EPA
PB80-213465
Support Document: Approaches to
Exposure Assessment
(U.S.) Environmental Protection Agency
Washington, DC
Jun 80
U.S. DEPARTMENT OF COMMERCE
National Technical Information Service
NTTS
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United States
Environmental Protection
Agency
Office of Pesticides and
Toxic Substances
Washington, D.C. '^0460
EPA-560/11-80-017
July 1980
Toxic Substances
Support Document
Approaches to Exposure
Assessment
Toxic Substances
Control Act
Section 4
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NOT ICE
THIS DOCUMENT HAS BEEN REPRODUCED
FROM THE BEST COPY FURNISHED US BY
- --
THE SPONSORING AGENCY. ALTHOUGH IT
IS RECOGNIZED THAT CERTAIN PORTIONS
ARE ILLEGIBLE, IT IS BEING RELEASED
IN THE INTEREST OF MAKING AVAILABLE
AS MUCH INFORMATION AS POSSIBLE.
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TECHNICAL REPORT DATA
. I?le';:!/! rcad IlJul1Icriu/ls Uti rhe rel'erse before comrleringj
:, .~~::I,,J~T ';0. 12. 3. RECIPIENT'S ACCESSIO"",,NO.
EPA-560jll-80-017 .. ..," ~.-
~, ~ ""
, .. . .' ~...~, ...;
.;. 71,L: '""NO SU8TITLE S. REPORT DATE
Support Document: Approaches to Exposure June 1980 (approved)
Assessment 6. PERFORMING ORGANIZATION CODE
7. ,""UTHOR(SI 8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATI;jN NAME AND ADDRESS 10. PROGRAM ELEMENT NO.
Assessment D~vision
Office of Pesticides and Toxic Substances 11. CONTRACT/GRANT NO.
401 M Street, SW
Washington, DC ~0460
12. SPQNSORINc; AGENCY NAME A.NO AOORESS 13. TYPE OF REPORT AND PERIOD COVERED
U. S. Environmental Protection Agency 14. SPONSORING AGENCY COOE
401 M Street, SW
Washington, DC, 20460
15. SUPPLEMENTARY NOTES
16. A8STRACT
The various activities involving a che.'I1ical (manufacturing, processing,
use, distribution in commerce. and disposal) and how the activities lead to
exposure are described. Environmental releases from these activities are
estimated and integrated with chemical and environmental data. sometimes through
mathematical modelling, to determine whether there is a potential for occupational,
consumer, or general population exposure.
..,
17. KEY WOROS ANO OOCUMENT ANALYSIS
a. DESCRIPTORS b.IOENTIFfERS/OPEN ENDED TERMS C. COSA TI Field/Group
1'3. =IST"'8UT:'~N STATEMENT 119. SECURITY CL.ASS (This Reporc} 21. NO. OF PAGES
u!'\clas~iripl'1
Release unlimited. 20. SEC"' 'ElITY CLASS (This page) 22. PRICE
un~lassified
EPA Form 2220-1 (9.73)
J
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EPA-560/11-80-017
June 1980
SUPPORT DOCUMENT
APPROACHES TO EXPOSURE ASSESSMENT
ASSESSMENT DIVISION
OFFICE OF TOXIC SUBSTANCES
Washington, D.C. 20460
U.s. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF PESTICIDES AND TOXIC SUBSTANCES
WASHINGTON, D.C. 20460
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Int:oduc"tion
A.
~is Support Docurnen"t desc:ibes the
fact~rs involved in
perfo~ing human exposure assessments in connection ~ith TSCA
~4. Each activity involving chemicals (manufacture, distribution
in commerce, processing, use, and disposal) and how they relate
to exposure are discussed. In addition, the primary sources of
info~ation used by EPA for these assessments are listed where
applicable. These reference lists are in no way exhaustive.
They are ~erely common basic references which give general infor-
mation regarding uses, production methods, physical and chemical
prope~ies, etc., about each chemical and serve as starting
points in the assessment process.
The exposure assessment helps dete~ine whether or not the
substance presents a hazard, identifies who should be responsible
for testing, and cont:ibutes to the design of the test. As dis-
cussed in the preamble to the fi:st test rule, the Administrator
must make certaL~ findings to requi:e testing of a chemical
substance in which exposure is taken into account. The fi:st
finding under section 4 (a) ( l) (A) . is .. tl1a t either the manufacture,
dist:ibution in commerce, processing, use, or disposal of a
chemical, or any cOmbination of these ac"tivities involving the
chemical, may present an unreasonable risk of injury to hgalth or
tl1e envi:onment." Instead of ma~ing the set of 4(a) (l)(A)
findings, the Administ:ator may make findings under ~4(a) (1)(8),
where EPA may find that a chemical is or will be produced in
substantial quantities and that there is or may oe significant or
substantial human exposure or that the chemical ~nters or may
reasonably :e expected to enter the envi:onment in substantial
quantities.
Two fac"tors are involved in making the ~4(a) (l)(A)
finding.
One is that it is necessar! to show that there are
grounds to suspec"t that the chemical may cause adverse envi:on-
mental or human health effec"ts.
~e other factor is that any of
the activities listed above. c~uld presen~ a possibility of
I.
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exposure to t~e chemical.
~is is because even
the most ~oxic
(or oncogenic, teratogenic, etc.) chemicals may not present a
hazard if there is no exposure to them. In ~aki~g the
~4(a) (1)(3) fi~ding, only exposure and production need be
considered. Therefore, in either case, it is necessarJ to
perform an exposure assessment on a chemical being considered for
a ~4 test rule. To accomplish this, EPA include~ a section
entitled EXDosure As~ects in each of the chemical specific
chapters of the support documents. This section presents
pertinent information for determining if there is or could
reasonably be expected to be human exposure to the subject
chemical associated with any of the activities listed above.
In
subsequent rules proposing testing for ecological effects, infor-
mation will be presented relating ~o potential enviro~~ental
exposure.
Only manufacturers and/or processors can be required to
perform testing of a Chemical ~nder TSCA.
The designation of
whether manufacturers or processors or bo~~ should
test is
based
upon an assessment by the Agency of the activities most likely to
present
a risk.
In order to do this,
the exposure assessment
identifies not only that there is the potential for exposure, but
the sources of the exposure as well.
For example, the assessment
may show that the majority of exposures (or most severe expo-
sures) cccur as a result of releases of the
subject chemical to
the a~~osphere during its manufacture.
facturers would be required to perform
In this
case, the manu-
testing.
Thus, the
exposure assessment is instrumental in determining whether
manufacturers or processors (or both) will be required to test.
Exposure assessments have a third significant role for
determining testing requirements--identification of the bes~
route of application.
In other words, each assessment will
identify 'Nhether the greatest amount of exposure occurs through
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inhalation,
ingestion, or de~al contac~.
!f a
chemical is
released to t~e air, inhalation may be t~e
:nost
impor'tant
route. Similarly, because most solvents evaporate af'ter use
(e.g. paints, glues, inks), inhalation might be a most important
route of exposure to a chemical 'Nhich is used largely in or as a
solvent. If, however, a solvent such as a cleaning fluid was
used by wetting a rag with it and applying it to the surface to
be cleaned, the most likely route of exposure would be dermal
contact. Clearly if testing is to be required, the results would
be most useful if the method of administration of the test sub-
stance corresponds to the- principal
actually occurs in the real world.
assessment will also help guide the
route of exposure that
, . ,
Therefore, the e~posure
choice of the route of
application required in testing.
!n performing an exposure assessment,
EPA has recognized
that there are essentially two types of pathways a chemical may
follow before there is any human exposure. Th,e first type of
exposure, sometL~es called direct exposure, occurs as an L~ed-
iate consequence of manufacturing, processing, distribution in
commerce, use, and disposal. This type is itself divided into
'two categories: occupational exposure and consumer exposure.
example of occupational e~osure is a worker inhaling chemical
fumes in ~~e course of perfo~ing his or her job. .;n example of
consumer exposure is a person inhaling fumes while using a
product containing the subject chemical. In these cases, the
path of the chemical substance may be traced directly from its
occurrence to the exposure.
An
The other type of exposure may be :nore difficult to trace.
It involves the substance entering the environment from one (or
more) of the five activities (manufacture, processing, distribu-
tion in ccmmerce, use, disposal) and ultimately reaching the
general population through its presence in some :nedi~ such as
ai= I 'Na t~r I
soil, or the food chain.
3ecause the ?a thway the
chemical follows between its
release and the
exposed individual
is i~di=ec~, i~'is scme~~~es
called L:'ldirect
ex;:osure.
~o""eve!',
the te st :'"..11 e
suppor":.
cocuments refer to it as
general
?opulaticn
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exposure.
An example of this type
of exposure
is when a chemical
is discharged into a ~iver and absorbed by fish. Human exposure
would occur through the consumption of the contaminated fish.
Ideally, all three types of exposure (occupational,
consumer, general population) would be described quantitatively
with respect to the level and duration of human contact with the
substance, as well as with the ~oute of exposure (inhalation,
absorption, or ingestion). While not necessary for ~4 purposes,
monitoring data, which show the quantity of a chemical at a
particular location at a specific point in time, could be used
for this type of assessment. fRhile such monitoring data are
available in some situations, they are not generally available
for most of the possible circumstances of exposure. Reliance is,
therefore, generally placed upon qualitative descriptions of the
pathways leading to human exposure, incorporating quantitative
data (such as production volume and use) and physical/chemical
properties (such as vapor pressure, solubility, and octanol/water
pa~ition coefficient). A more complete description of this
process may be found in the text of this document.
The info~tion presented in the Exposure Aspects section of
each chemical specific support document falls into four general
areas: (1) infonnation on the identity of t:"le substance,
including its chemical and physical properties~ (2) information
on the substance's production volume and methods, its industrial,
commercial and consumer uses, its distribution in commerce, and
its disposal~ (3) assessment of oc:upational and consumer
ex?osure~ and (4) assessment of general population exposure,
including the k~own and expected environmental transport and
transformations of the substance, its bioaccumulation potential,
and monitoring data when available. ~e nature of the informa-
tion presented in each of these areas and the sources of that
info~tion are discussed in the remainder of this document.
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3.
~emical Identitv and ?~~~e~~ies
Chemical identity info~ation includes the substance's
chemical ~ame, synonyms, and trade names. rhe support document
does not present an exhaustive list of the names that are or have
oeen used for the substance. Rather, the most frequently used
names are given. !n some instances where the chemical ~ame is
unwieldy, the Agency has selected a common :lame or abbreviation
to use throughout the support document.
~e oasic physical properties of i~terest to EPA are pre-
sented (when available) in ~,is section, such as the substance's
physical state (that is, whether it is a gas, solid, or liquid)
at a~~ospheric temperature and pressure, its color and odor, its
density or specific gravity, boiling point, melting point, vapor
pressure, solubility in water and other solvents, its octanol/
water partition coefficient, and sorption data.
'nlese properties
allow EPA to make certain suppositions about the pa~,way through
the enviror~ent and the mode of human exposure that might Occur.
For example, if the substance has a high vapor pressure (evapor-
ates =eadily), it ca~ be inferred that some exposure by inhala-
tion would be li~ely to occur if the manufacture, processing,
distri;,ution,
use, or
disposal of the substance is perfo~ed in
closed systems. The octanol/water
shows the equili~rium distri;,ution of the
other than completely
partition coefficient
subject chemical between two liquid phases: ~-octanol and water.
!t is the ratio of the concentration in the octanol phase to that
in ~'e water phase and indicates how readily the substance may be
absorbed by fatty tissue. !f a substance has a high octanol!
water partition coefficient,
accumulate in fatty tissue.
there is a high potential for it to
!'herefore,
it may accumulate
L"l fish
or other organisms that are used- as a food
source.
'nle chemical and physical properties presented as
part 0:
the chemical identity discussion are not,
however, the only
properties
."'hich may have
~~plications for exposure to the
substance.
More
specific i:lfor:nation en the properties and
=eactivities 0: the substance that affect its behavior in the
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environr.:ent
(e .g.,
soil adsol"?tion, rate
of ~ydrolysis, photo-
chemistry) '....ill be considered by the Agency '....here relevant and
available and ~ill be included in the discussion of the
chemical's environmental fate and
transpor-:..
Where ~~e subjec-:. is a category of subs-:.ances rather ~~an a
single subs-:.ance, the chemical identity discussion will include a
definition of the category and presentation of information on the
proper-:.ies of specific ~embers of the categorj where such infor-
~ation is available.
wi th regard to ~i;t-:.ure's,
the composition of each will be
described as completely as possible, and the proper~ies of the
mi;t-:.ure are presented. ~~ere appropriate, information will also
be ?resen~ed on the proper-:.ies of some or all of the components
of the mixture.
This sec-:.ion also discusses the differences that :night e;tis-:.
between the "pure" chemical and the substance as it appears in
commerce, including the identity of any L.-npurities or intentional
additives. This information contributes to !PA's decision on
what grade or form of the chemical to be used L~ testing.
The prblary sources of the informaticn presented in the
chemical identity discussion include several references, such as
the Merck Index, the ~andbcok of Chemistrv and Phvsics, the
Condensed Chemical Dic-:.ionarv, manufacturer's product information
bulletins, and studies appearing in the published literature.
The consideration of all commercial and consumer activities
involving the substance provides ~PA with information
for identi-
fying locations ~here the substance may be released to the
environment as ~ell as potential locations and modes of human
e;c~osure.
The following sections describe
these activities and
how they
rala te to
ex~osure.
,.
o
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....
'-.
General rnfo~atior.
This section describes t~e
five activities listed by ~SCA
and how they are rela~ed to h~an exposure. The type of informa-
tion needed about each activity and how it is i~corporated into
an exposure assessment is discussed.
1.
~anufacture
~
The manufacture of the substance or mixture is the
i.~i tial
stage i.~ its progress (transport) through commer:e, and it pre-
sents the first opportunity for both direct human exposure and
release of the material into the environment. There are several
pieces of producticn-related info~ation that are of particular
importance i~ assessing potential exposure to the substance. One
of the key items is the quantity of the substance that is manu-
factured and/or imported annually because this info~ation may
indicate the extent of t~e use of the substance as well as the
potentia.l
for exposure.
Production volumes for the most recent
years are considered by ~PA whenever possible so that both the
average vol~e of material produced and any trends in production
can be discerned. The trends can indicate whether or not a
chemical may present a greater risk of exposure in the future.
It may be useful to know if production is constant for the year
or varies seasonally because exposure potential may vary accord-
ingly. ?ublished info~ation on the number of fi~s producing
the substance, and the number of production plants in operation
and their locations is also presented when available.
This
information could show
ally, or nationally.
because when compared
if exposure could occur locally, region-
Sales figures are also very L~portant
to production volume, they can indicate
where
e:cposure.s may occur.
!n other 'Nords,
if a
chemical has a
large production vol.~e but a low sales volume, it generally
~eans that most of it is consumed within ~~e producing plant.
This chemical is then said to have high captive use.
1'his means
that occupational exposure ~ay be more
significant
t~an other
t~es
of exposure.
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""'"" .
....e maJor
scu=c~s
0: production data
used
i:1. the
support
documents are the a.s.
International
T~ade Commission
(a.s.!.T.C.) reports on united States sales and production of
synthetic and organic chemicals and the TSCA Chemical I~ven-
tory. The a.S.I.T.C. reports present, wit~ certai~ exceptions,
t~e annual volumes of chemicals produced or sold in quantities of
5,000 pounds or more or having a sales value exceeding $5,000 and
having at least three manufacturers. The exceptions are plastics
and resin materials (which must have production and sales mini-
mums of 50,000 pounds or $50,000 respectively) and pigments, med-
icinal chemicals, flavor and perfume materials, r~bber-processing
chemicals! and elastomers wit~ mini.:nums of 1,000 pounds or
$1,000. Other sources of production data include various trade
publications such as the Chemical Marketina Recorter, Chemical
Week, and Chemical and !naineerina ~ews.
It is also ;mportant to know the form in
.....hich
the substance
is produced as '~ll
as the intermediate fo~s
.....hich
appear duri:lg
manufacture.
!~ is
possible that the
poten"tial for
expcsure and
the route of expcsure could change at various points during the
manufacturing process as t:.he. chemical changes for:n (e. g., conden-
sation or vaporization of the chemical).
fNhenever possible, the processes used to manufacture the
substance or mixture are considered by E?A and described in the
support document. Information on the production process can
provide some insight into t:.he potential for direct worker
exposure and for release of the substance to the enviro~~ent.
The number and type of reactors, reaction conditions, and
operating procedures are verI useful pieces of infor:nation i:l
assessi:lg occupational exposure and possible general population
and environmental exposure :rom releases of the substance.
Basically, there are three t:.ypes of chemical reactors used in the
chemical industry, ~nown as batch, semi-batch, and continuous
flow reactors.
A manufacturing (or processing)
plant :nay be
composed of one reactor of ar.y type
or a nUl-ncer
. .
c: =eac":.~rs ::1
any combination
of types,
depending
on the reactions ~o =e
a
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carried cu":.,
t:"!e :":ac-:.icn
'co~di~ions (~=mperat~re, pressure,
etc.), and t~e quan~ity 0: ~at=rial involved.
In a batch
~eactor, a charge of reactan~s is added, brought to reaction
temperature and pressure, and held a~ these conditions tor a
specified leng~h of ti~e after which the product is removed. A
semi-batch reactor dif:ers from a batch ~eactor in that at leas~
.one of the reactants is added continuously during the reaction.
This is done so that a desired concentration of one of the ~eac-
tan~s ~ay be maintained at all
time s .
'!'hi s is
Lrnpo rtan t wh e nit
is desirable to obtain a predominant amount of one of several
possi~le products. In a continuous flow reactor, there is a
continuous, steady tlow of reactants in and products out. In
this case, the extent of the reaction (and therefore the com-
position of the
in t~e reactor.
material
in the reactor) varies with the position
In the batch and semi-batch processes, the
extent of reaction varies with tLrne.
\~en flexible operating
conditions are ~equired and production is to be on a small scale,
the batch-type process is often the ~ost suitable (Smith, 1970).
L~ situations where the production volwne is large and more
stable ~eaction conditions
are required, the
con~i!1uous-Elow
process is :nore ?rac~ical.
Chemical plants generally operate with periodic shutdowns
for discharging, clea~out, and/or reactivation. This is ?artic~-
larly true with ba~ch reac~ors or in sit~ations when the rate 0:
production decreases with time because of scaling, reduction of
efficiency or collection of a side product, etc. During the
shutdown, the ~eactors :nay be vented and it is otten necessary
for workers
to en~er the ~eactor vessel to ?erfo~ the cleaning
operation. ~us, there is a risk of exposure to
con~aminants and/or ?roduc~ left in the reactor.
the reac~an~s,
Sampling operations also present opportunities
for expo-
sure.
This is cne of the :nost common daily operations in the
chemical ind~st=7 (Lovelace, .19i9).
Sampling is done to estab-
e:ti~i:lg, and
lish a material balance (an accounting of materials entering,
acc1.:."!tulating
i.:1 a
system) ,
evaluate the opera~ion of
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a piece
of equipment,
assist in
trouble shcoting, or to aid in
quality control.
The diverse conditions under which samples must
be obtained often complicate the sampling technique and put the
person taking the sample at risk of exposure to the chemical.
When a sample is taken, some amount of material is actually
removeq from the process. This means that a no~ally closed
system must be opened at some point to allow the removal of the
sample. Unless sampling equipment and procedures are carefully
designed, some material could escape and endanger the sampling
personnel as well as sur=ounding workers (Lovelace 1979).
rNhen a process is operated at an elevated pressure, it is
necessa--y to provide protectiqe devices such as relief qalqes or
rupture discs to preqent the pressure from increasing to the
point of damaging the reactor qessel (?er=y et al. 1969). This
is also true for storage tanks in which qolatile materials are
stored. Pressure buildup could occur as a result of its exposure
to an unexpected heat source (such as fire), the malfunction of a
component of the control system, or perhaps from a change in
a~ospheric pressure.
When the overpressure condition
occurs, it'
is relieved by the release of reactor contents through the relief
~alves or rupture
qenting operation
addition, such an
discs.
Th us ,
anyone in the qicinity
0: tone
is at risk of being directly exposed. !n
event would add to general population exposure.
Within the chemical plant, the reactants and products are
transported to and from reactor qessels by various means.
Liquids and gases are handled by pumps, compressors, and blowers
and are transported in pipes, flumes, and ducts. Solids may be
transported by conveyors and lifts. !f the conqeyor is open to
the a~~osphere, exposure to a chemical may occur as a result of
sublL~ation or L~ the fo~ of a dust. L~ the case of a liquid or
gas being transported in a pipe, exposures ocour as a result of
leaks from piping connections or from cracks or ruptures. Cracks
and r-..:ptures occur because of ineffecti.,e supports, neglec-:ed
~ibration effects,
poor weld quality, and less inspection due to
inaccessibility of inside surfaces.
r..ar;e
welded branch con-
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r1ec~ions
i:l t:.:=cuce
d':'s~~t"tic~s
and ?oss~~i:i~ies
:~!: ~..:nde~ec'ted
cracks or flaws. as
a result:. of
di==i~~lt =i~~~~g
and r:.onuni.:o!'7n
weld stress.
Since
pipe s~ruct~res are restrained against ~ove-
ment, t~e operation 0: t~e plant may cause stresses to ~uild up
due to vibration, t~e~al expansion and contraction, etc. As a
::'esul~,
slight defo~tions may occur ~hich can result L~ flange
cracks and possi~ly ruptures (?er~ et al. 1969). It
leaks,
should
be r:.oted that
leaks
(also called fugitive emissions) often
occur in t~e absence of the conditions just decribed.
?'Jmp scan
leak material at the point 0: contact bet~een the moving shaft
and the pump casing.
Le aks
may also occur in
stirrec-<:.ank
=eactors
at the
point '.....here
t~e agitator (~ixer) enters the
::eac"tor.
':'h us ,
the use of a closed system ~o manUfac~~re or
process a chemical does
not insure that there
:.S ::'0
exposure to
the chemical from its manufacture or processing.
The chemical indust:y presents a wide range oŁ hazards due
to the presence oŁ large ~~antities
of hazardous
(toxic,
flarn-
mable,
explosive, corrosive, ~tc.) substances,
frequently at
elevated temperatures
and pressures which promo~e
igni~ion or
decomposition.
:n=o~ation on ~~e producticn process may be available from
any 0: several sources,
including reference ~orks
such as Faith,
Keyes, and Clark's Industrial -Chemicals, company product in=o~a-
tion bulletins, trade publications such as the ~emical ~arketin~
~eoorter, the Kirk-othmer !ncvclooedia of Chemical ~echnolocv,
and cccasionally from government
process information available ~n
reports.
usually, the industial
~~ese sources is
not very
detailed, owing
info t':':1ation.
to the
proprietary
nature or much
0: this
~:!pe c f
2.
Distribu~ion :n Commerce
::':lis ac-:.i'lity involves t:1.e flow or
t=avel
or ~:1.e substance
::et~een the other four
acti7i~ies (manu.:ac-:.~re, precessing,
use,
and disposa.l).
! t :nay
involve t~e ~rans?or~ation of t~e sub-
- . -
s~anc:e :rern ~ne
manu=ac~~=er ~= a
?rocessor
or =~cm a
processor
1.1.
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':.0 anot.~er
?r::cessor
or ':.0 '..15er3 at"
:=~m
a '.lser ':.0
i:.s::is-;=osal
site.
Mate=ial ~alanc9s
would show :.~e val~~es
'Of chemical
subs~ance :lcwi~g
to and
==om each ac~ivity.
Detailed info:-:na-
tion 'Of
t.:-'lis type
is
difficult
':.0 'Obtain, au":.
E:?A is
i:l ~~e
pracess of de~elaping material bal~~ces for a number 'Of chemi-
cals. ~ese balances, ~hen a~ailable, and the methods developed
i~ them will ~elp pro~ide the i~formation ~eeded to describe this
ac-:.ivity l~ g=ea~et" detail.
~e methods of transpor~ation are also an
L'!tpo r~an t
consid-
eration in this section since environ~en~alt"eleases may
occur as
a result of this acti7ity.
The type
of information available on
t~is subjec~
is typically l~'!ti':.ed to
descriptions of t~e princi-
pal modes of transpor-:.ation and/ot" delivery of the material.
:'Or
e~ample some chemicals are shipped
as liquids or gases in
tan:<
cars, barges, or trucks, others are
transpor-:.ed as solids packed
in bags, d=1~s or railroad cars
liquids or gases in pipelines.
and same may be
transpor't.ed as
:::tpo s u= e
to ~arious chemicals
occ'.Jrs
as a =esult of
and tank ':.ruck
pipeline
lea:
-------
l:::aei.:lg ~nc.
, . ,
~~n..:..cac:":lg
:::~e=a':i.or.s
~ay ~e ~c~e c~~s~an~ anc
?redic~abl:
. . ~ .
S~:lce '::lese are con':~:lUOUS
. ~ . . '
c?er:~~c~s Nn~c~ =equ~=e
t~e ~=ar:.s===
of ':~e subs-::ance
::=::m one
con':ai:1e= ':0
anot::e=.
~is sor~ 0: release
data
is,
t~ere fore,
~se ful
for ?reeic-:.i.:lg
?otential
exposure.
Some
c.ata of t~is t:~e ~ay
be allai.lable in
~!OSE criteria dcc~~ents or the ~ational
SU~ley, but t~ese sources are li~i~ed.
Gcc'..lpational
2azard
3.
?rocessi:1c
~SCA defines ?rocessi:1g as
the ?reparation of a
chemical
substance
or ~ixture, after its
~anufac~ure,
for
its distri=ution
in commerce
C~SC.;' ~3(lO)J.
'The substance ~ay be
-' .
re=l.:lea,
?uri-
fied, ~ixed with ot~er substances =epackaged,
molded, etc.
-...
-..
':.he case '""he:'e
the subject chemical reac-::s
wi~~ anot~e:' chemical
or catalyst to
=o~ another substance,
the amount 0: chemical
reacted is no longer 0: concern. ~e final product, howeve:,, ~ay
still be 0: scme concern if it contains residual amounts of the
subject chemica:.
:n :nany cases ?ublished repor~sare available
which show the ?rod'..lc~s
chemical substance.
and quantities deri~ed from 'the subject
Many processing operations are veri si~i:a= to the
manufac-
t'..lring operations described in Sec~ion 1.
!'hat is to say,
~:""e
same type 0: equipment is used, the ?rocesses
invol'Tee are
si~ilar,
and therefore, exposure ~ay ccc~r i~
the sarne 'flays.
20wever,
there are a number 0: operations which are
used in the
processing 0: a chemical which
may not occur during
:nanufactur-
ing.
Some
of these are listed
in the first ?aragraph,
such as
repackaging and molding.
It is not the ?urpose 0:: this dcc'..l~en':
to ;i'Te an exhaLlsti'le !.is't of al1. processing operati'Ons, ~u-::
:':1
ac-:.ual ?ractice ~ach ?rocessor may ~se c.i==erent
methods and ?rocedures, all 0: whic~ may ?resent
equi::ment,
dl.==eren'C.
exposure ?o'C.en-:.ials.
accurately, de~ailed
!'here fore,
:.n or::er t'O
assess ex;:os~re
mos-:.
k:"low1.e-:::.ge 0:
processing
'Ope=ations :.S ~elp-
f'.11.
'..."'hen a'Tai:'able,
i:l =0 ~a tion
en ~:~e
. .,
processl.ng o~eratl.on :5
?resen-:.ed
:':1 ':.his section.
20wever I
.:.ue ~~ t~e
:?r::prier:a=?
:.3
-------
:'1at':Jre 0: t~is
t::,?e
o t in fo r:ita t:.on,
process
~e':.ails
_. .
a=e o=-:.erl :"lO-:'
available.
4.
Uses
The uses of a substance
are o:':.en ~~e key stage
i.:1 its
progress through commerce in deter:itining
the potential for direc~
human exposure.
In the Ex~osure Asoects section of each support
-
document,
the Agency attempts
to descri=e as completely as pos-
sible t.~e use
patter:ls of the
substances under study.
Qualita-
tive descriptions of the function of the
substance in the
products containing it and the specific applications of those
products ar~ given whenever. such information is available,
as are
quantitative
data on the amount of the
substance that goes to
each use annuallYi and t~e
ac:ounted tor by t~at use.
fraction of
annual production
use L~fo~ation is particularly valuable to the Agency for
dete~ining whether there are certain populations, subpo~ula~ions
or environmental media that might be subj.ect to signifioant
exposure--such as machine workers exposed to
lubricants oonta:.n-
ing the subject :hemical or consumers exposed to
chemical as a result of its incorporation into a
the subjec":.
cleaning
-product.
Of particular interest are uses wh:.ch expose large
populations to the :hemical on a continuous or frequent basis,
such as cleaning solvents, aerosol propellents, motor :~els, and
dyes.
Chemical use info~ation is also valuable
for providing an
i:'1cication of points where t~e substance :nay be dispersed i:'1to
t~e general environment.
~or example, chemioals which are used
in the
tex'tile
or the
textile
industry for the dying
upon completion 0: the
process ::lay '=e
''''ashec. out
dyeing process and dis-
charged into a nearby river which
is a dri~ki~g wat=~ source
-""-
-""'..
downstream human populations.
amount 0: chemical discharged
!t :nay be possible to measure
into the ri7er, deter.:nine its
~:1e
ooncentration at the
points
where ~he 'Ka~er is withdrawn to
se ::-/e
. .
~..,
-------
t~wns or cities and
c::mbine
t:'e data
'....i-=.:'1
?o~Hll a tion
:neasuremer:ts
to est.irnate the
levels 0: human
exposure.
.~othe= aspect ~f
industrial
use is '~en ~~e subject
chemical substance is transfo~ed into another.
:::xamples
0: t:'is
are the manufacture of benzene :r~m toluene or the use oŁ 1,2,4-
trichlorobenzene to manufacture the herbicide 2,S-dichlorobenzoio
acid.
In these t~es of situations, the quantity of substance
available for general population ~xposure decreases.
:~owever ,
there is still concern about the substance if it is present in
emissions from the processing plant or as an impurity in the
final product.
!n the case of .uses involving cons~~er products,
if an
esti;:tate
can be made of the volume of product consumed, the
quantity of chemical contained in the product, and t:'e number of
people using the product, the levels of exposure through this
rou~e may be estL~ated.
The major sources of inio~ation on uses include varicus
trade' publications (again :lotably the Chemical ~ar1
-------
change
over
'=.i:ne,
so
t.hat t.he
grounewat.er concentrat.ion
o f ~:'1e
S:.l:Ojec~ chemical
:nay c:'1ange,
ane therefore expOS:.lre ~ay
ITa=:! '",it.;'
time. Secondly, the st~dy :nay only identify a chemical
measuring the quan~ity present. ~owever, these s~:.ldies
'.oIi t.hout
do
show
the existence of some chemicals
in groundwa te r as "a re sul t 0 f
landfills.
:'here fore
a rough esti:nate of human exposure may be
possible in ~any cases.
Other types
of disposal
~ethods include wastewater trea~~ent
plants and incinerators of various designs and efficiences,
eeepwell injection, encapsulation and solidification. Studies
may somet~~es be available on these :netheds as ~ell. !t. is
use f'..ll to k...ow if t.he substance :.s cisposed through a ::tunicipal
treat:nent
plant or one exclusi7ely designed ~nd operated by the
industry responsible for ~~e discharge.
- - .
-'-= ':ne
t.reat.~ent plant
is operated exclusively by the
industry,
it may be more efficient
in removing
certain substances
t.han
a municipal
plant because it
was designed specifically to remove them.
also ?rL~arily identify the effluen~s from
::owever,
these studies
t.he disposal plant.
Detailed
data
en t:,e
influents are not al~ays a7ailable.
!n :ac~,
t.here is
ITer"!
li~tle info~ation available showing the ~ethods of
disposal 0: many chemicals. The major
government re~orts and other published
infontation
sources are
lit.erat:.lre.
D.
:;irec-:. ::x-:=osure
-
1.
Occ:.l"Cational
~e t.hird general
area
addressed in the ::x-:=osure As-=ects
sections
is that concerning direct exposure to the substance or
~i:t-::.lr~
L, occupational settings (from m~~ufacaturing,
transpor-
t.ation,
processing, or use)
and frcm consumer uses 0: products
containing the substance.
A considerable amoun,:
of attention has =een
;i\1en
in recent
years to
~~e exposu:e
of '",o:'
-------
pro~uce~ by ~:OSH are t~e National 0c=~=a~ional ~azar~ Su=?ev,
the NIOSE criteria cocuments, which
~ecomme~d s~andards
for
occupational exposure to chemicals,
an~ various ~eports
-'I ,.
,-ea,,-~:1g
with exposure to substances i~ specific workplace setti~gs.
!ncluded in the last group of repor~s are Health Hazard ~valua-
tion Reports, the Industrial Hygiene Assessment Reports, and
plant survey reports that are prepared by NIOSE and its contrac-
tors.
The National OccuDational ~azard Survey (NOES), a ~No-year
:ield study initiated in 1972,
was i~tended to describe the
health and safety conditions in the ~merican wo~k environmen~
and, ~ore specifically, to determine the extent of worker
exposure to chemical and physical agents.
Briefly, the survey
involved the visiting of approxi~ately 5,000 business establish-
ments in 67 ~et=opolitan areas selected by the Bureau of Labor
Statistics as representative of the non-agricu~tural busi~esses
covered under
Approximately
identified as
the Occupational Safety and Health Act of 1970.
8,000 chemical substances and physical agents were
potential hazards duri~g the survey. !~ the
Exoosure Asoects sections, EPA has presented the ~OHS data,
where
available, on the total number of persons estimated to be poten-
tially occupationally exposed to the substance L~ the United
States. Where appropriate, a further breakdown of exposed popu-
lation size by type of industrial activity or
gory is presented.
occ'..:pational
cate'-
.~though the NOES data base
is an
extremely valuable tool to
gauge the extent of direct exposure to chemical
occupational settings, it has lL~itations which
substances i:1
~educe its
usefulness.
Beca use the da t:a
'....erecollec'ted
f i 'le
to seven
'fe ar s
ago, some may be obsolete.
Fur'the~ore, the
data coll:c'tion
method relied aL~os't exclusively on the observations 0: a
surveyor who interviewed plant management and personnel and
toured the premises 0: the plant noting the number of employees
potentially exposed
to certain materials.
,;1 though
the survey
17
-------
?rocedures were designed ~o
:ni!l i.:nize
subjec~i'Jity ::y
~:1.e sur-
~eyor., i~ is ?ossible
~ade by t~e surveyor,
t.~at
some
0: t~e data reflec~
jt.:.dg:nen~s
Another limi~ation of the NOHS is
that certain types and
some specific chemical facilities were excluded from the survey.
!hose excluded were either classified because of national defense
security, engaged in agricultural production, mining (except oil
and gas), or were private households. .;bout 5,000 different
facilities were surJeyed,
and the data
'....ere
extrapolated
to a
nationwide
scale.
The N!OSE criteria documents, which as stated above are
i~tended to support ~rOSH's
tional exposure to chemical
recommended standards for occupa-
substances
and physical agents, ha~e
also been used
by EP11. i~
prepari~g the Exposure Aspects sec~ions.
These criteria
documents
usually present a review of t~e
ex'tent
of occupational exposure, ~~cluding info~ation obtained
f=cm t:te
NOHS survey,
from historical reports appeari~g in
the pub1.ished
li~erature, and from other investigations
ca==iec. out
by )IIOSE.
~TrOSH also ca.:ries out industrial hygiene surveys and heal. th
hazard evaluations of specific plants and operations to dete~ine
the level of worker exposure to chemicals. !~cluded in t~ese
investigations are actual sarnpli~g and analysis of the workplace
environment.
In addition to L~fo~ation from ~IOSE, EP11. has also used
cli~ical, historical. and anecdotal.
reports from t~e
published
literature, and material
submitted
t.o ;::P11. by
industry under
~arious provisions of TSCA.
The Exposure Aspects sections also
:-e rerance
the OSF.A
Occupational Safety and ~ealth Standards,
the ~TIOSE recommended
sta~dards,
and/or the American Council of Government and
Industrial ~ygienists
(ACGIE) threshold limi~ ~alues
( TL V' s ) ,
whenever such information exists for the substance.
defined by the ACG!~, is the airborne concentration
The . -:'!.. ~l, as
of a sub-
stance
to which it. was believed at t.he t.ime of its adop~ion
t."a t
nearly all workers ~ay be repeatedly
exposed
day after day
La
-------
'..,.i t~out ad'''erse
etfec~.
Three categories of T~V's
:nay be
specified:
(1)
TLV-TWA. (ti..:~:.e-weighted a',erage) - t~e average
concentration
for a ~orrnal a-hour workday or 40-hour workweek;
(2) TLV-STEL (short-term exposure lL~it)--t~e maximum concen-
tration to which workers can be exposed for a period up to 15
minutes; and (3) TLV-C (ceiling)--the concentration that should
not be exceeded even instantaneously.
In 1971, OSHA adopted t~e
ACGIH's TLV's for approximately 400 chemicals as the official
federal standards for occupational exposure. Additional and
revised standards are recommended to OSHA by NIosa in the NIOSH
Criteria Documents; these recommended standards are generally in
the form of TLV's as described above. These TLV's and Occupa-
tional Safety and Health Standards for exposure do n.ot reflect
the actual levels of occupational exposure to these substances.
They may, however, provide an indication or the upper limits of
currently permitted exposure in most occupational settings (of
course, full compliance with such standards may not always
occur). Worker exposure may varj widely among different work
assignments-.in a given plant and .among different plants. !t
should also be pointed out that the TLV's are based on the health
effects info~ation existing at the
.. . .:oh
...J.me .... ey
'....ere set and
that
they are revised as more data become available.
Therefore,
measurements showing that certain cccupational exposures are at
or below the TLV are not automatically accepted by E?A to mean
tha t t.."'1ose exposures should not be of concern or are "safe."
2.
Consumer
Wit~ respect
to direct human exposure from t..~e consumer use
of products containing the
information available than
substance,
for direct
there is
usual.ly far less
exposure
L"1 occupational
set'tings.
As stated earlier, the principal
sources of informa-
tion
on the
uses of a substance are various
trade
publications
and E:naineer:..na
such as
the Chemical ~arketinC' ~eoorter,
Chemical
~, rererence works such as t~e Faith,
Keve s ,
and Clark's
!ndustrial
~emicals and the Condensed Chemical
Dic"tionarv.
Ty?ically,
there is information available on the general function
19
-------
of ~~e substance (e.g., flame retardan~, solvent or aerosel pro-
pellant), and less frequen~ly on its specific applications (suc~
as a flame retardant for children's clothing, a dry-cleaning
solvent, or an aerosol propellant for shaving creams). Although
there is usually some information available on the amount of the
substance consumed annually in its different uses, the level of
detail varies greatly from substance to substance, and even for a
given substance, the level of detail may vary from one use to
another. Measurement data are sometL~es available from the Con-
sumer Product Safety Commission (CPSC) on direct human exposure
to a substance from its use ir. a consumer product. Usually it is
necessary for E?A to rel~ upon a qualita~ive understanding of the
product's use and to consider the substance's chemical and physi-
cal properties to gain seme insight into the likelihood and
potential magnitude of human exposure. As with occupational
exposure, there are occasionally published reports of adverse
human and anL~al health effects associated with the use (or often
misuse) of the substance or a product containing it.
E.
C~neral poculation Ex~osure
As explained earlier in ~"'is attachment, the term "general
population exposure" is used for those circumstances or exposure
involving ~"'e substance's entering ~~e environment from its manu-
facture, processing, distribution in commerce, use, or disposal,
and ultimately reaching humans through its presence in some
environmental medium such as air, water, or soil. Assessment of
this type of exposure is more difficult than that for cons~~er
and occupational exposure because it requires the development of
predictive techniques based on structure/activity relationships,
laboratory data, physical/chemical properties and environmental
transport phenomena. The difficulties occur in determini~g how
laboratory data reflect the fate of the chemical in the environ-
ment and in accounting for how various properties (vapor ~res-
sure, solubility, sorption data, etc.) combine to determine the
most probable transport and transfor:nation 0: t~e c~emical in t:o.e
enviror"..ment.
:'or example,
if a chemical isdischarqed to ~ter,
20
-------
~~e available da~a ~ay i~dicate how ~uch of t~e chemical
volatilizes (evaporates i~to t~e air), how much goes in~o t~e
sediment and how much dissolves in t~e 'Nater. The data may also
oe used, in some cases, to show the approximate quantity which
may be taken up by organisms, such as plants or fish. The
assessment may also determine how persistent ~he chemical is in
the environment. That is, it may be possible to show whether the
chemical is quickly degraded wi~hi~ or dispersed from some
environmental medi~ or location or if there is a potential for
it to accumulate.
Often, only qualitative assessments of environmental
exposure can oe made. These assessments primarily consist of
identification of the probable environmental media '~ere it
appears that the chemical substance might accumulate and a rough
calculation of the range of concentrations that may be found
therein. Monitoring data, when available, may be used for
verifying ~~e validity of these assessments. These data are
generally found in published literature and gover~ent reports.
aasically, the reports indicate that the substance has been
detected i~ samples taken from various media. The locations of
the samples and the media are also identified. In many (out not
all) cases, the concentration at which the substance was detected
is also given. ffowever, rarely does the data encompass all
environmental media of interest.
11ethods for making quantitative assessments of the environ-
mental behavior of chemicals are being developed by ~PA and will
i~volve the use of mathematical models. However, until ~~ese
models are developed and validated, monitoring data, where avail-
able, must oe more heavily relied upon to identify potential
environmental exposure. !n some cases, there may be sufficient
monitoring data to trace the progress of the substance from its
source to the various environmental media in which it is found.
L10st often, however, the availab le ::1oni toring data are not
adequate for this, out rather provide an i~dication of the
presence and/or concentration 0: the substance i~ a particular
21
"
-------
place at a particular ti~e.
~ose data may ~ot ~eflect t~e
impact of changes in discharges or environmental conditions nor
t~e relative contribution of ~ulti?le sources to overall expo-
sure. They may also reflect a condition (especially high or low
concentration) which occurs infrequently, and therefore would ~ot
be an indication of normal enviro~~ental levels. Bowever, keep-
ing the se
limitations in mind, it may sometimes be possible to
"snap-shot" monitoring data together '..,i t."1 what is :.mown
manufacturing, processing, uses, etc., of the substance
use the se
about t~e
and its chemical and physical properties to reasonably describe
the relationship(s) between the source(s) of the substance and
its presence
;n the
various environmental media.
Even in
t~e absence 0: monitoring data showing the presence
of a substance in the environment, it is possible to predict, at
least qualitatively, whether a chemical will reach certain media
by considering the chemical identity and fo~, sources and rates
of expected environmental release, and the 1J'arious chemical and
physical properties that affect both its partitioning among
various media, and its behavior within those media. ~mong the
properties that are particularly useful, are the vapor pressure,
which plays a major role in dete~ining the exchange of a
substance between the atmosphere and other environmental media,
the solubility of the substance in water and factors t;"at might
influence its solubility such as pH and temperature, soil
sorption properties, and the chemical, photoc;"emical, and
biological reactivity of the substance. It is also important to
consider certain properties
that ineicate
t;"e potential
of the
substanoe to be taken up by organisms, to bioaccumulate ane/or
biomagnify in the fooe-chain. ~~owledge of the structure of t;"e
substance, its tendency to form complexes with biological mole-
cules and the relationship bet~een =at and water
sol'.lb ili ty
(usually measured as the octanol!water partition coefficient)
allow reasonable
predictions
0: the fate 0: the chemical to be
made.
22
-------
Once ~~ est;~ate has ~een ~ade
of t:i:e
e~"i=o:"_-nental
l=~;,els
of the substance,
population data along with appropriate
1.i=e-
style information can ~e cembined to obtain an esti~ate of the
potential level of exposure. If it is determined that the
substance under study is discharged
has the poten~ial for accumulating
further, that the local population
source, an estimate can be made of
i:lto a particular river and
in the fish in that river and,
utilizes the fish as a focd
the amount of the chemical to
which the popula~ion is exposed.
There are three ::tain facto.rs
used in assessing this exposure: amount, frequency, and dura-
tion. The envi=or~ental levels help determine the amount of a
substance to which h~ans are exposed. !t must then be deter-
mined how often contact (exposure) with a chemical occurs and hew
long the contact lasts. Duration may be difficult or irnpos~i~le
to measure for general population
exposure.
For occupational and
consumer exposure, it is less difficult. Duration may be ~s long
as a person is at his/her place of emplcyment or the length of
ti~e
it takes for a person to use a product.
~oweve r ,
for a
person consuming a contaminated fish, duration is difficult to
determine. !n a case li~e this, it may be ass~-ned the duration
is conti:luous. ~~ far as frequency is cencer~ed, an estimate may
be made of how often the fish are consumed. !xposure ~ay oceur
as a result of the discharge of the chemical to the air,result-
ing in local populations being exposed through inhalation. !~
this case, exposure occurs continuously over time.
wnen all of the factors described in this section are com-
bined, an estimate ~ay be made of general population exposure.
The estL~ate may be in
the form of t.he
?erson may ingest or inhale over
..'
,-~me ,
quantity of chemical a
the concentration to which
the person may be exposed during a number of incidents, or what-
ever form is appropriate to best describe how exposure occurs.
„hether or not the exposure is likely to be hazardous to humans
will be covered in a health effects assessment which fellows the
exposure assessment in each
suppor~ document.
23
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Re :erences
Lovelace SG. 1979. Safe sampling of liquid process
Chemical Engineering Progress. ~ovember: pp.Sl-57.
st:eams.
?er=y RH (ed), Chilton CH (ed), Kirkpatrick SD (ed). 1969.
C~emical engineers handbook, 4th ed. McGraw-Hill Soak Co. New
York.
Rober~son JM, Toussaint CR, Jorque MA.
entering g=ound water from a land:ill.
1974. Oraanic comcounds
EPA 660/2:74-077. ~
Smith JM.
Soak Co.
.1979. Chemical engineering kinetics.
New York.
McGraw-Hill
24
,
i
,
I
'-
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