PB91-921314
OSWER DIRECTIVE: 9285.6-03
March 25, 1991
RISK ASSESSMENT GUIDANCE FOR SUPERFUND
VOLUME I: HUMAN HEALTH EVALUATION MANUAL
SUPPLEMENTAL GUIDANCE
"STANDARD DEFAULT EXPOSURE FACTORS"
INTERIM FINAL
Office of Emergency and Remedial Response
Toxics Integration Branch
U.S. Environmental Protection Agency
Washington, D.C. 20460
(202)475-9486
REPRODUCED BY
U.S.DEPARTMENT OF COMMERCE
NATIONAL TECHNICAL
INFORMATION SERVICE
SPRINGFIELD, VA 22161
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
MAR 25 1991
OFFICE OF
SOLID WASTE AND EMERGENCY RESPONSE
MEMORANDUM
SUBJECT:
FROM:
OSWER Directive 9285.6-03
Human Health Evaluation Manual, Supplemental Guidance:
"Standard Default Exposure Factors"
Timothy Fields, Jr., Acting Director
Office of Emergency and Remedial Response
Bruce Diamond, Direct _
Office of Waste Programs
nforceinent
TO:
Director, Waste Management Division,
Regions I, IV, V, & VII
Director, Emergency & Remedial Response Division,
Region II
Director, Hazardous Waste Management Division,
Regions III, VI, VIII, & IX
Director, Hazardous Waste Division,
Region X
Purpose
The purpose of this directive is to transmit the Interim
Final Standard Exposure Factors guidance to be used in the
remedial investigation and feasibility study process. This
guidance supplements the Risk Assessment Guidance for Superfund:
Human Health Evaluation Manual, Part A that was issued
October 13, 1989.
Background
An intra-agency workgroup was formed in March 1990 to
address concerns regarding inconsistencies among the exposure
assumptions used in Superfund risk assessments. Its efforts
resulted in a June 29, 1990, draft document entitled "Standard
Exposure Assumptions". The draft was circulated to both
technical and management staff across EPA Regional Offices and
within Headquarters. It was also discussed at two EPA-sponsored
meetings in the Washington, D.C., area. The attached interim
final document reflects the comments received as well as the
results of recent literature reviews addressing inhalation rates,
soil ingestion rates and exposure frequency estimates.
Printed on Recycled Paper
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Objective
This guidance has been developed to reduce unwarranted
variability in the exposure assumptions used by Regional
Superfund staff to characterize exposures to human populations in
the baseline risk assessment.
Implementation
This guidance supplements the Risk Assessment Guidance for
Superfund (RAGS): Human Health Evaluation Manual, Part A. Where
numerical values differ from those presented in Part A, the
factors presented in this guidance supersede those presented in
Part A.
This guidance is being distributed as an additional interim
final guidance in the RAGS series. As new data become available
and the results of EPA-sponsored research projects are finalized,
this guidance will be modified accordingly. We strongly urge
Regional risk assessors to contact the Toxics Integration Branch
of the Office of Emergency and Remedial Response (FTS 475-9486)
with any suggestions for further improvement; as we will begin
updating and consolidating the series of RAGS documents in 1992.
Attachment
cc: Regional Branch Chiefs
Regional Section Chiefs
Regional Toxics Integration Coordinators
Workgroup Members
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* * NOTICE * * * *
The policies set out in this document are not final Agency
action, but are intended solely as guidance. They are not
intended, nor can they be relied upon, to create any rights
enforceable by any party in litigation with the United States.
EPA officials may decide to follow the guidance provided in this
document, or to act at variance with the guidance, based on an
analysis of site-specific circumstances. The Agency also
reserves the right to modify this guidance at any time without
public notice.
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ACKNOWLEDGEMENTS
This guidance was developed by the Toxics Integration Branch
(TIB) of EPA's Office of Emergency and Remedial Response,
Hazardous Site Evaluation Division. Janine Dinan of TIB provided
overall project management and technical coordination in the
later stages of its development under the direction of Bruce
Means, Chief of TIB's Health Effects Program.
TIB would like to acknowledge the efforts of the interagency work
group chaired by Anne Sergeant of EPA's Exposure Assessment Group
in the Office of Health and Environmental Assessment. Workgroup
members, listed below, and Regional staff provided valuable input
regarding the content and scope of the guidance.
Glen Adams, Region IV
Lisa Askari, Office of Solid Waste
Alison Barry, OERR/HSCD
Steve Caldwell, OERR/HSED
David Cooper, OERR/HSCD
Linda Cullen, New Jersey Department of Environmental Protection
Steve Ells, OWPE/CED
Kevin Garrahan, OHEA/EAG
Susan Griffin, OERR/TIB
Gerry Hiatt, Region IX
Russ Kinerson, OHEA/EAG
Jim LaVelle, Region VIII
Mark Mercer, OERR/HSCD
Sue Norton, OHEA/EAG
Andrew Podowski, Region V
John Schaum, OHEA/EAG
Leigh Woodruff, Region X
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TABLE OF CONTENTS
Page
1.0 Introduction
1 . 1 Background
1.2 Present and Future
Land Use Considerations
2.0 Residential 5
2.1 Ingestion of Potable Water 5
2.2 Incidental Ingestion of
Soil and Dust 6
2.3 Inhalation of Contaminated
Air 6
2.4 Consumption of Homegrown
Produce 7
2.5 Subsistence Fishing 8
3.0 Commercial/Industrial 9
3.1 Ingestion of Potable Water 9
3.2 Incidental Ingestion of
Soil and Dust 9
3.3 Inhalation of Contaminated
Air 10
4.0 Agricultural 10
4.1 Farm Family Scenario 10
4.1.1 Consumption of Homegrown
Produce H
4.1.2 Consumption of Animal
Products 11
4.2 Farm Worker 12
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5.0 Recreational 12
5.1 Consumption of Locally
Caught Fish 12
5.2 Additional Recreational
Scenarios 13
6.0 Summary 14
7.0 References 16
Attachment A
Attachment B
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1.0 INTRODUCTION
The Risk Assessment Guidance for Superfund (RAGS) has been
divided into several parts. Part A, of the Human Health
Evaluation Manual (HHEM; U.S. EPA, 1989a), is the guidance for
preparing baseline human health risk assessments at Superfund
sites. Part B, now in draft form, will provide guidance on
calculating risk-based clean-up goals. Part C, still in the
early stages of development, will address the risks associated
with various remedial actions.
The processes outlined in these guidance manuals are a positive
step toward achieving national consistency in evaluating site
risks and setting goals for site clean-up. However, the
potential for inconsistency across Regions and among sites still
remains; both in estimating contaminant concentrations in
environmental media and in describing characteristics and
behaviors of the exposed populations.
Separate guidance on calculating contaminant concentrations is
currently being developed in response to a number of inquiries
from both inside and outside the Agency. The best method for
calculating the reasonable maximum exposure (RME) concentration
for different media has been subject to a variety of
interpretations and is considered an important area where further
guidance is needed.
This supplemental guidance attempts to reduce unwarranted
variability in the exposure assumptions used to characterize
potentially exposed populations in the baseline risk assessment.
This guidance builds on the technical concepts discussed in HHEM
Part A and should be used in conjunction with Part A. However,
where exposure factors differ, values presented in this guidance
supersede those presented in HHEM Part A.
Inconsistencies among exposure assumptions can arise from
different sources: 1) where risk assessors use factors derived
from site-specific data; 2) where assessors must use their best
professional judgement to choose from a range of factors
published in the open literature; and 3) where assessors must
make assumptions (and choose values) based on extremely limited
data. Part A encourages the use of site-specific data so that
risks can be evaluated on a case-by-case basis. This
supplemental guidance has been developed to encourage a
consistent approach to assessing exposures when there is a lack
of site-specific data or consensus on which parameter value to
choose, given a range of possibilities. Accordingly, the
exposure factors presented in this document are generally
considered most appropriate and should be used in baseline risk
assessments unless alternate or site-specific values can be
clearly justified by supporting data.
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Supporting data for many of the parameters presented in this
guidance can be found in the Exposure Factors Handbook (EFH; U.S.
EPA, 1990) . In cases where parameter values are not available in
EFH, this guidance adopts well-quantified or widely-accepted data
from the open literature. Finally, for factors where there is a
great deal of uncertainty, a rationally-derived, conservative
estimate is developed and explained. As new data become
available, this guidance will be modified to reflect them.
These standard factors are intended to be used for calculating
reasonable maximum exposure (RME) estimates for each applicable
scenario at a site. Readers are reminded that the goal of RME is
to combine upper-bound and mid-range exposure factors in the
following equation so that the result represents an exposure
scenario that is both protective and reasonable; not the worst
possible case:
Intake = C x IR x EF X ED
BW X AT
c = Concentration of the chemical in each medium
(conservative estimate of the media average
contacted over the exposure period)
IR = Intake/Contact Rate (upper-bound value)
EF = Exposure Frequency (upper-bound value)
ED = Exposure Duration (upper-bound value)
BW = Body Weight (average value)
AT = Averaging Time (equal to exposure duration for
non-carcinogens and 70 years for carcinogens)
Please note that the Agency is presently evaluating methods for
calculating conservative exposure estimates, such as RME, in
terms of which parameters should be upper-bound or mid-range
values. If warranted, this guidance will be modified
accordingly.
1.1 BACKGROUND
An intra-agency workgroup was formed at the Superfund Health Risk
Assessment meeting in Albuquerque, New Mexico (February 26 -
March 1, 1990) . Its efforts resulted in a June 29, 1990, draft
document entitled "Standard Exposure Assumptions". The draft was
distributed to Superfund Regional Branch Chiefs, and members of
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other programs within the Agency, for their review and comment.
It was also presented and discussed at two EPA/OERR sponsored
meetings. The meetings, facilitated by Clean Sites, Inc.,
brought members of the "Superfund community" and the Agency
together to focus on technical issues in risk assessment.
A final review draft was distributed on December 5, 1990, which
reflected earlier comments received as well as the results of
more recent literature reviews addressing inhalation rates, Soil
ingestion rates and exposure frequency estimates (these being
areas commented on most frequently) .
1.2 PRESENT AND FUTURE LAND USE CONSIDERATIONS
The exposure scenarios, presented in this document, and their
corresponding assumptions have been developed within the context
of the following land use classifications: residential,
commercial/industrial, agricultural or recreational.
Unfortunately, it is not always easy to determine actual land use
or predict future use: local zoning may not adequately describe
land use; and unanticipated or even planned rezoning actions can
be difficult to assess. Also, the definition of these zones can
differ substantially from region to region. Thus, for the
purposes of this document, the following definitions are used:
Residential
Residential exposure scenarios and assumptions should be
used whenever there are or may be occupied residences on or
adjacent to the site. Under this land use, residents are
expected to be in frequent, repeated contact with
contaminated media. The contamination may be on the site
itself or may have migrated from it. The assumptions in
this case account for daily exposure over the long term and
generally result in the highest potential exposures and
risk.
Commercial/Industrial
Under this type of land use, workers are exposed to
contaminants within a commercial area or industrial site.
These scenarios apply to those individuals who work on or
near the site. Under this land use, workers are expected to
be routinely exposed to contaminated media. Exposure may be
lower than that under the residential scenarios, because it
is generally assumed that exposure is limited to 8 hours a
day for 250 days per year.
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Agricultural
These scenarios address exposure to people who live on the
property (i.e., the farm family) and agricultural workers.
Assumptions made for worker exposures under the
commercial/industrial land use may not be applicable to
agricultural workers due to differences in workday length,
seasonal changes in work habits, and whether migrant workers
are employed in the affected area. Finally, the farm family
scenario should be evaluated only if it is known that such
families reside in the area.
Recreational
This land use addresses exposure to people who spend a
limited amount of time at or near a site while playing,
fishing, hunting, hiking, or engaging in other outdoor
activities. This includes what is often described as the
'Trespasser" or "site visitor" scenario. Because not all
sites provide the same opportunities, recreational scenarios
must be developed on a site-specific basis. Frequently, the
community surrounding the site can be an excellent source of
information regarding the current and potential recreational
use of a site. The RPM/risk assessor is encouraged to
consult with local groups to collect this type of
information.
In the case of trespassers, current exposures are likely to
be higher at inactive sites than at active sites because
there is generally little supervision of abandoned
facilities. At most active sites, security patrols and
normal maintenance of barriers such as fences tend to limit
(if not entirely prevent) trespassing. When modeling
potential future exposures in the baseline risk assessment,
however, existing fences should not be considered a
deterrent to future site access.
Recreational exposure should account for hunting and fishing
seasons where appropriate, but should not disregard local
reports of species taken illegally. Other activities should
also be scaled according to the amount of time they could
actually occur; for children and teenagers, the length of
the school year can provide a helpful limit when evaluating
the frequency and duration of certain outdoor exposures.
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2.0 RESIDENTIAL
Scenarios for this land use should be evaluated whenever there
are homes on or near the site, or when residential development is
reasonably expected in the future. In determining the potential
for future residential land use, the RPM should consider:
historical land use; suitability for residential development;
local zoning; and land use trends. Exposure pathways evaluated
under this scenario routinely include, but may not be limited to:
ingestion of potable water; incidental ingestion of soil and
dust; inhalation of contaminated air; and, where appropriate,
consumption of home grown produce.
2 .1 Ingestion of Potable Water
This pathway assumes that adult residents consume 2 liters
of water per day, 350 days per year, for 30 years.
The value of 2 liters per day for drinking water is
currently used by the Office of Water in setting drinking
water standards. It was originally used by the military to
calculate tank truck requirements. In addition, 2 liters
happens to be quite close to the 90th percentile for
drinking water ingestion (U.S. EPA, 1990), and is
comparable to the 8 glasses of water per day historically
recommended by health authorities.
The exposure frequency (EF) of 365 days/year for the
residential setting used in RAGS Part A has been argued both
inside and outside of the Agency as being too conservative
for RME estimates. National travel data were reviewed to
determine if an accurate number of "days spent at home"
could be calculated. Unfortunately, conclusions could not
be drawn from the available literature; as it presents data
on the duration of trips taken for pleasure, but not the
frequency of such trips (OECD, 1989; Goeldner and Duea,
1984; National Travel Survey, 1982-89). However, the
Superfund program is committed to moving away from values
that represent the "worst possible case". Thus, until
better data become available, the common assumption that
workers take two weeks of vacation per year can be used to
support a value of 15 days per year spent away from home
(i.e., 350 days/year spent at home).
In terms of exposure duration (ED), the resident is assumed
to live in the same home for 30 years. In the EFH, this
value is presented as the 90th-percentile for time spent at
one residence. (Please note that in the intake equation,
averaging time (AT) for exposure to non-carcinogenic
compounds is always equal to ED; whereas, for carcinogens a
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70 year AT is still used in order to compare to Agency slope
factors typically based on that value).
2.2 Incidental ingestion of Soil and Dust
The combined soil and dust ingestion rates used in this
document were presented in OSWER Directive 9850.4 (U.S. EPA,
1989b), which specifies 200 mg per day for children aged 1
thru 6 (6 years of exposure) and 100 mg per day for others.
These factors account for ingestion of both outdoor soil and
indoor dust and are believed to represent upper-bound values
for soil and dust ingestion (Calabrese, et al., 1989;
Calabrese, et al., 1990a,b; Davis, et al., 1990; Van Wijnen,
et al., 1990). Presently, there is no widely accepted
method for determining the relative contribution of each
medium (i.e., soil vs. dust) to these daily totals, and the
effect of climatic variations (e.g., snow cover) on these
values has yet to be determined. Thus, a constant, year
round exposure is assumed (i.e., 350 days/year).
Please note that the equation for calculating a 30-year
residential exposure to soil/dust is divided into two parts.
First, a six-year exposure duration is evaluated for young
children which accounts for the period of highest soil
ingestion (200 mg/day) and lowest body weight (15 kg) .
Second, a 24-year exposure duration is assessed for older
children and adults by using a lower soil ingestion rate
(100 mg/day) and an adult body weight (70 kg).
2 . 3 Inhalation of fnntami nal-pri Air
In response to a number of comments, the RME inhalation rate
for adults of 30 m3/day (presented in HHEM Part A) was re-
evaluated. Activity-specific inhalation rates were combined
with time-use/activity level data to derive daily inhalation
rate values (see Attachment A). Our evaluation focused on
the following population subgroups who would be expected to
spend the majority of their time at home: housewives;
service and household workers; retired people; and
unemployed workers (U.S. EPA, 1985). An inhalation rate of
20 m /day was found to represent a reasonable upper-bound
value for adults in these groups. This value was derived by
combining inhalation rates for indoor and outdoor activities
in the residential setting. This rate would be used in
conjunction with ambient air levels measured at or downwind
of the site. Although sampling data are preferred,
procedures described in Hwang and Falco (1986) and
Cowherd, et al. (1985) can be used to estimate volatile and
dust-bound contaminant concentrations, respectively.
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In cases where the residential water supply is contaminated
with volatiles, the assessor needs to consider the potential
for exposure during household water use (e.g., cooking,
laundry, bathing and showering). Using the same time-
use/activity level data described above, a total of
15 m3 /day was found to represent a reasonable upper-bound
inhalation rate for daily, indoor, residential activities.
Methods for modeling volatilization of contaminants in the
household (including the shower) are currently being
developed by J.B. Andelman and U.S. EPA's Exposure
Assessment Group. Assessors should contact the Superfund
Health Risk Assessment Technical Support Center for help
with site-specific evaluations (FTS-684-7300) .
2.4 Consumption of Home Grown Produce
This pathway need not be evaluated for all sites. It may
only be relevant for a small number of compounds (e.g., some
inorganic and pesticides) and should be evaluated when the
assessor has site-specific information to support this as a
pathway of concern for the residential setting.
The EFH presents figures for "typical" consumption of fruit
(140 g/day) and vegetables (200 g/day) with the "reasonable
worst case" proportion of produce that is homegrown as 30
and 40 percent, respectively. This corresponds to values of
42 g/day for consumption of homegrown fruit and 80 g/day for
homegrown vegetables. They are derived from data in Pao, et
al. (1982) and USDA (1980). EFH also provides data on
consumption of specific homegrown fruits and vegetables that
may be more appropriate for site-specific evaluations.
Although sampling data are much preferred, in their absence
plant uptake of certain organic compounds can be estimated
using the procedure described in Briggs, et al. (1982). No
particular procedure is recommended for quantitatively
assessing inorganic uptake at this time; however, the
following table developed by Sauerbeck (1988) provides a
qualitative guide for assessing heavy metal uptake into a
number of plants:
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High
lettuce
spinach
carrot
endive
cress
beet and
beet leaves
Plant Uptake of Heavy Metals
Moderate Low
onion
mustard
potato
radish
corn
cauliflower
asparagus
celery
berries
Very Low
beans
peas
melon
tomatoes
fruit
2 .5 Subsistence Fishing
This pathway is not expected to be relevant for most sites.
In order to add subsistence fishing as a pathway of concern
among the residential scenarios, onsite contamination must
have impacted a water body large enough to produce a
consistent supply of edible fish, and there must be evidence
that area residents regularly fish in this water body (e.g.,
interviews with local anglers). If these criteria are met,
the 95th-percentile for daily fish consumption (132 g/day)
from Pao, et al. (1982) should be used to represent the
ingestion rate for subsistence fishermen. This value was
derived from a 3-day study of people who ate fish, other
than canned, dried, or raw. An example of this consumption
rate is about four 8-ounce servings per week.
This consumption rate can also be used to evaluate exposures
to non-residents who may also use the water body for
subsistence fishing. In this case, the exposure estimate
would not be added to estimates calculated for other
residential pathways, but may be included in the risk
assessment as an exposure pathway for a sensitive sub-
population.
For further information regarding food chain contamination the
assessor is directed to the following documents:
o Methodology for Assessing Health Risks Associated with
Indirect Exposures to Combustor Emissions (PB-90-
187055). Available through NTIS.
o Development of Risk Assessment Methodology for Land
Application and Distribution and Marketing of Municipal
Sludge (EPA/600/6-89/001) . Available from
OHEA/Technical Information at FTS 382-7326.
o Estimating Exposure to 2,3,7,8-TCDD (EPA/600/6-
88/005A). Available from OHEA/Technical Information at
FTS 382-7326.
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3.0 COMMERCIAL/INDUSTRIAL
Occupational scenarios should be evaluated when land use is (or
is expected to be) commercial/industrial. In general, these
scenarios address a 70-kg adult who is at work 5 days a week for
50 weeks per year (250 days total) . The individual is assumed to
work 25 years at the same location (95th-percentile; Bureau of
Labor Statistics, 1990]. This scenario also considers ingestion
of potable water, incidental ingestion of soil and dust, and
inhalation of contaminated air.
Please note that under mixed-use zoning (e.g., apartments above
storefronts), certain pathways described for the residential
setting should also be evaluated.
3.1 Ingestion of Potable Water
Until data become available for this pathway, it will be
assumed that half of an individual's daily water intake
(1 liter out of 2) occurs at work. All water ingested is
assumed to come from the contaminated drinking water source
(i.e., bottled water is not considered). For site-specific-
cases where workers are known to consume considerably more
water (e.g., those who work outdoors in hot weather or in
other high-activity/stress environments), it may be
necessary to adjust this figure.
A lower ingestion rate is used in this pathway so that a
more reasonable exposure estimate may be made for workers
ingesting contaminated water. However, it is important to
remember that remedial actions are often based on returning
the contaminated aquifer to maximum beneficial use; which
generally means achieving levels suitable for residential
use.
3.2 Incidental Ingestion of Soil and Dust
In the occupational setting, incidental ingestion of soil
and dust is highly dependent on the type of work being
performed. Office workers would be expected to contact much
less soil and dust than someone engaged in outdoor work such
as construction or landscaping. Although no studies were
found that specifically measured the amount of soil ingested
by workers in the occupational setting, the one study that
measured adult soil ingestion included subjects that worked
outside of the home (Calabrese, et al., 1990a). Although
the study had a limited number of subjects (n=6) and did not
associate the findings with any particular activity pattern,
it is the only study that did not rely on modeling to
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estimate adult soil ingestion. Thus, the Calabrese, et al.
(1990a) estimate of 50 mg/day is selected as an interim
default for adult ingestion of soil and dust in the
"typical" workplace. Please be aware that this value may
change when the results of ongoing soil ingestion studies
sponsored by EPA's Exposure Assessment Group are finalized
in 1991.
Attachment B presents modeled rates for adult soil ingestion
that should be used to estimate exposures for certain
workplace activities where much greater soil contact is
anticipated, but with limited exposure frequency and/or
duration.
3.3 Inhalation of Contaminated Air
As in the previous discussion regarding inhalation rates
for the residential setting, specific time-use/activity
level data were used to estimate inhalation rates for
various occupational activities. The results indicate that
20 m3per 8-hour workday represents a reasonable upper-
bound inhalation rate for the occupational setting (see
Attachment A). Although analytical data are much preferred,
procedures described in Hwang and Falco (1986) and Cowherd,
et al. (1985) can be used to estimate volatile and dust-
bound contaminant concentrations, respectively.
4 . 0 AGRICULTURAL
These land use scenarios include potential exposures for farm
families living and working on the site, as well as, individuals
who may only be employed as farm workers.
4.1 Farm Family Scenario
This scenario should be evaluated only if it is known or
suspected that there are farm families in the area. The
animal products pathway should not be used for areas zoned
residential, because such regulations generally prohibit the
keeping of livestock. Farm family members are assumed to
have most of the same characteristics as people in the
residential setting; the only difference is that consumption
of homegrown produce will always be evaluated. Thus,
default values for the soil ingestion, drinking water, and
inhalation pathways would be the same as those in the
residential setting.
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4. 1.1 Consumption of Homegrown Produce
The values used in evaluating this pathway are the same
as those presented in Section 2.4. While it is more
likely for farm families to cultivate fruits and
vegetables, it is not necessarily true that they would
be able to grow a sufficient variety to meet all their
dietary needs and tastes. Thus, the consumption rate
default values will be 42 g/day and 80 g/day for fruits
and vegetables, respectively. Again, EFH presents
consumption rates for specific homegrown fruits and
vegetables. The assessor is reminded that the plant
uptake pathway is not relevant for all contaminants and
sampling of fruits and vegetables is highly
recommended. However, in the absence of analytical
data, plant uptake of organic chemicals can be
estimated using the procedure described in Briggs, et
al. (1982). No particular procedure is recommended for
quantitatively assessing inorganic uptake at this time;
however, the table (presented in Section 2.4) developed
by Sauerbeck (1988) provides a qualitative guide for
assessing heavy metal uptake into a number of plants.
4.1.2 Consumption of Animal Products
Animal products should only be addressed if it is known
that local residents produce them for home consumption
or are expected to do so in the future. The best way
to determine which items are produced is by interviews
or consultation with the local County Extension Service
which usually has data on the type and quantity of
local farm products.
EFH provides average ingestion rates for beef and dairy
products and assumes that the farm family produces
75 percent of what it consumes from these categories.
This corresponds to a "reasonable worst case"
consumption rate of 75 g/day for beef and 300 g/day for
dairy products. Although sampling data are much
preferred, in their absence the procedure described in
Travis and Arms (1988) may be used to estimate organic
contaminant concentrations in beef and milk. This
procedure does not provide transfer coefficients for
poultry and eggs. Thus, the latter two pathways can be
evaluated only if site-specific concentrations for
poultry and eggs are available, or if transfer
coefficients can be obtained from the literature.
Additional references addressing potential exposures from
contaminated foods are listed in Section 2.0.
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4.2 Farm Worker
Many farm activities, such as plowing and harrowing, can
generate a great deal of dust. The risk assessor should
consider the effects of observed (or expected) agricultural
practices when using the fugitive dust model suggested under
the residential scenario. Note that soil ingest ion rate may
be similar to the outdoor yardwork scenario discussed in
Attachment B, although it will be necessary to modify the
exposure frequency and duration to account for climate and
length of employment. The local County Extension Service
should be able to provide information on agricultural
practices around a site. In addition, the Biological and
Economic Analysis Division in the Office of Pesticide
Programs maintains a database of the usual planting and
harvesting dates for a number of crops in most U.S. states.
This information may be very helpful for estimating times of
peak exposure for farm workers, and, if needed, can be
obtained through the Superfund Health Risk Assessment
Technical Support Center (FTS 684-7300).
5.0 RECREATIONAL
As stated previously, sites present different opportunities for
recreational activities. The RPM or risk assessor is encouraged
to consult with the local community to determine whether there is
or could be recreational use of the property along with the
likely frequency and duration of any activities.
5.1 Consumption of Locally Caught Fish
This pathway should be evaluated when there is access to a
contaminated water body large enough to produce a consistent
supply of edible-sized fish over the anticipated exposure
period. Although the local authorities should know if the
water body is used for fishing, illegal access (trespassing)
and deliberate disregard of fishing bans should not
necessarily be ruled out; the risk assessor should check for
evidence of these activities. If required, the scenario can
be modified to account for fishing season, type of edible
fish available, consumption habits, etc.
For recreational fishing, the average consumption rate of
54 g/day from Pao, et al. (1982) is used. This value is
derived from a 3-day study of people who ate finfish, other
than canned, dried or raw. An example of this consumption
rate is about two 8-ounce servings per week. Other values
presented in EFH, for consumption of recreationally caught
fish, are from limited studies of fishermen on the west
coast and may not be applicable to catches in other areas.
12
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When evaluating this pathway please consider the possibility
of subsistence fishing. Unlike the residential scenario,
exposure estimates from this pathway would not necessarily
be added to any other exposure estimates (see Section 2.5).
Instead, it would be included as an estimate of exposure for
a sensitive sub-population.
5.2 Additional Recreational Scenarios
A number of commentors requested standard default values for
the following recreational scenarios: hunting, dirtbiking,
swimming and wading. One approach to address exposure
during swimming and wading is presented in HHEM Part A. The
Agency is currently involved in research projects designed
to estimate dermal uptake of contaminants from soil, water
and sediment. Results of these studies will be used to
update the swimming and wading scenarios as well as other
scenarios that rely on estimates of dermal absorption.
Unfortunately, lack of data and problems in estimating
exposure frequencies and durations based on regional
variations in climate have precluded the standardization of
other recreational scenarios at this time. Additional
guidance will be developed as data become available.
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6.0 SUMMARY
This supplemental guidance has been developed to provide a
standard set of default values for use in exposure assessments
when site-specific data are lacking. These standard factors are
intended to be used for calculating reasonable maximum exposure
(RME) levels for each applicable land use scenario at a site.
Supporting data for many of the assumptions can be found in the
Exposure Factors Handbook (EFH; U.S. EPA, 1990). When supporting
information was not available in EFH, well-quantified or widely-
accepted data from the open literature were adopted. Finally,
for factors where there is a great deal of uncertainty, a
rationally conservative estimate was developed and explained.
As new data become available, either for the factors themselves
or for calculating RME, this guidance will be modified
accordingly.
The following table summarizes the exposure pathways that will be
evaluated on a routine basis for each land use, and the current
default values for each exposure parameter in the standard intake
equation presented below (refer to HHEM: Part A, U.S. EPA, 1989a
for a more detailed discussion of each exposure parameter):
Intake = CxlRxEFxED
BW x AT
c = Concentration of the chemical in each medium
IR = Intake/Contact Rate
EF = Exposure Frequency
ED = Exposure Duration
BW = Body Weight
AT = Averaging Time
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SUMMARY OF STANDARD DEFAULT EXPOSURE FACTORS (1)
Land Use
Residential
Commercial/
Industrial
Agricultural
Recreational
Daily
Exposure Pathway (2) Intake Rate
Ingestion of
Potable Water
Ingestion of
Soil and Dust
Inhalation of
Contaminants
Ingestion of
Potable Water
Ingestion of
Soil and Dust
Inhalation of
Contaminants
Ingestion of
Potable Water
Ingestion of
Soil and Dust
Inhalation of
Contaminants
Consumption of
Homegrown
ProcFuce
Consumption of
Locally Caught
Fish
2 liters
200 mg
100 mg
20 cum
15 cum
(child)
(adult)
(total)
(indoor)
1 liter
50
mg
20 cum/workday
2 liters
200 mg
100 mg
20 cum
15 cum
42 g
80 g
54
(child)
(adult)
(total)
(indoor)
(fruit)
(veg. )
g
Exposure
Frequency
350
350
350
250
250
250
350
350
350
350
350
days/year
days/year
days/year
days/year
days/year
days/year
days/year
days/year
days/year
days/year
days/year
Exposure
Duration
30
6
24
30
25
25
25
30
6
24
30
30
30
years
years
years
years
years
years
years
years
years
years
years
years
years
Body Weight
70
15 kg
70 kg
70
70
70
70
70
15 kg
70 kg
70
70
70
kg
(child)
(adult)
kg
kg
kg
kg
kg
(child)
(adult)
kg
kg
kg
(1) - Factors presented are those that should generally be used to assess
exposures associated with a designated land use. Site-specific data may warrant deviation
from these values; however, use of alternate values should be justified and documented
in the risk assessment report.
(2) - Listed pathways may not be relevant for all sites and, other exposure pathways
may need to be evaluated due to site conditions. Additional pathways and applicable default
values are provided in the text of this guidance.
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7.0 REFERENCES
Briggs, G., R. Bromilow, and A. Evans. 1982. Relationship
between lipophilicity and root uptake and translocation of
non-ionized chemicals by barley. Pesticide Science 13:495-
504.
Bureau of Labor Statistics. 1990. Statistical summary: tenure
with current employer as of January 1987. (Transmitted via
facsimile, 7 September 1990)
Calabrese, E.J., Barnes, R., Stanek, E.J., Pastides, H.,
Gilbert, C.E., Veneman, P., Wang, X., Lasztity, A., and P.T.
Kosteck. 1989. How Much Soil Do Young Children Ingest: An
Epidemiologic Study. Reg. Tox. and Pharmac. 10:123-137.
Calabrese, E.J., Stanek, E.J., Gilbert, C.E., and R.M. Barnes.
1990a. Preliminary Adult Soil Ingestion Estimates: Results
of a Pilot Study. Reg. Tox. and Pharmac. 12:88-95.
Calabrese, E.J. 1990b. Personal communication with J. Dinan,
Toxics Integration Branch. EPA/OSWER/OERR. October 24,
1990.
Cowherd, C., Muleski, G., Englehart, P., and D. Gillette. 1985.
Rapid Assessment of Exposure to Particulate Emissions from
Surface Contamination. Prepared by Midwest Research
Institute, Washington, B.C. for EPA/OHEA. EPA-600/8-85-002.
Davis, S., Waller, P., Buschbom, R., Ballou, J. and P. White.
1990. Quantitative Estimates of Soil Ingestion in Normal
Children between the Ages of 2 and 7 Years: Population-
based Estimates Using Aluminum, Silicon and Titanium as Soil
Tracer Elements. Arc. Environ. Health. 45 (2) : 112-122 .
Goeldner, C.R. and K.P. Duea. 1984. Travel Trends in the United
States and Canada. Business Research Division, University
of Colorado at Boulder.
Hawley, J.K. 1985. Assessment of health risk from exposure to
contaminated soil. Risk Analysis 5(4) : 289-302.
Hwang, S.T., and J.W. Falco. 1986. Estimation of Multimedia
Exposures Related to Hazardous Waste Facilities. In: Cohen
(ed.). Pollutants in a Multimedia Environment. New York, NY:
Plenum Publishing Corp. pp. 229-264.
National Travel Survey. 1982-1989. U.S. Travel Data Center,
Washington, D.C.
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OECD. 1989. National and International Tourism Statistics,
1974-1985. Organization for Economic Cooperation and
Development.
Pao, E.M., K.H. Fleming, P.A. Guenther, and S.J. Mickle. 1982.
Foods commonly eaten by individuals: Amounts per day and per
eating occasion. USDA, Human Nutrition Information Service.
Home Economics Report No. 44.
Sauerbach, D. 1988. Transfer of Heavy Metals in Plants. As
published in: Technical Report No. 40, Hazard Assessment of
Chemical Contaminants in Soil (August 1990). European
Chemical Industry Ecology & Toxicology Centre. Brussels,
Belgium. ISSN-0773-8072-40
Travis, C.C. and A.D. Arms. 1988. Bioconcentration of organics
in beef, milk, and vegetation. Environmental Science and
Technology 22(3):271-274.
U.S. Department of Agriculture. 1980. Food and nutrient intakes
of individuals in one day in the United States, Spring 1977.
Nationwide Food Consumption Survey 1977-1978. Preliminary
Report No. 2.
U.S. Environmental Protection Agency. 1990. Exposure Factors
Handbook. Office of Health and Environmental Assessment.
EPA/600/8-89/043, March 1990.
U.S. Environmental Protection Agency. 1989a. Risk Assessment
Guidance for Superfund, Volume I: Human Health Evaluation
Manual. Office of Emergency and Remedial Response.
EPA/540/1-89/002.
U.S. Environmental Protection Agency. 1989b. Interim Final
Guidance for Soil Ingestion. Office of Solid Waste and
Emergency Response. OSWER Directive 9850.4.
U.S. Environmental Protection Agency. 1985. Development of
Statistical Distributions of Ranges of Standard Factors Used
in Exposure Assessments. OHEA-E-161, March 1985.
Van Wijnen, J.H., Clausing, P. and B. Brunekreef. 1990.
Estimated Soil Ingestion by Children. Environmental
Research 51: 147-162.
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ATTACHMENT A
ACTIVITY SPECIFIC INHALATION RATES
Background
The standard default value of 20 m3/day has been used by EPA to
represent an average daily inhalation rate for adults. According
to EFH, this value was developed by the International Commission
on Radiologic Protection (ICRP) to represent a daily inhalation
rate for "reference man" engaged in 16 hours of "light activity"
and 8 hours of "rest". EPA (1985) reported on a similar study
that indicated the average inhalation rate or a man engaged in
the same activities would be closer to 13 m3/day. EFH, in turn,
reiterated the findings of ICRP and EPA (1985) then calculated a
"reasonable worst case" inhalation rate of 30 m3/day. This
reasonable worst case value was used in Part A of the Human
Health Evaluation Manual as the RME inhalation rate for
residential exposures.
Commentors from both inside and outside the Agency expressed
concerns that this value may be too conservative. Many also
added their concern that exposure values calculated using this
inhalation rate would not be comparable to reference doses (RfD)
and cancer potency factors (ql*) values based on an inhalation
rate of 20 m3/day. Thus, the Toxics Integration Branch of
Superfund (TIB) conducted a review of the literature to determine
the validity of using 30 m3/day as the RME inhalation rate for
adults. Members of EPA's Environmental Criteria Assessment
Office-Research Triangle Park (A. Jarabek, 9/20/90) and the
Science Advisory Board (10/26/90) have suggested that inhalation
rates could be calculated using time-use/activity level data
reported in the "Development of Statistical Distributions or
Ranges of Standard Factors Used in Exposure Assessments" (OHEA;
U.S. EPA, 1985) . Thus, TIB used this data to calculate an RME
inhalation rate for both the residential and occupational
settings, as follows.
Methodology
o The time-use/activity level data reported by OHEA
(1985) were analyzed for each occupation subgroup;
o The data were divided into hours spent at home vs.
hours spent at the workplace (lunch hours spent outside
of work and hours spent in transit were excluded);
o The hourly data were subdivided into hours spent
indoors vs. outdoors (to allow for estimating exposures
to volatile contaminants during indoor use of potable
water);
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o The corresponding activity level was assigned to each
hour and the total number of hours spent at each
activity level was calculated;
o For time spent inside the home, 8 hours per day were
assumed to be spent at rest; and
o The total number of hours spent at each activity level
was multiplied by average inhalation rates reported in
the EFH. Note: average values were used since only
minimum, maximum and average values were reported. The
use of maximum values would have to be considered
"worst case". Values for average adults were applied
to all but the housewife data (where average rates for
women were applied) .
The results showed that the highest weekly inhalation rate was
18.3 m3 /day for the residential setting and 18 m3/day for the
workplace. These values represent the highest among the weekly
averages and were derived from coupling "worst case" activity
patterns with "average" adult inhalation rates. It was concluded
from these data that 30m3/day may in fact be too conservative
and that 20 m3/day would be more representative of a reasonably
conservative inhalation rate for total (i.e., indoor plus
outdoor) exposures at home and in the workplace.
RAGS Part B will specifically model exposure to volatile organics
via indoor use of potable water. Using the method described
previously, it was determined that 15 m3/day would represent a
reasonably conservative inhalation rate for indoor residential
exposures.
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ATTACHMENT B
ESTIMATING ADULT SOIL INGESTION
IN THE COMMERCIAL/INDUSTRIAL SETTING
Most of the available soil ingestion studies focus on children in
the residential setting; however, two studies were found that
address adult soil ingestion that also have application to the
commercial/industrial setting (Hawley, 1985; Calabrese, et al.,
1990) .
Hawley (1985) used a number of assumptions for contact rates and
body surface area to estimate the amount of soil and dust adults
may ingest during a variety of residential activities. For
indoor exposures, Hawley estimated levels based on contact with
soil/dust in two different household areas, as follows:
0.5 mg/day for daily exposure in the "living space"; and 110
mg/day for cleaning dusty areas such as attics or basements. For
outdoor exposures, Hawley estimated a soil ingestion rate during
yardwork of 480 mg/day. The assumptions used to model exposures
in the residential setting may also be applied to similar
situations in the workplace. The amount of soil and dust adults
contact in their houses may be similar to the amount an office or
indoor maintenance worker would be expected to contact.
Likewise, the amount of soil contacted by someone engaged in
construction or landscaping may be more analogous to a resident
doing outdoor yardwork.
Calabrese, et al. (1990) conducted a pilot study that measured
adult soil ingestion at 50 mg/day. Although the study has
several drawbacks (e.g., a limited number of participants and no
information on the participants daily work activities), it
included subjects that worked outside the home. it is also
interesting to note that this measured value falls within the
range Hawley (1985) estimated for adult soil ingestion during
indoor activities.
From these studies, 50 mg/day was chosen as the standard default
value for adult soil ingestion in the workplace. It was chosen
primarily because it is a measured value but also because it
falls within the range of modeled values representing two widely
different indoor exposure scenarios. The 50 mg/day value is to
be used in conjunction with an exposure frequency of 250
days/year and an exposure duration of 25 years. For certain
outdoor activities in the commercial/industrial setting (e.g.,
construction or landscaping) , a soil ingestion rate of 480 mg/day
may be used; however, this type of work is usually short-term and
is often dictated by the weather. Thus, exposure frequency would
generally be less than one year and exposure duration would vary
according to site-specific construction/maintenance plans.
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o The corresponding activity-level was assigned to each
hour and the total number of hours spent at each
activity level was calculated;
o For time spent inside the home, 8 hours per day were
assumed to be spent at rest; and
o The total number of hours spent at each activity level
was multiplied by average inhalation rates reported in
the EFH. Note: average values were used since only
minimum, maximum and average values were reported. The
use of maximum values would have to be considered
"worst case". Values for average adults were applied
to all but the housewife data (where average rates for
women were applied).
The results showed that the highest weekly inhalation rate was
18.3 m3/day for the residential setting and 18 m3/day for the
workplace. These values represent the highest among the weekly
averages and were derived from coupling "worst case" activity
patterns with "average" adult inhalation rates. It was concluded
from these data that 30m3/day may in fact be too conservative
and that 20 m3/day would be more representative of a reasonably
conservative inhalation rate for total (i.e., indoor plus
outdoor) exposures at home and in the workplace.
RAGS Part B will specifically model exposure to volatile organics
via indoor use of potable water. Using^the method described
previously, it was determined that 15 m3/day would represent a
reasonably conservative inhalation rate for indoor residential
exposures.
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