in part

nership with industry

and environmental groups , r ecently

cre ate d a vol

untar y c hemic al tes ti ng effort , the high production volume (HP V) Ch allenge Program. This program was developed to make publi cly avai labl e a c omplet e se t of base li ne hea lt

h and environm ental effects data on HPV chemicals (those ma nu factu red in , or im por ted in to, the Un ited S tates in amounts equal to or exceeding 1 mill ion pounds per year) . Infor

mation on HPV chemicals i s avail able at http ://ww w.e pa.g ov/ch em rtk/rtkfa cts.h tm
. 4.2.6 Other Che micals The chemicals included in the various lists of air toxics d

escribe d above –

HAPs, cri

teria pollutants , TRI c

hemicals , and toxic chemicals that persist and which also may bioaccumulate – do not represent all of the chemicals potentially emitted to air in a given place. EPA is required to maintain an inventory, known as the “ Toxic Substances Control Act (TSCA) Inventory ,” of each chemica l substanc e which ma

y be legall y manufactured, processed, or imported in the U.S. The TSCA inventory curr ently contains over 75,000 chemicals (see: “enforc ement progra ms” at http://www.epa.gov/compliance/civil/programs/tsca/ ). At best, we have the capability to assess only

a few hundred in detail. As noted previously, this does not imply that risk assessments are always missing important information. To the contrary , the actual number of chemicals used in significant amounts and release d to air are relatively small compared to the number of

chemica ls known. N everthe less, it is im portant to keep in mi

nd that the

ability to evaluate air toxics releases is limited by current technology, the lack of toxicity information for all but a relatively small number of chemicals and, in some cases, costs (e.g., a single sample for certain analy tes such as dioxin can

cost upwa

rds of $1, 000 per sa

mple, mak

ing multip le sampling events cost prohibitive). 4.3 Sources of Air Toxics Many anthropogenic and natural activities are sources of a ir pollutants. Examples of human activities that result in the release of air toxics include:

• Fuel combustion a

ctivities in power plants, f actorie s, automob iles, and homes;

• Biomass b

urning a nd other a

gricul tural activities;

• Use of c onsumer products, such as pe sticides a nd clean ing ag ents;

• Commercial activities, such as dry cleaning; and

• Industr ial ac tivi ties, such a s petr oleum refin ing, ch emica l manu factur e, and metal plati ng. Sources o f air toxic s can be c ategor ized in var

ious way s – whethe

r they occur in doors or o

ut, whether they

are stationary

or mobile, by the amount of che micals they rele ase, or by othe r approaches. For the purposes of this discussion, air toxics have been plac ed into several major groupin gs that t rack EPA ’s prog

rams and emissions i

nventori es. Note

that some d

iffere nces in terminology e

xist between the CAA and the NEI (Exhibit 4-3).

• Point sourc es;
• Nonpoint s ources;
• On-roa

d mobile so

urces;
• Nonroad

mobile sou

rces;
• Indo or sourc es;
• Natural sources; and

• Exempt sour

ces.April 2004 Page 4-12 The first four ca

tegori es are g

rouping s of emissi on source s of HAPs a nd crite ria air p ollutants i

n EPA’s National Em

issions Inve ntory (NEI) . The NEI is a nationwide inventory of emissions that has b een dev eloped by EPA with inp

ut from nu

merous sta

te, loca l, and trib al (S/L

/T) air agenc ies. The N

EI is d iscussed in more de

tail as a s ource of

quantita tive emiss ions rele ase data in Section 4.4.1 below. For detailed information on NEI , refer to EPA’s main NEI web page. (5) NEI summaries were

posted in October 2003.
Exhibit 4-3. Term inology R elated to Group ings of Sou rce Types Sourc e Type How De fi ne d i n CAA How Rep or te d i n NEI Point source – Major Point source – Major Point source Point source – Area Point source – Area Point source i f location coordinate s report ed Area source if coordinates not reporte d Nonp oint source Nonp oint source Area Mob ile s ource – On-road Mob ile s ource – On-road Mod eled Mob ile s ource – Nonroad Mob ile s ource – Nonroad Mod eled or estimated Indoor Not defined Not reported Natural Not defined Not reported Exempt Not defined Not reported 4.3.1 Point Sources Point sources of air toxics are stationary sources (i.e., sources that remain in one place ) that can be located on a map. A large f acility that houses an industrial proce ss is an example of a point source – the facility

and its emission release points (e.g., stacks, vents, fugitive e missions from valve s) are s tati onary, and the em issi on rat es of ai r tox ics can be char acteri zed, eithe r thro ugh direct measurements, such as stack monitoring, or indirec t methods, such as engineering estimates based on throughput, process information, and other da ta. The CAA divides point sources into two ma

in categories pr

imarily on the bas is of annu

al emissions rates :

• Major sources are defined in Section 112(a)(1) as “a ny source or

group of stationary

sources located within a c ontiguou s area a nd under common control that

emits or has the pote

ntial to emit, considering controls, in the aggr egate, 10 tons per y

ear (tpy ) or more of any

hazardous air pollutant or 25 tpy or more of any combination of hazar dous air pollutants.”

• Area sources are def

ined in Sec

tion 112(a

)(2) as “any stationar y so urce of hazardou s air pollutants that is not a major source. For purposes of this section, the term ‘area source’ shall not include motor vehicles or nonroad vehicles subject to reg ulation under Title II .” Examples of area sources include dry cleaners, gas stations, chrome elec troplaters, and print shops. Tho

ugh emis sions from individua l area s ources may

be rela tively insignif icant in human health terms, collectively their emissions can be quite significant, particularly where large numbers of sources ar e located in heavily

populated areas. Note that sources that are classified as “area sources” pursuant to the CAA may be r eported in the NEI as “

point sources” if they

can be located on a map.April 2004 Page 4-13 Many source s of HAPs are subject to National Em ission Standar ds for Hazar dous Air Pollutan ts (NESHAP s) pursuant to Section

112 of the

CAA. This Se ction of the CAA dire cts EPA to issue

regula tions listing

categ ories an

d subcate gories

(commonly

refer red to co llective ly as source categories ) of major sources and area sourc es of HAPs and to develop standards for ea ch li st ed ca te go ry a nd su bc at eg or y. (6) EPA periodically update s the list of source categories (see Appendix E). (7) Physi calForms of Emis si ons Gas Em issions that are disti nguished from solid and liqu id states Fume Tiny parti cles t rapped in vapor in a gas s tream M ist Liqui d particl es mea suring 40 to 500 micr omete rs that are for med by condensation of vapor Parti culat

e Matt er (

and Aeroso ls) Fine liquid or sol id parti cles Air pollutants can be found in all t hree physical

phases: sol id, li quid, or gaseous. The distinct chemical and physicalattributes of e ach phase contribute t o the polluta nt’s tr ansport and fate. For example, as report ed in the Mercu ry Study R eport to C ong ress , (8) elemental mercury vapor is not thou ght to be su scep tible to any m ajor p roces s of d irect d epo sition to the earth ’s su rface d ue to its rel ativel y hi gh vapo r pr ess ure and low wa ter sol ubil it y. There for e, i t i s carr ied by t he wind a

nd subsequently disper sed throughout the atmosphere. However, divalent mercury , in ei ther vapor or part icul ate phase , i s thought to be subje ct to muc h fas ter at mospher ic remov al, and i s expe cte d to be deposited near

it s so urce . For

further det ail s on f

ate and trans port

anal ys is , s ee Chapt er 8. As noted in

Chapter 2 , EPA reg

ulates sta tionary sources in a two-phase pro cess. F irst, EPA issues technology-based MACT standards that require sources to meet spe cific emissions limits. The emission limits are typically expressed as maximum emission rates, or minimum percent emission r

eduction s, for spe cific po llutants f rom spec ific proc esses. I n the sec ond phase , EPA applies a risk-based approach to assess how we ll MACT emissions limits reduce health and environmental risks. Based on these residual risk assessments , EPA may implement additional standards to address any

significant remaining, or residual, hea lth or environmental risks (see Chapter 2 for a more detailed discussion of the MACT and residual risk prog rams). Area sources may

be subject to either MACT or Generally Available Control Technology (GACT) standards. GACT standards are gene rally less stringe

nt than MACT standards. Area sources subject to MACT standards include Commercial Sterilizers using Ethy lene Oxide, Chromium El ectropl aters a nd Anodize

rs, Halogenated So lvents Use rs, and A sbestos Pr

ocessors. 4.3.2 Nonpoint Sources The term nonpoint so

urce re fers to smaller an

d more dif

fuse sour ces withi n a rela tively small geographic are a. In the context of EPA’s NEI , nonpoint sources of air toxics are stationary sources for whic h emissions

estimate s are pr

ovided as an agg regat e amount o f emission s for all similar sources within a specific local geog raphic area, such as counties or cities, ra ther than on a facility- or sourc e-specific basis. Emission estimates for nonpoint sources are g enerated using “top-down” methods, when detailed information at the local level is lacking . Instead, the total emissions over a large geog raphic area (e.g., n tons in the northe astern states) are allocated to theApril 2004 Page 4-14 local level (e.g., x percent is assigned to loca lity 1, y percent is assigned to locality 2, and so on). Note that for the p urposes o f this disc

ussion, the

nonpoint so

urce ca tegory includes only stationar y so urces a nd does not

include mobile sour

ces. Source-specific information may be available for some (but not all) of the specific facilities within a certain nonpoint source ty pe. Area sources may

be reported as either point or nonpoint sources in the NEI. If a state or local agency reports an area source emission as a point source , then the N

EI r etains the area so urce em ission as a

point sour

ce. The NEI d oes not ag

greg ate point area sources as nonpoint sources, and EPA has taken steps to avoid “double-counting” of emissions in the point and nonpoint source inventories

. To compile nonpoint estimates for a category , the EPA first estimates county leve l emissions for nonpoint so

urce ca tegori es. Then

EPA repla

ces nonp oint EPA g enerat ed estima tes with sta

te and local agency

and tribal estimates. If a state or local agency

or tribe includes point source estimate s for an EPA gene rated nonpoint sour

ce cate gory, EPA removes the nonpoint est imate that it had gener ated and the point s ource in

ventory contains the S/L /T estimat

e. For e xample, in the Denver area, the State of Colorado inventorie s dry clea ners and service stations as point sources. The NEI c ontains point sources estimates for these two categorie s in the six county area of Denver and the NEI

does not contain nonpoint estimates for these two categories. Dr y cleaners and service station emissions are containe d in the NEI nonpoint inventory for the other fifty counties on Colorado. A variet y of sources are ca tegorized as nonp oint sourc es in the N EI, i ncluding some small industrial/commercial processes (e.g., small dry cleaning facilities, hospital sterilization facilities, and dental offices). Additional nonpoint sources that contribute to air pollution are agric ultural a ctivities , reside

ntial tra sh and y

ard-wa ste burni

ng, woo d stoves a

nd firep laces, releases from spills and other accidents, and volatilization and resuspension of pollutants from contaminated site s. Examples of agr icultura l activitie s contrib

uting to a ir pollution are biomass burning (e.g., for land cle aring) and the application of fertilizers and pesticide s. The open burning of forests (including wildfires) a re also categorized as nonpoint sources. (Note that forest fires are gene

rally considere d for the purposes of the NEI to be an anthropogenic source of air toxics because they a

re assumed to be directly

or indirectly, for

purposes of the NEI, ca

used by man.) Some nonpoint sources emit HAPs and are subject to NESHAPs pursuant to Section 112 of the CAA (see Section 4.3.1 above for more information on NESHAPs). These nonpoint sourc es are area sources in that they

emit less than 10 tpy of a single air toxic or less than 25 tpy of a mixture of air toxics. For example, facilities that perform perchloroethy lene dry c leaning belong to a source c ategor

y that is subje ct to NESHA Ps. 4.3.3 On-Road and Nonroad Mobile Sources Mobile sources pollute the air with fuel combustion products and evaporated fue l. These sources contribute greatly

to air pollution nationwide and are the primary cause of air pollution in many urban areas. Section 202(l) of the CAA give s EPA the authority to reg ulate air toxics from motor vehicles. Based on 1996 National Toxics Inve ntory data (the

NTI is the former name

of the air toxics portion of the current NEI), mobile sourc es contributed 2.3 million tpy or about half of all air toxics emissions in the U.S. Mobile sources emit hundreds of air pollutants – for example, exhaust and evaporative emissions from mobile sources contain more than 700April 2004 Page 4-15 compounds. EPA’s Final Rule, Control of Em issions of H azardous A ir Pollutan ts from Mob ile Sources , commonly known as the “Mobile Source Air Toxics” (MSAT) rule, (9) identified 21 compounds as HAPs emitted by mobile sources ( see Chapter 2). All of these compounds except diesel particulate matter and diesel exhaust organic gases (DPM + DEOG) are included on the CAA Section 112 HAPs l ist. Althou gh some m

obile sour ce air toxics are TRI chemicals, mobile sources are not general ly s

ubject to TRI r eporting . Other mo

bile sour ce reg ulations a ddress emissions of criteria pollutants and their precursors, including ca rbon monoxide (CO), nitrogen dioxide (NO 2 ) , particulate matter (PM), volatile organic compounds (VOCs), and sulfur dioxide (SO 2 ) . These c

riteria air pollut ant contr ol progr ams for mo

bile sour ces have and will c ontinue to result in s ubstantia l reduct ion of HAP r

elease s. Mobile sou

rces inc lude a wid

e variety o f vehicl es, engines, and equipmen

t that ge nerate air pollution a

nd that move, or ca

n be moved , from pla

ce to pla ce. I n the NEI , EPA divide s mobile sources into two broad categories. On-road mobile sources include motorized vehicles that are normally opera

ted on public roadway s for transportation of passengers or fr eight. This includes passeng er cars, motorcyc les, miniva ns, sport- utility vehicle s, light- duty

trucks, heavy

-duty trucks, and buses. Nonroad mobile sources , (sometimes also c alled “o ff-roa d”) incl ude airc raft, commercial marine vessels (CMVs), locomotives, and other nonroad e ngines and equipment. The othe r nonroa d engines and eq

uipment inc luded in N

EI c omprise a

diverse list of por

table equipmen t, such as lawn and garde n equipme

nt; constr uction eq uipment; e

ngines u sed in recre ational a

ctivities ; and port

able indu strial, c ommercia l, and ag ricultur al engi nes. EPA’s National Air Pollutant Trends Report, 1900–1998 (10) indicates that about 60 percent of mobile source air toxics emissions in the U.S. are from on-road sources, and 40 perc ent of mobile source air toxics emissions are from nonroad sources. The emissions distribution betwee n on- and off-ro ad sourc es emittin

g crite ria pollut ants depe nds on the c

hemical. CO comprises the majority of c riteria pollutants emitted, with over 100 million tons per year emitted in the U.S. Releases of CO are primarily the resu lt of mobile

sources – like HAPs , these emissions a

re split a pproximate ly 6 0/40 betw een on-r oad and o ff-roa

d source s. (The u se of CO as a monitoring surrogate for mobile sourc e emissions is discussed in Section 4.4.1.) Within the two broader categories of mobile sources, EPA fur ther distinguishes on-road and nonroad sources by

size, weight, use, horsepower and/or fuel ty pe. For example, categories of on-road vehicles include light-duty gasoline vehicles (i.e., passenge r cars), light-duty

gasoline trucks, heavy-duty gasoline vehicles, and diesel vehicles. Examples of nonroad sources include nonroad gasoline engines and vehicles, (e.g ., recreational off-road vehic les, construction equipment, lawn and garden equipment, and re creational marine vessels that use gasoline) , nonroad diesel engines and vehicles (including the ve hicles and equipment listed above, except those that use diesel fuel), aircraft, non-re creational marine vessels, and locomotives. An additional category

covers all nonroad sources that use liquified petroleum g as or compressed natural gas. 4.3.4 Sources Not Included in the NEI or TRI In a ddition to the four pr

imary categ ories use d in compili ng the N EI, f ive other sources of air toxics which are not

capture d by

either the NEI

or TRI are des cribed b elow: I

ndoor sou rces, natural sources , second

ary formation of air toxics, exempt s ources, and inter national transpor t.April 2004 Page 4-16 4.3.4.1 Indoor Sources Indoor pollution sources that release gases or particles into the air are the primary ca

use of indoor air quality problems in homes (Exhibit 4-4). I nadequate ventilation can increase indoor pollutant levels by not bringing in enough outdoor air to dilute emissions from indoor sources and by not carr yin g indoor air pollut ants out of

the home. High te

mperatu re and hu midity levels indoors c an incre ase the u ptake of some pollu

tants, the reby magnif yin g neg ative he alth eff

ects. There are many

sources of indoor air pollution in any home. These include combustion sources such a s oil , gas, k erosen e, coal , wood , and t obacco produ cts; b uild ing mat erial s and f urnis hings as diverse as deteriorated, asbestos-conta ining insulation, wet or damp carpet, and cabinetry or furniture made of certain pressed wood pr oducts; products for household cleaning and maintenance, personal care, or hobbie s; central heating and cooling sy stems and humidification devices; and outdoor sources such as radon, pesticides, a nd outdoor air pollution. The rela tive impor

tance of any single s ource de

pends on how much of

a given pollutant i

t emits and how hazardous those emissions are. In some c ases, factors such as how old the source is and whether it is properly

maintained are significant. For example, an improper ly adjusted gas stove can emit significantly

more carbon monoxide than one that is properly adjusted. Some sourc es, such as building materia ls, furnishings, a

nd household produc

ts like air fresheners, release pollutants more or less c ontinuously. Other sources, r elated to activities carried out in the home, release pollutants intermittently . These include smoking, the use of unvented or malfunctioning stoves, furnaces, or spa ce heaters, the use of solvents in cleaning and hobby activities, the use of pa int strippers in redecorating activities, and the use of c leaning products and pesticides in housekeeping. High pollutant conc entrations can remain in the air for long pe riods af ter some o f these a

ctivities

. In addition to the same indoor air problems as single-family homes, apa rtments can have indoor air problems similar to those in offices, which are caused by sources such as contaminated ventilati on sy stems, impr operly placed o utdoor ai r intake s, or main

tenance activitie s. One particularly

important indoor air toxics problem actually results from a n outdoor natural source. In fac

t, radon gas, a HAP, is one of the leading causes of lung cancer in the U .S. The most common

source o f indoor r

adon is ur anium in the

soil or roc

k on which

homes ar e built (thus, a natural source becomes an indoor air qua lity problem). As uranium natura lly breaks down, it releases radon as a colorless, odorless, ra dioactive gas. Radon gas enters homes through dirt floors, cracks in concrete walls and floors, floor drains, and sumps. When radon becomes trapped in building s and indoor conce ntrations build up, exposure to r

adon bec omes a concern. Sometimes radon enters the home through well water. I n a small number of homes, the building materials can give off radon, too. Howe ver, building materials alone rarely cause radon levels of concern (see http://www .epa.g ov/radon /risk_ass essment. html for more information on radon risks). E xhibit 4-5 shows EPA’s ma p of radon zones in the U.S.April 2004 Page 4-17

Exhibit 4-4. Ma jor Indoor A ir Pollutants and their Sources M ajor Ind oor Air P olluta nts Sources Radon (Rn) Ea rth an d roc k be nea th h om e; we ll wate r; bu ildin g m aterials Environmental Tobacco Sm oke (includes car

bon mon oxide, nitro gen diox ide, a nd resp irable particles) Cigar ett e, pi pe, a nd ci gar smoki ng

Biol ogi cal s ( e.g ., poll en, mol d, anim al da nd er, an d fu ngi) W et or m oist w alls, ceilin gs, ca rpets , and furn iture; p oorly maintained h umid ifiers, dehu midifiers, and air conditioners; bed din g; ho use hold pets Carbon Monoxi de Unvente d ker osene and ga s spa ce he ate rs; le aki ng chi mneys and furnaces; back-drafting from furn aces, gas water heaters, woodstoves, and fir eplaces; gas stove s. Automobile exhaust from attac hed garages Ni t ro ge n Di ox i de ( NO 2 ) Kerosene heaters, unvented gas stoves a nd heaters. Environmental tobacco smoke Volat il e Organic Compounds (such as xylene) Paints, paint strippers, and other solvents; wood preservatives; aeros ol sp rays; clea nse rs an d d isinfe ctan ts; mo th rep ellen ts and air fresheners; stored fuels and autom otive products; hobb y supplies; dry -c lea ned cl othi ng Respirable Parti cles Fireplaces, wood stoves, and kerosene heat ers. Environmental tobacco smoke Formal dehy de Pre ssed wo od p rod ucts (hard wo od p lywoo d w all pa nelin g, pa rticle board, fiber

board) and furniture made with thes e pressed wood products. Urea-f

ormaldehyde foam insulat ion (UFFI). Combu stion sources and en vironmen tal tobacco smoke. D urable press drape s, other textiles, and glues Pestici des Produ cts used to kill household p ests (insectici des, termiticides, and disinfecta

nts). Also, products used on lawns and gardens that drift or are t

racked inside the ho use Asbestos Deteriorating, damaged, or dist urbed insulati on, fir eproofing, acoustical materials, and floor ti les Lead Lead-based paint, cont aminated soil , dust, and drinki ng water Source : U.S . En viron me ntal P rotectio n A gen cy and the U nited State s Co nsu me r Pro du ct Sa fety Com mission . 199 5. O ffice of Ra diation a nd In door A ir (660 4J) E PA /402 /K/9 3/00 7, A pril 19 95. Av ailab le at: http ://ww w.e pa.g ov/iaq /pu bs/in side st.htm l.April 2004 Page 4-18 Exhibit 4-5. EPA Ma p of R adon Zones

• Zone 1 counties have a pre dicted avera ge indoor radon scree ning level gr eater t han 4 pC i/L (pi co curies p er liter)

• Zone 2 cou nties hav e a p redic ted a verag e ind oor ra don scree nin g leve l betw een 2 an d 4 pC i/L

• Zone 3 cou nties hav e a p redic ted a verag e ind oor ra don scree nin g leve l less th an 2 pC i/L

4.3.4.2 Natural Sources Natural processes are signific ant sources of some air pollutants, including VOCs, NO x , O 3 , PM and other pollutants (Exhibit 4-6). Examples of natural sources of air pollutants that are not covere d by

the four main cate gories

describ ed above

include natural processe s occurr ing in vegetation and soils (e.g., emissions from trees), in mar ine ecosystems, as a

result of geological activity in the form of geysers or volcanoes, as a result of meteorologica l activity such as lightning, and from fauna, such as ruminants and te rmites. Sources associated with biological activity are c alled biogenic sources. Natural pollutants contribute significantly to air pollution. For example, biogenic emission estimates for the United States were 28.2 million tons of VOC and 1.53 million tons of NO x in 1997. (10)April 2004 Page 4-19 Exhibit 4-6. Categories of N atural Sources Category Examples of Emiss ions Sources Geologi cal • Sulphur ic, hydr ofluori c and hy droc hlor ic aci ds

• Radon

• Nitrogen oxides • Volcanic gases

• Radioactive decay

of rock

• Soil s, li ghtni ng
Bio gen ic • Am mo nia

• Methane

• VOCs • Animals wastes

• Animal wastes, plant decay

• Vegetation Marine • Dim ethyl sulfide, ammonia, chlorides, sulfates,

alkyl halides, nitrous oxides • Sea s pray rel eas ed by breaking waves Source : Inter

national Fertili zer I ndustry Association. 2001. Food and A gricult ure Organization of

the United N ations. Gl oba les t i mates of ga se ous emi

ss i ons of NH3, NO an d N2 O f

ro m agr icul

tur al l and. ISB N 9 2-5 -10 46 98 -1. A vailab le at: www.fao .or g/DOCREP/004/ Y2 78 0E /y27 80 e01 .htm

. 4.3.4.3 Formation of Secondary Pollutants Some air p ollutants, in addition to being directly emitted to

the atmosp

here by identifia ble sources, are genera

ted in the atmosphere by

the chemical transformation of precursor c ompounds (a process called secondary formation ). For example, und er some me

teorolog ical con ditions, up to 90 percent of ambient formaldehy de originates from secondary formation from a variety of precursor compounds in the presence of lig ht (i.e., via a photochemical reaction ). Some of the precursor compounds include isoprene (an organic compound released from trees), isobutene , and prop ene. The

seconda ry formation of pollut

ants like f ormalde hyd e and ac etaldeh

yde is a complex process but can be estimated by some photochemical models (e.g., UAM-Tox, a special version of the Urban Airshed Model (UAM)). Other available models also address secondary formation but in a mu

ch more l imited wa

y ( see Chapter 9 for

a more de

tailed dis cussion of

air models). The NEI and other e

mission inventories generally do not include estimates of pollutants formed through secondary

formation – only the initially emitted species are included. Beca use the formation of secondary

pollutants depends on the meteorological conditions and the presence or absence of other compounds and/or light, a model that incor porates chemical transformation algorithms is required to estimate how much secondary product is formed from precursor compounds once they e

nter the atmosphere. EPA has in some instances developed estimates of seconda rily formed c hemicals to better inform the

assessme nt of exposu

re of pe ople to toxic

air pollutants . For exa

mple, for the 1996 N

ATA, Nat

ional-sc ale Air T oxics Asses sment, risk charac terization exercis e, EPA de veloped a special inventor y of precursor compo

unds to supplement the NTI, which was used in c onjunction with the Assessment System for Population Exposure Nationwide (ASPEN) model to calculate ambient concentrations (see http://www.epa.gov/ttn/atw/nata/ ). Formation of secondary pollutants is discussed in greater detail in Chapter 8.April 2004 Page 4-20 International Transp ort of Air To xics As note d ear li er i n Chapte r 2 and Sect ion 4. 2.5, cer tain ai r t oxic s may

be trans port ed ove r l ong distanc es, som etimes ac ross intern ational b orders. Int ernati onal sour ces may be an i mport ant cont ri butor to l ocal poll utant le vel s i n some s tudy areas. 4.3.4.4 Other Sources Not Included in NEI or TRI Many air toxics sources, usually relatively small ones, may not be covered or are exempt from various emissions control, reporting, and other requirements, a nd in some cases the number or stringe ncy of requi rements i s tiered a

ccordin g to sour ce size or other cr iteria. F or example , air pollution regulations for municipal waste combustors (MWCs) promulgated pursuant to Section 129 of the CAA include separate rules for large MWCs (i.e., with capacities greater than 250 tons per day) a

nd small MWCs (i.e., with capacities between 35 and 250 tons per day ). Ho we ve r, th er e a re no ru le s f or MW Cs wi th ca pa ci ti es le ss th an 35 to ns pe r d ay. Other miscellaneous sources of air pollution (e.g., agricultural and r

esidential burning) are controlle d primari ly by ot her S/L /T require ments. However, E

PA conducts research, provides information, and pursues other non-regulatory

means of addressing some of these pollution sources. For example, EPA, in conjunction with the Consumer Product Safety Commission and the American Lung

Association, has publ ished a guide for red ucing p ollu tion from r eside ntial wood c ombu stio n, in cludi ng desi gn informat ion for le ss-polluti

ng stove s and fir

eplace s. (11) Some local areas have ordinances that require new fireplace and wood stove installations to comply with the certification prog ram, and others have ordinances that prohibit the use of a wood stove or f ireplace on days that are conducive to the c oncentr ation of wood smoke e

missions. Ultimatel y, t here is no single

comprehensive so

urce of informat ion on all s ources o f air toxic s in a given area. The NEI

and TRI are good places to start an investigation of what is being re leased in a study area , but as noted above, in any given place, there are

probably a number

of air toxics sources that are not acco unted for in these in

ventorie s. Nonre gulate d source s, natura l source s, and mate rial movin

g into a study

area f rom distan

t source s all have

an impact on overa

ll air quality. Assessors need to c learly under stand what these limitations are as they move into the planning and scop ing stage of the r isk asses sment (se e Chapte r 6). (A d escripti on of how E

PA addressed background conc entrations for the NATA national-scale assessment is provided a t http://www .epa.g ov/ttn/atw /nata/na tsa2.html. ) 4.4 Emissions Inventories As mentioned previously, information on re leases of air toxics is primarily compiled and maintained in emissions inventories . The primary emission in

ventory for HAPs a

nd crite ria pollutants is EPA’s NEI. EPA’s TRI is a second inventory tha

t has some utility for planning and scoping an air toxics risk assessment, but is of limited use for risk assessment because of the nature of the way

the data are reported. I

n addition to the NEI and the TRI , S/L/T air agency permit files and, in some instances, S/L/T inventories that have be en developed, but not submitted to the NEI, can also provide information on the loca tion, identity, magnitude, and source characteristics of air toxics release s. The best inventory da

ta are collected near the g round, literally at the sourc e. For example, an urban scale study

might opt to do a “drive by ” or “windshield” verification of the number andApril 2004 Page 4-21 location of dry cleane rs and g as station s in the stud y a rea ra ther tha n rely on an aggreg ate county-level e stimate. Ultimately, the needs of the assessment (e.g., screening leve l or more refined) will determine the level of accur acy ne eded in the emissions inventory. This section will describe the

NEI a nd the TRI . Other p otential s ources o f air toxic s data ar e descr ibed in Chapter 7. The process of developing an e missions inventory is also described in Chapter 7. 4.4.1 National Em

issions Inve ntory (NEI) EPA’s Office of Air and Radiation compiles and maintains the National Emissions Inventory (NEI) that inclu

des quan titative d ata on an thropog enic emis sions of criteria pollutants

and HAPs and cha racter istics of t he sourc es of the se air toxic s. (5) It inc ludes poin t, non-poi nt, and mob ile sources for all 50 states, Wa shington , D.C., an d U.S. ter ritories

. Previousl y, e missions of

criteri a polluta

nts and HA

Ps were tr

acked se parate ly by EPA in databases that preceded the NEI . Criteria pollutant emissions data for 1985 through 1998 are availab le in the N ational E mission Tre

nds (NET)

databas e. Hazar

dous air p ollutant (HAP) emissions data are available for 1993 and 1996 in the National Toxics I nventory (NTI

) database. For 1999(the most r

ecent y ear for which da ta are a vailable ), crite

ria and H AP emission s data have been prepared separ ately but in a more integ

rated fashion. The final version of both the criteri a and HA

P inventor

ies (for 1999) ar e availa ble at http://www .epa.g ov/ttn/chi ef/net/ 1999inve ntory .html. Note that

the data collecti on and pr

ocessing require ments for this undertaking are significa

nt. As such, EPA plans to update the NEI eve ry three years. The NEI inventories ar

e developed by

EPA’s Emission Factors and Inventorie s Group with input from S/L/T agencie s, industry, and a number of EPA offices. In some ca ses, if a S/L/T agenc y does not submit data, EPA may use data f rom an earlier y

ear and “grow” the e

missions (e.g., for criteria stationary

sources) or use only

data available from other sources (e.g ., HAP collected by EPA as part of the development of emission standards, or data submitted by sources under the Toxics Release Inventory program). Separate inventory documentation files have been prepared for eac h part of NEI (i.e., for

criteri a polluta

nts and HA

Ps, and for point, nonpoint, an d mobile sources ). These

detailed document

ation file s are available online for criteri a polluta

nts (12) and HAPs. (13) The reader should refer to these doc umentation files for detailed information on NEI

. Summaries of data sources for the components of the curr ent version of NEI ar

e also provided below. An importa

nt fact to keep in mi

nd about the NEI

is that it inc ludes dat

a on HAPs f

rom both small and l arge stationar

y so urces a nd both on-

and off-road mobi le sourc es. Equa lly i mportant, it is much more likely

to include

the data necessa ry for mode ling (a

lthough many

of the da ta fields ne eded for

modeling

are not “ mandator y,” and thus st

ates ar e not req uired to provide th

is information to the NEI). I nformation such as stack height, emission rate, and tempera ture are critical to developing reasonably accurate estimates of human exposure in the areas surrounding a source. It is for this reason that the NEI can be of more use than other databases, for example, fo r g et ti ng a b et te r h an dl e o n r ea li st ic ex po su re an d r is k e st im at es in an ac tu al st ud y. NEI for HAPs – Point Sources . For the NEI f or HAP emi ssions from point sour ces, S/L /T agencies are asked to supply HAP emission inventory data to EPA. If they do not provide HA P emission inventory data to EPA, then EPA prepa res default emission inventory data (this has been done for the

1993, 1996 , and 1999inventor y y ears). As discuss ed previ ously , EPA uses a variety of method s to devel op data a nd fill in g aps, whe

re nece ssary

(for poi nt source s of HAPs,April 2004 Page 4-22 EPA uses S/L

/T data, E PA estimat

es for MACT and sour

ce cate gories , and TRI

data; all the TRI facilities are in the NEI) . This is one reason why the NEI provides, for some sourc es, data that may not accu rately reflect actual e

missions in a

ny g iven plac e. Depe

nding on a study ’s speci fic data quality objectives, c loser inspection and verification of emissions estimates may be ne ce ss ar y. The target area for

the NEI includes ever

y state and ter

ritory in the United States and eve ry county within a Sta

te. Ther e are no boundar y lim itations pe

rtaining to traditi onal cri

teria pollutant n

onattain ment are as or to de signate d urban a reas. If a fac ility

was inclu

ded in a S/L

/T databas e, it is inc luded in the NEI regar dless of w

here in t he state it was loc ated. The polluta nts inventor ied inclu ded all 18 8 HAPs iden

tified in Se ction 112(

b) of the CAA. Some S/

L/T agencies collect information on more than just these HA Ps, but only the 188 are included in the HAP NEI. I

n addition to numerous specific chemical species and compounds, the list of 188 HAPs inclu

des seve ral comp ound gr

oups (e.g ., individu

al metals and their compound s, polycy clic organic matter [POM], and gly col ethers); the NEI include s emission estimates for the individual compounds within these groups wherever possible. Appendix F lists all of the specific pollutants and compound groups included in the 1999 NEI along with their Chemical Abstract Services (CAS) numbers (for individual compounds). NEI for Criteria Pollutants – Point Sources . For the NEI for criteria emissions from point sources, EPA solicits point source data from S/L/T g overnments. EPA uses S/L/T point source data preferentially, except for NO x and SO 2 emissions from utilities. For utilities, EPA uses NO x and SO 2 emissions that facilities report to the Emissions Tracking Sy stem/Continuous Emissions Monitoring (ETS/CEM) Scorecard database. Some other c riteria pollutant emissions data in the most recent version of NEI ha ve been supplemented by EPA based on submissions to other emissions databases. In addition, emissions of ammonia (NH 3 ) (which is not a cri teria po llutant, but is a pr

ecursor for PM) ha

ve been added to N

EI based on re

ports subm

itted by S/L/T o ffices, TRI data, and (for loc ations where reports were not submitted) also based on EPA estimation methods. Nonpoint Sources (Both HAPs and Criteria Pollutants). Much of the nonpoin t source data in NEI for HAPs was initially compiled as a national-level inventory . National-level emission estimates are spatially

allocated to the county-level using a number of allocation factors, such as population and employment within certain industries. F or example, aggreg ate amounts of dry cleaner emissions for a county might be estimated from the number of people living within a county. For H

APs, EPA uses MACT data and S/L/T data, where a vailable. When S/L

/T- or loc ality

-specif ic emissions data a

re avai lable, those data

are substituted for data that had been allocated from national emission estimates. EPA prepare s emissions for several area source categories for the NEI e ach ye ar using the most current activity and emission factor data available. Emissions for other area source categories for which methodologies were not prepared in a given y

ear are extrapolated (and assumed to incre ase some percentage e ach ye ar) from the most recent S/L/T inventory submitted previously to EPA. For example, if an inventory was submitted in the past 3 y ears to EPA for the 1996 base y ear, the 1999 NEI emissions are extrapolated from the 1996 inventory . In some cases, criter ia air emissions may also be extrapolated from other inventories (e.g., the 1985 National Air Pollutant Assessment Program inventories). A more detailed discussion of emissions estimation routines for source categories with national-level emission estimates are de scribed in the documents referenced above.e Vo latile Or ganic C omp ound mea ns any o rganic com pou nd wh ich pa rticipate s in atmo sphe ric

photoch emica l re acti ons; or whi ch i s meas ured by a ref erenc e meth od, anequi vale nt me thod, an al ter native met

hod, or which is determined by procedures specifi ed under any subpart (40 CFR Part 60).

. April 2004 Page 4-23 EPA uses an emissions estimation model known as the Biogenic Emissions Inventory System (BEIS) to predict emissions of VOC and NO x from forests, crop lands, and fertilized lands. Emission rates are dependent on several meteorolog ical factors. VOC emissions are dependent on temperature and sunlight, and NO x emissions from fertilized soils are dependent on tempera ture and soil moistur

e. The B EIS mo del is use d to predi ct emissions that ar e include d in the NEI inventory

for criteria pollutants. (Keep in mind that VOCs, as a group, a re inventoried, but not speciated, to help evaluate an area’s pote ntial for ozone production. Non-speciated VOC data are of limited use for performing air toxics risk assessments.) (e) On-road Mobile Sources. In the final Ve rsion (V 3 .0) of the

1999 NEI , EPA used

the most recent version o f the MOB IL

E6 (Version 6.2) model to ca lculate e mission fa

ctors for criter

ia pollutants and 36 HAPs. On-road emissions inventories for CO, NO x , VOC, PM 10 , PM 2.5 , SO 2 , NH 3 , and the 3 6 HAPs are calcula ted by multiply ing an a ppropria te emission factor

in gram s emitted per mile by the cor responding vehicle miles traveled (VMT) in millions of miles, and then converting the product to units of tons of emissions. Emission estimates include calcula tions by month, cou

nty , road ty

pe, and vehicle ty

pe, with VOC broken

down by exhaust and eva porative emissions a

nd PM 10 and PM 2.5 broken down by e xhaust, brake wear, and tire wear emissions. The MOBILE6 model used is the publicly available version from EPA’s Office of Transportation Air Quality ’s (OTAQ) Website ( http://www .epa.g ov/otaq/m6 .htm ). This model incorporates both MOBILE6.0, which is used to estimate emission factors of VOC, CO, and NO x , and MOB IL

E6.1, whic

h is used to

calcula te emission factors of PM 10 , PM 2.5 , SO 2 and NH 3 and MOB TOX, whic h is used to

calcula te certa in HAPs. The partic

ulate an d SO 2 emission factors were previousl

y c alculate d using EPA’s PART5 m odel. Nonroad Mobile Sources. To develop this component of the NEI, data were compiled on criteria and HAP emissions data for aircraf t, commercial marine vessels, and locomotives. HAP emissions for other nonroad engines operating in the United States were estimated using the latest nonroad model. S/L/T data are use d when provided. In this effor t, national emission estimate s were o ften developed f or each of the ab ove ty

pes of non

road sour ces and a llocated to counties based on availab le Geog

raphic I nformati on Sy stem (GI S) data. F or some po llutants associa ted with the nonroa

d category , county

-level ( instead o f nationa

l) data were use d to estimate emissions. The metho dologie s used to e stimate e missions an

d the proc edures u sed to spatially allocate them to the

county level va ry by s ource c ategor

y a nd polluta

nt. For some pollutants and categories, the NONROAD model was utilized to estimate emissions (see http://www .epa.g ov/otaq/nonrdmdl.h tm ). Concurrent with the development of the national emission estimates, S/L/T agencies developed and provided to EPA emissions inventory data f or their areas based on local knowledg e and activity information. These S/L /T agency data replaced the national emission estimates when the pollutant, source type, a nd emission type matched with the national e stimates. Submitted S/L/T data that did not match the nationally -derived data were retaine d along with the national estimates. S/L/T data were used a s provided and not adjusted to better match the national data. Some S/L/T inventories did not provide estimates for all of the pollutants included in theApril 2004 Page 4-24 nationally-derive d emission estimates; in these cases, the submitted S/L/T data were use d and the national estima

tes were included only for the mi ssing pol lutants. Although the current NEI data files represent a valuable source of emissions data, there are numerous uncertainties associated with the current ver sions of these inventories that should be considered when using the data in a risk assessment. Sourc es of uncertainty include the following :

• The emission data included in NEI ar e of variable, and in some cases, undocumented derivation. Many of the

emission estimates were submitted by the sourc es of the emissions to S/L/T air agencies, a

nd then to EPA, without full explanations of how the emissions were estimated.

• Not all sources are accounted for. I n some S/L/T data sets, very small sources have been reported, while in others only the largest sources in certain ty pes of industry are

included.

• Not all S/L

/T age ncies ha ve submitte d data. Sp ecifica lly, for the N

EI f or crite ria pollut ants, 35 out of 50

states submitted dat

a to EPA for the 1999version o f NEI . For the other sta tes, EPA extrap olated the affe cted por tions of the

inventor y f rom an ea rlier y ear. Th is omits sources that came online in the target y ear and erroneously

include sources that have shut down. For more information on which S/L/T governments submitted data and for which states the inventory is extrapolated, the use r can refer to the documentation for the r espective inventory sector a

nd the respective pollutant type (see website addresses above). Some of the states for which 1999 data were not available w hen these inventory

versions were compiled have now

provided EPA with the ir data, and EPA is working t o incorporate this data into the next versions. For HAPs, 46 states have participated in the development of the 1999 NEI (with some revisions from states still under way ).

• Duplicat

e facili ties may be prese nt, but most o f the dupl icates have bee n remove d. Faci lity identific ation (I

D) code s are a p otential s ource of confusion. The NE I Uni que Fac ility ID is the ID for the

entire f acility, while the

state I Ds are u sually

for individual pro cesses; theref ore an N EI Un ique Fa cility ID c an have

multiple sta

te facil ity I

Ds.

• The prima

ry source o f uncer

tainty associa ted with the inventory

is the methodology

used to gener ate the e mission est

imates. T he emission estimati on methodo logy is often p oorly documented in the NEI I

nput Format - this data field is not mandatory . Data in the 1999 NEI for HAPs a

re made using dif ferent estimation methods. Future versions o f the NEI will include a data quality

rating to each emissions record, which should help cha racterize the quality of the emissions estimate. Emissions data in the NEI are submitted to EPA accor ding to the NEI I npu t Format ( NIF) Shell (see http://www .epa.g ov/ttn/chi ef/nif/i ndex.html ). This format consists of data fields grouped into tables that provide the basic structure of N EI. The NI

F shell consists of eight tables for point sources, five tables for area sour ces, three tables for mobile sources, and two tables f or biogenic sources. EPA has developed data e lement descriptions and data element validation rules to enforce mandatory data fields and relationships between the various tables and re cords of the NI F. As the NEI has evolve d (and co ntinues to be improved and de

veloped) , the NI

F shell has evolved as we ll. Versi on 3.0 of the NIF shell was rele ased in Ma y 20 03 and upd

ated in November 2003.April 2004 Page 4-25 In June 2002, EPA promulgated the final Consolidated Emissions Reporting Rule, (14) which simplifies and cons olidates e

mission inve

ntory reportin g requ irements (for cr iteria a ir polluta nts only) to a single

location within the Code of Fe deral Reg ulations (CFR), establishes new reportin g requ irements related to PM 2.5 and regional haze, and establishes new re quirements for the statewide reporting of area source and mobile source emissions. Many state and local agencies asked EPA to take this action to consolidate re porting requirements; improve reporting efficiency ; provide flexibility for data ga thering and reporting; and better explain to program managers and the public the need for a consistent inventory prog ram. Consolidated reporting should increase the efficiency of the emission inventory prog ram and provide more consistent and uniform data. In c onjunction with the N IF shell, EPA has devel oped an a utomated softwar e prog ram to he lp NIFusers pe

rform quality assur ance/qualit y contro l (QA/QC)checks on their files to ensure correct format specification. This software , available for download from the NI F shell web page, separates QA/QC che cks into format and content. Format checks ensure that the submitted information includes the minimum data elements required for Emission Factor and I nventory Group (EFIG

) to acc ept the su

bmitted da

ta. Conten

t checks are provided for

the user as a way to highlight possible errors in the submitted data. The latest version of the softwa re allows the user to choose whether to perform QA/QC checks on the da ta for format, the minimum standards require d to put the

data in the database, or the more re source i

ntensive content or reasonablene ss checks. When chec

king for content, the forma

t is also checked a s the for mat must be

correct in order f or conte nt checks to be per

formed a t all. 4.4.2 Toxics Release Inve ntory (TR I) The Toxics Release Inventory (TRI) is a publicly available EPA da tabase that contains informat ion about r

elease s and othe

r waste manage

ment acti vities re ported a nnually by c ertain covered industry

groups as well as federal fa cilities for over 650 toxic chemicals (see http://www .epa.g ov/tri/

). This inventory was e stablished under the Emergency Planning and Community Right-to-Know Act of 1986 (EPCRA) and e xpanded by the Pollution Prevention Act of 1990. TRI r eporting is requir ed only for fac ilities tha

t meet all of the fo llowing t

hree cr iteria:

• They have

ten or more full-time employe es or the equivalent (i.e., a total of 20,000 hours or greater; see 40 CFR 372.3);

• They ar

e included in specified industrial sectors (see Exhibit 4-7); and

• They exce ed any one r eport ing th resho ld for manuf acturi ng, pro cessi ng, or o therw ise us ing a TRI chemical (see E

xhibit 4-8). If a facility

meets these criteria, then it must report releases to environmenta l media as well as waste ma nageme nt data. I n 2001 (the

latest y ear for which da ta are p ublicly availab le), air emissions o f toxic che

micals tot aled 1.7 b illion pounds (over a quarte r of all r elease s of TRI chemicals to the environment).April 2004 Page 4-26 Exhib it4-7. Standa rd I ndust ri al Cl ass ifi cat ion ( SIC) Codes i n TRI Repor ti ng Original Indu strie s SIC Code Indus tr y Group SIC Code Indus tr y Group 20 Food 30 Rubb er and Plasti cs 21 Tobacco 31 Leather 22 Textiles 32 Stone, C lay, and Glass 23 App arel 33 Primary Metal 24 Lumb er and Wood 34 Fab ricated M etals 25 Fu rniture 35 M ach inery (e xclu din g elec trical) 26 Paper 36 Elec tr ica l a nd Elec tr onic Equipment 27 Pri nti ng and Publ is hing 37 Trans port ati on Equipment 28 Ch em icals 38 Instru me nts 29 Petroleum and Coal 39 Misce ll aneous Manufact uri ng New Industri es Repor ti ng to TRI as of t he 1998 Report ing Year SIC Code Indus tr y Group 10 Metal mini ng (e xcept for SIC co des 1011, 1081, and 1094) 12 Coa l minin g (exce pt for 12 41 a nd e xtraction activities) 4911, 4931, and 4939 Lim ited to electric al utilities that co mb ust co al an d/or oil for d istribu tion in

commerc e (SI C codes 4911, 4931, and 4939) 4953 Limi ted to ha zar dous was te tr eat ment and dis posal

fac il it ies reg ulat ed under the Resource Conservation and Recovery Act (RCRA ) Subtitl e C 5169 Che micals and allied produ cts wholesale distributors 5171 Petr oleu m b ulk p lants and term inals 7389 So lven t recov ery serv ices p rima rily eng aged on a con tract or f ee b asis Source : U. S. E nvi ro nmen ta l P ro te ct io n Age ncy . 2 004. Toxi c Re le as e I nve nt ory (TRI ) Progr am. Standa rd Ind ustrial C lassification (SIC ) Co des in T

RI R epo rting. Up dated M arch 2 , 200 4. Availa ble a t: http ://ww w.e pa.g ov/tri/re por t/sicco de.h tm . (Last accesse d A pril 20 04.)April 2004 Page 4-27

Exh i bi t 4- 8. Thr es hol ds fo r Re por ti ng t o t he TRI EP CR A S ectio n 3 13 no n-P BT che m icals (Section 372.25). A facil ity meeting the SIC code (or Fed eral fac ility) and em ploye e criteria mu st file a T RI re por t for a n on-P BT Sec tion 3 13 che mic al if the faci lity:

• Man ufactured (i ncluding imported) more than 25,000 poun ds per year ; or

• Processed more than 25,000 poun ds per year ; or

• Oth erwise u sed m ore than 10,0 00 p oun ds pe r year. EP CR A S ectio n 3 13 PB T c hem icals (40 CFR 372.28). If a f acili ty manufactures , processe s, or othe rwis e use s any

chemi cal s that are li st ed as pers is tent , bi oacc umulat ive , and toxic (PBT), the thresho ld qu antity is one of th e followin g (per S ection 3 13 c hem ical or category p er year):

Type of Chemical Re po rting Th resho ld by Activ ity Ma nufa cture Proce ss Otherw ise Used Highly persi stent and bioaccumulati ve compounds 10 pounds 10 pounds 10 pounds Dioxi n and di oxin- li ke co mpounds 0. 1 gr ams 0. 1 gr ams 0. 1 gr ams Other persist ent and bioaccumulative comp ound s (lead and lead com poun ds) 100 pounds 100 pounds 100 pounds Activity thresholds ar e calculat ed independently of each ot her based on cumulative quantiti es per Section 313 chem ical over the reporting year. Cu rren t list of Sec tion 31 3 P BT Ch em icals

• aldrin

• benzo( g,h, i) pery lene

• chlo rdane

• dioxi n and di oxin- li ke co mpounds

• heptachlor

• hexachl orobe nzene

• is odri n

• lead

• lea d compounds

• mercu ry • mercur y c ompounds

• methoxychlor

• oct achl oros ty

rene

• pen dim etha lin

• penta chlo robe nzene

• po lych lorin ated bip he nyl

• poly cy cli c ar omati c compounds

• tetrab rom obis ph eno l A

• toxa phene

• triflura linApril 2004 Page 4-28 Note in Exhib it 4-7 that

additiona l industrie s have be en adde d to the TRI over time . Thus, some industrie s were not requir ed to rep ort in the p ast and, as such, no records will exist f

or these facilities in the historical TRI files. The list of covere d chemicals has also grown over time. Thus, the ability to track trends f or more recently

added industries and chemicals is more limited th an f or i ndu st rie s an d ch emi cal s t hat hav e be en c ove red th rou gho ut th e hi st ory o f th e TR I. Industrial sectors subject to TRI reporting are identified by Standard Industrial Classification (SIC) codes. SI C codes are numerical codes developed by the U.S. government as a means of consistently classify

ing the primary

business of business establishments. A full list of the industry groups that are require d to repor

t can be f ound at http://www .epa.g ov/tri/re port/ siccode .htm

. Alt hou gh m ost of t he e xi st in g em is si ons dat a in th e TR I syst em a re o rga ni ze d ac cor di ng t o S IC codes, EPA has proposed regulations that would result in the use of the Nor th American Industry Classification System (NAICS) rather than SIC codes (see http://www.census.gov/epcd/www/ naics.ht ml ). Rather

than cla ssify

ing industries on the basis of severa l differ ent econ omic concepts (as the

SIC str ucture d oes), NA ICS cl assifies

establish ments ac cording

to similari

ties in the proc esses use d to produc e goods and serv ices. The TRI pr ogram i ssued a pr

oposed ru le to implement the NAICS system classification on March 21, 2003. (See 66 Fed. Reg. 13872.) I t is expected that the u se of NAI

CS in the TRI

system will al low EPA to more acc urately characterize the current state of the national economy (inc luding new and emerging industries not adequately c overed by SIC codes). The existing SIC structure will not be updated in the future b ecause

the Offi ce of Ma

nageme nt and Bu dget ha s adopted

NAI CS as the Un

ited State s’ new industry

classifi cation sy

stem. I n addition , using N

AICS f or TRI reportin g purpo ses will enable more efficient database integ ration and will promote public access to commonly defined data fr om dispar ate sour ces. This chang e will not a

ffect the universe of fa

cilities that is curr

ently req ui red to rep ort to TR I. EPCRA requires only that fac ilities report their releases of the listed chemicals. There are no additiona l control or mitiga

tion actions requir

ed. The i nformati on collected throu gh the TRI program is made public, however, and pre ssure from local citizen groups has been an ince ntive to many industries to reduce the quantity of pollutants they release. While the TRI data have utility for the scoping out of an air toxics risk assessment project, they have several limit

ations tha t assessors must

understa nd. I mportantl y f or risk a ssessors , the TRI progra m require s only

that one s ingle a

nnual val ue repr esenting total rel eases to

the air (segregated only

by stack re leases and fugitive releases) be reported by

the individual affected facilities. So while annual average emissions may be useful in screening-level assessments for chronic exposures , it may

be diffic ult to asse ss acute

noncanc er hazar

d associa ted with shortterm, pe ak emission levels. Source- specific informat ion within t

he faci lity is not routi

nely reporte d throug

h the TRI . Like

wise, no information is repor ted on re lease pa

rameter s critica l to air dispersion modeling (e.g., location of re lease on the facility property, re lease rates, stack height, stack diameter, release te mperature). (See Chapter 9, for more inf ormation on modeling parameters used in air quality and exposure modeling.) As discussed in Section 4.2, the list of TRI pollutants is organized differently than the list of HAPs in CAA

Section 11 2, causin

g some c omplicati ons in inte rpreting emission da

ta. I t is difficul t to corre ctly

relate s ome of the

SIC co des (unde

r which TRI em

issions ar e grou ped) to specific air emiss ion proce sses. Be cause qu antities a re only reporte d if a stat

utory threshol d isApril 2004 Page 4-29 1. United States Environmental Protection Agency . 1998. Handbook for Air Toxics Emission Inventory Development, Volume 1: Stationary Sources (Append ix C). Offic e of Air Q

uality Planning and Standards, Research Triangle Park, NC, November 1998. EPA/454/B98/002. Availabl e at: http://www.epa.gov/ttn/chief/eidocs/airtoxic.pdf

. 2. U.S. Environmental Protection Agency . 2003. Technology Transfer Network Air Toxics Website. The Origin al List of Haz ardous Air P

ollutants . Updated January 9, 2004. Ava

ilable at : http://www .epa.g ov/ttn/atw /188polls. html . (Last accesse d March 2004.) 3. U.S. Environmental Protection Agency . 2001 . The Eme rgency P lanning and

Community Right-to-Know Act: Section 313 Release and Other Waste Management Reporting Requirem ents . Washing

ton, D.C. EPA/260/K01 /001. Ava ilable at : http://www.epa.gov/tri/guide_docs/2001/brochure2000.pdf. 4. U.S. Environmental Protection Agency . 2001. Emergen cy Plann ing and Com munity Rightto-Know Section 313; List of Toxic Chemical

s . Office of Environmental I nformation. Washingt on, DC, Ma

rch 2001 . EPA/ 260/B 01/001. Available a t: http://www.epa.gov/tri/chemical/chemlist2001.pdf. 5. U.S. Envir

onmental Protection Agenc

y. 2 004. Technology

Transfe r Networ k Clearin ghouse for Inventories &

Emission Factors. National Emissions Inventories for the U.S. Updated Februa ry 4, 2004. A

vailable at: http://www .epa.g ov/ttn/chi ef/net/ . (Last accesse d March 2004.) 6. U.S. Environmental Protection Agency . 1992. Notice In itial Sourc e Categor y List

. Federal Register 57:31576, July 16, 1992. 7. U.S. Environmental Protection Agency . 2002. National Emission Standards for Hazardous Air Polluta nts: Revision of Sou rce Categ ory List Und

er Secti on 112 of the

Clean Air A ct. Federal R egister 67:6521, February 12, 2002. met, a fa cility may report e missions for one y

ear but n ot the next, even thou

gh the f acility is still in operation. Similarly, individual pollutants may not be reported consistently from yea r to year due to the thresholds that apply to individual pollutants (e.g ., a facility may report releases of 10 pollutants one year a

nd releases of only

five pollutants the next year bec ause the others dropped below the reporting threshold). Furthermore, for some facilities, it is possible that, for a variety of releases, the data included for a facil ity’s emi ssio ns in the TR I do not m atch t he sam e data r eport ed to t he NEI, i ndica ting a potential problem with either or both data sets. The risk assessor should apply care and discretion when using TRI infor mation to estimate exposures and risk from individual facilities. Ultimately, the TRI

provides information about the location, identity, a nd amount of air toxics emissions in a community. However, due to the nature of the way

the data are developed and reporte d, TRI

data shou

ld gene rally be consid

ered a s ource of

limited inf

ormation a

bout a facility and should

not be use d in risk a ssessmen ts involving

modeling

(as note d above, S/L/T and NEI data ar e more lik

ely to be usef

ul for mod

eling) . For ro

bust anal ysi s, it should

gener ally be considered a starting point, not an end. ReferencesApril 2004 Page 4-30 8. U.S. Environmental Protection Agency . 1997. Mercury Study Re port to Cong

ress . Office of Air Qual ity P lanning

and Stand

ards. Washington D .C. EPA/452/R97/0003. Availabl e at: http://www .epa.g ov/ttn/atw /112nmer c/mercu ry .html

. 9. U.S. Environmental Protection Agency . 2001. Control of Em issions of H azardous A ir Pollutants

From Mobile Source

s. Final Ru le

. Federal R egister 66:17230, March 29, 2001. Availabl e at: http://www .epa.g ov/fedr gstr/EPA -AIR/2001/Mar

ch/Day -29/a37. htm

. 10. U.S. Environmental Protection Agency . 2000. National Air Pollutant E

mission Tre

nds: 1900-1998 . Office of Air Quality Planning and Standards, Research Triangle Park, NC. EPA/454/R0 0/002. Ava

ilable at : ( http://www .epa.g ov/ttn/chi ef/tren ds/trend s98/index.h

tml ). 11. U.S. Environmental Protection Agency, Consumer Product Safety Commission (CPSC), and American Lung

Association. 1998. What You Should Know About Combustion Appliances and Indoor Air Pollution . CPSC Docume nt #452. Available a

t: http://www.cpsc.gov/cpscpub /pubs/452. html . (Last accesse d March 2004.) 12. U.S. Environmental Protection Agency . 2004. Technology Transfer Network Air Toxics Website. Area Source Standards . Update d January 15, 2004. A

vailable at: ftp://ftp.epa.gov/EmisInventory /finalnei99ver2/criteria/documentation/ . (Last accesse d March 2004.) 13. U.S. Environmental Protection Agency . 2003. Documentation for the Final 1999 Nonpoint Area Source National Emission Inventory for Hazardous Air Pollutants (Version 3)

. Emissions, Monitoring and Analysis Division, Researc h Triangle Park, NC, August 2003. Availabl e at: ftp://ftp.epa.gov/EmisInventory /finalnei99ver3/haps/documentation/

. 14. U.S. Environmental Protection Agency . 2002. Consolidated Emissions Reporting. Final Rule. Fe deral Reg ister 67:39602, June 10, 200 2. Availa ble at: http://www .epa.g ov/ttn/chi ef/cer r/index.htm

l

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