MEMORANDUM

SUBJECT: Exposure D escriptors f or CEB Rep orts - Final

FROM: Ward Penb erthy, Chie f

Chemical Engineering Branch (7406)

TO: CEB Staff and Management
We have revised the exposure descriptor tables to incorporate cons ensus and discussion from the three CEB exposure descriptors meetings, meetings with EPA’s Office of Research and Developm

ent (ORD), discussion s with the Ex posure Asse ssment Br

anch (EAB) , and comm

ents from wit hin OPPT. The revised

guidance in

cludes boile

rplate langu

age to be inc orporated in

to all CEB assessments. Attached is a document entitled “Guidance for Characterizing Assessme nts of Occu

pational Ex

posure and E

nvironme ntal Release

” dated Janu

ary 1997. T

his guidance will help to ensure that all CEB assessments of potential for occupational exposure and environm ental release

are consiste

nt with the Agency expo sure assessm ent guidanc e and the risk characteriza

tion policy. The guidance contains a checklist f

or evaluatin

g CEB asses sments wi

th respect to ex

posure descriptors and exposure cha racterizatio n, the revise d tables whi ch characterize CEB “base” methodologies and generic scenarios, and boilerpl ate language for CEB reports.
The attached tables will be updated as additional information is gather ed and as methods and tools are

evaluated an

d updated. T

his has been

a long and ar

duous proce ss, and I tha

nk all of you for your assistance with this task. If you have any questions, please contact me at 260- 1664.

cc: Mary Ellen W

eber Larry Long anecker Tom Murra

y Nhan Nguy en Cathy Fehr

enbacher Pat Kennedy Lynn Delpi

re Bob Boethling

### Guidance for Char acterizing As sessments of Occupational Ex

posure and Envir

onmental Rele ase A Supplement to the CEB Engineeri ng Manual

U.S. Envi ronmenta l Protection

Agency Office of Pollution Prevention an

d Toxics Chemical Engineerin

g Branch 401 M Street, S.W. (7406) Washington, DC 20460
January 1997

### Tab le of Con tents

Secti on Page #

I. Introduction 1 A. Background 1 1. EPA Guidelines for Exposure Assessment 2 2. EPA Ris k Character ization P olicy 3 B. Organization of this Document 4

II. Evaluatin g CEB Asse ssments for A ppropriat e Use of Exp osure Descriptor s - A Checkli st 5

III. Standard L anguage fo r Use in CE B Assessmen ts 6 A. Standard Language for IRERs 6 1. Assessme nt of Envir onmental R elease 7 2. Assessme nt of Inhala tion Expos ure 7 3. Assessme nt of Dermal Exposure 8 B. Standa rd Langua ge for SRER s and RM1 R

eports 9 1. Assessme nt of Envir onmental R elease 9 2. Estimated Number of Workers Using NOES 10 3. Assessme nt of Inhala tion Expos ure 10 4. Assessme nt of Dermal Exposure 12 C. Standa rd Langua ge for RM2 a nd Use/Ex posure Rep orts 13 1. Assessme nt of Envir onmental R elease 13 2. Estimated Number of Workers Using NOES 14 3. Assessme nt of Inhala tion Expos ure 15 a) OSHA PEL for Particulates (PNOR) 15 b) Other OSHA

Permissible

Exposure L imits 16 c) Mass Bala nce Ventila tion Model 17 d) OCIS Com pliance Mon itoring Dat a 19 4. Assessme nt of Dermal Exposure 20

IV. Listing of CEB Methods 24 Table 1. Listing of B ase Methods 24 Table 2. Listing of CEB Generic Scenarios 27 Table 3. Listing of C EB Generic Scenarios B ased on Mon itoring Dat a 33

V. References 38

VI. Appendic es 39
Appendix A. NOES Erro r Tables 40 Appendix B. Assumption s Regardin g Breathin g Rate and D uration of E xposure 41Appendix C. Suggestion s for Presen ting Monito ring Data in Reports 42 Appendix D. Definition s of Exposu re Descript ors 43 Appendix E. Potential Areas of Uncertainty Associated with an

Assessment

of Occupati onal Expo sure 451

1 U.S. Environmental Protection Agency. Guidelines for Exposure Assessment. Office of Health and Environmental Assistance, EPA/600/Z-92/001. 1992.

2 Carol M. Browner. Policy for Risk Characterization at the U.S. Environmental Protection Agency . U.S. Environmental Protection Agency. March, 1995. I. Introduction
This guidance document was prepared to assist the Chemical Engineering Branch (CEB) in developi

ng assessm

ents of occ

upational ex

posure and e

nvironme ntal release i

n accordanc e with the Agency Guidelines for Exposure Assessment 1 and the recent Risk Characterization Policy

2 . It is intend

ed to be used

to supplem

ent the Preparation

of Enginee

ring Assess ments Volume I: CEB Engineering Manual , and is an in -house work ing document which is

subject to change as new information and methods are developed.
A. Background

The CEB is

responsible

for provid

ing assessm

ents of the p otential fo r occupation al exposure and environmental release resulting from manufacture, processing, and use of chemicals and biological agents in support of Agency assessments of the potential for human and ecological risk. The Branch is also responsible for evaluati ng and providing recommendations for prevention and risk management options. Assessments developed by CEB are based on Agency gui dance and po licy, and m ethods and p olicies deve loped by the Branch and

EPA’s Office of Pollution Prevention and Toxics (OPPT). Many of CEB’s methods and policies for assessing o ccupationa

l exposure a

nd environm

ental release

are provided

in the Preparation of Engineerin

g Assessments Volum

e I: CEB Eng ineering Man ual

. Adequately

defining the populatio n which is th e subject of the occupat

ional expos

ure assessment is crucial to the appropriate interpreta tion and use of the results of the assessment. Many CEB e xposure ass essment m ethods were

developed f

or screening

level assess ments whe

re data is unav ailable, and

are based on

generic inf

ormation a

nd data whic

h is applicab le to an industry sec tor or overal l population . Exposure data and inf

ormation f

or the specif

ic subpopulation(s) of interest is often not available. For example, in the abse nce of data, CEB often assu

mes that w orker inhala

tion exposu

res to particu

lates are at or

below the O ccupationa

l Safety and

Health Adm

inistration ( OSHA) Per

missible E

xposure Lim

it (PEL) fo r Particulate s Not Otherwise Regulated (PNOR). Based on our evaluation of the OSHA compliance data for particulates , this is a val id assump tion for scr eening leve l assessme

nts, and the

exposure is appropriate ly character

ized as a high

end estima

te. While t

his assum ption may

be quite appropriate for a screening level assessment, additional evaluat ion of the available data for the specific su

bpopulatio n of interes t would be a l ikely next st ep when pre

paring a more detailed assessment of occupational exposure.
For example, if the identified subpopulation of interest is those workers who package powder dete

rgents, then

an evaluation of the OS HA compl iance data f or that speci fic Standa

rd Industrial Code (SIC), and for that activity would provide a more accurate ass essment of2

3 Memorandum from Breeda Reilly, Chemical Engineering Branch, to Pat Kennedy, Exposure Assessment Branch, date d March 18, 1994. exposure. T

he addition al effort re quired to de velop this o ccupationa

l exposure a ssessmen

t may not be justif

ied for a scr

eening leve l assessme

nt, but is ap

propriate f

or more detailed asses sments of exposure.
Because predictions of environmental release are not “exposure” or “dose” estimates, no exposure de scriptors are

presented w

ith release es timates. H owever, en vironmen tal release estimates are used to develop estimates of general population and environmental exposure, and appropriate

characteriza

tion of rele ases is critic al to selection of the appropriate exp osure descriptor for the resulting exposure or dose. Currently, CEB provides onl y the conditions and assumptions under which our estimates are made, the point estimate value of the release, and a statement that the estimate cannot be characterized as to where it falls on the distribution. 3 Where possible, additional information is provided to assist in selecting an e xposure descriptor for general population exposure assessments which are derived in part from CEB’s assessment of potential f

or environm

ental release . As metho dologies an d data sourc es are impr

oved, CEB will attempt to incorporate information and approaches which would help us to better charact erize the estimate in terms of where it falls on the distribution.

1. EPA Guidelines for Exposure Assessment
The Agency Guidelines for Exposure Assessment established standard terminology for characterizing exposures using exposure descriptors . As a result of the guidelines, CEB carefully e

valuated all

available m

ethodologi es and devel oped recom mendatio ns for appr

opriate exposure de scriptors. T

hose descrip tors are pres ented here. Exposure d escriptors f

or individual risk should

include bot

h central ten

dency and h

igh end estim

ates where p ossible. However, bounding e stimates a

nd “what-if

” estimate s are comm

on in screen

ing level ass essments d

ue to the lack of a

vailable dat

a and time c onstraints.
It is important to understand and distinguish between variabili ty and uncertainty. Variability

arises from

true diffe rences or het

erogeneity i

n characteri stics (e.g., differenc es in contaminant levels in the environment) and may vary with space and time across the population. The central t

endency and

high end exp osure descri ptors for in

dividual ris k are intende d to capture only

the variabil ity in expos

ure, lifest yles, worke

r practices, and other f

actors that le ad to a distribution of risk across a population. Differences between central tendency and high end estimates reflect the variability in the population of individua ls that are subjects of the assessment, not the uncertainty inherent in the assessment. If sufficient information about the variability i

n the exposu

re variable is

available, c omplex m

ethodologi es (e.g., Monte Carlo analysis or parametric statistical analyses) may be used to eval uate the overall variability of the exposure distribution. However, this level of detail is rar ely available for CEB assessments of occupational exposure

or release.3

Uncertainty

is the lack of

knowledge

about the co rrect value f or a specifi c exposure measure or estimate. There are several approaches for treating data with li mitations imposed by uncertainti es. These pr

ocedures ran

ge from re latively sim

ple metho ds (e.g., qu

alitatively characterizing uncertainties, presenting r anges), to methods which are quite complex (e.g., use of Monte Carlo analysis.) The selection of the appropriate uncer tainty analysis method depends on the type of

assessmen

t being deve loped, the a

vailable dat

a and knowl edge regard

ing uncertai

nty and variability, and the available resources. It is generally inappropriate to combine distributions reflecting both uncertainty and variability for purposes of deter mining an overall population distributio n. The ma

jority of C EB assessm

ents of occ

upational ex

posure and r

elease are dr

iven by uncertain

ty due to lack

of data, rat

her than vari ability, and

hence, ma

ny CEB ass essments a

re characterize d as either bo unding or “w

hat-if” esti

mates. W

here enough

informat ion exists to define the d

istribution

of exposur

e, an assess ment shou

ld present an

estimate o f both cent

ral tendency an

d high end ex

posure whe

re possible. A characteri zation of u ncertainty ( either qualitative or quantitative) should accompany all CEB numerical estimates of exposure and release.
The Agency guidelines also defined "exposure" and "potential dose". Me asurements of exposure are defined

as contact with the outer boundary o f the organ

ism integr

ated over tim

e, based on the concentration of the contaminant in the medium in contact. In terms of occupational exposure, the analogy is an airborne concentra tion (inhalation) or for dermal, a surface concentration, integrated over the duration of exposure. By combining the ai rborne concentrati on or the sur

face conce

ntration wit

h an assumed breathing

rate or surf

ace area of s kin contacted, a potential do se rate (PDR) is developed in units of mg/day. A PDR is the amount ingested, breathed, or bulk material applied to the skin per unit time. Thus, values of mg/day (or mg/kg/da y) for both

inhalation a

nd dermal

exposure should be char

acterized in

CEB report s as PDRs. As CEB computerizes the generation of reports, we will add the capability to present our results in un

its such as m

g/kg/day as

a Lifetim e Average D aily Dose (L ADD), etc. Additional guidance will be develo

ped for tho se calculations at that tim e.

B. EPA Ri sk Characte rization Policy
The recent Agency Policy for Risk Characterization also established requirements for exposure an

d other asses sments de

veloped in s

upport of r

isk assessm

ents. The po licy require s these assess ments to b e transparent , consistent , clear , and reasonable . For expos ure assessm

ents, a discussion of uncertainty should accompany the exposure descriptors used, and ass umptions made should be identified. Technical terms should be defined, and jargon should be avoided. The scientific and policy bases should be described, and the assessment should be cons istent with Agency policy and

guidance. T

he assessment should b e based on th e best availa ble scientific information and expert judgment, and sources should be documented. The assessment should be ba sed on com

mon sense , and be for

thright in ac knowledgi

ng uncertain

ty. Other reasonable alternatives or conclusions should be pres ented. The OPPT is currently developing a statement for implementation of the Agency policy, including specific guidance for screening level, inter

mediate le

vel, and com

prehensive

exposure as sessments

developed by CEB in su

pport4

of OPPT risk assessments.

B. Organization of this Document

The remai

nder of this

document

contains fi

ve sections. Section II pr ovides a general checklist for evaluating CEB exposure assessments with respect to exposure descr iptors and exposure characterization. Section III present s standard language to be incorporated into CEB reports, org anized by th e level of co mplexity o f the assess ment (e.g ., screenin g level, intermedi ate level, or

detailed ass essments) . This langu age will also

be distribut

ed electroni cally to facilitat

e incorporat

ion into CE B reports. A s CEB com puterizes re

port generat

ion, this language will be incorp orated into t he comput

erized repor

t format. Use of this

standard language in

CEB report s should hel

p to ensure that the expos ure assessm

ent is approp

riately characterize d within the

risk assessm

ent, and tha

t the risk cha

racterizatio n appropria

tely communicates this information for development of risk management options and decisions.
Section IV includes Tables A and B which list the CEB “base” methodologies and generic scenarios. A "base" method has wide applicability and can be used i n the absence of monitorin g data to asse ss exposure , depending on the physi cal/chemi cal state of the substance and the expo sure scenari o. Table A c ontains a lis ting of CE B "base" m ethods and t ools used to estimate occupational potential dose rates, the applicabl e exposure descriptor, and current status of the method. Table B contains a list of CEB generic scenarios for occupational exposure and environm ental release , the basis f or the assessm

ent, and the

applicable exposure des criptors. It should be no ted that the c urrent com

pilation of g eneric scena

rios does no t include exp osure descriptors or a characterization of exposure. Table B should be us ed by CEB to supplement the generic scenarios when developing an assessment of exposure and environmental release. Finally, Table C contains the key information, assumptions, uncertainty and a description of the population

for those g eneric scena

rios where m

onitoring d

ata is availab le. A copy o f Tables B and C will b e included in the Branch l ibrary copy

of the CEB Com

pilation of

Generic Sce

narios, 1994

. Section V presents a list of relevant references, and Section VI conta ins a series of appendices with additional information that may be helpful in preparing the assessment. Appendix A

contains the

error tables p

rovided by t

he National

Institute for Occupatio nal Safety and Health (NIOSH) for characterizing the population of workers potentiall y exposed to the substance u sing the Nat

ional Occup ational Exp osure Surve y (NOES) d

ata. In prepa

ring an assessment of potential dose rate, CEB makes assumptions regarding breathing rate and duration of exposure that may affect the variability of predicted exposures received by the popula tion of interest. Appendix B describes common assumptions made by CEB regarding breathing rate. Appendix C provides some specific suggestions for reporting monitoring data in CEB

assessmen

ts. Append

ix D provide s definitio ns of the ex posure estim

ators and de scriptors ba sed on the EPA Guidelines for Exposure Assessment . Appendix E presents information that may be helpful in d

escribing th e uncertaint

y associated

with assess ments of

occupational exposure

.5

II. Evaluating CEB Assessments for Appropriate Use of Exposure Descriptors and Character

ization o f Exposure

and Releas e - A Checkli st



### 9 Numbers a

re clearly ide

ntified as e stimates if

applicable.



### 9 “Potential dose rate” (PDR) is used to describe estimates present ed in units of mg/day or mg/kg/day.



### 9 Exposure d

escriptors (i .e., high en

d, arithme

tic mean, g eometric m

ean, etc.) ar

e included and are appropriately used.



### 9 The underly

ing assum ptions used

in developi

ng the asses sment of

exposure ar

e presented in the assessment. This is especially critical where a “what-if” or bounding estimate is presented.



### 9 Standard la

nguage desc

ribing the m

ethodology

used and def

ining the ex

posure descriptor h as been inclu

ded in the rep ort



### 9 Where standard language is unavailable, or needs to be supplemented, the

assessmen

t presents th e methods

used, assum

ptions ma de, and incl

udes a discussion

of uncertai

nty and bias

.



### 9 A discussio n of uncert ainty (and if

appropriate , an uncerta

inty analysi s) accompanies the numerical estimated PDR.



### 9 Tables are u sed when th ere is enoug h inform ation to war

rant one.



### 9 Tables are ap

propriately

titled (e.g. , make sur

e the table cl early distin

guishes estimates from monitorin

g data ), and footnotes highlight important sources of data and ass

umptions made.6

III. Stand ard Langu age for Use i n CEB Rep orts.

This section

presents sta

ndard langu

age to incorp orate into C EB reports t o assist in meeting the Agency Guidelines for Exposure Assessment and Risk Chara

cterization P olicy

. The standard language includes the most commonly-used methods in developing assessments of occupational exposure

and environ

mental rel ease. This l anguage sho uld be mod

ified wher

e appropriate based on the specifics of the assessment. If an assessment is prepared based on a generic scenario for which standard language has not yet been developed, a dditional information from Tab les B and C m

ay need to be

added to the

CEB report . This stand

ard languag e guidance will also be d

istributed in

electronic f

ormat to f acilitate inc orporation i

nto reports. As new information is developed and methods are updated, this language will be modified.

A. Standard Language to be Incorporated into All Screening Level Reports as an Appendix:
Screening l evel assessm

ents are curr

ently exem

plified by C EB’s Initial

Review Engineerin

g Report (IR

ER) prepare d for the ne

w chemica

ls program . CEB stand

ard methodol ogies and pr

ocedures f

or assessing

occupationa

l exposure a

nd environm

ental release are presented in Preparation of Enginee

ring Assess ment, Vo lume I: CEB Engineer ing Manual

. Screening l evel assessm

ents rely on t

he use of re adily availa

ble inform

ation and da

ta and are generally conservative (

protective) in nature. H owever, scr eening leve l estimates

are often qu

ite uncertain and may over- or under-estimate exposures by one or more orders of magnitude.
Where applicable, exposure descriptors such as central tendency and hi gh end accompany the numerical estimated Potential Dose Rates (PDRs). A PDR is the amount ingested, b reathed, or b

ulk materi al applied to

the skin per u

nit time. D efinitions

of applicab le terms used

in character

izing expos

ures are: High-end ex

posure (dos e) estimate

- A plausibl e estimate

of individ

ual exposur

e or dose for those persons at the upper end of an exposure or dose distribution, concept ually above the 90th percen

tile, but not

higher than

the individu

al in the pop

ulation who

has the high est exposur

e or dose.

Arithmeti c mean

- the sum of all the measurements in a data set divided by the number of

measurem

ents in the da

ta set. The a

rithmetic m

ean is one of

the measu

res of centr

al tendency for a distribution.

Median - value in the

measurem

ent data set s

uch that half

of the me asured values are greater and h alf are less. The media n is one of t

he measur

es of centra

l tendency f

or a distribution.
Bounding e stimate

- an exposur

e or dose wh

ich is higher

than any exp osure or dos e7

expected to occur in the actual population. The estimate is outside (higher than) the distribution of actual exposures. If the bounding estimated value does not pose an unacceptable ris k, then the exposure gr

oup can be el iminated f

rom furth er analysis.

“What-if ” scenario - an estima

te based on a

set of hypo thetical con

ditions or un

der a set of conditions for which actual exposure or release parameter data are incomplete or none xistent. The calculated exposure, dose, or release quantity is not i ntended to provide information about how likely t

he combination of ex

posure or rel ease parameter values m ight be in the

actual population

or about how

many, if any, person s might act

ually be sub

jected to the

calculated exposure or

release.
Many CEB assessments are based on what-if scenarios due to a lack of exposure data, or due to lim

ited exposu

re data which is anecdotal or of poor q

uality. For

these assess ments, CEB characterizes the assessment as what-if based on the hypothesis that the expos ure of the subpopulat

ion of inter

est is simil ar to the expo sure of the p opulation f or which exp osure data exists.

1. Assessme nt of Envir onmental R elease:

Generic Rel ease Assess ments : the release e stimate is a “what-if sc enario”. Du

e to a lack of data, CE

B provides only the cond itions and as sumption s under whic h our estimates are ma

de, the point est

imate valu

e of the rele ase, and a st

atement th at the estim

ate cannot b e characteriz ed as to where it falls on the distribution.
Releases from Degreasing Operations : the release e stimate is expected to re present a best estimate of the in

dustry avera

ge emissions for the eq

uipment c ategory. Th e estimate is based on an a

verage ma ss flux rate , a standard-sized degre aser for the category, a

nd a standar

d duty cycle.

2. Assessme nt of Inhala tion Expos ure:

General Ass

umptions :

Potential D ose Rate (PD R) estimat es are genera

lly for the e

ntire popula

tion of wor

kers potentially

exposed, an

d may not b e representa

tive of the s

pecific ope

rations asse ssed in this report. The breathing rate of 1.25 m 3 /hr for 8 hr/day is a default value used to predict inhalation exposure, unless otherwise stated. OSHA PELs do not apply to all industries, and OSHA generally inspects only facilities with greater t han 10 employees.

Specific A ssessmen

ts:8

Particulate

Exposures : OSHA PEL for Particulates Not Otherwise Regulated (PNOR). PDRs are hi gh end estim

ates assum

ing compl iance with the OSHA PE L of 15 m g/m 3 as an 8- hour TWA using primarily engineering controls.
Assessments Based on Compliance with OSHA PELs (other than the OSHA PNOR)

. PDRs are generally “what-if” scenarios assuming compliance with the applicable OSHA PEL, using prim

arily engine ering contro ls.
Vapor Expo sures : Mass balance model predictions of vapor exposure are bounding PDR estimates and "what-if" scenarios, depending on the default values used. Many simplifying assumptio

ns are mad

e when usin

g the mode l, such as ste ady state con ditions, no

use of cont

rols or protectiv e equipme

nt, as descri

bed in Preparation

of Enginee

ring Assess ment, Vo lume I: CEB Engineering Manual . Estimate s, overall ar e likely to be

protective, based on a li

mited evaluation.
Mist Exposure During Spray Application : Spray coating scenarios are high end PDR estimates assuming compliance with the OSHA PEL for Particulates Not Otherwise Regulated of 15 mg/m

3 as an 8-hour TWA, and "what-if" scenarios based on very limited data from 1981.
Weighing of Textile Dyes : Textile dye weighing scenario is used for dye weighing operations and very simil ar weighing o

perations w

here small

quantities a

re weighed w

ith precise scoop/shak

e/pour techn

iques. A mean and high

end PDR es timate are p

resented bas ed on data collected during the Textile Dye Weighing Monitoring Survey.
Oil Mist Exp osure : OSHA PE L for oil m ist; high end

PDR as a tim

e-weighted

average, assuming compliance with the O SHA PEL o f 5 mg/m 3 as an 8-hour TWA using engineering controls.
Printing Op erations (in

k mist) : a "what-if

" estimate i s presented b ased on very limited data collected in 1976 and 1978.

Tire Manuf

acture : PDR as a “what-if” estimate for total particulates while emptying bags into bins, based on a 1984 study of 20 plants and detailed surveys at 7 sit es.

3. Assessme nt of Dermal Exposure:
Dermal PDRs are bounding estimates for workers not wearing equipment or using controls, b ased on lim

ited data and

engineering

judgment . Estimate s are often b ased on lim ited informat ion and data

and include

many sim

plifying as sumption s.9

B. Standa rd Langua ge to be Inco rporated in to All Inter mediate Lev el Reports

Intermediate level assessments are currently exemplified by CEB reports prepared for the new chem

icals Standa

rd Review E

ngineering

Report (SR

ER), the ex isting chem

icals Risk Management 1 (RM1) report, and testing program reports. CEB standard methodologies and procedures

for assessi

ng occupati onal exposu

re and environmental re lease are pre sented in Preparation

of Enginee

ring Assess ment, Vo lume I: CEB Engineer ing Manual

. Screening l evel

assessmen

ts rely on the

use of read

ily availabl e informa

tion and dat

a and are gen erally conservativ e (protectiv e) in nature. However, s creening lev el estimate s are often q uite uncerta

in and may over- or under-estimate exposures by one or more orders of magnitude.
Where applicable, exposure descriptors such as central tendency and hi gh end accompany the numerical estimated Potential Dose Rates (PDRs). A PDR is the amount ingested, b reathed, or b

ulk materi al applied to

the skin per u

nit time. D efinitions

of applicab le terms used

in character

izing expos

ures are: High-end ex

posure (dos e) estimate

- A plausibl e estimate

of individ

ual exposur

e or dose for those persons at the upper end of an exposure or dose distribution, concept ually above the 90th percen

tile, but not

higher than

the individu

al in the pop

ulation who

has the high est exposur

e or dose.

Arithmeti c mean

- the sum of all the measurements in a data set divided by the number of

measurem

ents in the da

ta set. The a

rithmetic m

ean is one of

the measu

res of centr

al tendency for a distribution.

Median - value in the

measurem

ent data set s

uch that half

of the me asured values are greater and h alf are less. The media n is one of t

he measur

es of centra

l tendency f

or a distribution.
Bounding e stimate

- an exposur

e or dose wh

ich is higher

than any exp osure or dos e expected to occur in the actual population. The estimate is outside (higher than) the distribution of actual exposures. If the bounding estimated value does not pose an unacceptable ris k, then the exposure gr

oup can be el iminated f

rom furth er analysis.

“What-if ” scenario - an estima

te based on a

set of hypo thetical con

ditions or un

der a set of conditions for which actual exposure or release parameter data are incomplete or none xistent. The calculated exposure, dose, or release quantity is not i ntended to provide information about how likely t

he combination of ex

posure or rel ease parameter values m ight be in the

actual population

or about how

many, if any, person s might act

ually be sub

jected to the

calculated exposure or

release.
Many CEB assessments are based on what-if scenarios due to a lack of exposure data, or due to lim

ited exposu

re data which is anecdotal or of poor q

uality. For

these assess ments,10

CEB characterizes the assessment as what-if based on the hypothesis that the expos ure of the subpopulat

ion of inter

est is simil ar to the expo sure of the p opulation f or which exp osure data exists. 1. Assessme nt of Envir onmental R elease:

Generic Rel ease Assess ments : the release e stimate is a “what-if sc enario”. Du

e to a lack of data, CE

B provides only the cond itions and as sumption s under whic h our estimates are ma

de, the point est

imate valu

e of the rele ase, and a st

atement th at the estim

ate cannot b e characteriz ed as to where it falls on the distribution.
Releases from Degreasing Operations : the release e stimate is expected to re present a best estimate of the in

dustry avera

ge emissions for the eq

uipment c ategory. Th e estimate is based on an a

verage ma ss flux rate , a standard-sized degre aser for the category, a

nd a standar

d duty cycle.

2. Estimated Number of Workers Using NOES:

The Nation al Occupati onal Expos ure Survey (

NOES) data

base is freq

uently used

to estimate the number of workers potentially exposed to substances during industrial and

commer cial operations. The surv ey was cond ucted in 198 0 - 1983 and

informat ion was extrapolate d to make national estim ates of num

bers of wor

kers potenti ally expose d and num bers of facilities where the substance is present. Because of the age of the data, the survey itself, and the extrapolation to national averages, there ar e several uncertainties associated with the dat a. NOES estim

ates are unce

rtain, but ar

e believed to

be conserva

tive (e.g., over predict

ive).

3. Assessme nt of Inhala tion Expos ure:

General Ass

umptions :

Potential D ose Rate (PD R) estimat es are genera

lly for the e

ntire popula

tion of wor

kers exposed, and may not be representative of the specific operations addressed in thi s report. A breathing rate of 1.25 m 3 /hr for 8 hr/ day are def

ault values u sed for inh alation expo sure, unles s otherwise stated. Estimates are often based on limited information and data and include many simplifying assumptions

. Where compliance with an OSHA PEL is assumed, note that OSHA standards ap

ply only to c ertain indus trial sectors (e.g., Gen eral Industr

y, Shipbui lding, Marit

ime, Construction, and Agriculture), and the requirements may vary from sector to sector. OSHA generally in spects only

facilities w

ith greater than 10 empl oyees.

Specific A ssessmen

ts:

Particulate

Exposure : OSHA PE L for Partic ulates Not O therwise Re gulated. Es timates11

are high end PDRs as a time-weighted average, assuming compliance with the OSHA PEL of 15 mg/m

3 as an 8-hour TWA using engineering controls. An evaluation of the OSHA Compute rized Infor

mation Se

rvice (OCIS ) database confirms th at over all SI C codes fo r which compliance monitoring data is available, 95% of the personal samples collected are below the OSHA PEL.
Assessments Based on Compliance with OSHA PELs (other than the OSHA PNOR)

. PDRs are generally “what-if” scenarios assuming compliance with the applicable OSHA PEL, using prim

arily engine ering contro ls. The assu mption of compliance with the O SHA standa rd is a postulated

hypothesis

(a "what-if

" scenario) a

nd inform ation about

the probabi lity that exposures i

n the overall

industry are

below the O SHA standa

rd has not be en evaluated at this time.
Vapor Exposure During Transfer Operations : Mass balance model for transfer operations as described

in Preparation

of Enginee

ring Assess ment, Vo lume I: CEB Engineer ing Manual

to generate pre diction inha

lation boun

ding PDR a s a bounding

estimate u sing defau

lt input valu

es selected fr

om the upp er end of th e range of v alues, and a “what-if” e stimate ba sed on defa ult input values selected from the midrange of values. Assumes no use of controls or protective equipment. Based on a limited evaluation, overall, estimates are likely to be protect ive, and bounding e stimates m

ay overestim

ate exposur

es by 1 or 2 or

ders of m agnitude.
Vapor Exposure During Open Surface Operations : Mass balanc e model f or open surf

ace operations a s described i

n Preparation of Engineering Assessment, Volume I: CEB Engineering Manualto generate prediction in halation bo

unding PDR

as a boundin

g estimate

using defa

ult input value s selected f

rom the up

per end of t

he range of

values, and

a “what-if”

estimate b ased on default input values selected from the midrange of values. Assumes no use of controls or protective equipment. Based on a limited evaluation, overall, estimates are likel y to be protective, and boundi

ng estimat

es may ove

restimate exposures by

1 or 2 orders

of magni tude.
Mist Exposure During Spray Application : Spray coating scenario; PDR as a high end estimate of the 8-hour time-weighted average assuming compliance with the OSHA PEL for Particulates Not Otherwise Regulated using engineering control s. Note this standard does not apply to all industries, and OSHA generally inspects only faciliti es with greater than 10 employees. A "what-if" scenario based on limited data collected in 1978 may also be presented.
Weighing of Textile Dyes : Textile dye weighing scenario; for dye weighing operations and very simil ar

weighing operations using small quantity with precise scoop/shake/pour technique, mean and high end PDR; for weighing operations where the precision and technique are unknown, "what-if" scenario; based on data collected during a pr obability sampling of 24 sites of m ore than 100 0 identifie d printing an d dyeing sit

es during 19 89-1990. T

here are sampling and non-sam

pling errors

associated w

ith the study . The samp ling and ana lytical methodology was found to have an overall error rate of ± 40% based on an evaluation of 20 dyes. An eq

uation to pre dict total dy e airborne concentration was develop ed based on t he data collected. Mass weighed was found to be the best predictor of airborne concent ration with a12

correlation

coefficie nt (R 2 ) of 0.39.
Oil Mist Exp osure : OSHA PE L for oil m ist; high end

PDR as a tim

e-weighted

average, assuming compliance with the O SHA PEL o f 5 mg/m 3 as an 8-hour TWA using engineering controls. A

n evaluation

of the OSH

A Compu terized Inf

ormation S ervice (OCI S) database confirms that over all SIC codes for which compliance monitoring data is available, 88% of the personal samples collected are below the OSHA PEL.
Printing Op erations (in

k mist) : a "what-if

" scenario is

presented b ased on very

limited data collected in 1976 and 1978.

Tire Manuf

acture : PDR as a “what-if” estimate for total particulates while emptying bags into bins, based on a 1984 study of 20 plants and detailed surveys at 7 sit es.

4. Assessme nt of Dermal Exposure:

Dermal PD Rs are bounding estimates based o n limited d ata and engi

neering jud

gment; assuming 1 contact pe

r day and tha

t workers wa sh up at me al times an d/or end of

the shift, a s described in Preparation

of Enginee

ring Assess ment, Vo lume I: CEB Engineer ing Manual

. Assumes [

routine con

tact of 2 han

ds] and no u se of protec tive equipm ent or other c ontrols to mitigate e xposure. [ substitute r outine cont

act, 1 hand, immersi on, 1 or 2 ha nds, incide

ntal contact, 1 or 2 hands as needed]13

C. Standa rd Langua ge and Exa mples to be I ncorporat ed into All D etailed Rep orts:
Detailed assessments are currently exemplified by existing chemicals Risk Management 2 (RM2) reports, Toxic Release Inventory (TRI) reports, Design for the Envir onment (DfE) reports, and

Use and Exp osure Prof

iles. For detailed asses sments of occupational exposure , potential dose rate summary tables should include footnotes with key information and assumptions. The fo llowing des criptions of the metho d and standa

rd assump tions are qui

te lengthy and may appropriately be included in an appendix to the report. The sta ndard language from Sec tion B abov e for interm ediate level

reports can b e included in the text of t

he CEB report with referr

al to the appr

opriate appe

ndix for ad

ditional det

ail. Where

applicable, exposure descriptors

such as cent

ral tendency

and high end

accompan

y the nume

rical estimated Potent

ial Dose Rates (PDRs). A PDR is the amount ingested, breathed, or bulk material applied to the skin per uni

t time. De finitions o f applicabl e terms use d in characte rizing expo sures are: High-end ex

posure (dos e) estimate

- A plausibl e estimate

of individ

ual exposur

e or dose for those persons at the upper end of an exposure or dose distribution, concept ually above the 90th percen

tile, but not

higher than

the individu

al in the pop

ulation who

has the high est exposur

e or dose.

Arithmeti c mean

- the sum of all the measurements in a data set divided by the number of

measurem

ents in the da

ta set. The a

rithmetic m

ean is one of

the measu

res of centr

al tendency for a distribution.

Median - value in the

measurem

ent data set s

uch that half

of the me asured values are greater and h alf are less. The media n is one of t

he measur

es of centra

l tendency f

or a distribution.
Bounding e stimate

- an exposur

e or dose wh

ich is higher

than any exp osure or dos e expected to occur in the actual population. The estimate is outside (higher than) the distribution of actual exposures. If the bounding estimated value does not pose an unacceptable ris k, then the exposure gr

oup can be el iminated f

rom furth er analysis.

“What-if ” scenario - an estima

te based on a

set of hypo thetical con

ditions or un

der a set of conditions for which actual exposure or release parameter data are incomplete or none xistent. The calculated exposure, dose, or release quantity is not i ntended to provide information about how likely t

he combination of ex

posure or rel ease parameter values m ight be in the

actual population

or about how

many, if any, person s might act

ually be sub

jected to the

calculated exposure or

release.
Many CEB assessments are based on what-if scenarios due to a lack of exposure data, or due to lim

ited exposu

re data which is anecdotal or of poor q

uality. For

these assess ments, CEB characterizes the assessment as what-if based on the hypothesis that the expos ure of the subpopulat

ion of inter

est is simil ar to the expo sure of the p opulation f or which exp osure data exists.14

1. Assessme nt of Envir onmental R elease:

Generic Rel ease Assess ments : the release e stimate is a “what-if sc enario”. Du

e to a lack of data, CE

B provides only the cond itions and as sumption s under whic h our estimates are ma

de, the point est

imate valu

e of the rele ase, and a st

atement th at the estim

ate cannot b e characteriz ed as to where it falls on the distribution.
Releases from Degreasing Operations : the release e stimate is expected to re present a best estimate of the in

dustry avera

ge emissions for the eq

uipment c ategory. Th e estimate is based on an a

verage ma ss flux rate , a standard-sized degre aser for the category, a

nd a standar

d duty cycle.

2. Estimated Number of Workers Using NOES
NIOSH began work on the National Occupational Exposure Survey (NOES), a nationwide

data gatheri

ng effort, in 1980 in ord

er to develop

estimates of occupat

ional expos

ures in all industries except agriculture and mining. Data gatheri ng continued into 1983. The study was built around a field survey of industrial facilities in 98 different geogr aphic locations. Informat ion from these facil ities was ext

rapolated to

generate nat

ional estim

ates of pote

ntially exposed workers for m

ore than 10, 000 diffe

rent chemi cals. An exc erpt of the N OES databa se comprising approximately 70,000 individual records covering 20,000 chemicals and 66 different 2-digit Standard Industrial Codes (SIC) is used by CEB in the absence of other dat a for estimatin g the numb er of worke

rs potential ly exposed t

o the subjec t chemical . NOES als o includes inf

ormation on estimate d number o f facilitie s using the chemical.
There are several limitations on information in the database, including the a ge of the data. Due to a large number of facilities in the U.S., only a small sample (4,636 establishments with 8

or more workers in the U .S.) was se lected and su rveyed. NO ES estima

tes are uncer

tain, but are generally be lieved to ov er predict nu mber of w orkers.

Because the

survey was extrapolated

to make na

tional estim

ates of exp osure there a

re uncertainties associated with the data. NIOSH has developed a tabl e of standard errors to be used with NOES estimates. These standard error estimates have been incorporated into CEB

assessmen

ts based on N OES data. N OES does not provide e stimates o f actual exp osures, the ir duration, their level or w

hether chem

ical protecti

ve equipment or engin eering contr ols reducedor prevented them. NOES data is most appropriately used for the development of screeninglevel occupational exposure assessments. It is assumed that each industry pr ocesses or uses the subject chemical and, as a result, has reported occupational exposur es to the subject chemical. Care must

be taken wh en using NO ES data duri ng later stag es of the reg

ulatory proc ess.

Guidance an

d Example s for Presen

ting NOES Data in CEB Reports:15

NOTE: since this is not an estimate of exposure, no exposure descriptor is needed. However, we consider NOES data to be uncertain.

1. In all case s, present es timates to 2 significa

nt digits.

2. If the da

ta point is < 5 00, present

a range from

1 to (x + (2*(s td. error)), where x is th e data point. The standard error is the multiplier times x.
Example: data point is 339, multiplier is 0.5. Present the range in CEB reports as “1 - 680"

3. If the da

ta point is be

tween 500 a

nd 8000, pr

esent the ran

ge incorpor

ating the sta

ndard error.
Example: data point is 4,926, multiplier is 0.27. Present the range in CEB reports as “2,300 - 7,600.”

4. If the da

ta point is > 8 ,000, prese

nt the data po int and the st andard error

. Example: data point is 53,608, multiplier is 0.15. Present the range in CEB reports as 54,000 (8,000), with a footnote that denotes 8,000 as the standard error, or wit h 8,000 placed in a separate column labeled as the standard error. According to NIOSH, values <8,000 are not reliable and only ranges should be presented.
5. Multipliers for NOES can be found in the Standard Error Tables found in Appendix A.

3. Assessme nt of Inhala tion Expos ure

a) OSHA Permis sible Expo sure Limit fo r Particula tes Not Othe rwise Regulated (PNOR)

In the absence of mon

itoring data , complia

nce with the

OSHA Perm

issible Exp osure Limit (PE L) for Parti culates Not Otherwise R

egulated as d

escribed in t

he OSHA Air Contaminants Standard is assumed when estimating potential occupational exposures to dusts or particulate materials. Chemicals for which PELs have been promulgated are listed in the OSHA Air Contaminants Standards and are applicable to the General Industry, Shipyar ds, Marine Terminals, Longshoring, Construction and Agriculture only (29 CFR 1910, 1915, 1918, 1926, and 1928). The OSHA standard specifies that exposures to particulates that are not regulated by some othe

r standard shall not excee d 15 mg/m 3 as an eight hour time weighted average (TWA).
The assumptions that workers breathe at a rate of 1.25 m 3 /hr for an 8 h our day are frequently

used to estim

ate potentia

l inhalation

exposure f

or a full wo rk day. For p articulates this would g ive an estim

ated PDR of

150 mg/da

y. The assu

mption of compliance with this standard to estimate potential exposures usually results in a high end estimate of inhalation16

potential dose rate for the industry overall. The potenti al inhalation dose estimates do not take into accoun

t respiratory

protection or engineerin

g controls that may be u sed to miti gate inhalation exposures.

Note that a T

WA is base d on exposu

re averaged over an 8 hour period and i s calculated to allow for excursions above the exposure level provided they are compensated by equi valent excursions

below the ex

posure leve l during the w orkday. Th e estimate d exposure i s the total amount of

substance to

which a wor

ker can be ex

posed per 8 hour day whether the expo sures are for short duration at high concentrations or long duration at low concentrations. There is no need to compensate the value for periods of time the worker is involved in activities tha t do not result in exp osure. OSHA generally only inspects workplaces with greater than 10 employees for compliance. Hence, this approac h to estima

ting potenti al exposure s to particul ates is appli cable only to populations of workers that are employed in workplaces that are in compliance with the OSHA Stan

dard. A revi ew of the O SHA com pliance monitoring dat

a for total d

ust revealed

that about 95% of

the approxi

mately 20 0 measure

ments of total dust in

a wide range

of Standar

d Industrial C lassificati on codes we re below the

OSHA stan

dard. Whi le this dem

onstrates compliance overall f

or those fac ilities wher

e measurem

ents were tak

en, it is not k

nown whether the specific individual facilities or companies identified in this report are in compliance with the OSHA standard.

b) Other OSHA Permissible Exposure Limits (PEL)
Workplac e inhalation

exposures t

o air contam

inants are re gulated by O SHA Perm issible Exposure Limits (PELs). Chemicals for which PELs have been promulgated are listed in the OSHA Air C ontamina

nts Standar

ds and are ap

plicable to t

he General I

ndustry, Sh

ipyards, Marine Terminals, Longshoring, Construction and Agriculture only (29 CFR 1910, 1915, 1917, 1918, 1926, and 1928). Some OSHA requirements may vary between industrial sectors. Employer s may com

ply with OS HA PELs with the use of engineering

controls (e. g., local exhaust ven

tilation), b

ut personal p

rotective eq

uipment (e .g., a respi

rator) is also

allowed und

er certain circu

mstances.

In the abs ence of moni toring da ta, OPPT's C hemical En gineeri ng Branch may assume compliance with the O SHA PELs to estimat

e potential o ccupationa

l inhalation

exposure, w

here appropriate . For detailed assessments, CEB will often obtain, review, and evaluate OSHA compliance data, and may prepare an assessment based on this data. OSHA generally only inspects workplaces with greater than 10 employees.

PELs are us

ually expres sed in term s of time w eighted ave rage (TWA

) concentrat

ions that must not be exceeded any 8 hour work shift of any 40 hour workweek. A TWA is based on exposure averaged over an 8 hour period and is calculated to al low for excursions above the exposure le

vel provide d they are co mpensate d by equival ent excursions below the exposure le

vel17

during the w orkday. Th e estimate d exposure i s the total am ount of sub stance to wh

ich a worker can be exposed per 8 hour day whether the exposures are for short duration at high concentrations or long duration at low concentrations. Ther e is no need to compensate the value for periods

of time th e worker is in

volved in ac tivities that

do not resul

t in exposur

e.

OSHA ma

intains a dat

abase of ex

posure monitoring measuremen ts which has

been gathered at s elected indu strial sites in order to dete

rmine com

pliance with

PELs. This

database is the OSHA Computerized Information System (OCIS) and may give helpful insight into the level of com

pliance with

a specific P EL. It may

also provid

e more accu

rate exposu

re data for a given industrial sector and a better indicati on of whether exposures are in fact below the PEL.

Guidance an

d Example s for Presen

ting OSHA

PELs in CEB Reports:

1. If OSHA

compliance data has b een evaluate d as describe d in section d below (OCI S Compliance Monitoring Data): Based on a review of OSHA compliance data, about __% of approximately __ measurements were below the OSHA standard. Therefore, assuming compliance with the O SHA standa rd would res

ult in an esti

mated [h igh end] in

halation po tential dose rate for the overall

industry, a

lthough the

applicabili

ty to the spec ific facili

ties identif

ied in this report is unknown.
2. If OSHA compliance data has not been evaluated: The assumption of compliance with the OSHA standard is a postulated hypothesis (a "what-if" scenario) and i nformation about the probability

that exposu

res in the ove

rall industry

are below th e OSHA sta

ndard has no t been evaluated at

this time.

c) Mass Bala nce Ventila tion Model
When exp osure mon

itoring data

or other app roaches to as sessing occ upational ex

posures can not be used, OPPT's Chemical Engineering Branch often uses a mass-balance or "box" model to predict airbo rne concent rations of a

specific ch emical. T

his model is most app licable to vapor and

gaseous em

issions beca

use vapors f

ollow curre

nts freely a

nd are not gr

eatly influenced

by gravity. The steady s tate model used by CEB is described in Preparation of Engineerin

g Assessment, Volum

e I: CEB Eng ineering Man ual and is based

on the mas s balance of a substa

nce in an enc losed space . The simpl est form o f the mass balance model is used

to estimate a

irborne concentrations , based on th e followin g assumpt

ions:

! there is perfect and instantaneous mixing of the contaminant with incoming general dilu

tion air;
! the airborne

concentrati on of the contaminan t in the exfi ltration air i s the same a s in the ro om; ! only one sou

rce within th e work area e mits the contaminan

t;
! extinction of the chemical (adsorption, absorption, or chemical transformation)18

4 U.S. Environmental Protection Agency. 1991. Preparation of Engineering Assessments. Volume I: CEB Engineering Manual

. Draft. Washington, D.C.: Office of Toxic Substances, U.S. Environmental Prote ction Agency. pp 4-25 - 4-33.

5 A. A. Hummel, K. O. Braun, and M. C. Fehrenbacher. Evaporation of a Liquid in a Flowing Airstream. Am. Ind. Hyg. Assoc. J. Vol. 57, pp 519-525. June, 1996.

resulting f

rom depos ition on wal ls and equip ment, con densation o f hot vapor s, and photod

egradation o f chemica

ls is negligi

ble;
! the incom

ing air is con

taminant- free;
! the concent

ration of contaminan

t at initial tim

e (t=0) is neg ligible;
! the generati on and venti lation rates a re constant o ver time;
! room air and ventilation air mix ideally;
! the concentration approaches steady state; and
! the mass transfer resistance on the gas side is limiting.
Predictive equations for generation rate have been developed for tr ansfer operations (e.g., drumming, tank car loading, tank truck loading), and evaporation from open surfaces (e.g., sampling) 4 . The generation rate for transfer operations is based on displac ement of vapor equivalent t

o the volum

e of the con

tainer for e ach contain er filled. T he generation rate for op en surface op erations is b ased on evap oration of a liquid from

an open con

tainer in a f

lowing air stream. T he assump tion of stea

dy state conditions is an

important

factor, as m

any occupat

ional exposure scenarios are of short duration such that steady st ate conditions would not be reached. However, t

he simplic ity of the st

eady state m

odel lends it self to scre ening level e stimates w here data is lacking.

In addition t

o the assum

ptions liste d above, the

following

apply to use

of the ma ss balance model for open surface operations 5 :

! surface tem

perature of

the liquid an

d the evapor

ation rate are

constant;
! heat of eva

poration is provided by t

he surround

ings;
! diffusion

at the edge o f the pool a

nd in the dire ction of the

air stream a

re negligible;
! air velocity is constant and flowing only in one direction;
! there is no mixing in the area above the pool of liquid;
! no local exh aust or phys ical barriers are present a

t the edges o f the pool;
! substance has a low to moderate vapor pressure (< approximately 35 torr); and
! heat transfer is neglected.

A number

of defaul t input value s have been s elected for use in the m

ass balance m

odel in the absence

of data. For transfer o

perations, d

efault inpu

t values for

ventilation

flow rate, volume of

container, s aturation f

actor, fill r

ate, and m

ixing factor are selected

from eith er midrange or conservative values, depending on the type of assessment desired (e.g., “what-if” or bounding assessment. ) For open surface operations, default input values for surface area of the pool of liquid, ventilation flow rate, mixing factor, and length of the pool are selected from midrange or conserva

tive values. Values for

saturation f

actor and m

ixing factors are derive d19

6 M. C. Fehrenbacher and A. A. Hummel. Evaluation of the Mass Balan ce Model Used by the Environmental Protection Agency for Estimating Inhalation Exposure to New Chemical Substances. Am. Ind. Hyg. Assoc. J. . Vol. 57, pp 526-536., June 1996. from lim ited data pre sented in sta

ndard refer

ence mater

ials, and other default i

nput values

are based on pro fessional j udgment or knowledg e of comm on industria

l operations . Thus, m

odel estimates are fairly u

ncertain. T

he estimat

ed vapor pre ssure may

also be unce

rtain, espec ially for mixtu res and new c

hemicals. The incorporation of a m ixing factor term is a v ery simpli stic means of addressing

non-uniform mixin

g in a room , which is ac tually quite complex. However, it is comm

only used in

estimatin g occupatio nal inhalati on exposure

.
A sensitivit

y analysis o f the mass

balance mo del and unce

rtainty anal

ysis of model parameter s confirmed that value s selected f or ventilation flow rate

and vapor ge

neration rat

e have a significant impact on calculated airborne concentrations a nd must be carefully selected. Input value s for vapor

pressure m

ust also be se lected with c are 6 . A rigorous evaluation o f model estimates when com

pared with m

onitoring d

ata for sele cted industr

ial operatio ns demons trated that “what-if” model predictions were within one order of magnitude of the monitoring data but may over- or under-estimate exposures when mid-range default input values are selected. Estimates based on sel ection of u

pper bound

default inp

ut values res

ulted in esti

mates whi ch were one or two orders of magnitude higher than the monitoring data.

Guidance an

d Example

for Presen

ting Modelin

g Estimate s in CEB Re

ports:

Table XX. Estimated I nhalation Exposure f

or Dimethyl chickenwi re

W orker A ctivity Estimated Number of Workers Pote ntially Exposed 1 Estimated Airborne Concentra ti on, (mg /m 3 ) Potential Inhalation Dose Rate, (mg/day) Personal Protecti ve Equipment 1

Sampling 48 <<0.01 2,3 , 0.07 3,4 0.01 2,5 , 0.78 4,5 Cartridge resp irator, Tyv ek su it

Product Loadi ng (Drumming) 48 0.02 2,6 - 2.2 4,6 0.24 2,5 , 22 4,5 Cartridge resp irator, Tyv ek su it

Product Loadi ng (other tr ansfers) 143 0.01 2,7 - 0.06 4,7 0.15 2,5 , 0.62 4,5 Cartridge resp irator, Tyv ek su it

1 Based on infor

mation r eported by indust ry. 2 “what-i f” hypothe tica l est imate bas ed on midrange def ault input va lues 3 Estimated u sing mas s balance m odel per Preparat ion of Engi neering Assessments, Volume I: CEB Engineeri ng Manual , sampling operation using default input values. 4 Bounding estimate based on protective default i nput values.
5 Assumes breathi ng rate of 1.25 m 3 /hour f or an 8-hour

workday. 6 Estimated u sing mas s balance m odel per Preparat ion of Engi neering Assessments, Volume I: CEB Engineeri ng Manual , drumming operation using default i nput values.
7 Estimated u sing mas s balance m odel per Preparat ion of Engi neering Assessments, Volume I: CEB Engineeri ng Manual , tank car l oading oper ation using def ault input va lues, wind speed = 9 mph.20

d) OCIS Com pliance Mon itoring Dat a OSHA maintains a database of exposure monitoring measurements analyzed by the OSHA Salt

Lake City L aboratory w

hich has bee

n gathered b y OSHA com pliance insp ectors at selected industrial sites in order to deter mine compliance with PELs. This database is the OSHA Compute rized Infor

mation Sy stem (OCI S). Inform ation availa

ble within the database in cludes over 520,000 individual sampling results from 1981 to the present. Results can be searched by company n

ame, SIC code, CAS number or

sampling type (area vs . personal). This databa se is only one of

several OSH

A databases , and includ

es data colle cted by Fede ral OSHA in spectors only.
1. If you only have an OCIS Lab Sample Results printout: These results do not identify the activity

of the work

er sampled , and it is unclear if the r esults repre sent time- weighted average results or short-term samples. In addition, the analytical method used to quantify the

measurem

ent is not rep orted, but o ne could ass ume that th e method u sed is that re ported in other OSHA docu

ments. Be cause of th ese uncertai nties, only

a range of m

easuremen

t results is reported, an

d it is not known if the sa mpling res

ults are repre sentative of

the specifi c industries and worker activities that are described in this report. Potential dose rates for inhalation exposure based on OCIS data are generally “what-if” estimates. It should be noted t hat some of the results in

cluded in th e [ appendi

x or table] m

ay reflect a

rea or bulk sa

mples, an d often analytical o r field blan

ks are report

ed. In addit

ion, not eve

ry sample has been code d to distinguish between field blanks, bulk samples, personal samples, etc.
2. If you ha

ve addition al information on the analytical m

ethods used , the SIC and worker activity, yo

u should sum

marize thi s informa

tion in the as sessment, and characte rize the expo sure data appropriately. Where possible, data from the appropriate SIC should be used in assessi ng occupational exposure for detailed assessments.

Guidance an

d Example s for Presen

ting OCIS d

ata in CEB R

eports:
1. If you on

ly have an O CIS Lab Sam ple Results

printout: W

hen reportin

g OCIS data , include the data print-out in an appendix or table, incl uding the PELCODEs to aid in interpreting the results. Because we

can only int

erpret the da

ta that has be en coded wi th a PELCO DE, only make state

ments abo

ut that data. At best, you can only rep ort a range of values for a

ppropriate measurements. This data would be considered “Type 3" (anecdotal) data as reported in t he Guidelines

for Statist

ical Analys is of Occup ational Exp osure Data

. In addition to the above standard language, within the text of the r eport, include information similar to the following:
There were 245 OCIS monitoring records for dimethylchickenwire. Out of the 245

measurem

ents, 176 w ere either bla

nk sample s, bulk sam

ples, or wer

e not coded a

nd are assum

ed21

7 Versar, 1984. Exposure Assessment for Retention of Chemical Liquids on Hands . Office of Toxic S ubstance s, US EPA. Contract 68-01-6271.

8 Popendorf, W.J. and Leffingwell, J.T., 1982. Regulating O P Pesticide Residues for Farmworker Protection. Residue Review
, Vol. 82, pp 156-157. to be not rep resentative

of persona

l exposure. Without a

dditional in formation, only 69 s amples ranging from 0.99 to 25 ppm can be evaluated for predicting inhalation exposures during industrial operations. None of the coded samples were above the OSHA PEL.
2. If you ha

ve addition al information on SIC code and worker activity , you may be able to group the data into groups individuals with similar exposures, and may be able to provi de some statistical descriptors (mean, confidence limits, etc.) Consult the Guidelines for Statist

ical Analysis of

Occupational Exposure

Data for additional detail. T his data wou

ld be consid

ered “Type 2" dat

a as reported

in the guide lines.

4. Assessme nt of Dermal Exposure

The OPPT C

hemical E

ngineering

Branch's Dermal Ex

posure Meth od is frequently used to develo p boundin g estimate s of the pot ential a mount of a ch emical re maining on a worker's hand(s) (usu

ally express ed in terms

of mg/da y) and availa

ble for absorption, aft

er the worke

r completes various common industrial activities leading to occupational exposure. The method links assumptions based on limited experimental data contained in a study 7 which mea sured amounts of different materials remaining on the skin after completion of several tasks representing various degrees of exposure with estimates of skin surface area in c ontact with the contaminant 8 . The method does not consider volatilization, humidity, skin conditions, and clothing practices, or the presence or absence of warning proper ties such as visual changes to the skin or irritation. However, dermal exposure is assumed to be negligible when mitigated by the corrosivity

of the subs tance, high

temperatu

re or other conditions wh ich would p reclude derm

al contact. Absorption through the skin is considered separate ly and is evaluated by another group within OPPT. The method also assumes that a single contact with the chemical results in the total quanti

ty of subst

ance deposi

ted on the sk

in for a ful l work day an

d that no der

mal protection, such as gloves, is used by the worker to limit exposure. Therefore, the method generates es timates of

potential de

rmal dose r

ate only fo r the sub-po

pulation of

workers tha

t does not use dermal protection. Gloves and other chemical protective clothing and e quipment

are comm only used in

industrial o

perations, b

ut quantifi cation of th e level of pr otection pro vided by gloves du

ring actual u se is not perf ormed due

to a lack of d

ata.
There are many uncertainties associated with an assessment of dermal exposure, and characteriza

tion of the p otential fo r dermal ex posure and a

bsorption th

rough the sk

in is very complex. In addition, the perform ance of che

mical prot

ective cloth

ing and equi

pment in industrial operations adds another layer of uncertaint y and complexity to the assessment. An

assessmen

t of derma

l exposure e

ncompass es developi

ng an unders tanding of

the exposur

e scenario (including the

duration, f

requency, a

nd amoun t of contam

inant depos ited on the sk

in),22

9 U.S. Environmental Protection Agency, Risk Reduction Engineering Laboratory. Met hods to Assess the Permeation of Chemicals Through Protective Clothing Polymers. User Manual. Supplement to Manual for t he Preparation of Engineering Assessments. Arthur D. Little, Inc. Contract No. 68-C9-0037, September 1990. coupled with an assessment of the skin surface area contacted, and consideration for any mitigation of exposure based on the physical/chemical properties of the chemical, handling procedures, environmental conditions, or the use of protective equipment or clothing. Absorption through the skin is currently evaluated separa tely. The amount of contaminant contacting t

he skin can v ary by sever al orders of

magnitud

e, dependin

g on the indi

vidual work

er activities and work practices. Due to a lack of data and information to provide a more definitive characterization of the exposure scenario for most industrial opera tions, CEB must rely on default ass

umptions which are be lieved to be r easonable f

or the entire

population

of workers potentially exposed via dermal contact in industrial operat ions in general. As additional data and informat ion becomes available , CEB’s methodology will be upda

ted to refle ct the new information.
With respect to the performance of chemical protective clothing during actual use, CEB generally relies on the default assumption that gloves or other cont rol measures are not used due to a lack of d

ata and information with which to adequately

quantify th e protection

provided during use. There are many factors which impact the protection provided by chemical protective clothing, in

cluding ava

ilability, co st, worker c omplianc e, impact on job perfo rmance, chemical and physical properties of the substance and the protective c lothing, and use, decontamination, maintenance, storage, and disposal practices applicable to the industrial operation 9 . The physi cal and chemical performance of the chemical protective clothing are a function of the permeation, penetration, and degradation characteristics of the pr otective clothing/chemical combination and contribute to the overall effectiveness of the barrier. Permeation is t he process by which a chemical moves through the protective clothing material on a molecular level. Penetration i s the movement of a chemical through holes (e.g., seams, porous materials, imperfections, etc.) on a nonmolecular level by mechanisms such as wicking, wetting, pressure gradients, or bulk flow. Degradatio n is any unde sirable chan ge (e.g., sw elling, shri

nkage, loss

of punctur

e or tear resistance, increase in stiffness, etc.) in a physical pr operty or appearance of the clothing material due to contact with the substance of interest. There are st andard test methods for measuring

these physi cal and chem ical characte

ristics, but

these are onl

y a few of t

he factors which impact the protection provided by protective clothing during use. Ver y little is known about the pe

rformanc e characteris tics of com plex mixtu

res which ar

e common in industri al operations. The environmental and worker-related aspects of the issue of the per formance of chemical protective clothing during actual use are not well under stood. A few studies have identified several environmental and operation-specific factors that may adversely impact the performance of chemical protective clothing during actual use. The elevated temperature of the skin, and st

ress and flexing of the

glove durin

g use have be en found to

reduce the p erforman

ce23

10 E. T. Zellers, R. Sulewski. Modeling the Temperature Depende nce of N-Methylpyrrolidone Permeation Through Butyl- and Natural-Rubber Gloves. Am. Ind. Hyg. Assoc. J. (54): 465-478. September, 1993.

11 E. C. Gunderson, B. A. Kingsley, C. L. Witham, and D. C. Bomberger. A Practical Study in Laboratory and Workplace Permeation Testing. Appl. Ind. Hyg. 4(12): 324-329. December, 1989.

12 U.S. Environmental Protection Agency, Office of Toxic Substances. Assessment of Airborne Exposure and Dermal Contact to Acrylamide During Chemical Grouting Operations. EPA 560/5-87-009, July, 1987.

13 K. Cummins, D. Morton, D. Lee, E. Cook and R. Curtis. Exposure to Acrylamide in Chemical Sewer Grouting ope rations. Appl. Occup. Environ. Hyg. 7(6): 385-391. June, 1992. of gloves during actual use in industrial applications 10 , 11 . Finally, wearing gloves may impede the performance of the specific task or activity and thus, gloves may be inappropriately used or not used at a

ll 12 , 13 . Where glove permeation data is available, it is generally evaluated by CEB with a focus on identifying procedures and workplace practices which will help t o ensure that the protective clothing will be appropriately selec ted, maintained, and used.

Guidance an

d Example

for Presen

ting Derm

al Estimat

es in CEB R

eports:

Table XX. Estimated D ermal Poten tial Dose Ra te (PDR) for

Dimethylch ickenwire

W orker A ctivity Num ber of Workers Quantity Retained on

the S kin p er U nit Surface Area ** , (mg/cm 2 ) Skin Area Exposed ** (cm2) Dermal PD R*,

(mg/day)

Processi ng and Loading 130 1 - 3 1300 1300 - 3900

* Bounding esti mate, as suming rout ine, 2- hand dermal cont act, no dermal pr otect ion, s uch as gloves , are used by the worker to limit exposure. A bound ing estimate i s an exposure or dose which is higher than any exposure or dose expected t o occur i n the act ual popul ation. The esti mate is clear ly outs ide (hi gher tha n) the di stri bution of

actual exp osure s. ** Based on the Preparat ion of Engi neering Assessments Volume I: CEB Engineering Manual

.24

IV. Listin g of CEB Me thodologie s This section presents a series of tables which list the methods used by CEB, the type of esti mate or exposure descriptor resulting from use of the method, and the current status of the method. In addition, notations regarding the use and limitations of the method are included. Because the generic scenarios largely rely on default assumptions for predicting environmental release and potential for dermal exposure, this information is not included in the table. It i s important to note that while many of these methods are final, all methods are subject to change as new information and data are obtained. A discussi on of uncertainty associated with the monitoring data has been incorporated into Table C. Uncertainty is an important consi deration in developing any assessment of occupational exposure

and release. The standar d language presented in s ection III of this docum

ent identif

ies some o f the uncert

ainty associated with the base methods. This information is applicable to the methods and generic scenar ios presented in Tables A and B below. In addition, Appendix D presents information that may be helpful in identifying additional uncertai nties associated with CEB

assessmen

ts.

Table 1. L isting of Ba se Methods

CEB Base Method Exposure Descripto r or Type of

Estimate Current Status of the Method Notes Dermal Exp osure Assessme nt Bounding estimate for workers wearing no dermal protection. Final. This method is

currently un

der evaluation and will be

modified in the futu

re. Report values to 2 significant digits.

Mass Balance Ventilation Model "What-if" if scenari o using m id-range de fault values;
Bounding e stimate wh

en using d

efault valu

es selected fr

om the upp er end of th

e range. Final. This method has been evaluated by

comparison with available monitoring data. The method is currently un

der revisi on to incorporat

e new appro aches for p

redicting t

imedependent e

xposures and consid

eration for incomplete

mixing. Report valu es to 2 sig

nificant di gits (e.g. <0.1, <

<0.1).

OSHA PEL f

or Particul ates Not Otherwis e Regulate d (PNOR) High end es timate, bas ed on OSH

A Complia

nce Informati on System ( OCIS) dat abase for a

ll reported SIC codes combined. Final. OSHA Compliance data supports using this metho d as a high

end estim

ate for an o

verall estimate. Analysis of

individual

SIC codes

has not been do

ne. Report valu es using a ppropriate significant digits.25

CEB Base Method Exposure Descripto r or Type of

Estimate Current Status of the Method Notes

Other OSHA PEL “what-if” scenario i f no suppo

rting data ( e.g., OSHA com

pliance data

) is availab le. If supportin g data is av

ailable, care fully evaluate the data and

determine

the approp

riate expos

ure descriptor

. Final. A r eview of th

e OSHA co

mpliance d

ata may provide additional information on the appropriate exposure descriptor and the appropriat

eness of t he assump

tion that f acilities are in comp liance. Report valu es using a ppropriate significant digits.

OSHA Comp uterized Information System (OCIS) Data Carefully evaluate the data and determine the appropriat

e exposure

descripto r. Final. Report valu es using a ppropriate significan t digits. OCIS data is generally appl

icable to lar

ger facilities. There are other OSHA compliance databases which may be more applicable to smaller facilities.

NIOSH National Occupatio nal Expos ure Survey (NOES) Database NOES esti mates are f

airly uncertai

n due to da

ta limitations, and generally over predict the population of workers potentially exposed. Final. NIOSH has no plans to update NOES, and the information is dated. Report values to 2 significant digits, and report the uncertai

nty range.

Environme ntal Relea se:

Media of Release Media of re lease is based on sub mitter-su pplied informatio

n, documen

ted source (e.g., indus

try profile or TRI data), and/or engineering judgment. If the media is uncertain, it will be so noted, and the basis f

or the esti mation is provided i

n the asses sment. Final. As part of th e developm

ent of “ge neric scenarios”, CEB continues to gather data on quantity, frequency, and media of releases of chemicals from specific industries or uses. Developed f or new chem

ical assessments.

Environme ntal Relea se: Release of Liquid Residuefrom Unloading and Cleanup Operat

ions for B atch Operations. Estimates provided f

or the entir

e process,single vessel, tank car/truck, 40 - 60 gal. drums and smaller co

ntainers, b ased on dat

a collected during a la

boratory stu

dy. Assum

es that ves sel is emptied

by pumping

out the res idual mater

ial for process, drums or vessel; gravity draining for tanktruck/cars. Final. As part of th e developm

ent of “ge neric scenarios”, CEB continues to gather data on quantity, frequency, and media of releases of chemicals from specific industries or uses. Does not consider lining of containers, viscosity, type and amount of solvent, cleaning method, cleanup frequency, and treatment of residues p

rior to dis charge.

Environme ntal Relea se:

Release From Drum Residue for Solids Estimate of 1% by weight of drum based on engineering

judgment. Final. As part of th e developm

ent of “ge neric scenarios”, CEB continues to gather data on quantity, frequency, and media of releases of chemicals from specific industries or uses.26

CEB Base Method Exposure Descripto r or Type of

Estimate Current Status of the Method Notes

Environme ntal Relea se: Baghouse/Cyclone Efficiency Estimate of 99% efficiency, based on engineering

judgment. Final.

Environme ntal Relea se: Carbon Adsorption Eficiency Estimate of 50% efficiency, based on engineering

judgment. Final.27

Table 2. L isting of CE B Generic Sc enarios* ‡

Generic Scenario (Current Status) Inhalation Method (Descriptors for PDR) Notes

Adhes ives Manufa

cture (Fin al, Fe bruar y, 1992) Particulat es : OSHA PEL for Particulates Not Otherwise

Regulated (

high end es

timates), Vapor: Mass Bal ance Ventila tion Model (bounding or "what-if" estimates) Page A2: Calculation of vapor exposure: Where the scenario says “% PMN conc.” the eq

uation sho

uld read “ mole fracti on.” Calculation of particulates exposure: Where the scenario says “% PMN” the equation should read “% PMN/100" Bioprocessing (Draft, September, 1991, currently under revision) Bioaerosol s : “What-i f” scenario

based on a

rea monitoring data collected by NIOSH.

Carbonless

Copy Paper (

Final, Jun e, 1991) Particulat es : OSHA PEL for Particulates Not Otherwise

Regulated (

high end es

timates), Vapor: Mass Bal ance Ventila tion Model (bounding or "what-if" estimates)

CFC subs titutes - M anufacture; Foam Blowing; E lectronics Cleaning; M etal Cleaning (Draft, September, 1991) Vapor: High end and central tendency estimates based on monitoring data for CFCs and CFC substitutes.

CFC subs titutes - S terilant Car

rier (Draf t, September, 1991) Vapor: High end and central tendency estimates based on CFC substitutes - Refrigeration Servicing and Mobile Air Conditioning, Manufactur

e and Servi cing (Draf

t, September, 1991) Vapor: “what-if” estimate using a mass balance model with a Monte Carlo selection technique for calculating distributions of potential exposures. Coatings -

Conventio

nal; Emulsion/

Formulati on of Latex Particulat es : OSHA PEL for Particulates Not Otherwise

Regulated (

high end es

timates), Vapor: Mass Bal ance Ventila tion Model (bounding or "what-if" estimates) Page B7: The equation at the bottom of the page is inappropriate. The scenario provides no guidance for calculating the concentration in air, one of the parameters of the stated equation, and uses weight percent instead of mole fraction. Page B8: Th

e first equ

ation is in appropriat

e. The next paragraph d

iscusses inhalation exposure t

o powders , but infor

mation per

taining to OSHA PEL s is misstated. Coatings - Conventional; Automotive spray applica

tion (Fina l, Revised January, 1992; currently under revision) Particulat es: "what -if" s cenar

io us ing spraycoating dat

a.28

Generic Scenario (Current Status) Inhalation Method (Descriptors for PDR) Notes Coatings -

Conventio

nal; Furni ture Spray Appli catio

n (Fi nal, R evise d Feb

ruary, 1992; currently under revision) Particulates: "wha t-if" scena

rio if spraycoating data is used.

Coatings -

Radiation Curable; EB Curable - F ormulatio

n of Coatin

g (Draft, 1994) Particulat es : OSHA PEL for Particulates Not Otherwise Regulated (high end estimates) Page B7: The equation at the bottom of the page is inappropriate. The scenario provides no guidance for calculating the concentration in air, one of the parameters of the stated equation, and uses weight percent instead of mole fraction. Page B8: Th

e first equ

ation is in appropriat

e. The next paragraph d

iscusses inhalation exposure t

o powders , but infor

mation per

taining to OSHA PEL s is misstated. Coatings -

Radiation Curable; EB Curable - Roll Application (Draft, 1994) Particulat es : OSHA PEL for Particulates Not Otherwise

Regulated (

high end es

timates), Vapor: Mass Bal ance Ventila tion Model (bounding or “what-if” scenarios) Page B29: In calculating the inhalation exposures, mole fraction and not weight percent are to be used. The scenario only presents the worst case default values and not the more typical values.

Coatings - Radiation Curable; UV Curable - F ormulatio

n of Coatin

g ( Draft, 1994) Particulat es : OSHA PEL for Particulates Not Otherwise

Regulated (

high end es

timates), Vapor: Mass Bal ance Ventila tion Model (bounding or “what-if” scenarios) Page B36. The equation at the bottom of the page is inappropriate. The scenario provides no guidance for calculating the concentration in air, one of the parameters of the stated equation, and uses weight percent instead of mole fraction. Page B37: The first e quation is inappropr

iate. The ne

xt paragrap

h discuss es inhalation exposure t

o powders , but infor

mation per

taining o O SHA PELs

is misstated. Coatings - Radiation Curable; UV Curable - Roll Application (Draft, 1994, updated Sept. 1995) Mist: Based on li mited mon

itoring dat

a (“what-if ” scenario Vapor: Mass Bal ance Ventila tion Model (bounding or “what-if” scenarios) Page B45: The equations at the bottom of the page are inappropriate. The scenario provides no guidance for calculating the concentration in air, one of the parameters of the stated equation, and uses weight percent instead of mole fraction. Coatings -

Powder Co atings, Dr

y Blending (Draft, 1994) Particulat es : OSHA PEL for Particulates Not Otherwise Regulated (high end estimates) Coatings -

Powder Co atings, Mel

t Blending (Draft, 1994) Particulat es : OSHA PEL for Particulates Not Otherwise Regulated (high end estimates) Coatings -

Powder Co atings; Ele ctrostatic Application (Draft, 1994) Particulat es : OSHA PEL for Particulates Not Otherwise Regulated (high end estimates)29

Generic Scenario (Current Status) Inhalation Method (Descriptors for PDR) Notes Coatings P owder Coat

ings - Flu idized Bed Application (Draft, 1994) Particulat es : OSHA PEL for Particulates Not Otherwise Regulated (high end estimates) Coatings - Powder Coatings (Draft, 1992) Particulat es : OSHA PEL for Particulates Not Otherwise Regulated (high end estimates) Electroplating for Metal Treatment (Draft, 1994, currently under revision) Mist : use surr ogate data ( “what-if”

scenario). Page C2: Th e equation i s not a sta

ndard equat

ion from t he CEB Engineering Manual. The linear relationship between airborne concentration of mists and concentration in the solution is not supported, and is questionable as mist generation is a mechanical process which differs considerably from evaporation . The scena

rio does n ot address whether an

y surrogate d

ata is available an

d how to in

corporate t

he OSHA PEL into the assessme nt.
Electronics

- Wet Clean

ing Proces s in Integrated Circuit Fab

rication (D

raft, 1994) Vapor : mass balance model (bounding and “what-if” scenario, b ased on def

ault values used.)

Electronics

- Film De

position i n Integrated Circuit Fab

rication (D

raft, 1994) Gas : use surr ogate data ( “what-if”

scenario.) The scenari o does not address w

hether any su

rrogate dat

a is availab le.

Electronics - Printed Circuit Board; Material Fabrication Process for Manufacture of (Draft, 1994) Vapor : use surr ogate data ( “what-if”

scenario.) Page C24: The scenario suggests an inhalation rate of 1.75 rather than the

standard 1 .25 used b

y CEB with no

adequate ex

planation. The scenari o provides n

o guidance on how to calculate C o r whether d

ata is avail able. In addition, no explanation of the basis for assuming that C is linear with weight fraction is provided for these activities.

Electronics - Printed Circuit Card - Assembly Manufacturing Process Using Conformal Coating (Draft, 1994) Vapor : use surr ogate data ( “what-if”

scenario.) Page C31: The equation is presented correctly, but the scenario provides no

guidance on

whether s

urrogate da

ta is availa

ble.

Electronics -Semiconductors / Photolithography (Final, 1994) Not ad dress ed; re lease s onl

y.

Electronics - Transformer Manufacturing (Draft, 1994) Discu ssed quali tatively.

Fragrances - Manufacture and Use of (Draft, 1994) Particulat es : OSHA PEL for Particulates Not Otherwise

Regulated (

high end es

timates); “what-if” scenario b ased on NI OSH data. This NIOSH data needs to be evaluated.30

Generic Scenario (Current Status) Inhalation Method (Descriptors for PDR) Notes

Granular D etergents Manufacture (Final, March, 1991) Particulat es : OSHA PEL for Particulates Not Otherwise Regulated (high end) Vapor: Mass Balan

ce Ventilati on Model (bounding and "what-if" scenario, based on default val

ues used)

. Hardwood Plywood manufacturing, Exposure &

Release Sc enario (Ju

ne, 1991) Not ad dress ed; re lease s onl

y.

Leather Dyeing Spreadsheet (Final, ND) Particulat es : OSHA PEL for Particulates Not Otherwise

Regulated (

high end es

timates); “what-if” scenario i f based on

monitorin

g data This data needs to be evaluated.

Leather Tann

ing (Draft ) Particulat es : OSHA PEL for Chromium (“what-if” scenario) Need to eva luate OCISdata for co

mpliance w

ith Chrom

ium stand ard for thi s indus try.
Lube Oil Ad

ditives (D raft) Vapor: Negligible

Metal Clean

ing and Deg

reasing; S emiAqueous C leaners for

Degreasin

g (Draft, 1994) Limited mo nitoring d ata from N

IOSH stu dies of solvent degreasing

operations

(“what-if ” scenarios) No explanat ion is pro vided to s upport the

assumed linear relat

ionship between the airborne concentration and vapor pressure. Given that vapor degreasing

is not dri ven by vapor pressure d

ifferences (unlike eva

poration),it is possib le that som

e other par

ameter may b e more imp ortant. Metal Cleaning and Degreasing; Vapor Degreasing (Final, 1994) Vapor: Mass balance ventilation model using emission rates data (bounding

and "what

-if" scenario, b ased on def

ault values

used). Environme ntal Relea se: The assess ment of en

vironment

al release i s expected to represent a best estimate of the industry average emissions for the equipm

ent category. The estima te is based

on an avera

ge mass f lux rate, a standard sized degre aser for th e category, and

a standard

duty cycle. Paper Dyes - Manufacture and Use of (Draft, 1994) Particulat es : OSHA PEL for Particulates Not Otherwise

Regulated (

high end es

timates.) Petroleum Extraction; Drilling Muds (Final, 1991) Vapors: Generally neg ligible

Petroleum

Extraction ; Oil Well Treatment Chemicals (Final, 1991) Vapors: Generally neg ligible31

Generic Scenario (Current Status) Inhalation Method (Descriptors for PDR) Notes Petroleum Extraction; Well Casing and Cementing

- Applicat

ion of Chem

icals (Draft, 1994) Particulat es : OSHA PEL for Particulates Not Otherwise

Regulated (

high end es

timate.) Page D9: T he equation

is not a s tandard equ

ation from

the CEB Engineering Manual. The linear relationship between airborne concentration of mists and concentration in the solution is not supported, and is questionable as mist generation is a mechanical process which differs considerably from evaporation . The scena

rio does n ot address whether an

y surrogate d

ata is available an

d how to in

corporate t

he OSHA PEL into the assessme nt.
Petroleum

Extraction ; Enhanced O il Recovery Stea

m Stimul ation, Steam Flooding, and Polymer/Surfactant Flooding - Application of Chemicals (Draft, 1994) Particulat es : OSHA PEL for Particulates Not Otherwise Regulated (high end estimates)

Petroleum refining processing - crude separation

processes

and catalytic cracking (Final, February, 1991) Particulat es: OSHA PEL for Particulates Not Otherwise Regulated, Nickel and Vanadium (“what-if” scenarios) Vapor: Mass Balan

ce Ventilati on Model (bounding

and "what

-if" scena rio with appropriat

e default va

lues). Photographic/Film Paper, Manufacturing of (Draft, ND) Weighing of Powders: Texti le Dye Weighing M

onitoring data (“wh

at-if” scenario). Printing I nks; News

paper Prin

ting (Draf t) Particulat

es: based on limited monitoring data (“wha

t-if” scena

rio). Printing I nks; Prin ting Inks- Manufactur

e of (Draft, 1994) Solvents : Semi-em pirical mo del was developed b ased on lim

ited monit

oring data (“what-if ” scenario. ) Particulat

es : Based on limited monitoring data (“wha

t-if” scena

rio.) This model has not been evaluated. Based on data from 1981 for various solvents.

Synthetic Fib er Manufact ure (Draft , 1994) Solvents: OSHA P ELs for so lvents (“whatif” scenari o). Assumes solvents are the cont

aminants o f interest. Does not address f iber exposure.
Textile Fin

ishing/Dyein

g; Fabric Finishing (Draft, 19 94, current

ly under revision) Not availab le.32

Generic Scenario (Current Status) Inhalation Method (Descriptors for PDR) Notes Textile Finishing/Dyeing; Textile Dyeing (Final, 1988, currently under revision) Particulat es: OSHA PEL for Particulates Not Otherwise Regulated (high end) Dye Weighing: Textile Dye Weighing Monitorin

g data (me an and high

end). Textile Finishing/Dyeing; Textile Dyeing Spreadsheet (Final, ND) Dye Weighing: Textile Dye Weighing Monitorin

g data (me an and high

end).
Toner Used in Photocopier, Use of PMN Component (Draft, 1992) Not addres sed; releas es only

Water Cool

ing Towers

Chemicals

(Final, ND) Not ad dress ed; re lease s onl

y.

Water Treatment Coagulants - Application (Draft, 1994) Particulat es : OSHA PEL for Particulates Not Otherwise Regulated (high end estimates)

Water Treatment Disinfectants - Application (Draft, 1994) Particulat es : OSHA PEL for Particulates Not Otherwise

Regulated (

high end es

timates), Vapor: Mass Bal ance Ventila tion Model (bounding

or “what- if” scenari os.) Gases : Use surr

ogate data ( “what-if”

scenario.) Page C55: The equatio n is not a standard eq

uation fro m the CEB Engineering Manual. The linear relationship between airborne concentration of mists and concentration in the solution is not supported, and is questionable as mist generation is a mechanical process which differs considerably from evaporation . The scena

rio does n ot address whether an

y surrogate d

ata is available an

d how to in

corporate t

he OSHA PEL into the assessme nt.
Wood Preservatives - Application of Waterborne, Using Pressure Treatment (Draft, 1994) Particulat es : OSHA PEL for Arsenic, and other PELs

(“what-if ” scenarios ; need to evaluate OC IS data) * The Dermal Exposure Assessment Methodology is used in all generic scenarios for estimating dermal contact. In addition, default assumptions are used in predicting the potential for environmental release for all generic scenarios unless otherwise indicated. ‡ See Table C for additio

nal detail f

or Generic Scenarios based on m onitoring data.33 Table 3. CEB Generic Scenarios Based on Monitoring Data

CEB Generi

c Scenario Method and Population Exposure Descriptor or Type of E stimate Common Assumptio ns and D efault Va lues, Var

iability, and Uncer

tainty Notes

Coatings - Conventi onal; Automotive Spray Application.
Entire population of workers w

ho are employed in f

acilities applying fini shes to automobiles by means of spray coating. “what-if” scenario based on li

mited monitoring data from 1981. Assumes that the NIOSH 1981 study is applicable as a “what-if” . Inhalation is expected during touch up for automated operations

.
Limited NI OSH moni

toring data

based on a

1981 stud

y, as an 8-hour TWA of total mist based on geometric mean and variability is :

Automobile refinish : 5 mg/m 3 using air dry alkyd; urethane modified alkyd paint (compressed air in a drive-through side draft boot h, 7 cars/s

hift, 40 m in/car)
Uncertainty : The monitoring data is very limited and is dated. Many thousands of sites performing spray applications using a variety of app lication me thods and controls, a

nd work practices.

We are curr

ently unable t

o quantify th

e uncertaint

y associated

with thes e estimates

due to a lac

k of data. NIOSH has evaluated occupational exposure and

control methods used in automobile refinishing operations . Informa

tion has al so been su

bmitted wi

th a few PMN

cases. Thi s method has not yet b een updated to reflect the new information.34

CEB Generi

c Scenario Method and Population Exposure Descriptor or Type of E stimate Common Assumptio ns and D efault Va lues, Var

iability, and Uncer

tainty Notes

Coatings - Conventi onal; Furniture Spray Application.
Entire population of workers w

ho are employed in f

acilities applying fini shes to furniture by means of spray coating. “what-if” scenario based on li

mited monitoring data from 1981. Wood furn iture coatin

g: 0.1 to 2 .5 mg/m 3 using an a

crylic lacquer, oleoresin stain, or nitrocellulose lacquer (airless application

method, s ome compr

essed air, by robot w/ o

pen side draft booth);

Metal furn

iture coatin

g: 0.1 to 23 .5 mg/m 3 usin g an al kyd baking enamel or acrylic emulsion (compressed air w/ manual and

reciprocato

r applicatio

n methods , side draf

t booth w/ i

ntegral su pply air);
Uncertainty : The monito

ring data is

very limited

and is dat

ed. There ar

e hundreds of facilitie s perform ing wood o

r metal fur

niture coating.

We are curr

ently unable t

o quantify th

e uncertaint

y associated

with thes e estimates

due to a lac

k of data. Coatings - Radiation Curable; UV Curab le - Roll Application
Workers applying UV Curable Co atings via Roll Application “what-if” scenario Based on limited data provided in a PMN submission, the

estimated inhalation exposure due to misting is 0.04 to 0.26 mg/m

3

.
Uncer taint y: It is not k nown whet

her this da

ta is repre sentative o f other operations . The data i s limited and has no t been fully evalu ated f or un certa inty.35

CEB Generi

c Scenario Method and Population Exposure Descriptor or Type of E stimate Common Assumptio ns and D efault Va lues, Var

iability, and Uncer

tainty Notes

Metal Cleaning and Degreasin g; SemiAqueous Cleaners for Degreasing
Workers performing degreasing

using sem

iaqueous cl eaners. “what-if” scenario based on li

mited monitorin g data. Based on limited monitoring data collected by NIOSH

during stu

dies of the

degreasing

industry in

1989 - 19 92. The monitoring data was collected during operations using volatile so lvents (TC

A and TCE). The perso

nal sample s (as 8-hour TW

As) range from 8 pp

m TCA to 3 8 ppm TCE. It is assumed t hat the oper

ations usi ng volatile

solvents are similar to those usi ng semi-a queous so lvents, and

that exposures would be s imilar.
Adjustments are made for molecular weight, mole fraction, etc.

Uncer taint y:
It is unknown if the operations are similar. This data has not been carefully evaluated for applicability to semi-aqueous operations , and is un

certain. No explanat ion is pro vided to s upport the

assumed linear relationship between the airborne concentration and vapor pressure. Given that vapor degreasing

is not dri ven by vapor pressure differences

(unlike ev

aporation) , it is pos sible that some othe

r parameter

may be more

important

.

Metal Cleaning and Degreasing; Vapor Degreasing
Workers performing degreasing using vapor degreasers. “what-if” scenario based on m

athematical modeling using emissions data, using routine default values.
Bounding e stimate using mor

e conservati

ve default values. Measured e mission r ate inform

ation is us ed in CEB’s standard “

box” mode l to estim

ate airborn

e concentrat

ion. Uncer taint y:

This metho dology uses

a standard

mathemati cal model t

o predict airborne concentration based on measured emission rate data, and selection of default parameters for ventilation rate. Based

on a comp arison wit

h limited m

onitoring data, model estimates for two types of degreasers were within one order of magnitude of the measured data when more routine default parameters are selected, and one to two orders of magnitude higher whe

n more conservative d

efault valu

es are selected. F or conveyorized vapor de greasers, the model i s likely to over

estimate w

orker expo sures.36

CEB Generi

c Scenario Method and Population Exposure Descriptor or Type of E stimate Common Assumptio ns and D efault Va lues, Var

iability, and Uncer

tainty Notes

Printing Inks; Printing Inks- Manufacture of
Workers p otentially exposed during manufacture and use of printing inks. “what-if” scenario based on li

mited monitorin g data. A semi-em pirical mo del was dev

eloped bas ed on limi

ted monitoring data for solvent exposures collected by NIOSH during a s tudy of one s ite in 1980

.
Uncer taint y: This data is fairly old and it is not known how representative this site i s of the en

tire indus try. The mod

el has not been carefully evaluated and is very uncertain.
Adjustments are made for molecular weight, mole fraction, etc. The model and monitoring data needs to be evaluated.

Synthetic Fiber Manufactu re Entire population of workers w

ho are potentially ex

posed to specific solvents during manufactur

e of syntheti c fibers. “what-if” scenario. Assumes that solve

nts are the m

ain focus o f the asses sment. This generic scenario needs to be evaluated.
Uncertainty : Estimates

developed using this

generic sc enario is very uncer

tain and mu

st be caref

ully evaluated

.

We are curr

ently unable t

o quantify th

e uncertaint

y associated

with thes e estimates

due to a lac

k of data.37

CEB Generi

c Scenario Method and Population Exposure Descriptor or Type of E stimate Common Assumptio ns and D efault Va lues, Var

iability, and Uncer

tainty Notes

Textile Finishing/Dyeing; Textile Dyeing
Entire population of workers who weigh powder dyes in textile processing plants. Exposure D escriptor: Mean and high end estimate based on the TDWMS da

ta: Assumes

the TDWMS

is repres entative of

exposures

of all dyes used at the facility (and not individual dyes) for the subpopula

tion of int erest.

Default val

ues for in halation ex

posure: ce

ntral tende

ncy: 0.0314 mg x (% solids) x (no. weighings/day) and maximum exposure range: 0.170 mg x (% solids) x (no. weighings

/day).
Variability : The geometric mean of the distribution of active color

ant was 0.0

49 mg/m

3 , with a geo

metric sta ndard deviation of 2.85. The estimated values followed a lognormal

distribut ion, which is typical of occupationa l exposure d

ata. The geo

metric sta ndard devi ation of 2. 85 is typical of occupational exposure data, demonstrating high varia bilit y. The study fou

nd that dye ho

use operati ons vary considerably, although the mechanism for weighing and mixing po

wder dyes wa

s consist ent at thos e sites st

udied. There was a

universal absence of

engineerin

g controls to control dye d

ust expos ure, and ind

ustrial hygie

ne practices also v aried widel y. Uncertainty : There are

sampling and non-s ampling er

rors associated

with the s

tudy. A pred

ictive mod

el was developed b ased on the

data collect

ed. Mass w

eighed was found to b e the best p

redictor of

airborne c oncentratio

n with a correlatio

n coefficien

t (R 2 ) of 0.39.
Estimates of subpopulations (e.g. worker exposure to a particular d

ye) are limite d by the scop e of the st udy. Note: This method is currently being updated and

revised.38

V. Referen ces 1. U.S. Environmental Protection Agency. 1991. Prep aration of E ngineering

Assessmen ts Volume I: CEB Engineering Manual . Draft. Washington, D.C.: Office of Toxic Substances, U.S. Environmental Protection Agency.
2. U.S. Environmental Protection Agency. 1992

. Guidelines for Exposure Assessment

. Washingt on, D.C.: Office of

Health and E

nvironme ntal Assista

nce, U.S. E

nvironme ntal Protection A

gency. (EP A Pub. No. EPA/600/Z -92/001.)

3. Carol M. Browner. 1995. Policy for Risk Characterization at the U.S. Environmental Protection Agency . Washing ton, D.C. : Office o f the Adm inistrator, U .S. Enviro nmental Protection Agency.
4. Versar, 1984. Exposure Assessment for Retention of Chemical Liquids on Hands . Office of Toxic Substances, US EPA. Contract 68-01-6271.
5. Popendorf, W.J. and Leffingwell, J.T., 1982. Regulating OP Pesticide Residues for Farmworker Protection. Residue Rev iew , Vol. 82, pp 156-157.
6. IT Environmental Programs, Inc. and ICF Kaiser Incorporated. 1994. Guidelines for Statistical A

nalysis of O ccupationa

l Exposure D ata . Washing ton, D.C. U.S. Envi

ronmenta lProtection Agency, Office of Pollution Prevention and Toxics. EPA Report No. EPA/744/b94/003.
7. DRAFT Risk Characterization Statement for OPPT Headquarters, March 14, 1996.39

VI. Appen dices4041 Appendix

B. Assump tions Rega rding Brea thing Rate and Durat

ion of Expo sure

In addition t

o the assum

ptions iden

tified in Ta

bles 1 - 3, CE

B makes ad

ditional assumptions regarding breathing rate and duration of exposure that may impact whether the

assessmen

t is truly a cen

tral tendency, high end , etc., estim ate. CEB ge

nerally assu

mes a breathing rate of 1.25 m 3 /hr for occu pational exp osure. This

is based on i

nformati on develope d by NIOSH i

n 1976 and r

epresents a breathing rat

e associated

with a volum

etric flowr

ate slightly above that measured for light work. However, the volumetric flowrate varies as a function of the type of work being performed, and ranges from about 0.56 m 3 /hr to 7.9 m 3 /hr during maximum work. CEB is monitor

ing ongoing

research on b

reathing rat

es in industr

ial operatio ns and will update these assumptions as new information becomes available.
CEB also makes assumptions regarding the duration of exposure, based largely on informat ion provide d or on prof

essional jud

gement. I

nformati on on durati on of expo sure is often provided in premanufacture notifications (PMNs) and is also provided through the CMA/SOCM

A/EPA Vol

untary Use a

nd Exposur

e Project. T

hese and oth er assump tions shoul d be fully do cumented

in the report , and the unc ertainty cha racterized, as appropria

te.42 Appendix

C. Sugges tions for Pr esenting Mo nitoring D ata in CEB Ass essments

Present data

submitted , including

as much de

tail as is pos sible. The EPA Exposu re Assessme nt Guidelin es recomm

end providi

ng suffic ient backgro

und inform

ation to exp lain what was done and why, including clear documentation of the source of the data and including references . Importan

t data elem ents are num

ber of sam

ples, date o f samplin

g, type of s ample taken, sam

pling and analytical m ethods utili zed, protec tive equipm ent worn by

the workers , worker activity, etc. Monitoring data may be collected for a variet y of reasons, and the basis for sample collection should be identified to enable appropriate inte rpretation of the data collected. The assessor should determine the relevancy of the monitoring data to the population bei ng evaluated, and the quality of the data. When analyzing occupational exposure data, c onsult the Guidelines

for Statist

ical Analys is of Occup ational Exp osure Data
, August, 1994.

Personal co nfidential

informat ion (employee name, social secur ity numbe

r) must be h eld in confide

nce and mu st not be incl

uded in CEB reports.

Guidance and Example for Reporting Industry-P rovided Mon

itoring Data

in CEB Rep orts :

Table XX. Summary of M onitoring D ata Submitt ed by Indu stry

for Dimethy

lchickenw

ire

Com pany, Locati on, and Year of Sampling Worker

Activity Num ber of

Samples Personal Airborne Concentration, Range (mg /m 3 )* Personal Protect ive Equipment and Engineering Controls **

AC M E C hem icals (1990, 1991) Bagging 3*** 0.18 - 0. 28 Local exhaust venti lati on, dust mask ( worn for comfort only)

XY Z Ch emistry (1988, 1989, 1990, 1991, 1993) Bagging 9 < 0.11 - 0. 48 Local exhaust venti lati on, half- face re spira tor

Che mi ca ls R US (1979-1992) Process

Operator 5 0.15 - 0. 67**** Full- face re spira tor (because of acetic acid), gloves * An alysis condu cted by co llecting total dust samples , dissolving sam ples followe d by G C ana lysis. Samples w ere colle cted over

approximat ely 7 hours and are 8- hour ti me-weighted aver ages except where other

wise noted. **Equipment and cont

rols as repor

ted by t he Company.

*** On e sam ple is no t reporte d du e to sam ple fau lt. ****Short term samples.43

Figure 1 . Schematic of Exposure Estimators for an Unbounded Simulated Population Distribution. Appendix D. Definitions of Exposure Descriptors and Related Terminology

from the EPA Guidelines for Exposure Assessment
The exposu

re descripto rs as define d in the EPA Guidelines for Exposure Assessment are presented in Figure 1.

The exposu

re descripto rs used by EPA are defin ed as follow s: High-end ex

posure (dos e) estimate

- A plausibl e estimate

of individ

ual exposur

e or dose for those persons at the upper end of an exposure or dose distribution, concept ually above the 90th percen

tile, but not

higher than

the individu

al in the pop

ulation who

has the high est exposur

e or dose.
In developi

ng estimat

es of high e

nd exposure

or dose, the

estimate must

be on the expected di stribution, and the com bination of

values assig

ned to the ex

posure or do se factors c an be expected

to be found

in the actual

population . The high e

nd estimat

e of exposu

re or dose m

ay be determined directly from the distribution. If no distribution is availabl e, but data on the parameter s used to calc

ulate dose o r exposure a

re available , the distrib

ution can be

simulated using an exposure model or Monte Carlo simulation.

Central tend

ency exposu

re (dose) est

imate- May be eithe

r the arithmetic mean e stimate or the med

ian estima

te, but shou

ld be clearly

labeled as su

ch. Where

both the arit

hmetic mean and the median are available, it is helpful to present both. For occupati onal exposures, the geometric mean shou

ld also be pre sented, but

it should be

recognized

that the arith

metic me an44

(or median

) is often th e preferred

value for ri sk assessment purpose s.

Arithmeti c mean

- the sum of all the measurements in a data set divided by the number of

measurem

ents in the da

ta set.

Median - value in the

measurem

ent data set s

uch that half

of the me asured values are greater and h alf are less.
In addition to these exposure descriptors, other exposur e estimators (e.g., bounding and “what-if” s cenarios) ar

e also used, particularly

for screeni

ng level asse ssments. These term s are defined as

follows:
Bounding e stimate

- an exposur

e or dose wh

ich is higher

than any exp osure or dos e expected to occur in the actual population. The estimate is clear ly outside (higher than) the distribution of actual exposures. If the bounding estimated value is not signi ficant, then the pathway can

be elimina

ted from f urther refinement.

“What-if ” scenario - an estima

ted exposur

e or dose bas ed on a set of hypothetic al conditions

or under a set of conditi ons for wh ich actual ex

posure para

meter data

are incomp lete or nonexistent. The calculated exposure or dose is not intende d to provide information about how likely the combination of exposure parameter values might be in the actual population or about how m

any, if any , persons m

ight actuall

y be subject

ed to the calc

ulated expo sure. If data on the parameters used to calculate dose or exposure are avail able A bounding estimate is determined by selecting one or more exposure parameters at the upper end of the range, and calculating the results. A “what-if” scenario can be developed by constructing a hypothetical scenario postulated based on available da ta and information.45 Appendix E. Potential Areas of Uncertainty Associated with an

Assessment

of Occupati onal Expo sure

The inform

ation in this

appendix is

presented as

an exampl e of potent

ial uncertain

ties associated w

ith generati

ng an assess ment of o ccupationa l exposure. It may be h elpful in identifyin g areas of u

ncertainty i

n a specific

exposure as sessment, although th is will vary depending on the exposu

re scenario a

nd data and i

nformati on available

with which

to construct the assessm

ent. The general steps an d associated u

ncertainties

in determi

ning the occ

upational exposure to a population of workers for a given substance of concern include the following:

A. Characterize the industry and the population exposed.
1. Steps in

performing

the assessme nt:
a) Determine the number of sites where the substance will be manufactured, processed and used. b) Determine the types of processing operations that will occur at the si tes. c) Determine the types of worker activities (e.g. sampling, drumming, loading and unloading o f tank cars) that will pot entially resu

lt in occupat

ional expos

ure. d) Determine the population of workers who are potentially exposed to the substance, based on the

identified

activities.

2. Potentia

l Uncertain ties Associa

ted with th e Assessmen t:
a) Assume that we know the range of and types of processes used for manufacturing, processing, and using the substance. b) Assume that the proces s changes m ade over tim

e will not res

ult in an incr

ease in exposure. c) Assume that differe nces in type s of equipm

ent used (e. g., a rotary

drum filt er vs a tray dryer) b etween proc esses will not affect the exposures. d) Assume that we have id entified al l potential u ses of the su bstance and

that a new use will not result in additional exposure. e) Assume that the worker activities identified represent the range of activities and the range of potential exposure. f) Assume that we know the number of workers potentially exposed per shift and the number of shifts per site for all of the identified processes in manufacturing, processing , and use of

the substance.

B. Based o n the Ident

ified Activi

ties, Evalu ate the Pote ntial for Occ upational Exposure.
1. Steps in

performing

the assessme nt:46

a) Determin e the physic al and chem ical propert

ies (e.g., v apor pressu

re, molecu

lar weight, physical state, melting point, etc.) of the substance. b) Identify the physical form (e.g., vapor, particulate, mist, gas) of the substance for each worker

activity, f

or each proc essing oper

ation, durin

g manufa cture, processing and use. c) Determine for which workers and for which activities potential exposure will be assessed. d) Determine the frequency and duration of exposure (hours/day and days/year) for each worker

activity, f

or each proc essing oper

ation, durin

g manufa cture, processing and use. e) Determin e the magn itude of ex

posure by ca

lculating th e airborne concentration to which workers are potentially exposed. f) Determine what control measures are actually used during manufacturing, processing , and use of

the substance that will m itigate expo sure, and to

what extent.

A. If monito ring data is available:
1) Determine how the samples were collected, and analyzed. 2) Evaluate th e sampling strategy and

determine

whether the

data is representative of worker exposures of interest (e.g. personal sa mples and samples collected for 8 hours are preferable to area samples for determining occupational exposure). 3) Determin e what QA/Q C procedure s were used, and the accuracy and sensitivity of the analytical method. 4) Determine the recovery efficiency for the samples and analytical method, any biases and uncertainties associated with the samples and/or method. 5) Based on th e informa tion, determ

ine the work

er activity f

rom the job

title given. 6) Determin e whether th e data are representative of other worker exposu

res doing sim ilar activitie s for simi lar duration s at other site s, or indust ries.

B. If no dat a is availab le:
1) Determin e through th e use of a m odel or assu

mption of compliance with an OSHA Permissible Exposure Limit (PEL) what the potential for exposure is

.

2. Uncerta

inties assoc iated with

the assessme nt:
a) Assume that the physical and chemical properties of the substance are known or can be determined through models, etc. b) If modeled or predicted, assume we know the uncertainty associated with the47 estimation technique. c) Assume that we can identify the physical form of the substance during processing and handling will not change it (e.g. the manufacturer will always process the solid substance in solution and not dry and isolate the sol id as a particulate). d) Assume that the frequ ency and d uration of exposur e will not increas e over ti me and will not result in additional exposure. e) Assume that the magnitude of exposure will not increase over time and will not result in add

itional expo sure. f) Assume that we have information on the effectiveness of control methods used. g) Assume that you have enough information available to evaluate the data (e.g. the sampling strategy, analytical m ethod, wor ker activitie s during sam

pling, etc. are known). h) Assume that the job titl es are related to the actual

worker activ

ity, althoug

h they are often as signed by pe

rsonnel spe cialists and

may not correlate to the

actual worker activity. I) Assume that the data is representative of exposure of other workers performing similar act

ivities.

3. Prepare the Exposure Assessment and Characterization

Once the un

derlying ass

umptions and uncerta

inties have b een identif

ied, the nex

t step is to prepare the assessment of exposure, including the identified assumptions, uncertaint ies, etc. There are sev eral OPPT s tandard ope rating proce dures and A gency guida nce documents which include reco mmenda

tions for pr

eparing the a ssessmen

t of occupa

tional expo sure. These document s, which ha

ve been described in this

document , should be c onsulted f or additiona

l information.