PBS6-232774
DEVELOPMENT OF ADVISORY LEVELS FOR POLYCHLORIMATED
3IPHENYLS (PC3S) CLEANUP
U.S. Environmental Protection Agency
Washington, DC
May 86
U.S. DEPARTMENT OF COMMERCE
National Technical Information Service
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P5do-<: 3277U
EPA/600/6-86/002
May 1986
DEVELOPMENT OF ADVISORY LEVELS
FOR POLYCHLORINATED BIPHENYLS (PCBs) CLEANUP
Exposure Assessment Group
Office of Health and Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Washington, D.C.
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TECHNICAL REPORT DATA
(Please read Inuruciions on the revene before completing)
1 REPORT NO
EPA/600/6-86/002
3 RECIPIENT'S ACCESSION NO
4 TITLE AND SUBTITLE
Development of Advisory Levels for
Polychlorinated Biphenyls (PCBs) Cleanup
5. REPORT DATE
Mav 1986
6. PERFORMING ORGANIZATION CODE
EPA/600/21
7 AUTHOR(S)
Seong T. Hwang, James W. Falco, Charles H. Nauman
8. PERFORMING ORGANIZATION REPORT NO
9 PERFORMING ORGANIZATION NAME AND AOORESS
10. PROGRAM ELEMENT NO
Office of Health and Environmental Assessment (RD-689)
Exposure Assessment Group
U.S. Environmental Protection Agency
Washington, D.C. 20460
II. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND AOORESS
13. TYPE OF REPORT AND PERIOD COVERED
same as #9
14. SPONSORING AGENCY CODE
EPA/600/21
15. SUPPLEMENTARY NOTES
16 ABSTRACT
This document presents background information used in developing advisory level;
of PCBs in soil estimated to be permissible in protecting public health. The results
of exposure assessment and health effects studies are combined to arrive at the
permissible levels of PCBs. Health effects studies conducted using animals for the
duration of 10-30 days are used to determine the 10-day advisory levels for PCB clean-
.up. The long-term advisory levels are based on the carcinogenic risk evaluations.
Exposure pathways considered in estimating the 10-day and long-term average dail
intakes include soil ingestion, inhalation, dermal contact, ingestion of contaminatec
food, and ingestion of water. Exposure to drinking water contaminants is presumed to
occur independently of other pathways, because water could come from a clean public
water system. The exposure pathways most pertinent to the evaluation of permissible
PCB levels in soil are soil ingestion, vapor inhalation, and contaminant contact with
human skin.
The currently available modeling techniques considered most appropriate within
the constraints of availability of input data are used to estimate exposures. PCB
advisory levels are presented as ranges of values to reflect the difference in soil-ai
partition coefficients depending on soil type, different types of commercial Aroclors,
and variations in the soil ingestion rate.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
13 DISTRIBUTION STATEMENT
Release to the public
19 SECURITY CLASS (This Report/
Unclassified
21
NO OF PAGES
216
20 SECURITY CLASS (Thitpage/
Unclassified
22 PRICE
EPA Form 222O-I (»-73)
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DISCLAIMER
This document has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
publication. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
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CONTENTS
Tables v
Foreword vii
Preface ix
Abstract x
Authors and Reviewers xl
1. Executive Summary 1-1
2. Introduction 2-1
3. Chemical Compositions 3-1
4. Production 4-1
5. Uses 5-1
6. Disposal 6-1
7. Chemical and Physical Properties 7-1
8. Environmental Distribution 8-1
9. Environmental Fate and Transport 9-1
10. Toxicology 10-1
11. Existing Standards and Guidelines 11-1
12. Exposure Assessment Methodology 12-1
12.1 Estimation of Exposures for Contaminated Sites 12-3
12.2 Determination of Permissible Pollutant Level in Soil . . 12-10
12.3 Incorporation of Time-Varying Parameters 12-11
12.4 PCB Advisory Evaluations 12-14
13. Water Quality Limits 13-1
14. Leachate Contamination of Groundwater 14-1
15. Soil Ingestion Pathway 15-1
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CONTENTS (continued)
16. Inhalation Pathway 16-1
16.1. Intake by Air Exposure Route 16-1
16.2. Emission Evaluation Scenarios 16-2
16.3. Air Dispersion Modeling 16-8
16.4. Air Exposure Evaluation 16-10
17. Dermal Contact Pathway 17-1
18. Comparison of Exposures by Soil Ingestion, Inhalation, and
Dermal Contact 18-1
19. Results 19-1
19.1 Derivation of Permissible Soil Contamination 19-1
19.2 Summary of Results 19-4
20. Limitations of Application 20-1
21. References 21-1
APPENDICES
A. Models Used in Air Release Rate Calculations A-l
B. Example Emission Rate Calculations for Four Studied
Scenarios B-l
C. Summary of Computer Runs for Each Aroclor and at Each
Value of Soil-Air Partition Coefficients C-l
J). Health Advisories for PCBs in Soil
(Prepared by M.L. Dourson, Environmental Criteria
and Assessment Office, Cincinnati, OH) D-l
IV
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TABLES
1. Permissible PCB soil contamination levels (uncovered
surface contamination) 1-6
2. Permissible PCB soil contamination levels (25-cm-thick
clean cover) 1-7
3. Approximate composition of Aroclors 3-3
4. Chemical and physical properties of PCBs 7-3
5. Solubility of chlorobiphenyls in water 7-6
6. PCB monitoring in ambient air by NYSDEC 9-2
7. Existing PCB standards and guidelines 11-3
8. Maximum lifetime risk for ingesting soil contamination
at different PCB levels 15-1
9. Maximum daily PCB intake by ingestion of soil
at various PCB concentrations 15-2
10. Comparison of PCB intakes by Ingestion and inhalation
routes for acute effects 16-3
11. Comparison of PCB intakes by ingestion and inhalation
routes for carcinogenic effects 16-4
12. Concentration of PCBs in soil at saturation vapor
pressure based on Kj = 1,000 cm3/g 16-7
13. PCB emission rates from 1 yg/g PCB soil at different
control levels 16-7
14. Values of constants for standard deviation expression as
a function of downwind distance and stability condition .... 16-10
15. Ambient PCB concentrations at different locations
(PCB in soil = 1 yg/g, PCB-1254) 16-11
16. Comparison of intakes by various exposure routes 18-1
17. Evaluation conditions for each Aroclor 19-5
18. Low and high values of air-soil partition coefficient used
in the evaluation 19-6
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19. Permissible PCB-1242 soil contamination levels (uncovered
surface contamination) 19-7
20. Permissible PCB-1248 soil contamination levels (uncovered
surface contamination) 19-8
21. Permissible PCB-1254 soil contamination levels (uncovered
surface contamination) 19-9
22. Permissible PCB-1260 soil contamination levels (uncovered
surface contamination) 19-10
23. Permissible PCB-1242 soil contamination levels (25-cm-thick
clean soil cover) 19-11
24. Permissible PCB-1248 soil contamination levels (25-cm-thick
clean soil cover) 19-12
25. Permissible PCB-1254 soil contamination levels (25-cm-thick
clean soil cover) 19-13
26. Permissible PCB-1260 soil contamination levels (25-cm-thick
clean soil cover) 19-14
VI
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FOREWORD
The Exposure Assessment Group (EAG) of EPA's Office of Research and
Development has three main functions: 1) to conduct exposure assessments; 2)
to review assessments and related documents; and 3) to develop guidelines for
Agency exposure assessments. The activities under each of these functions are
supported by and respond to the needs of the various EPA program offices. In
relation to the third function, EAG sponsors projects aimed at developing or
refining techniques used in exposure assessments, and at applying these techniques
to develop health-based advisory levels for contaminant cleanup. This document
is one of these projects and was done for the Office of Solid Waste and Emergency
Response.
Polychlorinated biphenyls (PCBs), commercially known as Aroclors, consist
of mixtures of chlorinated biphenyl compounds. Many sites contaminated by PCBs
remain contaminated because of PCB persistence in the environment. Although
commercial PCB production has been banned by the Toxic Substances Control Act,
continued use in previously existing commercial equipment can result in spills
which require cleanup. EPA has become increasingly involved in the discovery,
assessment, and cleanup of these sites.
The purpose of this document is to provide advisory levels for PCB cleanup,
and to describe the detailed technical and scientific rationale and methods
used in developing these advisory levels for PCBs in contaminated soil. This
project required development of exposure and risk assesment methodology related
to hazardous waste and spill sites, and analyses of health effects data. The
advisory levels and the assessment methodology thus developed will help EPA set
VII
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priorities in PCB spill and cleanup management, and address other PCB contaminant
problems.
Michael Callahan, Director
Exposure Assessment Group
vm
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PREFACE
The Exposure Assessment Group of the Office of Health and Environmental
Assessment (OHEA) has prepared this development document for advisory
levels for polychlorinated biphenyls (PCBs) cleanup at the request of the
Office of Emergency and Remedial Response. This document summarizes the
procedures concerning multimedia exposure assessments for PCB-contaminated
sites, and literature information on chemical and physical properties and health
effects pertinent to evaluation of exposures to PCBs. The purpose of this
document is to serve as a technical and scientific basis for developing health-
based advisory levels for PCBs in soil at spill or cleanup sites. The literature
search supporting this document is current to May 1986.
IX
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ABSTRACT
This document presents background information used in developing advisory
levels of PCBs in soil estimated to be permissible in protecting public health.
The results of exposure assessment and health effects studies are combined to
arrive at the permissible levels of PCBs. Health effects studies conducted
using animals for the duration of 10-30 days are used to determine the 10-day
advisory levels for PCB cleanup. The long-term advisory levels are based on
the carcinogenic risk evaluations.
Exposure pathways considered in estimating the 10-day and long-term average
daily intakes include soil ingestion, inhalation, dermal contact, ingestion
of contaminated food, and ingestion of water. Exposure to drinking water con-
taminants is presumed to occur independently of other pathways, because water
could come from a clean public water system. The exposure pathways most per-
tinent to the evaluation of permissible PCB levels in soil are soil ingestion,
vapor inhalation, and contaminant contact with human skin.
The currently available modeling techniques considered most appropriate
within the constraints of availability of input data are used to estimate
exposures. PCBs advisory levels are presented as ranges of values to reflect
the difference in soil-air partition coefficients depending on soil type,
different types of commercial Aroclors, and variations in the soil ingestion
rate.
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AUTHORS AND REVIEWERS
The Exposure Assessment Group of the Office of Health and Environmental
Assessment was responsible for preparing this document.
AUTHORS
Seong T. Hwang
Exposure Assessment Group
Office of Health and Environmental Assessment
U.S. Environmental Protection Agency
James W. Falco
Office of Environmental Processes and Effects Research
U.S. Environmental Protection Agency
Charles H. Nauman
Exposure Assessment Group
Office of Health and Environmental Assessment
U.S. Environmental Protection Agency
REVIEWERS
The following individuals provided review comments and criticisms
during several peer-review processes to which this document was subjected.
Don R. Clay, Director
Office of Toxic Substances
•U.S. Environmental Protection Agency
Joseph A. Cotruvo, Director
Criteria and Standards Division
Office of Drinking Water
U.S. Environmental Protection Agency
Yoram Cohen
Department of Chemical Engineering
University of California, Los Angeles
Los Angeles, California
Barbara Davis
Office of Waste Programs Enforcement
U.S. Environmental Protection Agency
XI
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Karen Hammerstrom
Exposure Evaluation Division
Office of Toxic Substances
U.S. Environmental Protection Agency
Krishan Khana
Health Effects Branch
Office of Drinking Water
U.S. Environmental Protection Agency
Russell Kinerson
Office of Toxic Substances
U.S. Environmental Protection Agency
William Marcus
Office of Drinking Water
U.S. Environmental Protection Agency
Robert E. McGaughy
Carcinogen Assessment Group
Office of Health and Environmental Assessment
U.S. Environmental Protection Agency
Mary Lund Mortensen
Agency for Toxic Substances and Disease Registry
Atlanta, Georgia
Debdas Mukerjee
Environmental Criteria and Assessment Office—Cincinnati
U.S. Environmental Protection Agency
Judith A. Nelson, Director
Regulatory Coordination Team
Office of Pesticides and Toxic Substances
U.S. Environmental Protection Agency
Arnett No Id
Office of Toxic Substances
U.S. Environmental Protection Agency
Edward V. Ohanian
Health Effects Branch
Office of Drinking Water
U.S. Environmental Protection Agency
Suresh Rao
Soils Department
University of Florida
Gainesville, Florida
xn
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Danny Reible
Department of Chemical Engineering
Louisiana State University
Baton Rouge, Louisiana
Charles Ris
Carcinogen Assessment Group
Office of Health and Environmental Assessment
U.S. Environmental Protection Agency
Jerry F. Stara
Environmental Criteria and Assessment Office--Cincinnati
Office of Health and Environmental Assessment
U.S. Environmental Protection Agency
Louis Thibodeaux
Hazardous Waste Research Center
Louisiana State University
Baton Rouge, Louisiana
Edwin F. Tinsworth, Deputy Director
Office of Toxic Substances
U.S. Environmental Protection Agency
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1. EXECUTIVE SUMMARY
This report has been prepared in response to a memorandum dated April 9,
1985, from the Office of Emergency and Remedial Response (OERR), requesting
that the Office of Health and Environmental Assessment (OHEA) develop advi-
sory levels for polychlorinated biphenyls (PCBs) which can be used as guide-
lines for initiating removal action for sites contaminated with PCBs. Inter-
ested offices within EPA, including OERR, have advised OHEA that these advisory
levels for PCBs cleanup should be developed based on considerations of public
health protection from short-term and long-term exposures. The advisories
presented in this report include permissible levels of PCBs in soil correspond-
ing to 10-day and lifetime acceptable intakes.
Exposure routes considered in developing these advisory levels include
drinking water, ingestion of PCB-contaminated soil by children and adults, and
inhalation of ambient air contaminated with PCBs. Other exposure routes, such
as dermal exposure, food intake, and ingestion of fish which have bioaccumula-
ted PCBs, are considered in relation to their importance and their relevance to
the present document. In view of the high bioaccumulation factor for PCBs, the
consideration of bioaccumulation is important in setting PCB levels in surface
water in which aquatic animals live. If one of these routes is a controlling
factor in relation to the exposure route or human intake considered, the advi-
sories need to be reevaluated.
Commercial-grade PCBs marketed as Aroclors in the United States are mix-
tures of many chlorinated biphenyl compounds in various proportions. Each
PCB compound may exhibit its own toxicological characteristics and physical and
chemical properties. This fact complicates the exposure analysis in deriving
the allowable concentrations in drinking water and soil. It is conceivable
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that chemical and physical properties reported in the literature for each Aro-
clor designation represent an average property for the mixture. To define the
variability of safe levels for contamination by different Aroclor designations,
exposure analyses have been performed for several Aroclors: Aroclor 1242,
1248, 1254, and 1260. The steps used in developing the advisories include: (1)
the evaluation of toxicological effect studies, (2) exposure analysis for PCB
intake from drinking water, soil ingestion, air inhalation, and dermal contact,
and (3) risk assessment combining the toxicology studies and exposure analysis.
Ten-day noncancer health advisories are based on the short-term acceptable
intake (AI) derived from studies of animals treated with Aroclor-1254 for no
more than 30 days to examine noncarcinogenic effects. This AI value, which
forms the basis for establishing permissible levels of PCBs in soil, is 0.1 and
0.7 mg/day for a 10-kg child and a 70-kg adult, respectively. The permissible
PCB concentrations for each carcinogenic risk level are based on the potency
factor of 4 (mg/kg-day)'l rounded off from two independent evaluations based on
an Aroclor-1260 study.
It is likely that not all of the PCBs ingested or inhaled by humans are
absorbed. Proper calculations of absorption rate and hence exposure should be
based on realistic pharmacokinetics-type models to determine intake. Lack of
experimental data with which to estimate the parameters needed in the pharmaco-
kinetics models has prevented their applications to the analysis for PCB absorp-
tions through human exchange boundaries. Future work should consider these
models. Although most animal studies (in rats and mice) on the extent of
absorption in the gastrointestinal tract show absorption in excess of 90%,
there are two experiments on monkeys reporting less than 88% absorption in one
case and less than 13% and 40% absorption for a specific congener in another
case, based on the analysis of feces and urine. Vehicles used in administering
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PCBs were not specified. It is likely that the high adsorption characteristics
of PCBs on soil could retard the absorption rate in the human intestinal tract.
In the risk analysis performed in the present study, the absorption rate for
humans after ingestion of RGB-contaminated soil is considered to be 30%.
Absorption from dermal exposure has been reported to be as significant as
from other routes of exposure, but little information is available for the
quantitative evaluation of dermal absorption rates. Five percent dermal ab-
sorption is assumed for soil contaminants in contact with human skin. The
dermal absorption rate of contaminants present on soil is presumed to be less
than that for contaminants spilled on skin in pure form. Inhalation studies
using PCB aerosols show that the absorption of PCBs from inhalation exposure
readily occurs. In the present analysis, an absorption factor of 50% is
assumed for absorption of PCB vapors after inhalation into human lungs.
The circumstances under which human exposure occurs are divided into three
classes depending on population distribution: (1) Exposure occurs on-site.
This can be further subdivided into: (a) sites which are readily accessible
to children, and, hence, the soil from which will be subject to ingestion, der-
mal contact, and inhalation, and (b) sites for which there is no possibility of
soil ingestion, and, hence, exposure is only through inhalation; (2) sites
which no population is assumed to enter within a radius of 0.1 km from the
site; and (3) sites which no population is assumed to enter within a radius of
1 km from the site.
The soil ingestion rates used for Class (l)(a) evaluations are 3 and 0.6
g/day. The former is a value based on data from a study of an adult person
with pica, while the latter represents a long-term average value for soil
ingestion. If sites are not accessible to populations at distances of 0.1
km or 1 km from the site, as in Classes (2) and (3) above, it is assumed that
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no ingestion of contaminated soil occurs and the exposure route is that of
inhalation.
The emission rate of volatilized PCBs can be considerably reduced by
covering the contaminated soil by low-porosity uncontaminated soil or clay
material. The reduction in the emission rate will result in a decrease in
ambient air concentrations of PCBs by the action of blowing winds. When PCB-
contaminated material is directly exposed to the atmosphere, the PCB levels in
soil required to maintain the same level of exposure will be less than those
expected when the PCB-contaminated material is covered with low-permeability
material of appropriate thickness. The cover would also serve as a deterrent
to soil ingestion and direct dermal contact.
The depletion of PCBs from soil caused by volatilization is accounted for
in the exposure analysis by solving a partial differential equation simulating
PCB vapor diffusion through the soil air-phase pores, and the distribution of
PCBs between air and soil phases. Boundary conditions assume that the air-phase
resistance is relatively small compared to the diffusional resistance in the
soil air-phase pores. The available experimental data reasonably follow the
time-emission rate relationship predicted from the models based on this assump-
tion. Since the depletion rate varies over time, it is averaged over the
exposure period. Depletion averaged over a period of time should lead to a
lesser inhalation exposure than that based on the model assuming that depletion
does not occur.
The worst-case emissions would occur when the contaminated soil is initial-
ly exposed to the atmosphere and the soil is contaminated up to the conditions
exhibiting saturation vapor pressure. A constant emission rate can be assumed
if the vapor-phase concentration maintains a constant value at the surface of
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soil contamination for time-varying emission rates. Calculations corresponding
to Classes (1), (2), and (3) for exposure possibilities witn surface contamina-
tion are repeated at an assumed 25-cm thickness of a soil cover initially free
from PCB contamination. Among many factors affecting the emission rate (in-
cluding vapor pressure, soil-air partition coefficient, Henry's Law constant,
etc.), the value of the soil-air partition coefficient shows the most wide-
ranging variation, because of the variation of the experimental soil-water
partition coefficient available in the literature for soil textures ranging
from 40 to 1,000 cm3/g.
The method for determining the permissible PCB levels in soil,.which com-
bines the routes of soil ingestion, inhalation, and dermal exposure, has been
computerized to avoid the necessity for hand calculations.
The results of these computer calculations are summarized in Tables 1 and
2, which have been prepared using different combinations of the following
variables:
(1) Surface contamination representing a situation where the contaminated
soil surface has been left uncovered after removal action.
(2) 25-cm (10-inch) clean cover applied, representing a situation in
which clean soil material is used on top of the contaminated soil
surface.
(3) Two different soil ingestion rates (3 and 0.6 g/day) for Class
(l)(a), corresponding to sites accessible to children.
(4) Different AI levels (short-term AI, and AIs at different cancer risk
levels).
(5) Four Aroclors (Aroclor 1242, 1248, 1254, and 1260).
(6) Two selected values of the soil-air partition coefficient, repre-
senting the high and low values.
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en
TABLE 1. PERMISSIBLE PCB SOIL CONTAMINATION LEVELS
(UNCOVERED SURFACE CONTAMINATION)
Permissible levels (iig
Noncancer short-term8
acceptable Intake (uq/day)b
Location and
route of human 100 700
exposure for child for adult
On the contaminated site
- Soil IngestlonC. 25-100' 510-730
Inhalation6
- Soil Ingestlond, 42-420 2100-3000
Inhalation6
- Inhalation only6 47-vs9 vs
0.1 km from vs vs
PCB/g soil) corresponding to
Cancer risk specific doses (ug/day)
0.00175
(ID'7 risk)
0.008-0.01
0.01-0.06
0.01-0.2
2.0-220
0.0175
(10-6 risk)
.08-0.1
0.1-0.6
0.1-2.0
90-2. ZxlO4
0.175
(10-5 risk)
0.8-2
1-6
1-20
7.7x!03-vs
V5
(10-* risk)
8-17
35-61
77-470
8.7x!05-vs
contaminated site
- Inhalation only6
1 km from vs9 vs 220-1.3xl03 2.2xl04-1.3xl05 vs vs
contaminated site
- Inhalation only6
aShort-term 3 10-day Intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
cCMIdren ages 1-5, with pica (consuming 3 g soil/day).
dCM1dren ages 1-5, without pica (consuming 0.6 g soil/day).
6lnhalat1on rates are assumed to be 20 m'/da
._ __ __ ..3/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m'/day as a result of 182 days' exposure per year.
^Ranges result In each case because 1) four PCBs (1242, 1248, 1254, 1260) are considered, each with a different
vapor pressure, and 2) high and low values for soil-air partition coefficient are used In the calculations.
9vs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquids for the limit.
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TABLE 2. PERMISSIBLE PCB SOIL CONTAMINATION LEVELS
(25-cm-THICK CLEAN COVER)
Permissible levels (iig PCB/g soil) corresponding to
Noncancer short-term3
acceptable Intake (ug/day)b
Location and
route of human
exposure
On the contaminated site
- Soil IngestlonC,
Inhalation6
- Soil Ingest lond,
- Inhalation6
- Inhalation only6
0.1 km from
100 700
for child for adult
110-200? 800-1400
450-vs9 3100-vs
vs vs
vs vs
Cancer risk specific doses dig/day)
0.00175
(10-7 risk)
0.01-0.2
0.02-0.6
0.02-1.0
1-vs
0.0175
(10-6 risk)
0.1-2.0
0.2-6.0
0.2-vs
620- vs
0.175 1,75
(10-5 risk) (10-4 risk)
1-17 22-vs
1.0-48 93-vs
2.0-vs 770-vs
vs vs
contaminated site
- Inhalation only6
1 km from
contaminated site
- Inhalation only6
vs
vs
vs
vs
vs
vs
aShort-term a 10-day Intake,
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
cChildren ages 1-5. with pica (consuming 3 g soil/day).
dCh11dren ages 1-5. without pica (consuming 0.6 g soil/day).
elnhalatton rates are assumed to be 20 m3/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m'/day as a result of 182 days' exposure per year.
^Ranges result In each case because 1) four PCBs (1242, 1248, 1254. 1260) are considered, each with a different
vapor pressure, and 2) high and low values for soil-air partition coefficient are used In the calculations.
9vs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquids for the limit.
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(7) Exposures for 10 days after cleanup or spill of contaminants for
short-term advisories.
Table 1 shows the range of values for permissible PCB concentrations in
soil when the soil is contaminated up to the surface in contact with the atmo-
sphere and is left uncovered. Table 2 represents the case where the contami-
nated soil left at the site, or after remediation, is covered with a 25-cm
(10-inch) clean soil layer. The ranges in both tables result from the use of
four Aroclors and the use of high and low values for the soil-air partition
coefficient. Other factors reflected in the ranges are differences in vapor
pressures and Henry's Law constants for each Aroclor. The permissible PCBs
levels in soil specific to each combination of the scenarios are compiled in
Appendix C, as obtained from computer simulations.
The symbol "vs" in Tables 1 and 2 indicates that no upper-bound limit for
PCB concentrations in soil can be derived from the exposure evaluation, because
the PCB concentration in soil is above the vapor saturation concentration.
There are two reasons for such a result. First, the emission rate cannot
exceed the upper-bound value which can be expected when the air-phase concen-
tration of PCBs at the contaminated soil surface is maintained at the vapor
saturation point. The concentration at the vapor saturation point corresponds
to the vapor pressure concentration. Second, when the cover is applied, not
only is the emission rate retarded, but also the concentration of PCBs in soil
being ingested is controlled by the amount of PCBs adsorbed on soil in equili-
brium with the air phase being emitted. Therefore, the concentration of PCBs
in the initially clean soil material cannot exceed the concentration in equi-
librium with saturated vapor.
In actuality, the "no upper limit," or the level above vapor saturation,
designated by vs, should be interpreted with great care. The assumptions used
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in the exposure evaluation are critical. They include but are not limited
to: (1) no soaking of clean cover by liquid PCBs for the thickness of 25 cm;
(2) no disturbance of cover material by construction activities or children
digging the ground; (3) no exposure to initial spills when 25 cm of clean cover
(Table 2) is assumed; (4) no population enters the area within the respective
radius of distances from the site; and (5) the cover material is at least
equivalent to soil material.
From a practical point of view, Assumption 1 is tantamount to requiring
the presence of no free liquids in the soil, which may otherwise result in the
phenomenon of "wieking." Since the ranges shown in Tables 1 and 2 are depend-
ent upon the type of Aroclors and the values of the soil-air partition coeffici-
ent, site-specific or Aroclor-specific information should be used to establish
an appropriate level of PCBs for that particular condition. The methodology
for performing site-specific exposure evaluations is presented. Computer
outputs for the selected Aroclors under the ranges and conditions of common
environmental concern are presented in Appendix C, and can easily be used to
find the permissible concentrations in soil suitable to particular situations.
Table 1, for example, can be interpreted as follows:
(1) When the site is amenable to access by children with possibilities of
ingesting the contaminated soil exposed to the atmosphere, and when exposure
occuring to the children by inhalation and dermal contact is accounted for, the
permissible PCS levels in soil should range from 25 to 100 ug/g and 42 to
420 ug/g for prevention of noncancer effects from 10-day exposure for a child
with an average weight of 1U kg ingesting soil at the rates of 3 and 0.6 g/day,
respectively. For cancer effects, permissible levels in soil for a lifetime
exposure to PCBs resulting from ingestion of and dermal contact with contaminated
soil and inhalation of contaminated air should range from 0.08 to 0.1 u9/9
1-9
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and 0.1 to 0.6 pg/g, corresponding to an upper-bound risk estimate of 10"6 at
assumed soil ingestion rates of 3 and 0.6 g/day, respectively. The specific
level will depend on the types of Aroclor present, the likely ingestion rate,
and the extent of soil-air partitioning. For sites in which there is no possi-
bility of soil ingestion, PCB levels in soil, based on the inhalation route
only, should range from 47 u9/9 to no limit value for a 10-day exposure for a
child with an average weight of 10 kg, and correspond to no limit value for an
adult with an average weight of 70 kg. The permissible levels of PCBs in soil,
based on the inhalation pathway only, range from 0.1 to 2 ug/g, corresponding
to a lifetime AI at a risk factor of 10~6. Again, the level will be dictated
by the types of Aroclor present and the specific characteristics of the site
involved.
(2) If there is no possibility of a population entering the contaminated
site within a radius of 0.1 km from the site, the PCB levels in soil can remain
at no limit value and 90 to 2.2 x 104 ug/g, without exceeding 10-day AI and
lifetime AI at 10-6 risk, respectively.
Similar interpretations can be made for the results applicable to sites
without affected population up to 1 km from the site, and to the carcinogenic
-risks listed at lO'4, 10'5 and 10'7.
The short-term AI levels (100 yg/g day for a child and 700 yg/g day for
an adult) used in this report to develop 10-day advisories based on noncancer
effects are derived from animal studies, which collectively indicate that
the experimental threshold for adverse effects of Aroclor 1254 is at or near
a dose of 1.0 pg/kg body weight. Using this dose as a No Observed Adverse
Effect Level (NOAEL) and a safety factor of 100, the 10-day AI levels for non-
cancer effects described above (100 and 700 u9/day) were computed and serve
1-10
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Advisory levels for 1-day and lifetime noncancer effects cannot be derived at
this time because of the insufficiency of the available data. However, in view
of the experimental duration, the 10-day advisories may v/ell be used for the
1-day advisories.
1-11
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2. INTRODUCTION
The purpose of this document is fourfold: (1) to provide background
information compiled in the process of developing permissible health advi-
sories for polychlorinated biphenyls (PCBs) in soil and drinking water, in
response to a request from the Office of Emergency and Remedial Response, (2)
to outline the procedures used in developing the advisories, (3) to list per-
tinent input data necessary in carrying out the exposure analyses and in set-
ting the allowable concentration limits, and (4) to present an outline summary
of the results obtained from computer simulations of the techniques used.
The information and methods presented are intended for use in setting safe
advisory levels to protect public health from short-term, longer-term, and
lifetime exposures to PCBs released from hazardous waste facilities or from
spills at previously contaminated sites. Particular interests pertain to
levels of PCBs allowable in contaminated soil, and the potential of PCB migra-
tion to groundwater from PCB-contaminated or hazardous waste facilities. These
advisories are not concerned with setting PCB limitations in sediments contami-
nating surface water, which can be a source of bioaccumulation of PCBs in
aquatic animals.
The analyses presented in this report provide the basis for deriving PCB
levels allowable in soil and drinking water, which are likely to be primary
sources of exposure pathways. PCB problems that may exist in rivers and estu-
aries because of contaminated sediments are not dealt with in these analyses.
The analyses mainly address health concerns at hazardous waste sites or at
sites with contaminated soil. The primary health impacts considered include
adverse impacts associated with ingestion of contaminated soil, inhalation of
ambient air, and dermal contact with the soil. Other exposure routes, such as
2-1
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drinking water, food intake, and ingestion of bioaccumulated fish are consider-
ed to the extent that the pathways are relevant. PCBs that have migrated from
contaminated sites to various exposure media are evaluated for short-term and
lifetime impacts to arrive at corresponding advisory level values.
The total dose of PCBs is obtained by summing each dose from all major
exposure pathways, and is compared with acceptable intakes (AI) judged from the
health effects information available in the literature. A longer-term AI
considered most appropriate in deriving 10-day noncarcinogenic advisories is
used in the exposure evaluation. Advisories for protecting against carcino-
genic risks are similarly derived at various risk levels based on the potency
factor.
This report is not intended to address the achievability of the safe
levels developed. Although the report contains a brief statement, taken from
the available literature on analytical capability, control technology, and
environmental distribution of PCBs, the data base seems insufficient to make a
generalization concerning the level of PCB cleanup achievable in practice.
The Exposure Assessment Group distributed three earlier drafts of this
document under the title of "Development of Health Advisories for Polychlorin-
ated Biphenyls (PCBs)" for internal review and comment on May 9, 1985 and July
25, 1985, and under the title of "Development of Health Advisories for Poly-
chlorinated Biphenyls (PCBs) Cleanup" on December 16, 1985. As a result of
the comments from the Office of Drinking Water, on the December 16, 1985 draft,
the 1-day advisories have been replaced by 10-day advisories because no data
could be found indicating that 3,4,5,3',4',5'-hexachlorobiphenyl, used for
development of the 1-day advisories, is a component in commerical Aroclors.
This final draft reflects changes made to incorporate comments from the Office
of Toxic Substances, the Office of Emergency and Remedial Response, and OHEA's
2-2
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Environmental Criteria and Assessment Office.
2-3
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3. CHEMICAL COMPOSITIONS
A polychlorinated biphenyl (PCB) is any member in a family of organic
compounds with two or more chlorine substitutions on biphenyl rings, and can
be typified by the following chemical structure:
X X X X
The symbol, x, in the structural formula represents possible positions of
chlorine that can be substituted for hydrogen, which is one of the basic ele-
ments of aromatic hydrocarbons. Based on the possible distribution of substi-
tuted chlorine atoms on two benzene rings of biphenyl, it is calculated that
there could theoretically be 209 types (congeners) of PCBs.
Patents disclose that PCBs are prepared by the chlorination of biphenyl
in the presence of a catalyst. The process yields a complex mixture of
chlorinated biphenyl compounds. It is unlikely, however, that all combinations
of chlorinated biphenyls would be formed in the chlorination process. Although
the crude mixture is purified to remove reaction impurities, the resulting
product is still a mixture of chlorinated biphenyls in various proportions.
Their compositions depend upon the chlorination conditions.
Commercial-grade PCBs, consisting of mixtures of different composition,
are sold under the trade name Aroclors. Impurities such as chlorinated dibenzo-
furans and chlorinated naphthalenes are known to exist in commercial PCBs. The
sole producer of Aroclors in the United States for the period 1957 to 1972 was
the Monsanto Chemical Company. Their products are characterized by four-digit
numbers. The first two numbers represent the type of molecule (12 = biphenyl-
3-1
-------
based; 54 = terphenyl-based; 25,44 = blends of PCBs and chlorinated terphenyls);
and the last two digits refer to the percentage of chlorine by weight. PCB
products are also manufactured in other countries, including Germany, France,
Japan, and the U.S.S.R.
Table 3 illustrates approximate compositions of individual biphenyls for
some Aroclors (U.S. EPA, 1976b). Although one might expect some 140 to 150
separate congeners in an Aroclor, the actual analysis of Aroclor 1248, for
example, identified less than 50 peaks in the high-resolution gas chromatograph
using a typical Aroclor 1248 sample (U.S. EPA, 1976b). No compounds which can
be formed by addition of chlorine rather than substitution were found in a
detailed study of PCBs (U.S. EPA, 1976b). It is suspected that the conditions
prevailing during industrial manufacturing of PCBs do not favor the formation
of addition compounds, or that these latter compounds might have been destroyed
in the step used to purify the Aroclor. In constrast to the analysis shown in
Table 3, another publication reports an analysis of Aroclor 1221 to contain
_12.7% biphenyl, 47.1% monochlorophenyls, and 40.2% dichlorophenyls (Hutzinger
et al., 1974).
Major PCB components in foreign products bearing the names of Kanechlor
and Phenoclor for Japanese and French products, respectively, have been identi-
fied. The number of the major components separated from Kanechlor 400 is five,
and that from Phenoclor DP6 is seven.
3-2
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TABLE 3. APPROXIMATE COMPOSITION OF AROCLORS
Percent by weight for Aroclcr
Chlorobiphenyl
C12H10
C12H9C1
C12H8C12
Ci2H7Cl3
C12H6C14
Cl2H5d5
C12H4C16
C12H3C17
C12H2C18
Cl2Hld9
C12C110
1221
11
51
32
4
2
0.5
ND
ND
ND
ND
ND
1242
<0.1
1
16
49
25
8
1
<0.1
ND
ND
ND
1248 1254
<0.1
<0.1
2 0.5
18 1
40 21
36 48
4 23
6
ND
ND
ND
designation
1260 1016
<0.1
1
20
57
21
12 1
38 <0.1
41 ND
8 ND
1 ND
ND
ND = non-detectable.
3-3
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4. PRODUCTION
Commercial production of PCBs from the starting material benzene was begun
in the 1920s by Swann Research, Inc., of Annington, Alabama, which referred to
these products under the trade name Aroclor. PCBs were manufactured at that
location by Swann Research, Inc., and its successor, Monsanto Chemical Company,
until the plant was closed in 1971. Monsanto continued production at another
plant at Sauget, Illinois, until 1977. The only other known manufacturer of
PCBs is Geneva Industries of Houston, Texas, which manufactured PCBs from 1972
through 1974.
The domestic sale of Aroclor products peaked to 33,000 metric tons in
1970, and has declined since then due to restrictions on the use of PCBs
(Hutzinger et al., 1974). PCBs were available commercially as mixtures (Aro-
clors) of 20 to 75 chlorinated biphenyls, and were marked according to the
weight of chlorine contained in the mixtures. These commercial mixtures in-
cluded Aroclors 1242, 1254, 1248, 1260, 1262, 1268, 1221, 1232, and 1016, in
descending order according to domestic sales. In the year of peak production,
57% of the Aroclors produced were in the form of Aroclor 1242 (U.S. EPA, 1980a).
The production in Japan and the annual consumption in Finland are estimated at
26 million pounds and 0.5 million pounds per year, respectively. PCB-1016 (41%
chlorine) is a more recent product, and its sales prevailed for the period
1972-1976.
PCBs may be formed as side-products in other manufacturing processes in-
volving the use of chlorinated benzene or biphenyl in the reaction step. For
example, some of the trichlorobenzene used as a solvent in the manufacture of
the dry pigment phthalocyanine blue is converted to PCBs during the reaction.
PCBs formed can contaminate the pigment product at concentrations from a few
4-1
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parts per million to as much as 0.1%. Similarly, dichlorobiphenyl is formed
in the manufacture of diarylide yellow pigments as a product of side reaction
with the reactant dichlorobenzidine. The process of chlorinating water which
contains biphenyl in a compound used as a dye carrier in dyeing polyester
fibers can form PCBs as a side-reaction product which can contaminate the
water. No natural sources of PCBs have been identified.
PCBs have been imported into the United States for use in various applica-
tions. Decachlorobiphenyl was imported from Italy for use as a wax filler in
the investment casting industry until 1976. PCBs imported from France are used
in mining machinery cooling systems. The percentage of imported PCBs over the
total domestic sales for the period 1971 through 1975 in the United States is
in the range of 1.6% to 2.7% (U.S. EPA, 1976b).
4-2
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5. USES
Products containing PCBs have been used in agriculture and industry for
decades. Their use is are mainly attributable to high chemical stability and
physical properties desirable in certain applications. These properties include
nonflammability, high dielectric constant, plasticizing capability, and ease
of volatilization under heated conditions. Since 1930, PCBs have been exten-
sively used as dielectric fluids in electrical transformers and capacitors,
and have also been used for a variety of other purposes, including use in heat
transfer and hydraulic systems, in the investment casting industry, and as
plasticizers and solvents in sealants and adhesives. PCBs are also used as
flame retardants in the manufacture of hard plastic products in which heat
resistance is desired, as a dye carrier in carbonless copy paper, and as a
plasticizer in paints.
Several published sources provide a comprehensive breakdown of uses for
different types of Aroclors (Hutzinger et al., 1974; Nisbet and Sarofim, 1972;
Versar, Inc., 1977). The most widely used Aroclors were 1242, 1248, 1254, and
1260. Aroclor 1016 was used after 1970 but in much smaller quantities than the
four types mentioned above. A Monsanto marketing bulletin on PCBs, published
in the 1960s, also described their possible use as gaskets and packing materi-
als; as vehicles in graphic arts; as impregnation agents; as moisture-proof
coatings; as wax substitutes; as de-dusting agents; in insecticides; in abra-
sives, lubricants, and cutting oils; in inks; in mastics; and in tank coatings
(Monsanto Chemical Co., undated). A number of other uses have been patented.
In the United States, there are 17 companies that have used PCBs in the
manufacture of askarel capacitors, and 13 companies that have used PCBs in the
manufacture of askarel transformers. According to one study, in 1976 approxi-
5-1
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mately 25 investment casting foundries (out of a total of 135 in the United
States) used PCB-filled waxes in the manufacture of metal castings (U.S. EPA,
1976a).
In 1971, because of environmental concerns, the manufacturer voluntarily
restricted the sale of PCB products for use only in "closed" systems, which
include electrical transformers and capacitors with insulating fluids that
contain PCBs. These two applications account for all of the current use of
PCBs in the United States. The company was on a schedule to phase out pro-
duction of all PCBs by 1979. The cessation of the production will reduce the
amount of PCBs being released into the environment, but millions of pounds of
PCBs are still being used in electrical insulation applications. The environ-
mental contamination by existing PCBs, and their environmentally safe treatment
or disposal, continue to be of concern.
5-2
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6. DISPOSAL
A material balance performed on the amount of PCBs produced, sold, and
purchased provides an estimate of the amount of PCBs lost or disposed of in
the manufacturing process. The total estimated amount reported to have been
disposed of or lost for the year 1974 is about 3.8 million pounds (U.S. EPA,
1976b), of which about 1.8 million pounds are estimated to have been land-
disposed, and the rest to have been incinerated.
The 1.8 million pounds of PCBs in the land-disposed wastes generated from
the manufacturing process amounts to only a small fraction of the total PCBs
sent to land disposal facilities. The total land-disposed amount of PCBs for
the year 1976 is reported to have been about 12 million pounds (U.S. EPA,
1976b). The most important source of PCB waste has been capacitors that have
failed or become obsolete, or that are contained in obsolete equipment. Other
PCB wastes include solid wastes from PCB manufacturing facilities and from
operations using PCBs in non-electrical applications.
The data base for the WET Model, prepared by SCS Engineers (Undated),
shows that PCB fluids containing 50% PCB-1254 sent to hazardous waste treatment,
storage, and disposal facilities (TSDF) amount to about 4,500 tons per year.
This waste competes for the capacity of TSDF regulated under Subtitle C of the
Resource Conservation and Recovery Act. Water effluents from PCB production
and first-tier use facilties are relatively small compared with the amounts
being disposed of in landfills. Severe local impacts are evident by the dis-
charge into rivers of these effluents. PCBs are now found in the sediments,
water column, and biota in the rivers. A few examples of current PCB problems
include the Hudson River and the New Bedford, Massachusetts, harbor. As a
result of a strong tendency of PCBs to adsorb on sediments, and of sediment
6-1
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migration, PCB problems are identified farther downstream from the discharge
points.
Twenty spills involving PCB products have been identified (U.S. EPA,
1976c). These spills occurred in transformer installations from trucks and
railroad cars while they were en route to their destinations, and from leaking
drums.
6-2
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7. CHEMICAL AND PHYSICAL PROPERTIES
The chemical and physical properties of PCBs can be divided into two
groups: (1) those relevant to the commercial and industrial use of PCBs, and
(2) those that are needed in exposure evaluation and hence in developing media-
specific safe level-advisories for PCBs. The latter properties will be briefly
summarized herein.
The widespread distribution of PCBs in the environment suggests that the
major route by which PCBs are transported from treatment, storage, and dis-
posal facilities is through the atmosphere in the form of volatilized vapor
and adsorption on particulate matter. Vapor pressure is one of the important
properties affecting volatilization. The available vapor pressure data for
commercial Aroclors, as reported in the literature, have been compiled and
are presented in this chapter. Vapor pressure, as distinguished from partial
pressure or true pressure, refers to the maximum vapor-phase pressure achiev-
able under equilibrium conditions at the soil-air interface.
Experimental data (U.S. EPA, 1980a) suggest that PCBs are strongly ad-
sorbed on earth materials, including soil. PCBs adsorbed on soil, or present
in the soil mixture, will be subject to ingestion if the contaminated sites are
accessible to children or to adults with habitual pica. The bioaccumulation
factor (in the food chain and in aquatic biota) is also an important physical
parameter when there is a likelihood of PCB transport in water.
As pointed out previously, there are a number of congeners for each of the
Aroclors. Thus, the properties listed herein for Aroclors represent averages
over the various species that constitute the mixtures. The observation that
environmental samples have contained more chlorobiphenyls with high chlorine
levels than is characteristic of freshly manufactured Aroclors is attributable
7-1
-------
in large part to the possible metabolism and volatilization of lower chlorine
species, coupled with enhanced sorption of species with more chlorine.
The more common types of Aroclors are shown in Table 4. Thirteen Aroclors
were listed in a manufacturer's booklet (Monsanto Chemical Co., undated).
These compounds range from oily liquids to white crystals and hard transparent
resins, and generally have similar chemical and biological characteristics.
The properties and parameters commonly needed in estimating the environ-
mental fate and transport of a given chemical are vapor pressure, solubility
in water, soil-water partition coefficient, and bioaccumulation factor. These
properties of PCBs, and other relevant properties, are shown in Table 4 (Burk-
hard et al., 1985; MacKay and Leinonen, 1975; Hutzinger et al., 1974; Monsanto
Chemical Co., undated; Hwang, 1982; U.S. EPA, 1979a). Information on addition-
al physical and chemical properties such as viscosity, softening points, and
other factors, can be found in references authored by Hutzinger et al. (1974),
Monsanto Chemical Co. (undated) and U.S. EPA (1980a).
The vapor pressure of PCBs and their solubility in water are low, and
tend to decrease as the number of chlorine substitutions on the phenyl rings
increase. Aroclors are soluble in most aliphatic and aromatic solvents, and
are highly resistant to the action of strong alkali or acids, or high tem-
peratures. Aroclors subjected to bomb tests are reported to have shown no
evidence of oxidation (Hutzinger et al., 1974). PCBs have been shown to adsorb
relatively rapidly and strongly to various materials, including soil, wood,
plastic, and glass (Hutzinger et al., 1974).
Partition coefficients indicating a measure of partitioning under equili-
brium conditions between PCBs at the interfaces of air-soil, air-water, water-
soil media are important parameters in exposure analysis. Experimental data
are scarce. Data for the distribution between air and water in the form of
7-2
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TABLE 4. CHEMICAL AND PHYSICAL PROPERTIES OF PCBs
PCB
PCB-1016
(Arochlor
1016)
PCB-1221
PCB-1232
PCB-1242
PCB-1248
PCB-1254
PCB-1260
PCB-1262
PCB-1268
PCB-1270
PCB-2565
PCB-4465
PCB-5442
PCB-5460
2, 2', 5,5'-
tetra-
chloro-
blphenyl
? 7 ' 1 & F, _
£.,£. ,O,M,J,-
penta-
chloro-
biphenyl
Molecular
weight
257.9
200.7
232.2
266.5
299.5
328.4
377.5
Specific
KQW gravity
24,000
12,000 1.182
35,000 1.266
380,000 1.380
1,300,000 1.445
1,070,000 1.538
14,000,000 1.620
1.646
1.810
1.947
1.727
1.712
1.434
1.740
Solubility*
in water
(mg/L)
0.42
15.0
1.45
0.24
5.4x10'^
1.2xlO-z -0.03
2.7xlO-3
4.6x10-2
2.2x10-2
Vapor Henry's law
press. (mmHg) constant (atm.
at 25°C m3/g mol )
4xlO"4
6.7xlO-4,
4.06x10'; Ah
4.06xlO'J 5.73xlO'4u
4.94x10^ 3.51xlO'^f
7.71X10'5 8.37x10'^
4.05xlO-5 7.13x10-3
aHutzinger et al., 1974; Monsanto Chemical Co., undated.
bMacKay and Leinonen, 1975.
cHwang, 1982, and U.S. EPA, 1980c.
Bioaccumulation factor: 31,200 L/kg.
Soil-water partition coefficient (U.S. EPA, 1980a): 22 - 1938 L/kg.
-------
Henry's Law constant and water and soil, exist for some selected Aroclors.
Experimental data measuring the distribution of PCBs between air and soil are
nonexistent. Estimates of air-soil partition coefficient can be calculated
based on Henry's law constant and soil-water partition coefficient using one of
several empirical relationships. The Henry's Law constant and soil-water par-
tition coefficient, in turn, are dependent on water solubility and percent
organic carbon in soil, respectively.
The Henry's Law constants shown in Table 4 are based on information in
MacKay and Leinonen (1975) for PCB-1242, PCB-1248, and PCB-1260; and in a U.S.
EPA research report (1980c) for PCB-1254. Burkhard et al. (1985) recently
published a list of calculated Henry's Law constants for PCB-1242, PCB-1248,
PCB-1254, and PCB-1260. The value for PCB-1254 is an experimental value ob-
tained in the EPA laboratory in Cincinnati, Ohio, while others represent cal-
culated values. A comparison of Henry's Law constants for PCB-1254 shows that
the values in MacKay and Leinonen (1975) and Burkhard et al. (1985) differ by
a factor of 10, while those in MacKay and Leinonen (1975) and the experimental
-EPA value (1980c) differ by a factor of 3. Since MacKay and Leinonen's value
is closer to the experimental value, Henry's Law constants for PCB-1242, PCB-
1248, and PCB-1260 are taken from MacKay and Leinonen (1975).
In the absence of experimental data, the soil-water partition coefficient
•j
Kd (cnr water/g soil), and the air-soil partition coefficient, Kas (g soil/
cm^ air) can be estimated from water solubility and percent organic carbon
(%OC) in soil, using correlations presented by various researchers. For exam-
ple, the values for the octanol-water partition coefficient, Kow, can be used
to estimate the values for the soil sorption coefficient based on soil organic
•j
carbon content, KQC (cnr water/g organic carbon), and the bioconcentration fac-
tor (BCF) by the following formula:
7-4
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log KQC = 0.544 log Kow + 1.377 (Kenaga and Goring, 1980) (1)
log KOC = 1.00 log Kow - 0.21 (Karickhoff, 1979) (2)
log BCF = 0.76 log Kow - 0.23 (Veith et al., 1980) (3)
The Kg- and Kas values then can be estimated by
%OC
v =
d "OC V100' (4)
K = — (5)
where H represents Henry's Law constant. Since the common unit for H is given
in atm m3/g mol, a conversion factor of 41 (=1/2.44 x 10~2) should be multiplied
in the right-hand side of Eq. (5) when the units for Kas, H, and K^ are g soil/
cm3 air, atm m3/g mol, and cm3 water/g soil, respectively. The multiplica-
tion of Kas by the concentration of PCBs in soil will provide the concentration
of PCBs in the air phase above contaminated soil of interest under equilibrium
conditions. It should be recalled that the air-soil partition coefficient,
•j
Kfls, has the unit of g soil/cm0 air. This is equivalent to the ratio of the
air-phase to soil-phase concentration, or (mg/cm3 air)/(mg/g soil). The esti-
mation of Kas requires the knowledge of Henry's Law constant and the soil-water
partition coefficient as given by Eq. (5).
A listing of solubilities of each chlorinated biphenyl is shown in Table
5 (U.S. EPA, 1976c).
There has been much speculation as to the possible role of photochemical
reaction in the environmental decay of PCBs. The results of a study using
mercury vapor (UV) sources (U.S. EPA, 1976c) have been difficult to extrapolate
7-5
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to environmental conditions because the radiation wavelength is not within the
spectrum of solar radiation at the surface of the earth. More recent experi-
ments have been reported using a light source more closely approximating the
spectral distribution of solar radiation, but the values for the photochemical
reaction constants are not available.
The Monsanto Chemical Company has reported vapor pressure data only for
high-temperature conditions for Aroclors 1242, 1248, 1254, and 1260 (Monsanto
Chemical Co., undated). The temperature used in presenting the data ranges
from 150°C to 300°C. These vapor pressure values may be extrapolated to the
temperatures which are of common environmental concern, but their accuracies
would be doubtful.
An EPA report presents kinetic data obtained from biodegradation experi-
ments using water-soluble Aroclor 1242 (U.S. EPA, 1980a). The rate constants
are presented for biphenyl compounds with up to the three chlorine substitutions
present in Aroclor 1242. The data clearly show that many of the chlorinated
biphenyls with four chlorine substitutions do not biodegrade after 48 hours of
degradation run. Inferring from the compositions of Aroclors 1242 and 1254 as
given in Table 3, it is conceivable that Aroclor 1242 may biodegrade to some
extent because it contains a substantial amount of chlorinated biphenyls with
two and three chlorine substitutions. It appears that biodegradation of Aro-
clor 1254 would be insignificant or may not occur because most biphenyl com-
ponents have four or more substituted chlorine atoms.
PCBs have several properties which make them toxic in the environment.
In addition, they can significantly bioaccumulate and concentrate in the fatty
tissues of all organisms. For example, the PCB concentration in resident fish
is often many times higher than that in the surrounding water. PCBs are chem-
ically stable compounds that are able to persist in the environment for long
7-6
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TABLE 5. SOLUBILITY OF CHLOROBIPHENYLS IN WATER
Compound Solubility mg/L (ppm)
Monochlorobi phenyls
2- 5.9
3- 3.5
4- 1.19
Dichlorobiphenyls
2,4- 1.40
2,2'- 1.50
2,4'- 1.88
4,4'- 0.08
Trichlorobiphenyls
2,4,4'- 0.085
2',3,4- 0.078
Tetrachlorobi phenyls
2,2',5,5'- 0.046
2,2',3,3'- 0.034
2,2',3,5'- 0.170
2,2',4,4'- 0.068
2,3',4,4'- 0.058
2,3',4',5- 0.041
3,3',4,4'- 0.175
Pentachlorobi phenyls
2,2',3,4,5'- 0.022
2,2',4,5,5'- 0.031
Hexachlorobi phenyl
2,2',4,4',5,5'- 0.0088
Octachlorobi phenyl
2,2',3,3',4,4',5,5'- 0.0070
Decachlorobiphenyl 0.015
4,4'-Dichlorobiphenyl
+Tween 80 0.1% 5.9
+Tween 80 1% >10.0
+Humic acid extract 0.07
7-7
-------
periods. Impurities in commercial PCBs could amplify the PCB problem because
of their similarity in chemical structure and toxicity (Monsanto Chemical Co.,
undated).
7-8
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8. ENVIRONMENTAL DISTRIBUTION
The release of PCBs into the environment through disposal on or in land,
and through effluent discharges into waterways, together with their high atten-
uation characteristics and long half-life, has resulted in detectable levels in
ambient air, soil, rivers, sediments, and in tissues of fish, wildlife, cattle,
poultry, and a large portion of the human population. Measurable amounts of
PCBs have been found in Antarctic ice, showing that atmospheric transport
over long distances does occur (U.S. EPA, 1976b). Monitoring shows that the
soils in the rural and urban areas where there is no record of PCB disposal or
contamination, contain detectable amounts of PCBs (U.S. EPA, 1976c). One study
estimates that 70% of the PCB load to Lake Michigan is through atmospheric
transport (University of Wisconsin, 1980).
The results of soil sampling show that PCBs are more prevalent in urban
soil than in agricultural soil. Data indicate that PCBs are rarely detected
in agricultural soil, while urban soils'showed PCB contaminations up to about
12 wg/g soil, with averages ranging from 0.01 to 0.21 yg/g (U.S. EPA, 1976c;
Carey, undated). Sixty-three percent of the soil samples showed detectable PCB
levels. The most prevalent PCBs in soil were Aroclor 1254, and, to a lesser
extent, Aroclor 1260.
The PCB concentrations in air samples over Lake Michigan taken during 1977
(University of Wisconsin, 1980) were lower than in those taken in the urban
portion of Milwaukee. The main components were identified as Aroclors 1242 and
1254, while the particulate-phase PCBs contained Aroclor 1260 in some instances.
The average concentration of PCBs in the air over Lake Michigan was 0.87 ng/m^
(0.44 to 1.33 ng/m3). The concentrations of PCBs in the particulate samples
were similar to those in the air samples. Air samples taken in later years
8-1
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from Lake Michigan showed an average concentration of 1 ng/m3. These concen-
trations are lower than those reported in the ambient air in the continental
United States.
The ambient air concentrations of PCBs for urban Chicago averaged 7.7 ng/
m3. The average composition in the air sampled was 86% Aroclor 1242, 13% 1254,
and 1% 1260. The particulate-phase PCBs had a slightly different composition
for the same Aroclors. The ambient air in Milwaukee showed an average PCB
concentration of 2.25 ng/m3.
8-2
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9. ENVIRONMENTAL FATE AND TRANSPORT
PCBs have been found in samples of air, water, soil, sediments, fish,
birds, and mammals (including humans) all over the world (U.S. EPA, 1980a).
Once released into the environment, PCBs persist and collect in animal tis-
sues. Environmental problems caused by PCBs were largely unreported until
1966, when PCB contamination of fish, eagles, and humans was detected. The
best-documented incident concerning the effects of ingested PCBs on humans is
the case that occurred in Yusho, Japan, in 1968 (U.S. EPA, 1980a). Several
other cases have also been reported (U.S. EPA, 1980a, U.S. EPA, 1976c).
Sediments containing PCBs have been reported in rivers, estuaries, and
harbors (U.S. EPA, 1981b), in concentrations ranging from 20 to 50,000 pg/g.
Leaching of PCBs could occur, although it will be constrained by the low solu-
bility limits. Once PCBs dissolved in water enter the soil medium, it is
possible that further migration will be severely retarded in view of the high
soil-water partition coefficients. The retardation factors calculated from
these coefficients can be used to simulate the arrival time and concentration
decrease in groundwater. This will be further explained later.
Despite their low vapor pressures, PCBs can volatilize into the atmo-
sphere. The migration of PCBs through air is considered to be one of the basic
mechanisms by which the ubiquitous presence of PCBs occurs in nature (U.S. EPA,
1980a). The New York State Department of Environmental Conservation (NYSDEC)
analyzed samples of PCB-contaminated air at several localities. These analyses
are shown in Table 6 (NYSDEC, 1979; U.S. EPA, 1981b). Concentrations of PCBs
in the ambient air as high as 300 gg/m3 were reported at the disposal site.
The average values ranged from 130 to 0.3 ug/m3. Concentrations of suspended
particulates in the air in the vicinity of dump sites were also monitored by
9-1
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TABLE 6. PCB MONITORING IN AMBIENT AIR BY NYSDEC
Max. PCB cone. Average PCB cone.
Site (ug/m3) (ug/m3)
Caputo dump 300 130
Fort Miller dump 35 24
Remnant area 10 9
Moreau site 15 5.6
Buoy 212 site 0.7 (one sample)
Old Moreau Site (Summer 1979) 0.3
9-2
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NYSDEC, using high-volume air samplers (NYSDEC, 1979; U.S. EPA, 1981b). The
geometric annual mean concentration of particulate matter was 36 to 63 ug/m^,
while the 24-hour averages were 71 to 144 ug/m^. The amount of PCBs adsorbed
to the collected suspended particulates was not reported.
Based on mass-transfer models, MacKay and Leinonen (1975) calculated the
half-lives of PCBs present in solution in a water column of 1 m depth. Half-
lives provide some indication of how fast a compound can volatilize from
solution. The half-lives for Aroclor-1242, Aroclor-1248, Aroclor-1254, and
Aroclor-1260 are reported to be 12.1 hr, 9.5 hr, 10.3 hr, and 10.2 hr, respec-
tively. Half-lives will be longer when depths are greater than 1 m. The cal-
culated half-lives are for evaporation from a calm, liquid surface. Turbulence
provides exchange of contaminants between the surface layer and the bulk of the
water column. This exchange results in increased emission rates, thus pro-
viding shorter half-lives.
In addition to the importance of attenuation mechanisms when PCBs inter-
.act with soil, biodegradation is also suggested as a potentially important
mechanism. Biodegradation studies using pure and mixed microbial cultures,
and the resulting metabolic changes in PCB compounds, have been summarized by
Hutzinger et al. (1974) and Hwang (1982). Photochemical degradation of PCBs
in the atmosphere is also of interest, since a number of pesticide compounds
have been shown to break down through the photochemical route. However, very
little information is available in the literature to determine the extent of
PCB degradation in the atmosphere.
The safe disposal and treatment of PCBs discarded after their use in
electrical applications is a matter of great concern with regard to human
health. Incineration techniques are frequently applied to PCB material at
elevated temperatures and high residence times. Several experiments involving
9-3
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pyrolysis of commercial PCBs have been reported (Buser and Rappe, 1979). The
PCBs used in the pyrolysis experiments included tetrachlorobiphenyl, penta-
chlorobiphenyl, hexachlorobiphenyl, heptachlorobiphenyl, and octachlorobiphe-
nyl. The analysis of the pyrolysis residues showed the presence of chlorinated
furan compounds. However, the researchers concluded that the formation of
furan compounds is the result of uncontrolled burning of PCBs, and that the
emission of these compounds can be reduced by controlling the burning process.
The high-temperature combustion of PCBs, such as in the case of transform-
er fires, results in the formation of polychlorinated dibenzofurans (PCDFs) and
other toxic compounds. In an experiment studying conditions favoring the
formation of polychlorinated dibenzodioxins (PCDDs), researchers found that the
optimum conditions for the formation of PCDFs are a temperature of near 675°C
at a residence time of 0.8 seconds or longer, with 8% excess oxygen (Midwest
Research Institute [MRI], 1984). No conditions for the formation of PCDDs are
represented. The report states that detection of PCDDs was occasional and at
low levels.
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10. TOXICOLOGY
The advisory levels for PCB cleanup presented in this document (i.e.,
the permissible PCB soil contamination levels) are health-based values. These
advisories are derived through calculations which first estimate human risk-
specific (cancer end point) or acceptable intake (AI) (noncancer end point)
levels, and then determine the exposure rates which will effect these intake
levels. Risk-specific doses are derived for the cancer end point, and a 10-day
AI level is derived for an approximate 10- to 30-day exposure considering only
noncancer effects. A detailed assessment of the available cancer and noncancer
health effects data for PCBs is presented in Appendix D. Only a brief overview
and major issues will be presented here.
The determination of risk-specific intake levels is accomplished through
a mathematical process which makes use of a cancer potency factor and a
reflected risk level or levels to estimate the intake level that would cor-
respond to such risk levels. Cancer potency factors for PCBs have been
determined through an exhaustive analysis of animal studies. Values have been
calculated by ORD (EPA, 1980b) to be 4.34 (mg/kg-day)'1 and by OTS (EPA, 1985b)
to be 3.57 (mg/kg»day)~l. An average of these values, or 4.0 (mg/kg«day)~l
is used in the calculations presented in this document. A discussion of the
data and methods used to estimate cancer potency factors for PCBs is included
in Appendix D. The determinations made by ORD and OTS are both based on the
same animal study (Kimbrough et al., 1975), with only slightly different
assumptions being incorporated.
A noncancer AI level was derived for PCBs during the preparation of this
report. It must be emphasized that this AI ignores the cancer end point and
is based on toxicity other than cancer. The 10-day AI level of 100 ug/day
10-1
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for a child and 700 ug/day for an adult, derived for use in this document,
is based on feeding studies with rabbits and rats in which a NOAEL for de-
creased reproductive rate, and effects on thyroid and liver, were evaluated.
These studies are described briefly below.
Villeneuve et al. (1971) found increased incidences of fetal death, re-
sorptions, and abortions at 12.5 mg/kg/day of Aroclor 1254 in rabbits when
exposed on days 1 through 28 of pregnancy. A dose of 1.0 mg/kg/day appeared
to be without effect. Collins and Capen (1980a, b, c) in a series of studies
on thyroid effects in rats, determined that 50 ug PCB per g of diet (~ 2.5
to 5.0 mg/kg/day) for 4 weeks was associated with clearly defined adverse
effects, but that doses of 5 wg PCB per g of diet (~ 0.25 to 0.5 mg/kg/day)
were not. Carter (1983) demonstrated liver hepatomegaly in rats at doses of
20 ug Aroclor 1254 per g of diet (~ 2 mg/kg/day) for 14 days; such an ef-
fect, in the absence of other signs of toxicity (e.g., fatty infiltration of
the liver), might not be considered adverse. Grant and Phillips (1974) ob-
served increased liver weights in rats at doses as low as 5 mg/kg/day Aroclor
1254 given in corn oil for 7 consecutive days. Collectively, these studies
indicate that the experimental threshold for adverse effects of Aroclor 1254
in studies of 30 days' duration or less is at or near a dose of 1 mg/kg/day.
Thus, it seems reasonable to use this latter dose, a No Adverse Effect dose,
as a basis for health advisories for Aroclor 1254 for short exposure durations,
10-2
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11. EXISTING STANDARDS AND GUIDELINES
The 1968 incident in which toxic symptoms were experienced by Japanese
people exposed to contaminated cooking oil gave rise to a great deal of concern
in the United States with regard to hazardous chemicals. The U.S. Food and
Drug Administration (FDA) started sampling foods for possible contamination by
PCBs in 1969, and detected levels of PCBs in fish from the Great Lakes, in milk
caused by use of materials containing PCBs, and in chickens as a result of the
existence of PCBs in the feed. The temporary tolerance levels for residues of
PCBs proposed by FDA became effective June 29, 1979 (U.S. FDA, 1984).
In the early 1970s, EPA proposed the establishment of criteria for PCBs
being discharged in industrial effluents, but has not so far issued effluent
limitations concerning PCBs.
The Occupational Safety and Health Administration (OSHA) adopted standards
for PCB exposure by industrial workers. Subsequently, the National Institute
for Occupational Safety and Health (NIOSH), after their extensive assessment,
recommended lowering the allowable concentration of PCBs in the workplace.
However, OSHA has not acted on this recommendation. The New York State Depart-
ment of Health issued an interim guideline for the allowable ambient air con-
centration of PCBs to which individuals may be exposed during the duration of
a PCB reclamation project planned for the Hudson River (NYSDEC, 1979).
The EPA promulgated regulations relating to manufacture, processing,
distribution in commerce, use, diposal, storage, and markings of PCBs and PCB
items. The regulations originally became effective May 31, 1979, and were
later amended. A complete presentation of the effective regulations can be
found in the latest edition of 40 CFR Part 761 (U.S. EPA, 1984b). The PCBs
referred to in these regulations include any chemical substances or their
11-1
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mixtures containing concentrations of chlorinated biphenyls of 50 ppm or
greater. The regulations pertain to prohibitions on manufacturing, pro-
cessing, distribution in commerce, and use, and specifically apply to PCB
incinerators, chemical waste landfills disposing of PCBs, transformers,
pigments, electrical and heat transfer equipment, natural gas pipeline com-
pressors, microscopy mounting medium, capacitors, PCB containers, and
hydraulic systems (U.S. EPA, 1984b).
The PCB standards and guidelines for numerical limitations of PCBs in
food, drinking water, and ambient air existing at the present time are shown
in Table 7. Because of the complicated nature of the EPA's regulations pro-
mulgated under TSCA, these regulations are not presented in tabular form.
11-2
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TABLE 7. EXISTING PCB STANDARDS AND GUIDELINES
Exposure pathways Maximum allowable PCBs
Food (FDA standard)3
Milk fat and dairy products 1.5 ug/g (ppm)
Poultry 3.0 ug/g (ppm)
Eggs ' 0.3 ug/g (ppm)
Fish and shellfish 2.0 ug/g (ppm)
Finished animal feed 1.0 ug/g (ppm)
Drinking water (New York State) 1.0 ug/L (ppb)
Ambient air
Populated areas (New York State guideline)15 1.0 yg/m3
Workplace (OSHA standard) 500 ug/m3
Work site (NIOSH guideline)0 1.0 yg/m3
aU.S. FDA, 1984.
bNew York State Department of Health, 1981.
CNIOSH, 1977.
11-3
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12. EXPOSURE ASSESSMENT METHODOLOGY
The presence of PCBs in environmental media poses a potential health
risk to humans from the following sources of intake:
• ingesting contaminated soil
• inhaling contaminated air
• ingesting contaminated food
• drinking contaminated water
• dermal absorption of PCBs in contact with skin
Other exposure pathways affecting ecological communities, such as phytotoxicity
to plants, may also need to be considered. If multiple-route exposures are
possible, the concentrations allowable for a single-route exposure should be
adjusted to"meet the acceptable levels of acute and chronic health effect
exposures from all sources of intake. The amounts of each medium subject to
human intake used in this analysis are as follows: daily iintake of drinking
water, 2 L/day; daily inhalation of air, 20 m3/day (U.S. EPA, 1984b).
Acute effects result from short-term or long-term intakes. Carcinogenic
effects are normally treated as resulting from lifetime intakes. Safe levels
of PCBs in soil corresponding to 1-day and 10-day acceptable intakes should
be based on consideration for preventing acute health effects from short-term
and longer-term exposures. Levels of PCBs in soil corresponding to acceptable
intakes for long-term effects can be derived from the acceptable daily intake
(ADI) based on long-term health studies for acute effects, or from the car-
cinogenic potency slope based on lifetime exposure for carcinogenic effects.
The long-term risk level for ingestion of contaminated soil over a 70-year
lifetime exposure can be obtained by
12-1
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69 vrs ~kt
Risk = 7 (GI) (SM) Co e (POT) (IR)
t=0 (BW) (LT)(6)
where Risk = lifetime risk; GI = gastrointestinal tract absorption of PCBs; SM
= exposure frequency over a lifetime; Co = initial concentration of PCBs in
soil; k = biodegradation constant (I/day); POT = potency slope factor (mg/kg/
day)'1 for PCBs; IR = daily ingestion rate of soil; BW = body weight (70 kg for
adults and 10 kg for children); and LT = exposure time over a lifetime (70
years). If the contaminant undergoes biological or chemical degradation in
soil, and follows first-order kinetics in its disappearance under isothermal
conditions, the contaminant concentration will change as a function of time
according to C^"1^. The summation in Eq. (6) is necessary in order to add
all the rt-sks associated with the daily dosage over a lifetime. The initial
concentration of PCBs in the soil is calculated at an assumed lifetime risk
according to Eq. (6). A computer is convenient to use to sum all the daily
risks. The soil ingestion scenario will be applicable to sites which are
readily accessible, especially by children. Since the population is living
on or near the site, the exposure to PCBs due to inhalation of contaminated air
cannot be neglected. In order to account for the inhalation exposure in deter-
mining the allowable PCB levels in soil due to the combined routes of ingestion,
inhalation and dermal absorption, the ambient air concentrations at the expo-
sure points are needed. The concentration of PCBs in the vapor phase is the
result of the volatilization of the PCBs from the contaminated soil and their
dilution by winds. The dilution factor for ambient air concentrations can be
defined as
D = Ca/Cas (7)
12-2
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where C, (ug/m3) = the ambient air concentration at an exposure location,
and Cas (ug/m3) = the concentration of PCBs in air at the soil surface where
the emission occurs. The value of Cas continuously increases as the PCB con-
centration in soil increases, until the concentration of PCBs in the air phase
corresponds to that of PCB vapor pressure. Beyond this point, a further in-
crease in PCB concentration in soil will have a minimal effect on the vola-
tilization rate.
Once exposure pathways are identified, exposure evaluation requires infor-
mation on the levels of concentration to which a given target population may be
exposed. Each pathway may require route-specific evaluation. A general method
for estimating exposures for contaminated sites will be described first. The
method can be simplified by eliminating those pathways that are unimportant or
unrelated in the evaluation of PCB advisories. The relevant assumptions for
the simplification are described below.
12.1 Estimation of Exposures for Contaminated Sites
The combined human intake of contaminants from all exposure pathways
should not exceed the acceptable intake (AI, in mg/day) needed for preventing
adverse effects from short-term and lifetime exposures. The intake from an
individual route when soil is contaminated can be expressed quantitatively as
follows:
i) Intake by soil ingestion (mg/day):
I, = (CS)(IR x 1(T3)(GI)(SM)(F)
(8)
The term (CS)(IR) in Eq. (8) represents the daily amount of a contami-
nant ingested resulting from soil ingestion, in ug/day, because Cs repre-
12-3
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sents the contaminant concentration in soil (ug/g) or ppm (both units are
equivalent), and IR is the soil ingestion rate (g/day) and GI is defined in Eq.
(6). The factor 10'3 is needed to convert the unit from yg/day to nig/day.
The fraction of the ingested contaminants that will enter human organs and
systems to cause toxicity is given as 61. An individual may not always be
present on the contaminated site over his lifetime. The frequency factor of
exposure over a lifetime, SM, represents the fraction of a lifetime that an
individual will be exposed to the contaminants under consideration. The factor
F is necessary because soil ingestion only occurs during childhood (1 to 5
years of age), and the weight of the human body changes from childhood to
adulthood.
ii) Intake by air inhalation of volatilized contaminants (mg/day):
I2 = (Kas)
-------
partial differential equation, as described in the Section 16.
If the concentration of PCBs in soil is at or above saturation conditions,
under which the air phase concentration of PCBs is equal to the vapor pressure
concentration for a particular Aroclor or a mixture of Aroclors, the further
increase in Cs will not increase the ambient air concentration, assuming that
other factors, such as temperature, remain constant. Therefore, the daily
intake by inhalation remains constant above the concentration of PCBs in soil
providing saturated air concentration. This concentration of PCBs in soil,
or the saturated concentration in soil for air inhalation, will be denoted by
iii) Intake by dermal absorption (mg/day):
I3 = (CS)(CR x 1(T3)(ABS)(SM) (10)
There are many occasions when children playing in the yard or adults
working in the garden will come in direct contact with contaminated soil.
Dermal contact does not necessarily constitute adverse exposure. The
contaminant needs to be systemic to be absorbed into the human body and to
exert toxicity. In Eq. (10), the term (CS)(CR) represents the contaminant
contact rate with skin in ug/day since Cs is in ug/g (=ppm) and CR is
the dermal contact rate of soil in g/day. The factor 10'3 is used to con-
vert the contact rate from vg/day to mg/day, and SM will be 1 when the
short- or longer-term (10-day) exposure is estimated, and will be between
0 and 1 when the lifetime exposure is estimated.
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iv) Intake by drinking water (mg/day):
lA = (CW)(IW)(SM)
(11)
In Eq. (11) it is assumed that the contaminant in drinking water is
completely absorbed into the human body at the average daily water con-
sumption rate of IW or the absorption fraction is 1. In order to relate
the contaminant concentration in groundwater, Cw, to the contaminant con-
centration in soil, Cs, a fate and transport model can be used to estimate
the concentration in the leachate entering groundwater, or
Cy, = CL/fg, mg/L
(12)
where fg represents a functional relationship describing contaminant trans-
port in groundwater. This function should be selected to suit the most
appropriate conditions for the system. The leachate concentration, CL,
referring to the contaminant concentration in liquids just before entering
groundwater, should not be confused with the contaminant concentration in
groundwater, which results from mixing of the leachate with groundwater.
Also, care should be exercised in using groundwater transport models, be-
cause some models will treat the leachate concentration as a boundary con-
dition, while others require the contaminant concentration in groundwater
as a boundary condition, which should be obtained by groundwater monitoring.
When the units of Cw and C|_ are all in mg/L, then the function fg becomes
dimensionless. Most leachate from hazardous waste land disposal sites may
enter groundwater over a finite surface area, favoring area source models for
simulating pollutant transport in groundwater.
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There is no reliable method of predicting the leachate concentration
from the contaminant concentration in soil, or vice versa. For the exposure
evaluation, an equilibrium relationship vetween soil and leachate will pro-
vide a first approximation. Monitoring data can also be used relating the
concentrations between leachate and soil. An equilibrium condition can be
written as
where KLs is a partition coefficient in (mg/kg)/(mg/L). Eqs. (11), (12), and
(13) are combined to get
I4 = Cs (IW)(SM)
(fg)(KLS) (14)
When the equilibrium condition is not appropriate, it can be modified to
include transport processes between the soil and leachate.
v) Intake by fish ingestion (mg/day):
At the average daily fish consumption rate of IF (kg/day), and under
the assumption of complete absorption of the contaminant associated with
the consumption of fish, the exposure can be estimated as
15 = (CF)(IF)(SM) (15)
where Cp is the contaminant concentration in fish. The use of the biocon-
centration factor BCF, (mg/kg fish)/(mg/L water), to relate pollutant con-
centrations in fish and water, gives
12-7
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I5 = (BCF)(CW)(IF)(SM) (16)
where it is assumed that contaminants are present in water in dissolved form
and that bottom sediments or benthal deposits on which pollutants may be ad-
sorbed are not directly swallowed by fish. Under the condition of equili-
brium between the pollutant-containing soil and leachate which is generated
from the soil, substitution of Eqs. (12) and (13) into Eq. (14) results in
(17)
The transport functions, fg, in Eqs. (14) and (17) may assume distinct
mathematical descriptions, because one pertains to transport in groundwater
and the other to that in surface water.
vi) Intake by inhalation of contaminants adsorbed on particulates
(mg/day) may be expressed by
I6 = (C )(IH)(CS x 10-9)(ABP)(SM) (18)
Contaminant-containing soil can be airborne by blowing winds. In
addition, toxic substances volatilized from contaminated soil can be ad-
sorbed on particulate matter present in the ambient air. Exposure to con-
taminants occurs because of inhalation of air containing these particulates.
The exposure location could be distant from the source of emission, or in
the vicinity of the emission source. Exposure concentrations will change
accordingly. Another form of exposure relates to inhalation of air con-
12-8
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taining participate matter on which volatile constituents are adsorbed.
The intake rate can be estimated based on the concentration of contami-
nants in wind-dispersed soil or on participate matter, Cs ug/g (=ppm),
and the concentration of the particulates in the ambient air, Cp yg/m^,
as shown in Eq. (18). The absorption fraction, ABP, is used because
contaminants present in or on soil (or particulate matter) may be bound on
the solid material, reducing the contaminant's absorption rate. Finally,
the factor 10'^ is a conversion factor to make the units consistent.
vii) Intake by ingestion of vegetables (rug/day):
The intake rate due to ingesting IV kg/day of vegetables, plants, or
agricultural products containing Cv mg/L of contaminants will be
I? • (CV)(IV)(SM)
(19)
If it is assumed that equilibrium is established between the contaminant
concentrations in plant and soil, then the exposure can be modified as:
I? = (KSV)(CS)(IV)(SM)
(20)
where Ksv is a partition coefficient defined as contaminant concentration in
plant/total contaminant concentration in soil (mg/kg plant)/(mg/kg soil).
viii) Intake by ingestion of food meat:
The contaminant intake at consumption rate of IM (kg/day) of meat con-
taining Cm (mg/kg) of pollutant is
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18 = (Cm)(IM)(SM) (21)
Here again, an equilibrium relationship is assumed between the contaminant
concentrations in the animal body and plants. Therefore, the intake rate
due to meat consumption is
IS = (Kv
(22)
where Kvm and Ksv are the partition coefficients used to describe pollu-
tant distribution between meat and vegetables, and the partition between
vegetables and soil, respectively.
12.2 Determination of Permissible Pollutant Levels in Soil
The total intake from all possible exposure pathways is set equal to
the acceptable intake (AI) for short-term and chronic health effects; or
AI = l! + I2 + 13 + ••• (23)
Eq. (23) can be solved for permissible contaminant levels in soil correspond-
ing to each acceptable intake. It is possible that some exposure pathways
occur independently of others. For example, a residence which is located on
a contaminated site may use drinking water from a clean public water treat-
ment system, and may thus be free of contaminants found on the site. It is
also possible that domestic animals are not raised for food consumption on
the contaminated site under consideration. Under such circumstances, all
exposure pathways need not be considered. If exposure pathways of significant
concern are related to soil ingestion, inhalation of contaminated air, or
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dermal contact with soil, as is the case for development of PCB advisories,
Eqs. (8), (9), and (10) can be added to solve for Cs,
(AI)(1000)
CS=
C(IR)(GI)(F) + (Kas)(D)(IH)(ABA x 105) + (CR)(ABS)]SM
(24)
The emission rate is limited by the air phase concentration in equili-
brium with the contaminant concentration in soil. Once the contaminant soil
concentration reaches the level at which the vapor phase concentration in
equilibrium with the soil is at the vapor pressure concentration, a further
increase in contaminant concentration in soil (Cs > Csm) does not increase
the emission rate. At or above this concentration, the ambient air concen-
tration remains constant regardless of the concentration of the contaminant
in soil. Under such conditions, Cs in Eq. (9) is no longer a variable,
and therefore Eq. (24) does not apply. This situation can be remedied by
considering the intakes by the individual route of exposure at a constant
value of Cs [Cs = Csm in Eq. (9)] for inhalation exposure, and solving for
Cs. The form of the equation will be slightly different from that for Eq.
(24).
(AD(IOOO) - (Kas)(Csn|)(D)(IH x 103)(ABA)(SM)
(CR)(ABS)]SM
12.3 Incorporation of Time-Varying Parameters
The body weight of a human constantly changes until maturity. The cal
culation of AIs from the safe dose level (SL) given in mg/kg«day requires
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an assumption of body weight. For rigorous treatment, the estimation of
lifetime exposure should take into account changes in body weight. In this
case, it is convenient to work with SL instead of AI for exposure calcula-
tions. For carcinogens with a potency value at POT (mg/kg-day)'^, the
equivalent SL at an assumed risk level, R (such as 10~6, etc.), can be
obtained by
(SL)eq. = R , mg/kg-day (26)
POT
The risk level shown represents an upper-bound estimate. An upper-bound
estimate of risk of 10~6, for example, means that upon lifetime exposure
to a contaminant, a person experiences an increased maximum risk of devel-
oping cancer in a probability of 1 in one million.
Snyder (1975) presented data on the change of body weight as a func-
tion of age. A regression analysis on Snyder's data for average male weight
provides the following relationship.
BW = 3.14 + 3.52 (age), kg for age 0 - 18 yr (27)
BW = 70, kg for age greater than 18 yr (28)
To obtain the daily exposure averaged over an individual's lifetime,
intake rates given by Eqs. (8) - (10), (10), (17), (18), (20), and (24)
should be divided by the body weight, and the daily intake per unit body
weight should be averaged by summing the total intake per unit body weight
over the period during which exposure occurs and dividing the result by
LT. For purposes of illustration, Eqs. (8) and (9) are repeated below:
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i) The average daily exposure by soil ingestion per unit body weight
in mg/kg-day can be determined as
_ (C0e-kt)(IRX103)(GI)(SM)
BW " 1 day (BW)(LT)
Again, in Eq. (29) [also in in Eq. (30)], the contaminant present in
soil is assumed to disappear by biodegradation and other reactions, accord-
ing to first-order kinetics. Other processes affecting the concentration
in soil are considered in the exposure analyses for individual pathways.
ii) The average daily exposure by inhalation of volatilized contami-
nants in mg/kg-day is calculated from
_ _ (Kas)(C0e"kt)(D)(IH x 1Q3)(ABA)(SH)
BW ' 1 day (BW)(LT)
Similar expressions can be written for other exposure pathways. For conser-
vative contaminants, the term C0e *• in Eqs. (29) and (30) can be replaced
by Cs. The total dose from all exposures should not exceed SL, or (SL)eq>
cL = l + 2 + j3 f for noncarcinogenic effects (30)
BW BW BW •"
/SL\ - il + il + il + for carcinogenic effects (32)
v 'eq. BW BW BW
12-13
-------
As before, Eq. (31) or (32) can be solved for the permissible concentrations in
soil, Cs. From Eqs. (8) and (29), one can solve for the factor F for use in
Eq. (8). The use of LT = 25550 days, and the assumption that soil ingestion
occurs during ages 1 through 5 (t = 365 to 1825 days), yield F = 0.323. The
factor F does not depend on the soil ingestion rate. Eqs. (8) and (29) use
Eqs. (28) and (27), respectively, for BW.
12.4 PCB Advisory Evaluations
Under normal conditions, significant soil ingestion is limited to
children (Lepow, 1975). Although very limited information is available on
the ranges of age subject to soil ingestion, one investigation presented a
case study of an adult with a history of habitual eating of garden soil,
which may have been associated with a pica illness (Wedeen et al., 1978).
The fraction of soil contaminant absorbed by humans is dependent upon the
type of compound and its soil contaminant adsorption characteristics, and
is generally smaller than that which can be expected when contaminants are
present in food or drinking watder.
PCBs can be removed from surface water, leaving it suitable for drinking.
Well water that comes from ground water could be a direct source of drinking
water. The location of the drinking water exposure does not necessarily have
to be at the site of the contamination. It is assumed that the population
which may be subject to PCB contamination in drinking water is remote from the
RGB-contaminated sites, and the allowable water concentration is separately
calculated on the basis of not eating contaminated soil and not inhaling con-
taminated air in the immediate vicinity of the site. The water concentra-
tion for a single-route exposure can be calculated as
12-14
-------
AI
w " 2 L/day
where Cw = concentration of PCBs in water in mg/L, and AI = the acceptable
intake for prevention of acute and carcinogenic adverse health effects, in
mg/day. If fish caught in PCB-contaminated surface water are eaten, and if
the same water is the source of drinking water, the allowable concentration
of PCBs (Cw mg/day) should be determined as
AI
C^ =
W 2 L/day + F • BCF
where F is the daily fish consumption, BCF is the bioconcentration factor
(31,200 L/kg) (U.S. EPA, 1980b; U.S. EPA, undated). The national average of
fish consumption is 0.0065 kg/day (U.S. EPA, 1984b). However, it is more
appropriate to use regional values where such data are available.
The variabilities of input values needed in Eq. (24) (appropriate for PCB
exposure pathways) are wide-ranging for some values, and narrow for others.
The inhalation rate of air used for calculation is 20 m3/day for both adults
and children (U.S. EPA, 1985d). Soil ingestion rates used for evaluating
short-term exposures are 3 and 0.6 g/day, representing conditions with and
without pica, respectively (further explained in Section 15). One lifetime
exposure evaluation is based on an average daily rate of 0.6 g/day multiplied
by factors to correct for the changing weight of the body as a person grows
from a child to an adult. This exposure is assumed to occur from age 1 to 5
years. However, the soil ingestion rate of 3 g/day is also used in long-term
exposure evaluation. The absorption factors for PCBs through the gastrointes-
tinal tract for ingested soil, through the pulmonary organs for inhaled air,
12-15
-------
and through the skin for contacted soil are assumed to be 0.3, 0.5, and 0.05,
respectively (U.S. EPA, 1984a; U.S. EPA, 1985e). The off-site factor is
assumed to be 1 for longer-term (10-day) exposure evaluations, and 0.5 for
lifetime exposure evaluations, using the carcinogenic potency factor. A
similar approach can be used for short-term (1-day) and lifetime noncancer
exposure evaluations. However, these evaluations are not performed because of
a lack of data regarding health effects.
If all intake routes, including drinking water, soil ingestion, air inha-
lation, dermal contact, and intake of PCBs by means of fish or other food are
of relevant importance, the allowable concentration levels can also be com-
bined in similar fashion. Since the scope of the present study pertains to
site cleanup, the applicable formulas for combining concentrations are not
presented, but they should be considered as the situation "warrants.
12-16
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13. WATER QUALITY LIMITS
The concentration levels of PCBs in drinking water are based on single-
route exposures that are estimated to result in acute and chronic toxic effects.
This does not imply that bioaccumulation in aquatic organisms does not occur.
The assumption pertains to absence of fish contaminated with PCBs in the diet.
If other routes are of concern, the allowable concentrations in water should be
redefined. The following levels of PCBs in drinking water, corresponding to
10-day AIs, can be calculated for children and adults:
• 10-day health advisory:
Safe 1 mg/kg-daylO kg
concentration = 100-1 L/day— = 0>1 m9/L (= 10° PPb) (child)
Safe 1 mg/kg'day70 kg
concentration = 100-2 L/day = 0-35 mg/L (= 350 ppb) (adult)
Similarly, the concentration levels at the various upper-bound cancer risks
assumed are calculated, and the results can be tabulated as follows:
Advisory
Upper-bound level
cancer risk (ng/L)
ID'4 875
ID'5 87.5
10-6 8.75
10-7 0.9
Example chronic toxicity advisory level (at 10'^ maximum risk)
IP"6 risk 70 kg = 8.75xlo-6 mg/L (=8>75 pg/L)
4(mg/kg-day)~1-2 L/day
13-1
-------
As indicated previously, an Aroclor constitutes a mixture of many con-
geners. Since each congener compound exhibits different solubility charac-
teristics, the applicability of these limits to individual congeners is ion
question. In the absence of short-term data for non-carcinogenic effects, the
10-day health advisory may be used as the 1-day health advisory for commercial
Aroclors.
13-2
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14. LEACHATE CONTAMINATION OF GROUNDWATER
Contaminated leachate will impact groundwater quality. To date, ground-
water monitoring data showing major contamination of groundwater by PCBs has
been rarely reported. If the contaminated site is located above an unsatur-
ated zone, soil through which leachate has to migrate to reach groundwater
will adsorb PCBs and will greatly retard PCB migration, as evidenced by the
high soil-water partition coefficients. Experimental work (U.S. EPA, 1980a)
has shown that the adsorption characteristics vary depending upon the type of
soil used. The experimental values are comparable to the partition coeffici-
ents estimated from the values of Kow (water-octanol partition coefficient)
given in Table 4. PCBs entering groundwater at hazardous waste sites could
also be retarded as They'are carried along the flow lines.
The area-source groundwater model (Hwang, 1985) has been used to evalu-
ate the extent of retardation and dilution of contaminants in groundwater. A
typical precipitation rate has been used to estimate a leachate generation
rate which is a source term in the groundwater rate and transport model. Two
different values of the retardation factor covering the extreme variations of
the soil-water partition coefficients were considered: Rj = 127, corresponding
•3 O
to Kj = 22 cnr/g; and R^ = 5715, corresponding to K^ = 1000 cnr/g, where Kd
represents the soil-water partition coefficient, and Rj is the retardation
factor (Rd = 1 + ^b K^, Pjj = bulk density, e = porosity). The results of
e
modeling show that when the concentration of PCBs in leachate is maintained
at 0.12 mg/L, the vertically averaged PCB concentration in groundwater at
1000 cm away from the center of a disposal site after two years of release is
0.5 x 10'4 mg/L and 1.9 x 10"? mg/L for the low and high values of the retar-
dation factor, respectively. Other parameter values used in this simulation
14-1
-------
were: leachate flow rate = 23.4 cm-Vs, groundwater seepage velocity = 5 x
10'4 cm/s, porosity of groundwater medium = 0.35, depth of the aquifer = 300
cm, size of disposal site = 0.5 acre, and the bulk density of the medium =
2 g/cm^. The simulation was repeated for a distance of 1 km away from the
site. The concentration values at that distance were very small.
The groundwater transport analysis back-calculated allowable leachate con-
centrations entering groundwater below a hazardous waste facility, given the
maximum allowable concentrations at a compliance point. These calculations do
not account for "facilitated transport" via dissolved organics, cosolvents,
etc. As indicated previously, the maximum allowable concentrations were based
on the allowable daily intakes designed to prevent acute and chronic health
effects. For the purposes of simulation, the maximum allowable drinking water
concentrations at-such distances as 1000 cm and 1 km from the contaminated site
can be estimated. For acute toxicity, the drinking water concentration of 0.1
mg/L is assumed; for chronic carcinogenic toxicity, the concentration of PCB in
groundwater assumed was 8.7 ng/L, corresponding to a 10"^ lifetime risk.
The down-gradient groundwater concentration is a complex function of
leachate concentration, dispersion and retardation in groundwater, initial
dilution in groundwater, biodegradation (if any), and groundwater velocity.
The functional relationship can be found elsewhere (Hwang, 1985), and takes
the form
CL = fg CM (35)
where CL represents the leachate concentration corresponding to the drinking
water concentration Cw at a point of interest, and fg is a functional relation-
ship which incorporates fate and transport of PCB in the groundwater medium.
14-2
-------
At the lower end of the retardation coefficient (R
-------
15. SOIL INGEST ION PATHWAY
i
A literature search shows that there is very limited information on the
rate of likely soil ingestion by children and adults which can be used in
exposure assessment. The situation for which the information is derived dif-
fers from study to study. Lepow (1975) studied the mouthing behavior of ten
2- to 6-year-old children in connection with investigations into the principal
cause of the excessive lead accumulation in the children. The total soil
ingestion rate for a 2-year-old child based on the average amount of street
dirt, house dust, and soil ingested by the child by putting his hands and
fingers in his mouth, can be summed as 0.6 g of soil per day.
Wedeen et al. (1978) observed the lead concentration in blood of a black
woman with a 12-year history of habitual eating of garden soil. Using the
levels of blood lead concentration and the concentrations of lead in the soil
analyzed, they estimated the amount of lead the subject had consumed each year
from her garden soil. From this estimate, the soil ingestion rate is estimated
to have been in the range of between 1.96 and 3.9 g/day, with an average value
at about 3 g/day. The lead concentration in the dried garden soil is reported
to be between 690 ug/g and 700 ug/g of soil.
Investigators at the Centers for Disease Control present the lifetime
ingestion rate of contaminated soil according to age group (Kimbrough et al.,
1984). The paper states that the data presented are "based on work done study-
ing lead uptake from contaminated soils." However, the writers of this report
were unable to locate the original experimental work or its source to cite in
this evaluation. The ingestion rate is assumed to change at different ages,
and is given as 0 for the age group 0 to 9 months, as 1 g/day for the age group
9 to 18 months, as 10 g/day for the age group 1.5 to 3.5 years, as 1 g/day for
15-1
-------
the age group 3.5 to 5 years, and as 0.1 g/day for a 5-year-old child.
The second column of Table 8 shows the lifetime carcinogenic risk posed
by ingesting soil contaminated with PCBs at various concentrations. This
table is prepared using Eq. (6) at the soil ingestion rate of 3 g/day for
children aged 1 through 6 and an average weight of 10 kg. The values for
other parameters used are SM = 0.5, GI = 0.3, and k = 0. The risk values in
the second column compare with those in the third column, which are prepared
using the soil ingestion rate applicable to different age groups, as suggested
by the Centers for Disease Control.
TABLE 8. MAXIMUM LIFETIME RISK FOR INGESTING SOIL CONTAMINATION
AT DIFFERENT PCB LEVELS
PCB level in soil (ug/g)
0.1
1
5
10
20
50
(IR = 3)
1.54 x ID"6
1.54 x 10-5
7.7 x lO-5
1.54 x lO'4
3.08 x lO'4
7.7 x ID'4
Lifetime risk
Age-dependent
1.92 x 10~6
1.92 x ID'5
9.6 x ID'5
1.92 x lO'4
3.8 x 10-4
9.6 x ID'4
aTaken from Kimbrough et al., 1984.
15-2
-------
A computer program was convenient to use in carrying out the summation of
daily intakes over a lifetime period. The lifetime risk represents an upper-
bound estimate of the unit risk that can occur as a result of ingesting PCB-
contaminated soil over a lifetime, and indicates the risk posed by a single
exposure pathway; that is, soil ingestion is the sole route for PCB intakes,
and other pathways, including air, water, fish are assumed to be insignificant
sources of human intake of PCBs. Since the population that will be subject
to soil ingestion resides in the area and must breathe the air affected by
PCB emissions, the magnitude of PCB intakes by the ingestion and inhalation
routes needs to be compared to determine the significant pathway. The compari-
sion is presented in Section 18.
Similarly, in order to determine the daily health advisory levels for a
single exposure pathway, the daily PCB intakes equivalent to ingesting 3 g of
soil in a day at various PCB concentrations are calculated. The results are
shown in Table 9.
TABLE 9. MAXIMUM DAILY PCB INTAKE BY INGESTION OF SOIL
AT VARIOUS PCB CONCENTRATIONS
Daily PCB intake at 30% absorption
PCB level in soil (ug/g) (mg/day)
0.1
1
5
10
20
50
0.00009
0.0009
0.0045
0.009
0.018
0.045
15-3
-------
The exposure pathways for soil ingestion, air inhalation, and other routes
must be evaluated. If one pathway is found to be dominant over the other, the
insignificant pathway based on short-term and long-term intake rates can be
ignored. If they are comparable, the concentration levels need to be adjus-
ted to reflect the combined intake rates by using Eq. (24) or combinations
of Eqs. (8) through (22).
15-4
-------
16. INHALATION PATHWAY
16.1. INTAKE BY AIR EXPOSURE ROUTE
Exposure to PCBs occurs at or near contaminated sites through inhalation
of ambient air contaminated with PCB vapors or particulate matter on which
PCBs are adsorbed. The PCB vapors emitted from contaminated soil will be
diluted by the action of winds before a person inhales the ambient air. When
PCBs are adsorbed on soil, the vapor pressure of the PCBs above the soil sur-
face will be always less than the vapor pressure exerted by PCBs when they are
present in pure form. In other words, the adsorption phenomena depress the
vapor pressure that can exist under saturated conditions. This true vapor
pressure is referred to as "partial pressure." When adsorption reaches its
saturation capacity on soil, the partial pressure will be equal to the pure PCB
vapor pressure.
Estimates of PCB concentrations in the ambient air impacting the popula-
tion at hazardous waste sites are discussed in this section, as well as com-
parison with the intake rates of PCB through soil ingestion. In calculating
ambient air PCB concentrations, the first task was to estimate the emission
rates of PCBs from the bulk of soil contaminated at various concentrations of
PCBs. The emission rate calculations can be rigorously performed by the
methods summarized by Hwang (1982) for steady state conditions, and by methods
presented in the Appendix for transient conditions.
Based on the inhalation rate of 20 m^/day, and absorption rates of 50% and
30% for inhaled and ingested PCBs (U.S. EPA, 1984b), respectively, the concen-
trations of PCBs in inhaled air and particulates equivalent to the dosage
causing acute and chronic toxic effects can be estimated. The purpose of this
exercise is to evaluate the concentrations of PCBs in the air, which are compa-
16-1
-------
rable to the ingestion dosage. Tables 10 and 11 show this comparison for
intake rates corresponding to acute and chronic effects respectively.
Table 10, for example, shows that a daily intake of 3 g of soil contain-
ing 5 yg/g of PCBs is equivalent to a daily inhalation of air containing 0.45
yg/m3. The concentration of PCBs on participate matter must be as high as
7,500 ug/g for the inhalation of particulates at an assumed concentration of
60 yg/m3 to be comparable to the ingestion of soil and inhalation of air
described above. This concentration is used because the concentration should
not exceed the primary ambient air quality of 75 yg/m3 for particulate matter.
Since the concentrations of PCBs on soil under consideration are in the range
which is less than this concentration, it can be assumed that the PCB intake by
inhalation of particulate matter at contaminated sites is relatively unimpor-
tant. Similar arguments can be made for the results shown in Table 11 for
long-term intakes. The equivalent air concentrations Ce shown in Tables 10 and
11 are calculated by the following formula:
, / 3\ _ daily intake (mg/day) x 103 yg/mg
e m 20 m3/day 0.5 (absorption factor) (36)
16.2. EMISSION EVALUATION SCENARIOS
Emission rates are estimated for four different scenarios: Case 1—as
the PCBs volatilize from the initial contaminated soil column, they are depleted
from the column of soil by diffusional transfer of PCBs across the soil-air
interface, resulting in unsteady-state emission rates, and the layer depleted
of PCBs acts as cover material retarding the volatilization rate; Case 2—the
same scenario as in Case 1 except that the contaminated soil is initially
covered with 25 cm of cover material; Case 3—PCBs are volatilized from the
16-2
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TABLE 10. COMPARISON OF PCB INTAKES BY INGESTION AND INHALATION ROUTES
FOR ACUTE EFFECTS
PCB levels
in soil
(ppm)
Daily acute
intake
(mg/day)
Equiv. air
cone, for
acute ingestion
(ug/m3)
Cone, of PCBs
on particulates
(ug/g)
0.1
1
5
10
20
50
0.00009
0.0009
0.0045
0.009
0.0018
0.045
0.009
0.09
0.45
0.9
1.8
4.5
150
1,500
7,500
15,000
30,000
75,000
16-3
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TABLE 11. COMPARISON OF PCB INTAKES BY INGESTION AND INHALATION ROUTES FOR CARCINOGENIC EFFECTS
PCB levels in soil
(ug/g)
0.1
1
5
10
20
50
Lifetime risk
at IR = 3
1.54 x 10~6
1.54 x 1C'5
7.7 x 10-5
1.54 x 10-4
3.08 x 10-4
7.7 x 10-4
Average daily intake
(mg/day)
3.86 x 10-6
3.86 x ID'5
1.93 x lO-4
3.86 x 10-4
7.72 x 10-4
1.93 x 10-3
Equiv. air cone.
for the risk
(pg/m3)
0.00039
0.0039
0.019
0.039
0.077
0.19
Cone, of PCBs on
participates
(ug/g)
6.4
64.3
322
643.7
1287
3217
-------
surface of contaminated soil, and the PCB concentration at the surface is kept
at a constant value; Case 4--the contaminated soil is covered with 25 cm of
clean cover soil to retard the volatilization rate, and the concentration of
PCBs at the surface is kept at a constant value.
As pointed out previously, there exists a PCB saturation point above which
the air-phase PCB concentration in equilibrium with (or partitioned with) the
contaminated soil remains constant, and hence the emission rate of PCBs will
also remain essentially steady over time. Below this point, a concentration
profile of PCBs across the contaminated soil column starting from the surface
to the depth of contamination will be created as volatilization progresses.
This will result in unsteady-state emission rates which will vary over the
period that exposure occurs. The period considered includes 10 days for 10-day
advisory, and estimated lifetime (70 years) for long-term advisory.
The concentration of PCBs in soil corresponding to the saturation point
can be estimated from the knowledge of vapor pressure and air-soil partition-
ing. For example, since the vapor pressure of Aroclor 1254 (7.71 x 10~5 mmHg)
as reported in a publication, corresponds to the saturation concentration of
1,362.7 ug/m3, the PCB concentration in soil at the saturation point is
C =
1.362.7 ug/m3
s (Xc(9 soil/cm3 air) x 106 cm3/m3]
aS
= 1.362.7 (2.44 x 1Q-2)(1.000) a 4 ug/g
(8.37 x lO'3 x 106)
for an assumed value for Kd of 1,000 cm3/g. The saturation concentration is
dependent upon the value of the air-soil partition coefficient. PCB saturation
16-5
-------
concentrations in air, and the corresponding concentrations in soil for the
Aroclors considered as part of this evaluation, are tabulated in Table 12,
based on the soil-water partition coefficient of 1,000 cm3/g for highly ad-
sorbable earth material (U.S. EPA, 1980a), which is used in calculating the
air-soil partition coefficient. A similar table can be prepared at the lower
end value of the soil-water partition coefficient, which is approximately 40
cm3/g for sandy material (U.S. EPA, 1980a).
Case 3 and perhaps Case 4 may be unrealistic, because as volatilization
continues, the PCS concentration in soil decreases and the surface layer,
depleted of PCBs, should act as an uncontarninated layer decreasing the emission
rate. But this estimate should provide upper-bound values for emission rates.
Cases 3 and 4 would be applicable in real-case situations when the concentra-
tion of PCBs in soil is high enough so that the air-phase concentration in
equilibrium with soil remains constant until the concentration of PCBs in soil
decreases to the saturation point (Csm, as defined on p. 12-5). Below the
saturation point, the air-phase concentration will no longer remain constant,
but will decrease in direct proportion to the soil-phase concentration. In the
emission rate calculation, the partial pressure of PCBs as a result of parti-
tioning between the air and soil phases is used. Since the vapor pressures and
Henry's Law constants are different for most PCBs, some typical PCBs are used
for the purpose of illustrative calculations. Table 13 summarizes the results
of calculations for emission rates for soil containing 1 vg of Aroclor-1254
and Aroclor-1242 per g of soil. The values shown for Cases 1 and 2 are the
averages for one day emitted after the initial contamination at the concentra-
tion. This is for illustration only because Aroclor-1248 and Aroclor-1260 are
also used for emission rate calcualations. The models used for the emission
rate estimation and necessary calculations are shown in Appendix A. The emis-
16-6
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TABLE 12. CONCENTRATION OF PCBS IN SOIL AT SATURATION VAPOR PRESSURE
BASED ON Kd = 1000 cm3/g
PCB concen- Saturated
tration in soil vapor
with saturated concentration
vapor (gg/g) (ug/m3)
Aroclor-1254
Aroclor-1242
Aroclor-1260
Aroclor-1248
4
250
28.2
55.3
1362.7
5823.3
822.8
7962.8
TABLE 13. PCB EMISSION RATES FROM 1 yg/g PCB SOIL
AT DIFFERENT CONTROL LEVELS
Scenario
Case 1
Case 2
Case 3
Case 4
Emission rates
Aroclor-1254
1.03
3.67
1.13
1.67
x 10'11
x lO'13
x 10-10
x 10-13a
(g/cm2«s)
Aroclor-1242
2.7 x 10-12
2.8 x 10-14
8.57 x 10-12
1.14 x 10-l4a
aThe models for estimating emissions from landfills underpredict the emission
rate in comparison to Case 2. The estimates for Cases 2 and 4 are based on
the mathematical model (described in Appendix A) and the empirical model
(Farmer et al., 1980), respectively.
16-7
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sion rates at various concentration levels of PCB in soil are made for evalua-
ting the impact of volatilization on the exposed population at various loca-
tions. Table 13 shows that the emission rate of Aroclor-1254 is different
from that of Aroclor-1242 at the same soil contamination level. The table also
shows that the use of cover material is very effective in reducing the emission
rate. The average emission rates over a period of 10 days, or a lifetime, for
Cases 1 and 2 can be similarly estimated by the rigorous mathematical formulae
provided in Appendix A. As PCBs volatilize, the partial pressure of PCBs at
the soil-air interface decreases, and the soil layer, depleted of PCBs, pro-
vides the barrier for mass transfer, causing the emission rates given for Cases
3 and 4 to approach values comparable to those for Cases 1 and 2, respectively.
The Thibodeaux and Hwang model (1982), originally developed for land treatment
facilities, provides emission rates similar to those shown for Case 1 and 2 in
Table 13.
PCBs volatilized into the atmosphere from a contamination site will im-
pact the population in the surrounding region. The concentrations of PCBs at
the point of impact need to be determined in order to evaluate the signifi-
cance of the air emissions compared with the soil ingestion and dermal path-
ways. Acute and chronic impacts are based on the daily concentrations and
the concentrations averaged over an annual period. Emission rates correspond-
ing to all four cases of maintenance levels are used to estimate the concen-
trations of PCBs in the ambient air at the site and at distances of 0.1 km
and 1 km.
16.3. AIR DISPERSION MODELING
Dispersion modeling is used to estimate the ambient air concentrations
which may be possible for daily and annual exposures. Dispersion modeling for
estimating the annually averaged concentrations makes use of six stability
16-8
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classes, six wind speed classes, and 16 sectors, assigning the receptor point
to one of the 16 sectors. The wind rose data consisting of 6 x 6 x 16 = 576
elements are compiled by the National Climatic Center in Asheville, North
Carolina. The dispersion model for the annual concentration sums the con-
centration contributions over the entire range of stability classes and wind
speeds for each exposure location downwind of the contamination site, and can
take the following form (Bruce, 1969):
6
C(X,k) = 2.03 x 106Q I 1 6> fijk
x i u (37)
where C(X,k), the annual concentration located in a sector k at a distance
of X downwind of the site (pg/m3);(a)i,X = standard deviation of the plume
in the z-direction (vertical direction) at distance X for stability class i,
Q = emission rate, g/s, Uj = mean wind speed for wind speed class j, m/s and
f^k = frequency of wind in stability class i, wind speed class j, and direc-
tion in sector k. Both X and the standard deviation have the the units of
meters.
The values for the standard deviation can be found in an air pollution
textbook (Wark and Warner, 1981), or can be determined by a curve-fitting
equation of the form
(az)i>x = aXb + d (38)
where a, b, and d are empirical constants varying according to stability i
and distance X (Wark and Warner, 1981; Martin, 1976). The values for these
constants are given in Table 14 (Martin, 1976).
16-9
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TABLE 14. VALUES OF CONSTANTS FOR STANDARD DEVIATION EXPRESSION
AS A FUNCTION OF DOWNWIND DISTANCE AND STABILITY CONDITION
Stability
A
B
C
D
E
F
a
440.8
106.6
61.0
33.2
22.8
14.35
X < 1 km
b
1.941
1.149
0.911
0.725
0.678
0.740
d
9.27
3.3
0
-1.7
-1.3
-0.35
a
459.7
108.2
61.0
44.5
55.4
62.6
X > 1 km
b
2.094
1.098
0.911
0.516
0.305
0.180
d
-9.6
2.0
0
-13.0
-34.0
-48.6
The estimation of the on-site ambient air concentration does not require
the use of air dispersion modeling presented above. The ambient air concen-
tration is controlled by the extent of dilution before dispersion occurs down-
wind of the source. The dilution can be estimated from the knowledge on the
rate of PCB emissions and volumetric rate of wind being mixed with PCB vapors.
The method for estimating the on-site ambient air concentrations is described
in detail in Appendix A.
16.4. AIR EXPOSURE EVALUATION
Table 15 summarizes the results of dilution estimation and dispersion
modeling to obtain the concentration levels of PCBs in ambient air at various
locations considered for emissions of PCB-1254. This table is a summary of one
set of calculations for the PCB concentration of 1 ug/g in soil for each
scenario. The wind speed of 10 mph is used for both one-day and annual concen-
tration averages. The Climatic Atlas of the United States provides information
16-10
-------
on annual average wind speed. A default value of 10 mph represents a typical
annual wind speed in the United States. A site-specific evaluation will require
detailed wind rose information based on local measurements..
TABLE 15. AMBIENT PCB CONCENTRATIONS AT DIFFERENT LOCATIONS
(PCB IN SOIL = 1 wg/g, PCB-1254)
Concentrations (wg/ra3)
0.1 km from site
Case 1
Case 2
Case 3
Case 4
On-site
0.61
1.4xlO-3
11
0.017
Daily
0.026
5.9xlO-5
0.48
7.1xlO-4
Annual
0.0065
1. 47xlO-5
0.12
l.SxlO'4
1 km from site
Daily
0.0016
3.5xlO-6.
0.03
4.3x10-5
Annual
0.0004
8.9xlO-7
7.3xlO-3
1.1x10-5
The standard deviation curve for D stability is employed in estimating the
ambient air concentrations at the distances of 0.1 and 1 km from the site as
shown in Table 15, since D stability is by far the most frequently occurring
stability class. Although D is the most common stability, an exposure-weighted
average stability should be used for site-specific evaluations. The frequency
with which winds blow toward a sector of interest is assumed to be 1 for evalu-
ating the worst-case daily concentrations, while it should be based on the most
common of the standard 16 wind directions for estimation of the average annual
concentration levels. The concentrations in ambient air on-site and at dis-
tances of 0.1 km and 1 km from the site are given in the table. Calculations
are performed for the ambient air concentrations of PCB-1242, PCB-1248, and
16-11
-------
PCB-1260, but these are not tabulated here. The values in the table should not
be construed as representing fixed ambient air concentrations at the location
and under the mode of exposure. The values are presented by way of illustra-
tion to compare the contributions to ambient air occurring given the different
assumed conditions.
The concentration of PCBs in equilibrium with soil containing 1 ug/g
PCB-1254, which corresponds to the partial pressure of PCBs partitioned above
the soil, is 340 yg/m3. This represents the maximum vapor concentration when
PCB is emitted from the soil surface. Based on this concentration and the
estimated ambient air concentrations given in Table 15, one can calculate the
dilution factors of the emissions for use in Eq. (9) or (24). For example,
the air dilution factor for the on-site exposure corresponding to the Case 1
emission
rate would be
0 = 0.611/340 = 0.0018
The values shown in Table 15 can also be used to determine the daily in-
takes and lifetime risk levels corresponding to breathing each ambient air le-
vel. For example, the daily intake from the exposure to the ambient air con-
centrations of PCB-1254 at 0.1 km from the site for the Case 1 emission rate
can be based on a daily inhalation rate of 20 m3/day of air and 50% absorption
factor for inhalation.
Daily intake (mg/day) = C(ug/m3) • 20 m3/day • (1/1000 mg/yg)
= 0.026 (20)(1/1000)(0.5) = 0.00026 mg/day
16-12
-------
The same daily intake can be obtained by using Eq. (9):
Daily intake = Kas'Cs-D'IH'10+3(ABA)(SM)
= (8.37xlO-3/1000)(l/2.44xlO-2)(l)(0.026/340)(20)(103)(0.5)(l)
= 0.00026 mg/day
Similarly, the lifetime risk associated with breathing the ambient air can
be calculated as follows:
Risk = C(wg/m3) • 20 m3/day • 1/70 kg • 1/1000 mg/yg (4) (mg/kg/day)-l (0.5)(0.5)
where C is the ambient air concentrations shown in Table 15 and the value 4
(mg/kg'day)'1 represents the potency factor for PCBs, and an additional factor
of 0.5 is the off-site factor under the assumption that a resident stays in the
area 50% of the time.
A series of calculations can be performed as shown above, or the procedure
shown above can be reversed to back-calculate the PCB contaminations in soil
which will provide the allowable ambient air concentrations at the locations
considered and at the acute and chronic effect levels.
16-13
-------
17. DERMAL CONTACT PATHWAY
Deposition of contaminated soil, dirt, or dust on human skin can provide
another pathway for human intake of PCBs. PCBs can be absorbed through skin
when PCB-contaminated particulates come into contact with skin. Exposure
evaluation requires an estimation of the amount of the particulates on skin,
and the extent or rate of absorption. The absorption rate is dependent upon
the type of chemicals. Some chemicals are readily absorbed, while others are
not.
There are many factors affecting the amount of soil which can be accumula-
ted on skin. Factors include the exposed human skin area, contact time, type
of soil, soil conditions, and type of activities. For example, the amount
deposited on children playing in a contaminated area may be different from that
on adults working in a garden.
OHEA (U.S. EPA, 1984b) has made an estimation of the amount of soil depo-
sition on skin based on the studies by Lepow (1975) and Roels et al. (1980).
Both investigators, using adhesive tape, measured the amount of soil and dirt
accumulated by children on exposed areas such as hands, palm, and fingers. The
measured amount of soil ranges from 0.5 to 1.5 mg/cm2, with an average value of
1 mg/cm2. It should be noted that this is an average value over the surface of
the exposure area, and that some parts of the body may have more accumulation
of soil than others.
The area of human skin that will come in contact with soil or dirt
depends upon the protective measures used during the time that such contact
occurs, as well as the age group involved. The exposed surface area of an
adult is estimated to range from about 900 to 2,900 cm^. The exposed surface
area of a child may be smaller in proportion to their total surface area.
17-1
-------
The ranges of values associated with the factors mentioned above makes it dif-
ficult to arrive at an average value for the amount of soil and dirt accumula-
ted on soil. An assumption of an average soil deposition at 1 mg/cm^, and
exposed surface area of about 1,000 cm^ on a daily basis, provides an average
daily deposition rate of 1 g per day. The variability is such that this value
may be different by a factor of as much as two.
Investigators at the Centers for Disease Control present an estimated
daily deposition of soil on skin according to age group (Kimbrough et al.,
1984). Their tabular presentation shows that the daily amount of soil de-
posited on skin is 0 for the age group 0 to 9 months; 1 g for the age group
9 to 18 months; 10 g for the age group 1.5 to 3.5 years; 1 g for the age group
3.5 to 15 years; and 100 mg at age 15 years.
17-2
-------
18. COMPARISON OF EXPOSURES BY SOIL INGESTION, INHALATION, AND DERMAL CONTACT
Table 16 shows comparisons of PCB intake by various exposure routes.
Calculations apply for PCB-1254 because the emission rate is dependent upon
the soil-air partition coefficient, which is different for each PCB. The
ambient air concentration is the on-site value based on the emission rate
averaged over 1 day after soil is contaminated up to the surface without
cover.
TABLE 16. COMPARISON OF INTAKES BY VARIOUS EXPOSURE ROUTES3
Exposure route
Soil ingestion
Inhalation
Dermal absorption
Dust inhalation
Contact Absorption
rate fraction
3 g/day (with pica)
0.6 g/day
20 m3/dayb
1 g/day
20 m3/dayc
0.3
0.3
0.5
0.05
0.5
Daily intake
(mg/day)
9 x 10-4
1.8 x 10-4
6.1 x lO-3
5 x 10-5
6 x 10-7
Lifetime
intake
(mg/70 yrs)
Id
0.2
786
0.64f
7.7 x 10-3e
aUsed for illustration: PCB-1254 at concentration of 1 ug/g in soil.
bOn-site ambient air concentration based on 1-day average emission rate
after surface contamination (no cover).
Concentration of suspended particular matter: 60 pg/m3.
d!83 days/year for 6 years.
eOff-site factor = 0.5.
fy\n average exposure of 1.5 mg/cm2 and the exposure surface area of 1000
assumed; off-site factor = 0.5.
18-1
-------
Evaluation under the scenario of the use of cover, or longer-term emission
averages, may change the daily intake by inhalation considerably. For example,
a calculation shows that the use of 25-cm clean soil cover will reduce the
daily intake by inhalation to 1.4 x 10'^ mg/day instead of 6.1 x 10~3 mg/day.
On the other hand, exposures by soil ingestion, dermal absorption, and dust in-
halation will be likely to decrease because clean soil is used. The ingested
soil or the soil on the surface of the cover that may be accumulated on skin is
initially clean. Hence, the daily intakes by pathways other than inhalation
also become small. However, the concentration of PCBs in the initially clean
cover material could increase as the PCBs in the air phase being emitted are
adsorbed on the cover material as the liquid PCBs rise toward the surface due
to capillary potential. The table suggests that soil ingestion and inhalation
are two competing exposure routes for PCB intake. The dermal contact can also
become a contributing route for some conditions of exposure duration. When a
high concentration of particulate matter in the ambient air is prevailing, the
comparison shown in Table 16 can no longer apply. Consequently, the contribu-
tion to PCB intakes by inhalation of particulate matter will increase. There
are a range of other possibilities which may result in a comparison different
from that shown in Table 16.
18-2
-------
19. RESULTS
19.1. DERIVATION OF PERMISSIBLE SOIL CONTAMINATION
Determination of the permissible PCB levels in soil for intake through
the combined exposure routes makes use of 1) Eq. (24) when the soil concen-
tration is below the saturation point; and 2) the summation of Eqs. (8), (9),
and (10), equated to the acceptable intake otherwise. For each Aroclor under
consideration, a separate exposure evaluation can be made for the following
classes of exposure location and route: 1) Exposure occurs on-site. This
can be further subdivided into: (a) sites which are readily accessible to
children, and hence for which soil ingestion is a possibility, and (b) sites
for which there is no possibility of soil ingestion, and hence exposure is
only through inhalation; 2) sites which no population is assumed to enter
within the radius of 0.1 km from the site; and 3) sites which no population is
assumed to enter within the radius of 1 km from the site.
Two classes of soil ingestion rates are evaluated when exposure occurs on-
site (Class 1 above). For the first class, estimates of exposure are calcula-
ted for a person with pica who consumes 3 g per day between the ages of 1-5
years. For the second class, estimates of exposure are calculated for soil
ingestion of 0.6 g per day between the ages of 1-5 years. For both classes,
frequency of exposure is assumed to be every other day for lifetime exposures.
For a 10-day exposure, soil consumption is assumed to occur consecutively for
10 days. No soil ingestion is assumed for sites which are not accessible to
population within 0.1 km or 1 km from the contaminated site. The route of
exposure in these cases is by inhalation only. For lifetime inhalation expo-
sure estimates, it is assumed that the population is exposed 50% of the time,
i.e., 12 hours/day, or 6 months/year.
19-1
-------
The emission rate of volatilized PCBs can be considerably reduced by
covering the contaminated soil by low-porosity uncontaminated soil or clay
material. The reduction in the emission rate will result in a decrease in
ambient air concentrations of PCBs by the action of blowing winds. When PCB
material is directly exposed to the atmosphere, the PCB levels in soil required
to maintain the same level of exposure will be less than those expected when
the PCB material is covered with low-permeability material of appropriate
thickness. The cover would also serve as a deterrent to soil ingestion and
direct dermal contact.
The worst-case emissions would occur when the contaminated soil is initial-
ly exposed to the atmosphere and the soil is contaminated up to the conditions
exhibiting saturation vapor pressure. Models are used to estimate emission
rates which can be constant or time-varying depending upon the degree of soil
contamination. The constant emission rate can be assumed if the vapor phase
concentration maintains its constant value at the surface of contamination.
There will be a profile along the layer of soil contamination for time-varying
emission rates. The models for constant and time-varying emission rates are
applied with or without cover material. Calculations corresponding to Cases 1,
2, and 3 for exposure possibilities are repeated at an assumed 25-cm (10-inch)
thickness of a soil cover initially free of PCB contamination.
The ambient air concentrations given in Table 15, and the resulting air
dilution factors calculated, are based on an annual average wind speed of 10
mph. When wind speed is lower than this, it is possible that the daily dilu-
tion factors could be higher than the values in the calculations (less dilu-
tion). The combined soil concentration values based on Eq. (24) will be lower
when the dilution factor is higher. More accurate considerations of meteoro-
logical conditions will require site-specific evaluation.
19-2
-------
Among many factors affecting the emission rate (including vapor pressure,
soil-air partition coefficient, and Henry's law constant), the variability
associated with the soil-air partition coefficient is more pronounced than any
other chemical and physical properties. This is caused by the wide variation
in experimental values for the soil-water partition coefficient reported in
the literature (U.S. EPA, 1980a), ranging from 22 to 2,000 cm3 water/g soil.
For clay and sandy materials, the range includes about 40 to 1,000. The
values of K
-------
(5) Noncancer and cancer effects are evaluated at the acceptable intakes
corresponding to 10-day exposure on the first day of cleanup and
after 10 days of elapsed time upon cleanup, and lifetime permissible
exposures.
(6) Two extreme values of the soil-air partition coefficients are used
in the evaluation. The high values of Kj (soil-water) correspond to
low values of Kas (soil-air).
(7) Area contaminated is 45 m x 45 m or approximately 0.5 acres.
The combinations of these evaluation conditions are presented in tabular
form in Table 17. The soil ingestion rates of both 3 and 0.6 g/day are used
in the evaluation pertaining to the longer-term (=10-day) intakes. The
soil ingestion rate of 0.6 g/day between ages 1 and 5 is used for lifetime
exposure evaluation, and this value is averaged with respect to soil ingestion
and changing body weight over a lifetime. For each Aroclor, there are 120
different situations demanding different permissible levels of PCBs in soil
depending upon the location, route and duration of exposure, elapsed time
after site cleanup, and the type of health effects to be protected. Table
18 shows the corresponding values for K
-------
TABLE 17. EVALUATION CONDITIONS FOR EACH AROCLOR
to
I
tn
Values for partition
Location and route
of exposure
Intake rates
Ten-day intake, Kda
child (100 pg/d) L
Ten-day intake, Kd
adult (700 Mg/d) L
10'7 risk Kd
(0.00175 pg/d) L
10'6 risk Kd
(0.0175 pg/d) L
10'5 risk Kd
(0.175 iig/d) L
10'4 risk Kd
(1.75 pg/d) L
Soil ingestion
(3 g/d)
inhalation
dermal
1,000
Ob
1,000
0
1,000
0
1,000
0
1,000
0
1,000
0
40
25^
40
25
40
25
40
25
40
25
40
25
On-site
3
coefficient (Kd cm /9)
Soil ingestion
(0.6 g/d)
inhalation
dermal
1,000
0
1000
0
1,000
0
1,000
0
1,000
0
1,000
0
40
25
40
25
40
25
40
25
40
25
40
25
Inhalation
only
1,000
0
1,000
0
1,000
0
1,000
0
1,000
0
1,000
0
40
25
40
25
40
25
40
25
40
25
40
25
and cover depth (L cm)
0.1 km
from site
Inhalation
1,000
0
1,000
0
1,000
0
1,000
0
1,000
0
1,000
0
40
25
40
25
40
25
40
25
40
25
40
25
1 km
from site
Inhalation
1,000
0
1,000
0
1,000
0
1,000
0
1,000
0
1,000
0
40
25
40
25
40
25
40
25
40
25
40
25
aKd = soil-water partition coefficient in units of cm3 water/g soil (= cone, in soil/cone, in water), high
values close to clays, low values close to sand.
bMeans no cover designated as "surface contamination."
cMeans 25 cm (10") clean soil cover applied immediately after remedial action.
-------
TABLE 18. LOW AND HIGH VALUES OF AIR-SOIL PARTITION COEFFICIENT
USED IN THE EVALUATION
Kd (cm3 water/g soil)3
PCB type
1242
1248
1254
1260
High
1,000
1,000
1,000
1,000
Low
40
40
40
40
"as
Low
2.35 x
1.44 x
3.43 x
2.92 x
(g soil
10-5
10-4
10-4
10-4
/cm3 air)b
High
5.87 x 10-4
3.6 x ID'3
8.58 x ID'3
7.31 x ID'3
aK(j is the soil-water partition coefficient and has the unit of cnr* water/g
soil which is equivalent to concentration in soil/concentration in water.
DKflS is the soil-air partition coefficient and has the unit of g soil/cm3
air, which is equivalent to concentration in air/concentration in soil.
This is calculated by (H/Kd) (1/2.44 x 10'z).
19-6
-------
TABLE 19. PERMISSIBLE PCB-1242 SOIL CONTAMINATION LEVELS
(UNCOVERED SURFACE CONTAMINATION)
Permissible levels (ug/g) corresponding to
Noncancer short-term3
acceptable Intake MQ/day** Cancer risk specific doses tug/day)
Location and
route of human
exposure
100
for child
700
for adult
0.00175
(10-7 risk)
0.0175
(10-6 risk)
0.175
(10-5 risk)
(10l4
risk)
On the contaminated site
- Soil IngestlonC. 55-60f 510-690 0.008-0.01 0.08-0.1 0.8-1.0 8-13
inhalation6
- Soil Ingest ion*1, 92-247 2100-2800 0.03-0.06 0.3-0.6 3.0-6.0 35-61
inhalation6
- Inhalation only6 116-vs9 vs 0.04-0.2 0.4-2.0 4.0-20 110-200
0.1 km from vs vs 4.0-20 110-200 l.lxlO4 vs
contaminated site
- Inhalation only6
1 km from vs9 vs 310-430 3.1xl04 vs vs
contaminated site
- Inhalation only6
aShurt-term = 10-daj Intake.
''Based on average weights of 10 and 70 kg for a child and an adult, respectively.
••Children ages 1-5, with pica (consuming 3 g soji/day).
''Children ages 1-5, without pica (consuming 0.6 g soli/day).
elnhalation rates are assumed to be 20 m'/da
'/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 nr/day as a result of 182 days exposure per year.
'Ranges result In each case because 1) four PCBs (1242, 1248, 1254, 1260) are considered, each with a different
vapor pressure, and 2) high and low values for soil-air partition coefficient are used In the calculations.
9vs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquids for the limit.
-------
•TABLE 20. PERMISSIBLE PCB-1248 SOIL CONTAMINATION LEVELS
(UNCOVERED SURFACE CONTAMINATION)
i
oo
Permissible levels (pg/g) corresponding to
Noncancer short-term6
acceptable Intake ug/dayb
Location and
route of human 100 700
exposure for child for adult
On the contaminated site
- Soil IngestionC, 32-80f 612-710
Inhalation6
- Soil tngest1ond. 42-330 2500-2900
Inhalation6
- Inhalation only6 47-vs9 vs
0.1 km from vs vs
Cancer risk specific doses (pg/day)
0.00175 0.0175 0.175 1.75
(10-7 risk) (10-6 risk) (10'5 risk) (10-1 risk)
0.01 0.1 1.0 8-10
0.02-0.04 0.2-0.5 2.0-5.0 37-49
0.02-0.08 0.2-0.8 2.0-8.0 87-110
contaminated site
- Inhalation only6
1 km from
contaminated site
- Inhalation only6
vs
vs
2.0-8.0 90-110 8.7x103 8.7xlo5-vs
250-270 2.4x104-2.5x10* vs vs
aShort-term a 10-day Intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
cCMldren ages 1-5, with pica (consuming 3 g soil/day).
dCMldren ages 1-5, without pica (consuming 0.6 g soli/day).
elnhalat1on rates are assumed to be 20 mVda
3/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m3/day as a result of 182 days exposure per year.
'Ranges result In each case because 1) four PCBs (1242, 1248. 1254, 1260) are considered, each with a different
vapor pressure, and 2) high and low values for soil-air partition coefficient are used in the calculations.
9vs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquids for the limit.
-------
TABLE 21.' PERMISSIBLE PCB-1254 SOIL CONTAMINATION LEVELS
(UNCOVERED SURFACE CONTAMINATION)
Location and
route of human
exposure
Noncancer short-term3
acceptable Intake vg/day"
100 700
for child for adult
Permissible levels (wg/g) corresponding to
Cancer risk specific doses (pq/day)
0.00175 0.0175 0.175
(10-' risk) (10-6 risk) (10-5 rtsk)
1.75
(ID*4 risk)
On the contaminated site
- Soil IngestlonC, 90-100f 720-730 0.009-0.01 0.09-0.1 1.0-2.0 12
Inhalation6
- Soil 1ngest1ond, 370-420 2980-3000 0.01-0.04 0.1-0.4 3.0-4.0 36-59
Inhalation6
- Inhalation only* vsg vs 0.01-0.05 0.1-0.5 5.0-7.0 460-470
0.1 km from vs vs 5.0-7.0 460-470 4.7xl04 vs
contaminated site
- Inhalation only6
1 km from vs vs 1.3xl03 1.3xl05 vs vs
contaminated site
- Inhalation only6
aShort-term » 10-day Intake.
DBased on average weights of 10 and 70 kg for a child and an adult, respectively.
Children ages 1-5. with pica (consuming 3 g soil/day).
Children ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalat1on rates are assumed to be 20 m3/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m3/day as a result of 182 days exposure per year.
'Ranges result In each case because 1) four PCBs (1242, 1248, 1254, 1260) are considered, each with a different
vapor pressure, and 2) high and low values for sod-air partition coefficient are used In the calculations.
9vs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquids for the limit.
-------
TABLE 22. PERMISSIBLE PCB-1260 SOIL CONTAMINATION LEVELS
(UNCOVERED SURFACE CONTAMINATION)
Location and
route of human
exposure
Noncancer short-term3
acceptable Intake ug/dayD
100 700 ,
for child for adult
Permissible levels (pQ/g) corresponding to
Cancer risk specific doses (tig/day)
0.00175 0.0175 0.175
(10-' risk) (10-6 risk) (10-5 Ms|()
1.75
(10-4 risk)
On the contaminated site
- Soil Ingestlont, 25-87* 640-710 0.01 0.1 . 1.0 12-17
Inhalation6
- Soil 1ngestiond, 61-360 2670-2900 0.01-0.04 0.1-0.4 1.0-4.0 40-48
£> Inhalation6
i
o - Inhalation only6 vs9 vs 0.01-0.06 0.1-0.6 1.0-6.0 77-91
0.1 km from vs vs 6-220 90-2.2xl04 7.7xl03-vs vs
contaminated site
- Inhalation only6
1 km from vs vs 220-240 2.2x10* vs vs
contaminated site
- Inhalation only6
'Short-term a 10-day Intake.
"Based on average weights of 10 and 70 kg for a child and sn adult, respectively.
cCh11dren ages 1-5, with pica (consuming 3 g soil/day).
Children ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalat
-------
TABLE 23. PERMISSIBLE PCB-1242 SOIL CONTAMINATION LEVELS
(25-cm-THICK CLEAN SOIL COVER)
Location and
route of human
exposure
Noncancer short -term9
acceptable Intake uQ/dayb
100 700
for child for adult
Permissible levels (gg/g) corresponding to
Cancer risk specific doses (gg/day)
0.00175 0.0175 0.175
(10-7 risk) (10-6 risk) (10"5 risk)
1.75
(10-4 risk)
On the contaminated site
- Soil Ingestlon'. 170-200f 1200-1400 0.03-0.2 0.3-2.0 3-17 170-vs
Inhalation6
- Soil 1ngest1ond. 450-820 3100-5700 0.1-0.6 1.0-6.0 12-48 260-vs
Inhalation6
- Inhalation only6 vs9 vs 0.9-1.0 9-vs 86-vs vs
0.1 km from vs vs 85-vs vs vs vs
contaminated site
- Inhalation only6
1 km from vs vs vs vs vs vs
contaminated site
- Inhalation only6
aShort-term = 10-day Intake.
"Based on average weights of 10 and 70 kg for a child and an adult, respectively.
Children ages 1-5, with pica (consuming 3 g soil/day).
('Children ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalat
-------
TABLE 24. PERMISSIBLE PCB-1248 SOIL CONTAMINATION LEVELS
(25-cm-THICK CLEAN SOIL COVER)
10
i
Permissible levels (wg/g) corresponding to
Noncancer short -term3
acceptable Intake pg/dayb
Cancer risk specific do&es (u9/day)
Location and
route of human
exposure
100
for child
700
for adult
0.00175
(10-' risk)
0.0175
(10-6 risk)
0.175
(10-5 risk)
1.75
(10-* risk)
On the contaminated site
- Soil 1ngest1onc, 160-190f 1100-1300
inhalation6
- Soil 1ngest1ond. 650-vs9 4500-vs
Inhalation6
- Inhalation only6 vs vs
0.1 km from vs vs
contaminated site
- Inhalation only6
1 km from vs vs
contaminated site
- Inhalation only6
0.01-.09
0.02-0.1
0.02-0.1
2-14
vs
0.1-1.0
vs
1-10
26-460
0.2-1 2.0-10 93-2,500
0.2-1 2.0-14 1.9x10*
1.9xl04 vs vs
vs
vs
aShort-term * 10-day Intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
GCh11dren ages 1-5, with pica (consuming 3 g soil/day).
^Children ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalat1on rates are assumed to be 20 tn3/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m3/day as a result of 182 days exposure per year.
fRanges result In each case because 1) four PCBs (1242, 1248, 1254, 1260) are considered, each with a different
vapor pressure, and 2) high and low values for soil-air partition coefficient are used In the calculations.
9vs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquids for the limit.
-------
TABLE 25. PERMISSIBLE PCB-1254 SOIL CONTAMINATION LEVELS
(25-cm-THlCK CLEAN SOIL COVER)
I
I—•
U)
Location and
route of human
exposure
Noncancer short-term3
acceptable Intake pg/day°
100 700
for child for adult
Permissible levels (wg/g) corresponding to
Cancer risk specific doses (gg/day)
0.00175 0.0175 0. 175 1.7
(10-7 risk) (ID"6 risk) (10'5 risk) (10'4
risk)
On the contaminated site
- Soil
-------
TABLE 26. PERMISSIBLE PCB-1260 SOIL CONTAMINATION LEVELS
(25-cm-THICK CLEAN SOIL COVER)
vo
Permissible levels (ug/g) corresponding to
Noncancer short-term9
acceptable Intake ng/dayb
Location and
route of human 100 700
exposure for child for adult
On the contaminated site
- Soil IngestlonC, 110-184? 800-1300
Inhalation6
- Soil Ingest 1on««, 550-800 4000-5000
Inhalation6
- Inhalation only6 vs9 vs
0.1 km from vs vs
Cancer risk specific doses dig/day )
0.00175 0.0175
(10-' risk) (10-6 risk)
0.01-0.02 0.1-1.0
0.02-0.07 0.2-0.7
0.02-0.08 0.2-0.8
1-8 620-770
0.175 1.75
(10-5 risk) (10-* risk)
1.0-2.0 22-360
1.0-7.0 120-550
1.0-8 620-770
vs vs
contaminated site
- Inhalation only6
1 km from
contaminated site
- Inhalation only6
vs
vs
vs
vs
vs
vs
aShort-term s 10-day Intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
cCM1dren ages 1-5, with pica (consuming 3 g soil/day).
^Children ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalat1on rates are assumed to be 20 mVday for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m'/day as a result of 182 days exposure per year.
fRanges result In each case because 1) four PCBs (1242, 1248. 1254, 1260) are considered, each with a different
vapor pressure, and 2) high and low values for soil-air partition coefficient are used In the calculations.
9vs denotes no theoretical upper-bound Hm1t. Practical reasons require no free-flowing PCB liquids for the limit.
-------
The symbol "vs" indicates that no upper-bound limit for PCB concentra-
tions in soil can be derived from the exposure evaluation. This results mainly
for two reasons. First, the emission rate cannot exceed the upper-bound value
which can be expected when the air phase concentration of PCBs at the contami-
nated soil surface is maintained at the saturation point. The concentration at
the saturation point corresponds to the vapor pressure concentration. Second,
when the cover is applied, the emission rate is not only retarded, but also the
concentration of PCBs in soil being ingested is controlled by the amount of
PCBs adsorbed on soil in equilibrium with the air phase being emitted. Hence,
the concentration of PCBs in the initially clean soil material cannot exceed the
saturation point concentration. The PCB concentrations in soil corresponding to
vapor saturation concentrations are 250, 55, 4, and 28 vg/g when K
-------
Since the ranges shown in these tables are dependent upon the values of
the soil-air coefficient, the site-specific or contaminant-specific informa-
tion will help find an appropriate level of PCBs for that particular condition.
This can be done either by using the procedure outlined in the main body of the
report, or can be conveniently done by looking up the values listed in the
Appendix for each Aroclor at low and high values of soil-air partition coef-
ficient.
The results in Tables 23 through 26 for each Aroclor assume that the 25-cm
clean cover material is placed on top of contaminated soil. In this case, the
intake rate by exposure to soil ingestion is calculated based on the estimated
concentration profile existing in the cover material. This profile exists
because of the establishment of the vapor-solid adsorption equilibrium between
the vapors being emitted and the soil. The concentration profile, which changes
as a function of time, is estimated by mathematical models, the concentration
used for soil ingestion is the average concentration along the thickness of the
initially clean cover material.
If the prevailing contaminants at a site are PCB-1242, for example, Table
19 can be interpreted as follows:
(1) When the site is amenable to access by children with possibilities
of ingesting the contaminated soil exposed to the atmosphere, the permissible
PCB concentrations levels in soil should range from 55 to 60 ug/g, and 92 to
247 ug/g for prevention of noncancer effects from 10-day exposures at soil
ingestion rates of 3 g/day and 0.6 g/day, respectively.
When the site is accessible to children and the population has the poten-
tial of on-site exposures to the contaminated soil and air over a lifetime, the
permissible PCB levels in soil should range from U.008 to 0.01, 0.08 to 0.1,
0.8 to 1.0, and 8 to 13 pg/g, corresponding to the best estimate of an upper-
19-16
-------
bound oncogenic risk at 10'7, 10'6, 10'5 and 10'4, respectively. The specific
level will be dependent upon the likely soil ingestion rate and the extent of
soil-air partitioning. Because of the PCB concentration profile being esta-
blished in the soil column as volatilization occurs, the PCB concentration
averaged over the depth will gradually decrease over time. Hence, if the popu-
lation is allowed to enter the site at some time after site cleanup, the per-
missible levels for preventing 10-day noncancer health effects can change.
Again, the specific level will be dictated by site-specific characteristics
such as the soil-air partition coefficient.
(2) If there is no possibility of population entering the contaminated
site within a radius of 0.1 km from the site, the PCB levels in the soil can
remain at the no theoretical upper-bound limit value (vs ug/g) without exceed-
ing the 10-day AI upon inhalation exposure for 10 days; and at 110-200 ug/g
without exceeding the average daily dose corresponding to a 10~6 risk for life-
time exposure. Similar interpretations can be made for the results applicable
to the carcinogenic risk listed at 10"4, 10~5, and 10~7, and to sites without
affected population up to 1 km from the site.
19-17
-------
20. LIMITATIONS OF APPLICATION
It Is assumed that the 25-cm (10-inch) clean cover material used remains
undisturbed in the process of human activities on the site. At times this
assumption may be found arbitrary, because an opportunity could exist that
would expose the contaminated soil surface in contact with the atmosphere by
inadvertent disturbances of soil surfaces, construction activities, utility
installation, precipitation, or children playing on the site, to name a few.
In this case, additional thickness of cover material should be used, or the
site should be made inaccessible to children or should be kept from any activ-
ities that would lead to disturbance of the soil surfaces. Spills on top of
the clean cover will result in a situation equivalent to the surface contami-
nation case, requiring a more stringent concentration limit in soil. In this
case, the results given for the 25-cm-thick clean cover material do not apply.
The tabulated results are intended to be applicable under certain specific
conditions. Under conditions similar to those used in preparing the tables,
the values can be used without additional evaluations. A particular situation
may warrant a site-specific evaluation which may require the use of conditions
different from what has been assumed in preparing the tables. If the analysis
is available to show the specific type of Aroclor contaminating the soil, the
individual table should be used. If the value for the soil-air partition coef-
ficient can be better defined, the range of the permissible PCB concentration
should be further narrowed.
20-1
-------
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21-5
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APPENDIX A
MODELS USED IN AIR RELEASE RATE CALCULATIONS
-------
DERIVATION OF MODELS FOR ESTIMATING VOLATILE EMISSIONS
FROM CONTAMINATED SOIL COLUMNS UNDER TRANSIENT CONDITIONS
Because of the limited aqueous solubility and high soil affinity of PCBs,
it has been assumed that these compounds move vertically in soils, primarily
by diffusion in the vapor phase. If transport of PCBs is by vapor phase dif-
fusion through interstitial spaces between soil particles, a mass balance over
an infinitesimal vertical element of soil can be written as follows:
AE(-Dei3C) - AE(-DeijC) = AAZ3C + A&zFsaj_ (A-l)
3z z.t 3Z z+Az,t 8t 3t
where:
A = cross-sectional area of interest, cm2
C = concentration of PCBs in the vapor phase in soil pores, g/cm^
Cs = concentration of PCBs in soil, g/g
D^ = molecular diffusivity, CIT//S
D! = effective diffusivity, cmz/s (=Di'E1/'J)
_E = pore porosity
Ps = bulk density of soil = true density of soil, Ps, multiplied by
- m3
t = time, seconds
z = depth measured from the soil -air interface, cm
In Eq. (A-l), the effective diffusivity, Dgi , is used in place of
to account for the tortuosity effect in porous media. The use of effective
diffusivity is consistent with the findings which describe emission rates of
volatile chemicals from landfills and soils (Hwang, 1982; Thibodeaux, 1979;
Farmer et al., 1980). The effective porosity for dry soil is used for sim-
plicity. The effect of moisture can be incorporated in the porosity term as
shown by Farmer et al . (1980).
Since changes in soil and vapor phase PCB concentrations occur slowly, it
can be assumed that vapor phase concentrations and soil concentrations of PCBs
A-l
-------
are in local equilibrium. If PCB concentrations in soil and in interstitial
vapors approach equilibrium, they are related by the following equation:
C = KH • C
°s TT (A-2)
where
Kd = soil/water partition coefficient
H = Henry's constant
Rearranging Eq. (A-l) and substituting Eq. (A-2) into the resulting rela-
tionship yields
Dei l!C . (1 + IsJ^d) 3C (A-3)
32- E'H 3t
or
a 32C = JC (A-3)
3t
where
a = Dei'E, (A-4)
(E+Ps'[l-E]'Kd/H)
a can also be defined as
ei (A-5)
1 + K-S
A-2
-------
where
K = JSd • D
H ps
Eq. (A-3) can be solved to estimate PCB soil concentration, vapor
phase concentration, and emission rate into air above soil for the various
cases described in this report if initial and boundary conditions are speci-
fied for each of these cases.
Case 1. Surface is exposed to the atmosphere. The boundary and initial
conditions are
1. I.C. C = (H/Kd)Cso, at t = 0, z > 0
2. B.C. C = (H/Kd)Cso, at z = », t > 0
3. B.C. C = 0, at z = 0, t > 0
where C$o is the initial concentration of PCBs in soil. The solution to Eq.
(A-3) for the above initial and boundary conditions is
= (H/Kd)Cso ' erf ,
where
2 n
erf (n) = error function = /* / exp(-n<-) dn
o
The flux rate at the soil-air interface (N^) can be estimated as a
function of time from equation (A-6) by using the concentration gradient
A-3
-------
as follows:
NA = -E-D . !£.
H ei 3z
E D
ei
z=0
/Hat
v- so
(A-7)
The boundary conditions used here are superior to those used by Jury et
al . (1983), assuming that the vapor-phase boundary layer is rate-controlling.
Experiments by DuPont (1985) on emission rates from contaminated soil show
that when the emission rates for volatile organics are plotted against the
reciprocal of ^t, a straight line is obtained. This observation is consis-
tent with the relationships given by Eq. (A-7), and Thibodeaux and Hwang
(1982). The model derived by Jury et al . (1983), based on the boundary con-
ditions of the controllirrg boundary layer in the air phase, does not provide
a straight-line relationship between emission rate and 1/Tj.. For this
reason, the relationship derived in this report is used for exposure evalua-
tion.
The average flux rate, NA, over an exposure interval, T, can be calculated
using Eq. (A-7).
T /IlaT Kd
or
NA(T) = 2 NA(T) (A-9)
To estimate the total average emission rate, Q, the flux rate defined in
Eq. (A-9) must be multiplied by the area of soil contaminated.
A-4
-------
Q = A • NA (A-10)
Furthermore, while Eq. (17) in Section 16 can be used at any distance
X from the site to estimate air concentrations of PCBs, it cannot be used on-
site. Although at present there is no generally accepted methodology for
estimating on-site concentrations from an area source, on-site PCB air con-
centration was estimated based on a "box model" approach, by using the equation
C =
LS-V-H (A-ll)
where
H = mixing height = 2 m
V = average wind speed within mixing zone
= 0.5 wind speed at the mixing height = 0.5 x 4.5 meter/sec = 2.25 m/s
LS = width dimension of contaminated area perpendicular to the wind direc-
tion = /A = 45 m
A need exists for development of a more rigorous approach to estimating
on-site ambient air concentrations. Time constraints did not allow development
and validation of a rigorous model.
Estimation of ingestion of contaminated soil required the calculation of
an appropriate soil concentration. This concentration was calculated by deter-
mining the average concentration of PCB in soil to a depth of or 25.4 cm (10
inches) for a period of 6 years beginning at time 0. Because the error func-
tion has no closed-form solution it was approximated by
A-5
-------
2
_ a(2n+l) iTt
e L2 .. cinl(2n±l)n z i (A-12)
n L 2n+l
n=0
sin{(2nH)nz }
where L Is a depth which was selected such that
Cs (L.t)
for all exposure durations. In calculations reported in this report, L was
set equal to 250 cm. Integrating Cs of the exposure duration tQ (5 years) and
depth £ (25 cm) yields an equation for average PCB soil concentration, C^
to
n« Q m «^^9n4>1^^^
— , , v>\ r ~ \ ., ' n2tn
C =—L- / / C dz = 7 so I {i-CQS(2n+l n £u . fl-e 41-^ ui
(A-13)
Case 2. The contaminated surface is covered with PCB-free soil material. Let
i = thickness of cover, cm, and L = the depth of contamination mea-
sured from the top of cover material, cm. The initial and boundary
conditions become:
1. I.C. C=0, 0 0
4. B.C. JC_ = 0, z = L, at t > 0
3z
where Cg is the initial concentration of PCBs in the vapor phase, which can be
obtained by CQ = (H/KjjCso. E(l- (A~3) witn these initial and boundary condi-
tions can be solved using the Fourier Series technique. The solution is
A-6
-------
« -g(2n+l)2 II2t
C = 4CQ I e4T2
n n=0
sin { 2"+l n zi Cos{ln±lnl}
1 2 Lf l 2 LJ
(A-14)
The flux rate at the soil-air interface (N^) can be estimated as a func-
tion of time from equation (A-14)
2 2
z=0
o r c n " a (2n+ir n t
2 C0 E>Dei v e 4L2 cos(^IniDMl (A~15)
i 2 LJ
n=0
The average emission rate over a time period, T, can be obtained by inte-
gration of Eq. (A-15). The result is
NA
^8(H/Kd)'Cso-E-Dei-Ly
air2T n=0 (2n+l)2
,-
- e
a (2n+l)2 n2)t? . cos((2n+l) nil
4-L^ J 2 L
(A-16)
or
DiE1/3(2nfl)2
y 1
n=0 (2n+l)2
(1+K-S)-L2 '4
2 L (A-17)
A-7
-------
The summation of terms given in Eq. (A-16) can be conveniently carried out
by means of computer simulation. The time interval t£-ti should be set equal
to the exposure interval. In calculating exposures, the maximum average expo-
sure was estimated. This was achieved by calculating NA as a function of time
and determining the time at which the maximum value of N/\ occurred; tj was then
set equal to this time.
2 2
It should be noted that when the value of the expression a(2n+l) n -jn
4L2
the exponential term of Eq. (A-16) is small or considerably less than 1, the
average of the exponential term over a time, t, will be close to 1. In this
situation, averaging of the exponential term of Eq. (A-15) by the integration
formulae given by Eq. (A-16) or Eq. (A-17) may easily result in an erroneous
answer because one has to evaluate very precise numbers of many decimal points
for the values of the exponential term. It is more practical to numerically
average Eq. (A-15) than to obtain the average value by using the integration
formula given by Eq. (A-16) or Eq. (A-17):
(A-18)
The steps of the summation and the integration with respect to n and t, respec-
tively, need to be carried out by means of a computer.
As in Case 1, Eqs. (A-10) and (A-ll) are used to estimate emissions rate
and on-site air concentration of PCBs. However, Eq. (A-17) or (A-18) is sub-
stituted into Eq. (A-10) as an estimate of flux rate.
Also as in Case 1, the average soil concentration used to estimate inges-
tion of soil must be calculated. This can be accomplished by noting that C$Q
A-8
-------
= CQ • Kd/H, substituting this relationship into Eq. (A-14) and integrating
the resulting equation over the depth interval z and over the time interval
tj to t} + tQ. The result is
1 + p ^ - oo
1 f f Cs dz = 32L-*CSO 7 M cos(2n+l)na, f -a (2n+l)2 n^t,
~fi t 0S n^ait n=0U COS-2~!r e4^
(2n+l)2
_ e
cos f(2n+l)nti
2 L
(A-19)
where to = 5 years and ? = 25 cm.
When the initial PCB soil concentration used in estimating exposures ex-
ceeds the concentration at which the vapor pressure of PCB is achieved, a
different model must be used in both Case 1 and Case 2. The vapor phase PCB
concentration that can be achieved in the interstitial voids in soil is
limited to the concentration corresponding to the vapor pressure. While this
limits the emission rate, it should be noted that as the soil zones nearest
the air-soil interface become depleted of PCB, the emission rate decreases.
If PCB is present in soil concentrations that produce the vapor pressure in
the vapor phase, the average emission rate may be increased because soil near
the surface is depleted less rapidly.
In modeling this phenomenon it has been assumed that at any given time,
the concentration profile of PCB in soil as a function of depth is a steady-
state profile. As in the previous models, the concentration of PCB in the
interstitial soil void space is assumed to be in equilibrium with PCB soil
A-9
-------
concentrations. Given these assumptions and the initial conditions that
H . C
Cs ' CSO
where
Css = PCB soil concentration at which the vapor pressure is achieved.
A mass balance can be written to determine the rate of depletion from
soil. If the soil concentration profile is as defined in Figure A-l, this
mass balance is
aC
E«r\ • -
Dei 3z
dz. = (A-20)
2 f Css[P(l-E)+E'Kd/H]l + Ps(l-E)(CSo-Css)
Because we assume that any any time the soil and vapor PCB approach
their steady-state concentrations,
dz
substituting equation (A-21) into equation (A-20) and integrating the result-
ing equation over the time interval 0 to t and the corresponding depth inter-
val 0 to z yields the result
A-10
-------
o
0)
Z
III
O
z
o
o
•88
t3>*2
DEPTH (z)
Figure A-l. Model of chemical vapor movement through soil when
partial pressure is equal to vapor pressure.
A-ll
-------
z _ 2 / E ' Dei ' Css' t (A-22)
E'CSS + 2'P'(l-E)-Cso-Kd/H - (l-E)'P'Css-Kd/H
As in the previous case, the flux rate can be calculated as
E'D'C.«.fH
°
" ei 3x ei z z Kd (A-23)
or
_ / E-Dei'Css * |2-(1-E)'P-CSO + E-Css'H/Kd - (1-E)-P-C5S)
"A
2 / t'Kd/H
(A-24)
If the average flux is determined for the time interval T, it is easy to
show that
NA (T) = 2NA(T) (A-25)
As indicated previously, Eqs. (A-10) and (A-ll) can be used to estimate emis-
sion rate and on-site air concentrations. However, Eq. (A-24) is substituted
into Eq. (A-10) as an estimate of flux rate in this case.
The average soil concentration to a depth of 25 cm over the exposure
duration of up to 5 years of exposure must be determined to estimate ingested
dose of PCBs. The equation used to estimate this average depends on whether
the depth z in Eq. (A-22) is less or greater than LI (25 cm) at the end
of the ingestion exposure periods. The time TS at which z = LI is easily
A-12
-------
calculated using the following equation:
T5 = O^S-L^-tE-Css - 2(l-E)P'Cso-Kd/H - P-(l-E)-Css'Kd/H)/(EM)el-Css) (A-26)
If the ingestion exposure period, T, is less than 15, the depth, z, will
always be less than LI, and the average soil PCB concentration, Cs, can be
calculated as follows:
1/2
Cs = 2'(Css-2-Cso) {E-Dei'Css-T/[E'Css+2(l-E)-P-Cso-Kd/H - (1-E)-P-CSS-Kd/H]}
+ CSO
(A-27)
If the ingestion exposure period is greater than 15, the depth, z, will be
greater than Lj at the end of the exposure period, and the average soil PCB
concentration can be calculated as follows:
Cs = 2-(Css-2'Cso) {E-Dei-Css/[E-Css+2(l-E)-P-CSQ-Kd/H
°'5 i t
- (l-E)-Css-P'Kd/H]} 'Is1'5 /(3-L!-!) + CSQ-T5/T
2'(CSS-L1) {[E-CS5+2(1-E)'P-CSO - (l-E)-P'Css-Kd/H]
[E'Dei-Css]} -5 {T°-5 - T5°-5}/T (A-28)
A-13
-------
When clean cover is placed over contaminated soil, a similar model can
be developed as in the case where soil is contaminated to the surface. For
such situations, assuming that local equilibrium between vapor and solid
phases and steady-state concentration distributions at any time are attained,
the following mass balance which yields relationships illustrated in Figures
A-2 and A-3, which define the concentrations of PCB in soils as a function of
depth
L4 = U'L^U-EJ
+ ^-(E'H/Kjj + (1-E)-P)-CSS-[2(1-E)-P'(CSO-CSS) + E'H/Kd + (1-E) -P) -Css )]}
/ {2-[2-d-E)'P-(Cso-Css) + [E'H/Kd+(l-E)-P]'Css]} (A-29)
The time at which PCB reaches the air-soil interface, Tj,, can be estimated
by rearranging Eq. (A-22) and substituting 14 + LI for z, as follows:
Tb = (L4+L1)2-{E-Css+2'(l-E)-P-Cso-Kd/H - (1-E)-P'C^-Kj/H}
•{A-E'Dgi-C^}-1 (A-30)
Integrating Eq. (A-24) over the exposure time interval Tjj to T+Tb and
dividing the result by T yields the following expression for the average flux
over the exposure period:
A-14
-------
_i CSO
o
m
O C
UJ
O
z
o
o
88
DEPTH (z)
Figure A-2. Model of chemical vapor movement through soil when partial
pressure is equal to vapor pressure.
A-15
-------
o
H
<
UJ
o
z
o
o
o
CO
o
o
Q.
DEPTH OF CLEAN COVER
DEPTH
Figure A-3. Mass balance for vapor movement through soil when
partial pressure is equal to vapor pressure.
A-16
-------
,
NA= - / NA dt
/ E-Dei'Css (Z-(1-E)-P-CSO + E'Css-H/Kd - (1-E)-P-CSS
/ Kd/H
As before, Eqs. (A-10) and (A-ll) can be used to estimate emission rates
and on-site air concentrations.
Finally, the average soil concentration to a depth of 25 cm over the
exposure of duration up to 5 years must be determined in order to estimate
ingested dose of PCBs. The equation used to estimate this average is:
/(T-(L1+L4)} (A-32)
Calculation of the Depth-Averaged Concentration for Uncovered Surface
We want to find the average concentration of PCBs in soil over the expo-
sure period. As time progresses, the concentration in soil decreases because
of volatilization. First, we want to find the time when the emission rate at
any time equals the average emission rate. We equate Eqs. (A-7) and (A-8).
Then
E'Dei H C _ 2E "Dei H C
- ' F ' $0 ~ - • -J7 • SO
/Hat Kd /naT Kd
A-17
-------
The emission rate equals the average emission rate at t = T/4, where T is
the exposure time (1 day, 10 days, or 70 years), and t is any time. From Eq.
(A-6), the vertically-averaged concentration over a depth of 2 cm is:
_ z
C = H . C If erf(_L_) dz (A-34)
Kd SO z J0
2/at
or
_ z
C = C If erf(_L_) dz (A-35)
s SO z j 0
2/at
The integral should be numerically evaluated at t = T/4, T being the exposure
period for developing health advisories, and at an appropriate depth within
which the concentration average is desired.
A-18
-------
REFERENCES (APPENDIX A)
DuPont, R.R. (1985, Nov.) Evaluation of air emission release rate model pre-
dictions of hazardous organics from land treatment facilities. Presented
at American Institute of Chemical Engineers meeting, Chicago, IL.
Farmer, W.J.; Yang, M.-S.; Letey, J., Dept. of Soil and Environmental Sciences,
University of California-Riverside; Spenser, W.F., Science and Education
Administration, Federal Research, USOA. (1980) Land disposal of hexa-
chlorobenzene wastes: controlling vapor movement in soil. EPA-600/2-80-
119. Prepared for U.S. Environmental Protection Agency, Municipal
Environmental Research Laboratory, Cincinnati, OH.
Hwang, S.T. (1982) Toxic emissions from land disposal facilities. Environ.
Prog. 1:46.
Jury, W.A.; Spencer, W.F.; Farmer, W.J. (1983) Behavior assessment model for
trace organics in soil. I. Model description. J. Environ. Qual. 4:558-
564.
Thibodeaux, L.J. (1979) Chemodynamics. New York, NY: John Wiley and Sons.
Thibodeaux, L.J.; Hwang, S.T. (1982) Landfarming of petroleum wastes:
modeling the air emission problem. Environ. Prog. 1:42-46.
A-19
-------
APPENDIX B
EXAMPLE EMISSION RATE CALCULATIONS FOR FOUR STUDIED SCENARIOS
-------
Example calculations for estimating volatile emissions of PCBs based
on the models presented in Appendix A for unsteady-state conditions, and
under steady-state conditions are presented below.
Case 1. Unsteady-state emission: no cover.
The contaminated soil is exposed to the atmosphere, and no clean soil
cover is applied on top of the contaminated surface. PCB-1254 is used as an
example. The average emission rate, which is obtained by averaging the
instantaneous emission rate over a time period, t (sec), can be obtained by:
d cm air
where a = §1
E + PS(1-E)
. "tl
1 + S • K
with S
= __ , and K = -1 Ps
Dei = 0.05 (0.35)1/3 = 0.0352 cm2/s
1L in 9 so11 = 8.37 x IP"3 x 41 = 0 000343
"
Kd cm3 air 100° " m9/9 soil
B-l
-------
Hence:
0-0123 = 2.45 x 10'6 cm2/s
0.35 + ?.fi5(n.fiS) 1
0.000343
The average emission rate when the initial concentration in soil,
C
-------
contamination depth, L = 200 cm, can be obtained by Eq. (A-13):
- . 2(H/Kd)Cso.E.Qe1 . i J
For an average emission over a period of 10 days (864,000 sec)
2(0.000342)(10"6)(0.35)(0.0352)
NA =
(200)(864,000)
„ 864,000 2.45x10 (2n+l) n2t m f2n+l)n(25.4) ,
I / e 4(200)2 l 2 200 '
n=0 °
= 7.6 x lO'14 g.'cm2.s
Similarly, the average emission rate over a period of 70 years
= 5 x lO'14 g/cm2-s
NOTE: The emission rate equation is programmed in a computer, and the sum-
mation is carried out using the program.
Case 3. Steady-state emission—no cover.
The same scenario assumes that the contaminated surface is exposed to the
atmosphere, and its surface is maintained at the concentration of interest over
the period of emission. This will apply to the case where a large reservoir of
PCBs is available for emission until the concentration at the surface reaches
B-3
-------
the saturation value. This will be the upper-bound emission rate for contami
nated soil with no clean cover applied.
PCB-1254
H_ 0.34 g/cm3 air/g/cm3 water
Kd " s 1000 mg/g soil/mg/cm3 water s
mg/cm3 ai r
= 0.00034 mg/g S0ii 0.001 mg/g soil
= 3.4 x 10-7 mg/cm3 air = 3.4 x 10~7 x 10'3 x 10'6 '-g/m3
= 340 ng/m3
Partitioned vapor concentration: 340 ng/m3
Vapor pressure at 25°C = 7.71 x 10 ~5 mmHg
C* = PMW = 14.7 (7.71x10-5/760) • 328.4 = 8.5x10-8 #/ft3
RT 10.73 (460 + 77)
where F = 1.8 (25) + 32 = 77°F,
C* = saturation concentration of PCB-1254 in #/ft3 or ng/m3,
P = vapor pressure,
MW = molecular weight,
R = gas constant.
8.5x10-8 (454) x Ip6 ug = 1362.7 ng/m3
(0.3048)3 m3
When PCB-1254 is greater than 4 ppm in soil, the partial pressure in the air
phase is equal to vapor pressure. An average temperature of 25°C is used for
evaluating the saturation concentration in the vapor phase. Since the vapor
B-4
-------
pressure is dependent upon temperature, a specific evaluation will require a
temperature of interest. The temperature in the subsurface soil may not fluc-
tuate considerably over the average value.
PCB-1242
Concentration in air above soil with 1 ug/g PCB
340 x 5.73xlO-4 = 23.3
8.37xl03
Saturated vapor concentration
1362.7 4.06xlO-4 266.5 = 5823.3 yg/ra3
7.71xlO-5 328.4
Note: When the PCB concentration in soil = 250 pg/g = 5823.3 the
( 23.3 ),
vapor phase is saturated.
In order to calculate the emission rate, the values for gas-phase mass
transfer coefficients are estimated using the relationship given by Hwang
(1982).
PCB-1254; kg = 5.8x10-5 18 0-5
(328.4) = 1.36xlO-5 g mol/cm2 • s
PCB-1242; kg = 5.8x10-5 . 18 °'5 = 1.51X10'5 g mol/cm2 . s
(266.5)
Mole fractions of PCBs in the gas phase (y) when the concentrations are
retained at 340 ug/m3 and 23.3 ug/m3 for PCB-1254 and PCB-1242, respec-
tively, are:
B-5
-------
PCB-1254 y = 340 pg/m3 • 0.0742 ppb/(ug/m3) x 10-9 = 2.52x10-8
PCB-1242 y = 23.3 wg/m3 • 0.0916 ppb/(yg.m3) x 10'9 = 2.13x10-9
The emission rate, Q, can be obtained from the formula Q = MW-kg-y,
where MW = molecular weight (Hwang, 1982). Thus, the emission rate for each
Aroclor is:
PCB-1254 Q = 328.4 (1.36xlQ-5)(2.52xlO-8) = l.lSxlO'10 g/s cm2
PCB-1242 Q = 266.5 (1.51x10-5) (2.13x10-9) = 8.57x10-12 g/s Cm2
Case 4. Steady-state emission—cover applied.
It is assumed that the contaminated site is covered with PCB-free soil
cover, and that the concentration at the top of the contaminated soil is main-
tained at 1 ug/g over the period of emission. The emission rate can be obtained
from the formula (Hwang, 1982).
Q = D1 PT4/3 C* , g/cm2-s
h
where D^ = diffusivity, cm2/s,
PT = total porosity,
C^ = true vapor pressure in equilibrium with soil, g/cnr,
h = cover thickness, cm.
Using the diffusivity value of 0.05 cm2/s, one can get for PCB-1254, an
emission rate of
Q = (0.05K0.35)4/3 340 ug/m3 ID"6 g/ug x 1Q-6 cm3/m3
25.4 cm
= 1.67 x 10-13 g/cm2-s
B-6
-------
Similarly, for PCB-1242:
Q = (0.05) (0.35)4/3 23.3xlQ-6 x IP"6 = 1.14xlO'14 g/cm2 • s
25.4
B-7
-------
REFERENCES (APPENDIX B)
Hwang, S.T. (1982) Toxic emissions from land disposal facilities. Environ.
Prog. 1:46.
B-8
-------
APPENDIX C
SUMMARY OF COMPUTER RUNS FOR EACH AROCLOR AND
AT EACH VALUE OF SOIL-AIR PARTITION COEFFICIENTS
-------
TABLE C-l. PERMISSIBLE PCB-1242 SOIL CONTAMINATION LEVELS9
(UNCOVERED SURFACE CONTAMINATION. Kd = 1000)
o
i
Permissible levels (ug/g) corresponding to
Noncancer short-term3
acceptable Intake
Cancer risk specific doses (ug/day)
Location and
route of human
exposure
100
for child
700
for adult
0.00175
(10-' risk)
0.0175
(10-6 riS|(]
0.175
1 (10-5 risk)
1.75
(10-4 risk)
On the contaminated site
- Soil 1ngest1onc, 55
inhalation*
- Soil ingest1ond, 92
Inhalation6
- Inhalation only6 116
510
2100
vs
0.008
0.06
0.2
0.08
0.6
0.8
20
61
204
0.1 km from
contaminated site vsf
- Inhalation only6
1 km from
contaminated site vs
- Inhalation only*
vs
vs
20
428
204
l.lxlO4 vs
3.1xl04 vs
vs
aShort-term 5 10-day Intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
cChildren ages 1-5, with pica (consuming 3 g soil/day).
Children ages 1-5, without pica (consuming 0.6 g soil/day).
elnha1ation rates are assumed to be 20 m^/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m^/day as a result of 182 days exposure per year.
'vs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
9So11-a1r partition coefficient = 2.35 x 10"5 g soil/cm3 air (=• H.41/Kd = 5.73 x 10"1 (41J/1000 =
2.35 x 10-5).
-------
TABLE C-2. PERMISSIBLE PCB-1242 SOIL CONTAMINATION LEVELS?
(UNCOVERED SURFACE CONTAMINATION. Kd » 40)
Permissible levels (ug/g) corresponding to
Location and
route of human
exposure
Noncancer short-term9
acceptable Intake iig/dayb
100 700
for child for adult
Cancer risk specific doses dig/day)
0.00175 0.0175 0.175 1.75
(10-' risk) (ID'6 risk) (10'5 risk) (10"4 risk)
o
(S3
On the contaminated site
- Soil IngestlonC, 60
Inhalation6
- Soil ingestiond, 247
Inhalation6
- Inhalation only6 vsf
690
2800
vs
.01
.03
0.04
0.1
0.3
.4
1.0
3.0
13
35
110
0.1 km from
contaminated site
- Inhalation only6
1 km from
contaminated site
- Inhalation only6
vs
vs
vs
310
110
1.1x10* vs
3.1xl04 vs
vs
aShort-term » 10-day Intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
cCh1ldren ages 1-5, with pica (consuming 3 g soil/day).
^Children ages 1-5, without pica (consuming 0.6 g soil/day).
6Inhalation rates are assumed to be 20 m^/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m-Vday as a result of 182 days exposure per year.
fys denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
^Soil-air partition coefficient - 2.35 x IO'5 g soil/cm3 air (= H.41/Kd = 5.73 x 10'* (41)/1000 =
2.35 x ID'5).
-------
TABLE C-3. PERMISSIBLE PCB-1248 SOIL CONTAMINATION LEVELS0.
(UNCOVERED SURFACE CONTAMINATION. Kd = 1000)
Location and
route of human
exposure
Permissible levels (pg/g) corresponding to
Noncancer short-term3
acceptable Intake pg/dayp
100 700
for child for adult
Cancer risk specific doses (pg/day)
0.00175 0.0175 0.175 1.75
(10-7 risk) (10-6 risk) (10'5 risk) (10'4 risk)
i
CO
On the contaminated site
- Soil IngestlonC, 32
Inhalation6
- Soil 1ngest1ond, 42
Inhalation6
- Inhalation only6 47
612 •
2500
vs
0.01
0.04
O.OB
0.1
0.5
0.8
10
49
110
0.1 km from
contaminated site
- Inhalation only6
1 km from
contaminated site
- Inhalation only6
VST
vs
vs
8.0
270
110
8,700 8.7xl05
2.5xl04 vs
vs
aShort-tenn = 10-day Intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
cCh1ldren ages 1-5, with pica (consuming 3 g soil/day).
^Children ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalat1on rates are assumed to be 20 m3/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m3/day as a result of 182 days exposure per year.
fvs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
9Soil-air partition coefficient = 2.35 x 10'5 g soil/cm1 air (= H.41/Kd = 5.73 x 10'" (41J/1000 =
2.35 x ID-5).
-------
TABLE C-4. PERMISSIBLE PCB-1248 SOIL CONTAMINATION LEVELS9
(UNCOVERED SURFACE CONTAMINATION. Kd = 40)
Permissible levels (ug/g) corresponding to
Noncancer short-term3
acceptable Intake pg/day°
Cancer risk specific doses (tig/day)
Locatto and
route of human
exposure
100
for child
700
for adult
0.00175
(10-' risk)
0.0175
(lO'6 risk)
0.175
(lO"5 risk)
1.75
(10-4 risk)
On the contaminated site
- Soil 1ngest1onc.
Inhalation6
- Soil Ingest 1ond,
Inhalation6
- Inhalation only6
80
330
710
2900
vs
0.01
0.02
0.02
O.I
0.2
0.2
2.0
2.0
37
87
0.1 km from
contaminated site vs
- Inhalation only6
1 km from
contaminated site vs
- Inhalation only6
vs
vs
2.0
250
90
2.5x10*
8,700
vs
vs
vs
aShort-tenn s 10-day Intake.
DBased on average weights of 10 and 70 kg for a child and an adult, respectively.
cCMldren ages 1-5, with pica (consuming 3 g soil/day).
^Children ages 1-5, without pica (consuming 0.6 g soil/day).
^Inhalation rates are assumed to be 20 m^/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m^/day as a result of 182 days exposure per year.
fvs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
^Soil-air partition coefficient = 2.35 x 10~s g soil/cm3 air (= H.41/Kd = 5.73 x 10'" (41)71000 =
2.35 x 10-5).
-------
TABLE C-5. PERMISSIBLE PCB-1254 SOIL CONTAMINATION LEVELS?
(UNCOVERED SURFACE CONTAMINATION, Kd * 1000)
Location and
route of human
exposure
Permissible levels (ng/g) corresponding to
Noncancer short-term3
acceptable Intake ug/dayb
100
for child
700
for adult
Cancer risk specific doses (tig/day)
0.00175
(10-7 risk)
0.0175 0.175 1.75
(10-6 risk) (10-5 risk) (10'4 risk)
On the contaminated site
- Soil IngestlonC, 90
Inhalation6
- Soil Ingest1ond, 370
Inhalation6
- Inhalation only6 vs'
720
2980
vs
0.01
0.04
0.05
0.1
0.4
0.5
12
59
460
0.1 km from
contaminated site vs
- Inhalation only6
1 km from
contaminated site vs
- Inhalation only6
vs
vs
'•f
460
4.7xl04 4.7xl06
1.3xl05 vs
vs
aShort-terai a 10-day Intake.
''Based on average weights of 10 and 70 kg for a child and an adult, respectively.
cCh11dren ages 1-5. with pica (consuming 3 g soil/day).
dCh11dren ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalatlon rates are assumed to be 20 nvvday for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m^/day as a result of 182 days exposure per year.
rvs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
^Soli-air partition coefficient - 2.35 x W5 y soil/cm* air (= H.41/Kd = 5.73 x 10'" (41)71000 =
2.35 x lO*5).
-------
TABLE C-6. PERMISSIBLE PCB-1254 SOIL CONTAMINATION LEVELS9
(UNCOVERED SURFACE CONTAMINATION. Kd = 40)
Permissible levels (pg/g) corresponding to
Location and
route of human
exposure
Noncancer short-term3
acceptable Intake ug/dayD
100
for child
700
for adult
Cancer risk specific doses (pg/day)
0.00175 0.0175 0.175 1.75
(10-' risk) (10-6 risk) (10'5 risk) (10'4 risk)
i
(ft
On the contaminated site
- Soil Ingest Ion*. 100
Inhalation6
- Soil 1ngest1ond, 420
Inhalation6
- Inhalation only6 vsf
730
3000
vs
0.009
0.01
O.dl
0.09
0.1
0.1
2.0
12
36
470
0.1 km from
contaminated site vs
- Inhalation only6
1 km from
contaminated site vs
- Inhalation only6
vs
vs
1300
470
4.7x10* vs
1.3xl05 vs
vs
aShort-term s 10-day Intake.
''Based on average weights of 10 and 70 kg for a child and an adult, respectively.
cChtldren ages 1-5, with pica (consuming 3 g soil/day).
dCh11dren ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalat1on rates are assumed to be 20 m-Vday for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 nr/day as a result of 182 days exposure per year.
fvs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
9So1l-a1r partition coefficient = 2.35 x 10~s g soil/cm1 air (= H.41/Kri = 5.73 x lO'" (41)/1000 =
2.35 x ID'5).
-------
TABLE C-7. PERMISSIBLE PCB-1260 SOIL CONTAMINATION LEVELS9
(UNCOVERED SURFACE CONTAMINATION. Kd = 1000)
Permissible levels (n9/9) corresponding to
Location and
route of human
exposure
Noncancer short-term3
acceptable Intake ug/dayp
100
for child
700
for adult
Cancer risk specific doses (ug/day)
0.00175
(10-' risk)
0.0175
(10-6
J-175
risk)
1.75
(10-4 risk)
On the contaminated site
- Soil 1ngest1onc, 25
Inhalation6
- Soil ingest1ond, 61
Inhalation6
- Inhalation only6 vs'
640
2670
vs
0.01
0.04
0.06
0.1
0.4
0.6
12
48
91
0.1 km from
contaminated site vs
- Inhalation only6
1 km from
contaminated site vs
- Inhalation only6
vs
vs
240
91
7.7xl03 vs
vs
aShort-term a 10-day Intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
cCh11dren ages 1-5, with pica (consuming 3 g soil/day).
''Children ages 1-5, without pica (consuming 0.6 g soil/day).
6lnhalat1on rates are assumed to be 20 m3/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m3/day as a result of 182 days exposure per year.
fvs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
«Soil-air partition coefficient = 2.35 x 10"5 g soil/cm3 air (= H.41/Kd = 5.73 x 10"1 (41J/1000 =
2.35 x ID'5).
-------
TABLE C-8. PEKHISSIBLE PCB-1260 SOIL CONTAMINATION LEVELS?
(UNCOVERED SURFACE CONTAMINATION, Kd = 40)
Permissible levels (ug/g) corresponding to
Location and
route of human
exposure
Noncancer short-term3
acceptable Intake nq/dayb
100
for child
700
for adult
Cancer risk specific doses Ug/day)
0.00175
(10-' risk)
0.0175
(10-6 r1sk)
i-8
'175
1.75
(10-4 risk)
o
i
co
On the contaminated site
- Soil 1ngest1onc,
Inhalation6
- Soil 1ngest1ond,
inhalation6
- Inhalation only6
0.1 km from
contaminated site
- Inhalation only6
1 km from
contaminated site
- Inhalation only6
87
360
vs'
vs
vs
710
2900
vs
vs
vs
0.01
0.01
0.01
1.0
220
0.1
0.1
0.1
76
2.2xl04
1.0
1.0
1.0
7600
vs
17
40
77
7.6x10*
vs
aShort-term s 10-day Intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
cChildren ages 1-5, with pica (consuming 3 g soil/day).
dCh1ldren ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalatlon rates are assumed to be 20 m3/da
3/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m-vday as a result of 182 days exposure per year.
fys denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
9So1l-a1r partition coefficient = 2.35 x 10'5 g soil/cm' air (- H.41/Kd - 5.73 x 10"« (41)/1000 =
2.35 x 10-5}.
-------
TABLE C-9. PERMISSIBLE PCB-1242 SOIL CONTAMINATION LEVELS9
(25-cm-THICK CLEAN SQIL COVER, Kd = 1000)
Permissible levels (ug/g) corresponding to
Location and
route of human
exposure
Noncancer short-term8
acceptable Intake ug/day°
100
for child
700
for adult
Cancer risk specific doses (ng/day)
0.00175 0.0175 0.175
(10-7 risk) (10-6 rtsk) (10-5 rtsk)
1.75
(10-4 risk)
£->
I
IO
On the contaminated site
- Soil ingestlonC, 200
inhalation6
- Soil ingest 1ond, 820
inhalation6
- Inhalation only6 vsf
1400
5700
vs
0.2
0.6
0.9
48
86
170
260
vs
0.1 km from
contaminated site vs
- Inhalation only6
1 km from
contaminated site vs
- Inhalation only6
vs
vs
85
vs
vs
vs
vs
vs
vs
vs
aShort-term 2 10-day intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
Children ages 1-5, with pica (consuming 3 g soil/day).
Children ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalation rates are assumed to be 20 m'/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 nryday as a result of 182 days exposure per year.
fvs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
9Soil-air partition coefficient = 2.35 x ID'S g soil/cm* air (= H.41/KH = 5.73 x 10"11 (41)/1000 =
2.35 x ID-5).
-------
TABLE C-10. PERMISSIBLE PCB-1242 SOIL CONTAMINATION LEVELS^
(25-cm-THICK CLEAN SOIL COVER, Kd = 40)
o
i
Permissible levels (ug/g) corresponding to
Noncancer short-term9
acceptable Intake pg/dayb
Cancer risk specific doses (ug/day)
Location and
route of human
exposure
100
for child
700
for adult
0.00175
(10-7 risk)
0.0175
(10-6 risk)
0.175
(10-5 risk)
1.75
(10-4 risk)
On the contaminated site
- Soil Ingest1onc, 170
Inhalation6
- Soil 1ngest1ond. 450
Inhalation6
- Inhalation only6 vsf
1200
3100
vs
0.03
0.1
1.0
0.3
1.0
vs
3.0
12
vs
vs
vs
vs
0.1 km from
contaminated site vs
- Inhalation only6
1 km from
contaminated site vs
- Inhalation only6
vs
vs
vs
vs
vs
vs
vs
vs
vs
vs
aShort-term s 10-day Intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
'Children ages 1-5, with pica (consuming 3 g soil/day).
dCMldren ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalat1on rates are assumed to be 20 m^/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m-Yday as a result of 182 days exposure per year.
fvs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
9So11-a1r partition coefficient = 2.35 x 10'5 g soil/cm* air (= H.41/Kd = 5.73 x 10"1 (41)/1000 =
2.35 x 10-*).
-------
TABLE C-ll. PERMISSIBLE PCB-1248 SOIL CONTAMINATION LEVELS9
(25-cm-THICK CLEAN SOIL COVER, Kd = 1000)
Permissible levels (ug/g) corresponding to
Location and
route of human
exposure
Noncancer short-term3
acceptable Intake pg/dayp
100
for child
700
for adult
Cancer risk specific doses tug/day)
0.00175 0.0175 0.175 1.75
(10-7 risk) (10-6 risk) (lO'5 risk) (lO'4 risk)
On the contaminated site
- Soil Ingest Ionc, 190
Inhalation6
- Soil 1ngest1ond, 650
Inhalation0
- Inhalation only6 vs^
0.1 km from
contaminated site vs
- Inhalation only6
1 km from
contaminated site vs
- Inhalation only0
1300
4500
vs
vs
vs
0.09
0.1
0.1
I
14
vs
10
10
14
19.000 vs
vs
vs
26
93
19,000
vs
vs
aShort-tenn a 10-day Intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
cCh<1dren ages 1-5, with pica (consuming 3 g soil/day).
^Children ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalation rates are assumed to be 20 nvVday for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 nvvday as a result of 182 days exposure per year.
fys denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
9Soll-air partition coefficient = 2.35 x 10'5 g soil/cm* air (= H.41/Kd = 5.73 x 10'" (41)71000 =
2.35 x 10-*).
-------
TABLE C-12. PERMISSIBLE PCB-1248 SOIL CONTAMINATION LEVELS9
(25-cm-THICK CLEAN SOIL COVER. Kd = 40)
Permissible levels (pg/g) corresponding to
Location and
route of human
exposure
Noncancer short-terma
acceptable Intake ng/dayb
100
for child
700
for adult
Cancer risk specific doses (ug/day)
0.00175
10-7 risk)
0.0175
_ 0.175
(10-6 risk) (10-' r)skj
1.75
(10-* risk)
r>
i
On the contaminated site
- Soil 1ngest1onc, 160
inhalation6
- Sol I Ingest Ion*1, vs^
inhalation6
- Inhalation only6 vs
1100
vs
vs
0.01
0.02
0.02
0.1
0.2
0.2
1.0
2.0
2.0
460
2500
1.9x104
0.1 km from
contaminated site vs
- Inhalation only6
1 km from
contaminated site vs
- Inhalation only6
vs
vs
2.0
vs
1.9xl04
vs
vs
vs
vs
vs
aShort-term 3 10-day intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
Children ages 1-5. with pica (consuming 3 g soil/day).
dChildren ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalation rates are assumed to be 20 mVday for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m3/day as a result of 182 days exposure per year.
fvs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
^Soil-air partition coefficient = 2.35 x lO'* g soil/cm* air ( = H.41/Kd = 5.73 x 10'" (41)/1000 =
2.35 x 10-*).
-------
TABLE C-13. PERMISSIBLE PCB-1254 SOIL CONTAMINATION LEVELS9
(25-cm-THICK CLEAN SOIL COVER. K«j = 1000)
Permissible levels (ug/g) corresponding to
Location and
route of human
exposure
Noncancer short-term9
acceptable Intake pg/day"
100
for child
700
for adult
Cancer risk specific doses (ijg/day)
0.00175
(10-' risk)
0.017S
0.175
(10-5 risk) (ID-5 risk)
1.75
(10-4 risk)
o
i
On the contaminated site
- Soil 1ngestlonc. 180
Inhalation6
- Soil 1ngesttond, 520
Inhalation6
- Inhalation only6 vs'
1300
4000
vs
0.02
0.06
0.08
0.2
0.6
0.8
14
vs
vs
vs
0.1 km from
contaminated site vs
- Inhalation only6
1 km from
contaminated site vs
- Inhalation only6
vs
vs
14
vs
vs
vs
vs
vs
vs
vs
aShort-term a 10-day Intake.
''Based on average weights of 10 and 70 kg for a child and an adult, respectively.
Children ages 1-5, with pica (consuming 3 g soil/day).
dCh11dren ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalatton rates are assumed to be 20 m3/da
Vday for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 nrvday as a result of 182 days exposure per year.
fys denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
^Soil-air partition coefficient = 2.35 x 10-s g soil/cm* air (= H.41/Kd = 5.73 x 10'" (41)/1000 =
2.35 x lO'3).
-------
TABLE C-14. PERMISSIBLE PCB-1254 SOIL CONTAMINATION LEVELS9
(25-cm-THlCK CLEAN SOIL COVER. Kd - 40)
Permissible levels (ug/g) corresponding to
Location and
route of human
exposure
Noncancer short-term9
acceptable Intake ug/day"
100
for child
700
for adult
Cancer risk specific doses (ug/day)
0.00175 0.0175 0.175 1.75
(ID'7 risk) (10-6 HS)C) (JO-5 r1sk) (i0-4 nsk)
o
i
On the contaminated site
- Soil 1ngesttonc, 140
Inhalation6
- Soil 1ngest1ond, vs
Inhalation6
- Inhalation onlye vs
970
vs
vs
0.01
0.02
0.02
0.1
0.2
0.2
10
vs
vs
vs
0.1 km from
contaminated site vs
- Inhalation only6
1 km from
contaminated site vs
- Inhalation only6
vs
vs
10
vs
vs
vs
vs
vs
vs
vs
aShort-term a 10-day Intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
cCh1ldren ages 1-5. with pica (consuming 3 g soil/day).
^Children ages 1-5, without pica (consuming 0.6 g soil/day).
elnhalatton rates are assumed to be 20 m^/day for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 mVday as a result of 182 days exposure per year.
fvs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
^Soil-air partition coefficient = 2.35 x lO'* g soil/cm* air {= H.41/Kd = 5.73 x 10'* (41)/1000 =
2.35 x 10-s).
-------
TABLE C-15. PERMISSIBLE PCB
(25-cm-THICK CLEAN S
-126<
SO|lL
;60 SOIL CONTAMINATION LEVELS?
COVER. Kd = 1000)
Location and
route of human
exposure
Permissible levels (ng/g) corresponding to
Noncancer short-term9
acceptable Intake gg/dayb
100
for child
700
for adult
Cancer risk specific doses (gg/day)
0.00175 0.0175 0.175 1.75
(10-7 risk) (10-6 risk) (10*5 risk) (10"4 risk)
I
t—•
en
On the contaminated site
- Soil Ingest1onc, 184
Inhalation6
- Soil 1ngest
-------
TABLE C-16. PERMISSIBLE PCB-1260 SOIL CONTAMINATION LEVELS?
(25-cm-THICK CLEAN SOIL COVER. Kd = «)
Permissible levels (pg/g) corresponding to
Location and
route of human
exposure
Noncancer short-term9
acceptable Intake pg/day°
100 700
for child for adult
Cancer risk specific doses (gg/day)
0.00175 0.0175 0.175 1.75
(10-' risk) (10-5 risk) (10"5 risk) (10"4 risk)
o
i
On the contaminated site
- Soil 1ngest1onc,
inhalation6
- Soil 1ngestiond,
inhalation6
- Inhalation only6
110
800
800
5000
vs
0.01
0.02
0.02
0.1
0.2
0.2
1.0
1.0
1.0
360
550
620
0.1 km from
contaminated site vs
- Inhalation only6
1 km from
contaminated site vs
- Inhalation only6
vs
vs
1.0
vs
620
vs
vs
vs
vs
vs
aShort-term 2 10-day Intake.
bBased on average weights of 10 and 70 kg for a child and an adult, respectively.
cChildren ages 1-5, with pica (consuming 3 g soil/day).
^Children ages 1-5, without pica (consuming 0.6 g soil/day).
6lnha1ation rates are assumed to be 20 iWday for the short-term and longer-term noncancer exposures;
all other (more chronic) exposures assumed to be 10 m^/day as a result of 182 days exposure per year.
fvs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquid for the limit.
9soil-a1r partition coefficient = 2.35 x 10'* g so11/cm3 air (= H.41/Kd = 5.73 x lO'" (41)/1000 =
2.35 x 10-5).
-------
APPENDIX D
HEALTH ADVISORIES FOR PCBs IN SOIL
Prepared by
Michael L. Dourson
Environmental Criteria and Assessment Office
Office of Health and Environmental Assessment
U.S. Environmental Protection Agency
Cincinnati, Ohio
-------
APPENDIX D
CONTENTS
EXISTING GUIDELINES, RECOMMENDATIONS, AND STANDARDS D-2
NONCARCINOuENIC EFFECTS D-4
QUANTIFICATION OF SHORT-TERM HEALTH ADVISORY LEVELS D-ll
CARCINOGENIC EFFECTS D-14
QUANTIFICATION OF CARCINOGENIC RISK D-17
SPECIAL CONSIDERATIONS D-20
High-Risk Subpopulation D-20
Cocarcinogenesis, Initiation, and Promotion D-21
SUMMARY D-21
REFERENCES D-25
D-l
-------
EXISTING GUIDELINES, RECOMMENDATIONS, AND STANDARDS
The manufacture, sale, and distribution of PCBs have been restricted
under Section 6(e) of the Toxic Substances Control Act (TSCA) (P.L. 94-469).
PCBs were restricted to sealed systems as of 1977, and manufacture and distri-
bution were banned in 1979. Rules for the disposal of PCBs were proposed in
1978 (43 FR 7150).
The U.S. EPA (1980) has set ambient water quality criteria for PCBs for
the protection of humans from increased risk of cancer over a lifetime of 10~5,
10'6 and 10'7 at 0.79, 0.079, and 0.0079 ng/L. As a result of the large bio-
concentration factor in fish, these criteria apply regardless of whether expo-
sure occurs through consumption of 2 L of water and 6.5 g of fish/day or
through consumption of fish alone. The Food and Drug Administration (FDA) has
set temporary tolerances for PCBs in food and food related products, as shown
in Table 0-1.
Occupational exposure limits for PCBs have been recommended by the American
Conference of Governmental Industrial Hygienists (ACGIH, 1980), and criteria
have been set for PCBs in workplace air by the National Institute for
Occupational Safety and Health (NIOSH, 1977). The time-weighted average (TWA)
and short-term exposure limit (STEL) for Aroclor 1254, are, respectively, 0.5
and 1.0 mg/m3, and for Aroclor 1242, 1 and 2 mg/m3 (ACGIH, 1980). The NIOSH
(1977) criterion is 1.0 ug/m3 for a 10 hours/day, 40 hours/week exposure.
The National Academy of Sciences developed a 24-hour suggested no adverse
response level (SNARL) for PCBs of 350 ug/L based on the induction of
mixed-function oxidase enzymes in the liver of rats administered Aroclor at
doses of 1 to 2 mg/kg (NAS, 1980). For this analysis, an uncertainty factor of
100 was used, since only enzyme induction was reported in this dose range.
D-2
-------
TABLE D-l. FDA REGULATIONS FOR PCBs
Temporary tolerances
Commodity (ppm)
Milk (fat basis) 1.5
Manufactured dairy products (fat basis) . 1.5
Poultry (fat basis) 3.0
Eggs 0.3
Finished animal feeds 0.2
Animal feed components of animal origin 2.0
Edible portion of fish and shellfish 5.0
Infant and junior foods 0.2
Paper food packaging material 10.0
SOURCE: 21 CFR 109.30.
D-3
-------
NONCARCINOGENIC EFFECTS
Tests of the acute lethality of PCB products in laboratory animals, with
the exception of the guinea pig, suggest that, in general, PCB products have
similar toxicity regardless of route of administration, species, or age of
animal. The single dose oral LQ$Q value in rats, rabbits, mice, and mink
ranged from 0.5-20 g/kg bw (Grant and Phillips, 1974; Bruckner et al., 1973;
Kimbrough et al., 1978; Fishbein, 1974; Garthoff et al., 1981, Aulerich and
Ringer, 1977). Route of administration also had little effect (less than one
order of magnitude) on lethality, with the lethal dose for dermal administra-
tion in rabbits ranging from 0.7-3 g/kg bw (Nelson et al., 1972), while the
lethal dose in mice administered PCBs by intraperitoneal injection ranged from
0.8-1.2 g/kg bw (Lewin et al., 1972).
There are only two indications of major differences in the acute toxicity
of PCBs. First, there is limited evidence that the guinea pig may be more
sensitive to the lethality of PCBs than other species. Miller (1944) observed
a 100% mortality in a small group of guinea pigs receiving two oral doses of
PCB (43% chlorine) at levels of 67 mg/animal at an interval of 7 days apart;
and McConnell and Kinney (1978) reported an 1059.30 of 0.5 mg/kg for the PCB
isomer 3,4,5-sym-hexachlorobiphenyl (HCB) in guinea pigs. This indication of
possible large interspecies differences in sensitivity is of concern in
species-to-species extrapolation when there is insufficient data to indicate
which experimental animal most accurately reflects the sensitivity of humans.
The second problem concerns the possible large difference in toxicity of speci-
fic isomers of PCBs. There are indications, on the basis of limited data
available from Biocca et al. (1981), that four different hexa-PCBs differ in
value from 19 mg/kg to >64 mg/kg after oral administration to mice. It
D-4
-------
would not be unreasonable to assume that even larger differences will be en-
countered as more isomers are tested. Variation in toxicity of the different
isomers is not of great concern in defining acceptable environmental levels,
since individual isomers were not commercially made and released to the envi-
ronment. The analytical methods used to measure environmental PCBs determine
the levels, in mg, of specific Aroclors. Since, as described above, the
Aroclors do not differ greatly in acute toxicity, using data from the most
toxic Aroclor should be protective without overly penalizing the other
Aroclors.
Some data are available on the nonlethal acute toxicity of PCBs admini-
stered by the oral route for periods of 30 days or less. The effects described
in these studies were alterations of the liver, thyroid, and reproductive
system. Rosin and Martin (1983) reported that a dose of 500 mg/kg of Aroclor
1254 for 14 days to CD-I mice decreased pentobarbital sleeping time, indicating
a substantial induction of microsomal enzymes. At lower doses, Sanders et al.
(1974) reported that exposure of ICR mice to diets containing 250 to 62.5 ppm
of Aroclor 1254 for 14 days resulted, respectively, in hepatomegaly and eleva-
ted serum corticosterone (the latter presumably as a result of altered liver
steroid metabolism). These exposures would result in doses of 32.8 and 8.1
mg/kg bw/day, assuming that a mouse consumes 13% of its body weight per day.
Similarly, Narbonne (1979) reported decreases in phenobarbital sleeping
time in Sprague-Dawley rats maintained fro 8 days on a diet containing 100 ppm
of Phenoclor DPS (dose of 5 mg/kg bw/day, assuming that a rat consumes 5% of
its body weight/day). PCB-induced increases in liver enzymes were suggested as
the reason for the increase in testicular acid phosphatase observed by Dikshith
et al. (1975) in Sprague-Dawley rats fed Aroclor 1254 at a dose of 50 mg/kg
bw/day for 7 days.' Increases in liver-to-body weight ratio appear to be one of
D-5
-------
the sensitive indicators of PCS exposure. Carter and Mercer (1983) reported
that 64 mg/kg bw/day of Aroclor 1254 caused increased liver weight, while Grant
and Phillips (1974) observed increased liver weight at doses as low as 12.5 and
5 mg/kg bw/day in male and female Wistar rats, respectively, receiving Aroclor
1254 in the diet for 14 days. Carter (1983) observed hepatomegaly in rats in-
gesting diets containing as little as 20 ppm Aroclor 1254 (1 mg/kg bw/day) for
14 days. Doses as low as 1 ppm in diet of 3,4,5,3',4',5'-hexachlorobiphenyl
(345 HCB) for 28 days caused liver microabscesses and an increased liver weight
in 18-20 g 5-week-old C57B1/6J mice (Biocca et al., 1981). Although adverse
this study, 0.3 ppm in diet could be considered a lowest observed adverse
effects were observed at concentrations as low as 0.3 ppm in diet in this
study, there is no documentation indicating that commercial Aroclors contain
345 HcB. Hence, this study for 345 HcB cannot be used for establishing the
short-term Health Advisory (HA), corresponding to an acceptable intake (AI)
level.
Besides changes in the liver, other effects reported for exposure to low
levels of PCBs were increased thyroid activity in Sherman rats maintained on
diets containing 250 ppm of Aroclor 1254 (12.5 mg/kg bw) for 14 days; in
Sprague-Oawley rats, administration of Aroclor 1254 by gavage for 21 days at
a dose of 0.05 g/kg bw/day resulted in weight loss and decreased body tempera-
ture (Komives, 1979; Komives and Alayoku, 1980). Enlarged thyroid has also
been found in Osborne-Mendel rats maintained on diets containing 5 ppm of
Aroclor 1254 (0.25 mg/kg bw/day) for 4 weeks (Collins and Capen, 1980b). This
exposure level also resulted in increased liver enzymes in Holtzman rats
(Garthoff et al., 1977).
The toxicity of PCBs resulting from exposures of between 30 and 90 days
has been more extensively studied. Alterations in liver histopathology
D-6
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occurred at doses as low as 5 ppm in diet for 5 weeks in Holtzman rats (Kasza
et al., 1978b). In the mouse (MNRI), a dose of Clophen A-60, as low as 0.025
mg/mouse (0.8 mg/kg bw/day, assuming a mouse weight of 0.03 kg) for 62 days,
increased the estrous cycle, probably as a result of PCB-induced changes in
liver steroid metabolism (Orberg and Kihlstrom, 1973). At higher dietary con-
centrations of 167 ppm (22 mg/kg bw) for 6 weeks, Aroclor 1016 and 1242 de-
creased the immunologic capabilities of BALB/CJ mice (Loose et al., 1978).
Species other than rats and mice have been tested to a lesser extent for
this duration. Rabbits exposed to diets containing 3 ppm of Aroclor 1254 (0.15
mg/kg bw/day, assuming that a rabbit consumes 4.9% of its body weight per day)
for 8 weeks developed hepatomegaly and immunosuppression. In the guinea pig,
Vos and van Genderen (1973) reported that diets containing 250 ppm of Clophen
A-60 (7 mg/kg bw/day, assuming that a guinea pig consumes 2.8% of its body
weight per day) for 4-7 weeks was lethal, while diets containing 50 ppm of
Clophen A-60 or Aroclor 1260 (1.4 mg/kg bw) for 4 to 7 weeks produced immuno-
suppression. Allen et al. (1974) and Allen (1975) observed comedones and
facial edema in rhesus monkeys ingesting diets containing 25 of ppm Aroclor
(1.1 mg/kg bw, assuming that a monkey consumes 4.2% of its body weight per day)
for 2 months.
Studies of subchronic and chronic exposure (i.e., ^90 days) to PCBs have
failed to use sufficiently low doses to define a no observed adverse effect
level (NOAEL) in rats. In Sprague-Dawley rats, Allen et al. (1976) and Allen
and Abrahamson (1979) reported that a 52-week exposure to diets containing 100
ppm of Aroclor 1248, 1254, or 1262 (5 mg/kg bw/day) followed by a 13-week
observation period resulted in hepatomegaly and liver necrosis. At a lower
exposure of 75 ppm in the diet (3.75 mg/kg bw/day) for 36 weeks, Sprague-Dawley
rats developed focal necrosis (Jonsson et al., 1981). Elevated liver porphy-
D-7
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rine levels were detected by both Kimbrough et al. (1972) and Zinkl (1977)
after exposure of Sherman rats for 8 months to 20 ppm of Aroclor 1254 or 1260
(1 mg/kg bw/day) and of CD rats for 20 weeks to 10 ppm of Aroclor 1254 (0.4
mg/kg bw/day). In a study employing near-lifetime exposure (2 years), Morgan
et al. (1981) reported an increase in mortality (33% as compared with 8% in
controls) in Fischer 344 rats at the lowest dose tested (25 ppm; 1.25 mg/kg
bw/day). The subchronic studies demonstrated increasing liver pathology over
the dose ranges studied, 0.5-5 mg/kg bw/day; while in the only chronic study,
the lowest dose tested (1.25 mg/kg bw/day) resulted in early deaths.
In mice, dietary exposure levels to Kanechlor-300, -400 or -500 or Arochlor
1254 of between 100 and 500 ppm (13-65 mg/kg bw/day) for periods from 23 weeks
to 11 months produced hepatomegaly (Ito et al., 1973; Bell, 1983; Kimbrough and
•Under, 1974). Koller (1977) used groups of BALB/CJ mice which were maintained
for 9 months on diets containing 0, 3.75, 37.5, or 375 ppm of the Aroclors 121,
1242, or 1254 (0.46, 4.57, or 47.75 mg/kg bw/day). The Aroclor with the lowest
chlorine content (1221) produced no liver lesions, while exposure to Aroclor
1242 resulted in increased liver weight in the high-dose group. In mice ex-
posed to Aroclor 1254, increased mortality was observed in the high-dose group,
mild hepatopathology was observed in the median dose group, and no liver lesions
were detected in the low-dose group. The no observed effect level (NOEL) in
this study in mice of 0.45 mg/kg bw/day is nearly identical to the lowest ob-
served effect level (LOEL) of 0.5 mg/kg bw/ day associated with porphyria in
rats (Kimbrough et al., 1972; Zinkl, 1977).
The only other species tested in chronic bioassays was the monkey, and it
proved to be highly sensitive to the toxic effects of PCBs. The most common
observations in monkeys exposed to Aroclor 1248 in the diet for a period of
from 8 to 39 months were skin lesions, palpebral edema, and erythema (Barsotti
D-8
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and Allen, 1975; Allen and Barsotti, 1976; Allen et al., 1980; Becker et al.,
1979). These effects were observed at the lowest doses tested, ranging from
2.5 to 3 ppm in the diet (0.095-0.126 mg/kg bw/day). In addition, Becker et
al. (1979) reported that monkeys fed diets containing 3 ppm of PCBs had gastric
lesions, body weight loss, and reduced hemoglobin and leukocytes. In the
monkey, doses as low as 0.1 mg/kg bw/day produced frank toxic effects; no
studies have been conducted from which a NOAEL can be derived or to indicate
how close 0.1 mg/kg bw/day is to the NOAEL for monkeys.
Although PCBs have not been demonstrated to be animal teratogens following
oral exposure, these compounds have been demonstrated to adversely affect
reproduction. When adminstered to pregnant Wistar rats at a dose of 100 mg/kg
bw/day on days 6 to 15 of gestation, Villeneuve et al. (1971) observed no
adverse effects; however, using the same treatment schedule, Spencer (1982)
reported that Sprague-Dawley rats were infertile after receiving 15 mg/kg
bw/day, that animals receiving 5 mg/kg bw/day had reduced litter weights, and
that 2.5 mg/kg bw/day was the NOEL. Rabbits had resorptions, abortions, and
fetuses at similar dose levels of 12.5 mg/kg bw/day administered on days 0
to 28 of gestation; however, slightly smaller doses of 10 mg/kg bw/day were
reported to be the NOEL. The Hartly guinea pig, which has been shown to have
greater sensitivity to the toxicity of PCBs than most other species, had
macerated fetuses after receiving 2.2 mg/day (6/5 mg/kg bw/day) of Clophen A-50
on days 10 to 60 of gestation (Brunstroem et al., 1982).
Effective doses of PCBs were lower than exposure occurred before and dur-
ing gestation. In a two-generation study, Sherman rats maintained on diets
containing 20 ppm Aroclor 1254 (1 mg/kg bw/day) had reduced litter size, and at
100 ppm (5 mg/kg bw/day) the pups that were born died during nursing (Linder et
al., 1974). In this study, 5 ppm (0.25 mg/kg bw/day) was the NOEL. Complete
D-9
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loss of fertility was observed in male and female Wistar rats caged together
for 9 weeks while ingesting 6.4 mg/kg bw/day of Aroclor 1254 emulsified in
their drinking water (Baker et al., 1977). Males regained normal fertility
after removal from treatment for 2 weeks. When Aroclor 1254 was administered
to lactating Holtzman rats at 32 mg/kg bw/day on days 3, 5 and 7 of lactation,
the future mating behavior of nursing male pups was adversely affected (Sager,
1983). A lower dose of 8 mg/kg bw/day was a NOEL.
Of the species tested, the mink and the monkey are the most sensitive to
the reproductive toxicity of PCBs. Bleavins et al. (1980) maintained mink on
diets containing 5 ppm Aroclor 1242 or 20 ppm Aroclor 1016 (doses of 0.75 and
3 mg/kg bw/day, assuming that a mink consumes 15% of its body weight per day)
for 18 months and observed complete reproductive failure in the Aroclor 1242
group and 25% mortality and infertility in the Aroclor 1016 group. A more
recent study by Aulerich et al. (1985) tested yet lower doses fed to mink via
diet. Aroclor 1254 at 2.5 ppm; 3,4,5,3',4',5'-hexachlorobiphenyl (345 HCB) at
0.1 or 0.5 ppm; 2,4,5,2',4',5'-hexachlorobiphenyl (245 HCB) at 2.5 or 5.0 ppm;
or 2,3,6,2',3',6l-hexachlorobiphenyl (236 HCB) at 2.5 or 5.0 ppm of diet were
fed to groups of 10 standard dark mink (proven breeders). A group of 20 ani-
mals served as controls. All of the mink fed 0.5 ppm 345 HCB died within 60
days, while those fed 0.1 ppm showed 50% mortality after 3 months. One still-
born kit was whelped in the Aroclor 1254 group. 245 HCB and 236 HCB did not
affect reproductive performance at either dose.
In a limited study (8 animals/group), Allen et al. (1980) maintained
rhesus monkeys on diets containing 2.5 or 5 ppm (0.1 or 0.2 mg/kg bw/day) of
Aroclor 1248 for 18 months. In the low-dose group, increased abortions were
observed, while in the high-dose group, the mothers showed overt signs of
toxicity and no live births occurred. After removal from exposure for 1 year,
D-10
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fertility had still not returned to normal, and some pups died during nursing.
It is apparent that frank effects in reproduction were observed in mink at
lower doses than in monkeys and still lower than the NOEL in rats, rabbits, and
guinea pigs following repeated exposure to PCBs.
QUANTIFICATION OF SHORT-TERM HEALTH ADVISORY LEVELS
PCBs belong to a class of chemically stable, multi-use industrial chemicals
that have been widely distributed in the ecosystem. Technical preparations con-
sist of complex mixtures of discrete PCB isotners. Because of. their physicochem-
ical properties, PCBs have been used as heat exchangers, dielectric, hydraulic
and lubricating fluids, plasticizers, pesticide extenders, adhesives, printing
inks and surface coatings.
The physical and chemical properties and the chemical formulations of PCBs
vary considerably, depending on the amount and position of chlorine substitu-
tion. Such properties as stability, volatility, and water solubility are par-
ticularly important in regard to frequency of occurrence in the environment.
The higher chlorinated biphenyls are less volatile than the lower chlorinated
biphenyls (Mieure et al., 1976). PCBs are extremely insoluble in water. The
solubility of commercial mixtures (for example, the Aroclors) ranges from 25 to
200 ppb (25 to 200 ug/L), depending on the chlorine content (Nisbet and Saro-
fim, 1972; Haque et al., 1974). The solubility of discrete PCB isomers has
been examined, and ranges from 1 to 600 ppb (1 to 600 wg/l.) depending on the
degree of chlorine substitution in the biphenyl ring (Haque and Schmeddig,
1975).
PCBs elicit a variety of adverse health effects. This is true of even
partially well-defi.ned compositions such as Aroclor 1254. For example, toxi-
D-ll
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cology studies on Arqclor 1254 of less less than 30 days' duration report
liver toxicity (Grant and Phillips, 1974; Carter, 1983), thyroid toxicity
(Collins and Capen, 1980a, b, c) and reproductive toxicity (Villeneuve et al.,
1971), as well as other types of toxicity (U.S. EPA, 1985b). At first, it
would seem that this variety in elicited adverse effects would make it diffi-
cult to distinguish the critical toxic effects of PCBs. However, it appears
that the experimental thresholds for these effects may be similar, at least for
studies of 30 days' duration or less.
Villeneuve et al. (1971) found increased incidences of fetal death, re-
sorptions, and abortions at 12.5 mg/kg/day of Aroclor 1254 in rabbits when
exposed on days 1 through 28 of pregnancy. A dose of 1.0 mg/kg/day appeared
to be without effect. Collins and Capen (1980a, b, c), in a series of studies
on thyroid effecs in rats, determined that 50 ppm of diet (~ 2.5 to 5.0
mg/kg/day) for 4 weeks was associated with clearly defined adverse effects, but
that doses of 5 ppm of diet (~ 0.25 to 0.5 mg/kg/day) were not. Carter
(1983) demonstrated liver hepatomegaly in rats at doses of 20 ppm Aroclor 1254
of diet (~ 2 mg/kg/day) for 14 days; such an effect in the absence of toxicity
(e.g., fatty infiltration of the liver) might not be considered adverse. Grant
and Phillips (1974) observed increased liver weights at doses as low as 5 mg/
kg/day Aroclor 1254 given in corn oil for 7 consecutive days. Collectively,
these studies indicate that the experimental threshold for adverse effects of
Aroclor 1254 in studies of 30 days' duration or less is at or near a dose of 1
mg/kg/day. Thus, it seems reasonable to use this latter dose as a basis for
health risk assessments for Aroclor 1254 for short durations.
Utilizing a dose of 1 mg/kg/day weight as a No Adverse Effect dose, a 10-
day exposure level for PCBs may be calculated as follows:
D-12
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10-day exposure level = 1 mg/kg/day x 10 kg = 0.1 rig/day for a 10-kg child.
100
where
10 kg = assumed body weight of a child, and
100 = uncertainty (safety) factor chosen in accordance with the
National Academy of Sciences guidelines, in which a NOAEL
from an animal study is employed.
For a 70-kg adult the 10-day exposure level would be 0.7 mg/day.
CARCINOGENIC EFFECTS
A number of short-term assays predictive of carcinogenic potential have
been performed using the Aroclors and individual isomers of PCBs. Negative
results have been obtained in the reverse mutation assay using S^. typhimurium
(Schoeny et al., 1979; Schoeny, 1982; Meddle and Bruce, 1977), and in the
dominant lethal assay in rats (Green et al., 1975). PCS products also did not
produce chromosomal changes in ]). melanogaster (Nilsson and Ramel, 1974) or in
the sperm and bone marrow cells of rats (Green et al., 1975; Garthoff et al.,
1977; Dikshith et al., 1975). Wyndham et al. (1976), however, observed
increases in reversion frequency in S.. typhimurium exposed to 4-chlorobiphenyl
and to a lesser extent with Aroclor 1221, while the more highly chlorinated
2,2',5,5'-tetrachlorobiphenyl and Aroclor 1254 were negative. The positive
response was observed in one strain, TA1538, in the presence of a metabolic
activation system derived from rabbit liver. In addition, a weak positive
response was observed by Peakall et al. (1972) in an assay of chromosomal
aberration in the embryos of ring doves fed Aroclor 1254. The variable data
observed with PCBs is consistent with the poor response and lack of correlation
D-13
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with animal carcinogenicity data reported for many highly chlorinated compounds
in short-term assay.
Early bioassays of PCBs were inadequate as a result of small group size
or periods of exposure extending for less than 1 year. These studies failed to
demonstrate that PCBs were carcinogenic when fed to rats or mice (Kimura and
Baba, 1973; Ito et al., 1973; Ito et al., 1974; Kimbrough and Under, 1974).
The study by Kimbrough and Linden (1974) in which 50 BALB/CJ male mice were fed
diets containing 300 ppm.of Aroclor 1254 for 6 or 11 months was suggestive that
Aroclor 1254 was a liver carcinogen. Of the 22 animals surviving PCB treatment
for 11 months, all had areas of adenofibrosis in the liver, and seven had his-
tologically identified hepatomas. In animals surviving 11 months which are
maintained on PCB-contaminated diets for 6 months, and in control animals,
there were, respectively, only 0/24 and 0/58 livers with areas of adenofibrosis
and 1/24 and 0/58 animals with hepatomas. There were no histologically identi-
fied hepatocellular carcinomas in.any group.
In a later study in rats using a larger group size and a longer exposure
period, Kimbrough et al. (1975) reported an increased incidence in hepato-
cellular carcinomas in animals exposed to PCBs. In this study, 200 female
Sherman rats were exposed to diets containing a nominal 100 ppm (range 70-107
ppm) of Aroclor 1260 for 630 days. The incidence of hepatocellular carcinomas
in the treated group compared with control animals was 26/184 and 1/173,
respectively; while the incidence of hepatic neoplastic nodules was 144/184
and 0/173, respectively.
In the only other chronic bioassay performed (NCI, 1978), 24 male and 24
female Fischer 344 rats/group were maintained on diets containing 0, 25, 50, or
100 ppm of Aroclor 1254. Although dose-related increases in nodular hyper-
plasia were observed, there was no significant increase in neoplastic lesions.
D-14
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With respect to the tumor incidence reported by Kimbrough et al. (1975), the
number of rats/group in the NCI study may have been too small to detect a
carcinogenic response.
Very limited information is available on the carcinogen!city of PCBs in
humans. In a survey of 1,200 patients in Yusho, Japan, 5.5 years after expo-
sure to PCBs, 41% of the 22 deaths were attributed to neoplasia (Kuratsune,
1976; Urabe, 1974). The relevance of these findings is unclear since the
tumors were at various common sites, and comparable incidences for an unexposed
population were not presented. In two letters to the editor, Bahn et al.
(1976, 1977) described suspected increases in malignant melanomas in a small
group of workers exposed to Aroclor 1254. In the 31 "heavily exposed" workers,
there were two cases of melanoma, while in the 41 "less heavily" exposed
workers, there was one melanoma. The International Agency for Research on
Cancer (IARC) estimates that only 0.04 cases would be expected in this number
of individuals (IARC, 1978). The only epidemiologic study (Davidorf and Knupp,
1979) examined the association between ocular melanomas and populations resid-
ing in areas -of known high environmental levels of PCBs. The authors concluded
that a causal relationship between PCBs and ocular melanomas was not demon-
strated. The IARC (1978) considered the association between exposure to
Aroclor 1254 and malignant melanomas described in the two letters to the editor
of the New England Journal of Medicine (Bahn et al., 1976, 1977) to be sugges-
tive evidence that PCBs are human carcinogens.
D-15
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QUANTIFICATION OF CARCINOGENIC RISK
WEIGHT OF EVIDENCE FOR HUMAN CARCINOGENICITY
The likelihood that a chemical such as PCB Is a human carcinogen Is ex-
pressed through a characterization or stratification of the "weight of evi-
dence" (human, animal, short-term test) and a final indiction of the "overall
weight of evidence" for human carcinogenicity.
The IARC has characterized the evidence for the carcinogenicity of PCBs in
humans as "inadequate," the evidence for carcinogenicity in animals as "suffi-
cient," and the supportive evidence from short-term tests as "inadequate,"
(IARC, 1982). The overall weight-of-evidence designation for PCBs under the
IARC scheme is 2B (probably carcinogenic in humans; evidence inadequate in
humans and sufficient in animals). The EPA has recently proposed a similar
scheme, which is an adaptation of the IARC scheme (U.S. EPA, 1984a). There are
some differences in the two schemes; however, for PCBs the requirements for
inadequate evidence of carcinogenicity in humans and for sufficient evidence in
animals are essentially identical. Similarly, the overall weight-of-evidence
under the new EPA scheme would be designated as B2, which has the same require-
ments as the 2B designation of the IARC scheme.
To comply with the EPA proposed guidelines for carcinogen risk assessment
(U.S. EPA, 1984a), any final risk estimate developed or used in risk charac-
terization should be coupled with the EPA classification of the qualitative
weight-of-evidence. Thus, those risk levels used in this paper are understood
to carry the "B2" designation; for example, 1 x 10~5 (B2), 1 x 10'6 (B2), etc.
POTENCY SLOPE FACTORS
The use of a potency slope factor, necessary in calculating risk or back-
calculating permissible PCB soil concentrations from selected risk levels, does
D-16
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not definitely indicate that the chemical is a human carcinogen. The likeli-
hood that the agent is a human carcinogen is a function of the weight-of-
evidence described above. The proposed EPA guidelines for carcinogen risk
assessment (U.S. EPA, 1984a) suggest that agents falling into Groups A and B
are suitable for quantitative risk assessments.
The U.S. EPA Carcinogen Assessment Group (CAG) has used the data from
female rats in the study by Kimbrough et al. (1975) to quantify the carcino-
genic risk from exposure to PCBs (U.S. EPA, 1980). In this analysis, the TWA
concentration of PCB (Aroclor 1260) in the diet was determined to be 88.4 ppm,
associated with a daily dose of 4.42 mg/kg bw/day, by assuming that an adult
rat consumes food equal to 5% of its body weight per day. In addition, for
this analysis, the incidence of hepatocellular carcinomas (26/184 in treated
animals and 1/173 in controls) and neoplastic nodules (144/184 in treated
animals and 0/173 in controls) were combined to produce tumor incidences of
170/184 and 1/173 in the treated and control groups, respectively. Using these
data and the linearized multistage model, a cancer potency value (q^) for
human exposure to Aroclor 1260 of 4.34 (mg/kg/day)'1 was calculated using the
data in Table 0-2. The U.S. EPA Office of Toxic Substances (OTS) has also used
the data from the same study, but by altering two of the variables (see Table
D-2), calculated a qj of 3.57 (mg/kg/day)'1 (U.S. EPA, 1985a). The average
of these two values is 4.0 (mg/kg/day)'1, and this value has been adopted by
this health advisories appendix for use in developing advisory levels for PCBs
clean-up.
Using this q^, a risk-specific dose (RSD) of Aroclor 1260 that would
result in an increased lifetime risk level of 10~5 for a 70-kg man can be
calculated as follows:
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TABLE D-2. DATA USED AS THE BASIS FOR THE
Species
Strain
Sex
Body weight (assumed)
Length of exposure
Length of experiment
Tumor site
Tumor type
PCB product tested
Dose
(mg/kg/day)
0
4.42
rat
Sherman
female
0.4 kg (0.35 kg)a
645 days (730 days)3
730 days
liver
combined hepatocellular carcinomas
and neoplastic nodules
Aroclor 1260
Incidence
(No. responding/No, tested)
1/173
170/184
aThe data in parentheses indicate the alternative values used by OTS in
computing a cancer potency factor.
SOURCE: Kimbrough et al., 1975.
D-18
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RSD = 1 x 10'5 x 70 kg bw * qj (mg/kg/day)'1
= 0.175 yg/day.
Thus, using the q^ for humans of 4.0 (mg/kg/day)"1, the RSOs corresponding to
lifetime risks of 10'4, 10'5, and 10'6 are 1.75, 0.175, and 0.0175 wg/day,
respectively. The adoption of these potency and concentration levels for all
PCBs requires a further assumption that all PCB compounds are carcinogenic and
that the potency of Aroclor 1260 is representative of any mixture of any other
PCB compound.
SPECIAL CONSIDERATIONS
HIGH-RISK SUBPOPULATION
Two separate groups of high-risk subpopulations for exposure to PCBs may
be identified. The first group includes those persons with the potential for
frequent or high exposure, namely, occupationally-exposed workers and breast-
fed infants, as PCBs are excreted in the breast milk of lactating humans
(Miller, 1977; Rogan et al., 1980; Wickizer et al., 1981; Mes and Davies, 1979;
Kuwabara et al., 1979; Hofvander et al., 1981). The second group includes
those persons with an inability to oxidize PCBs via glucuronidation to facili-
tate detoxification and elimination of these toxicants, such as embryos,
fetuses, and neonates (2 to 3 months old) (Calabrese and Sorenson, 1977;
Gillette, 1967; Nyhan, 1961), especially breast-fed infants who receive a
steroid via human breast milk that inhibits glucuronyl transferase activity
(Calabrese and Sorenson, 1977; Gartner and Arias, 1966), children simultane-
ously exposed to the antibiotic novobiocin (Lokietz et al., 1963; Calabrese
and Sorenson, 1977), persons with Gilbert's syndrome or Crigler and Najjar
D-19
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syndrome (Lester and Schmid, 1964; Calabrese and Sorenson, 1977), or persons
with hepatic infections such as infectious hepatitis (Calabrese and Sorenson,
1977).
COCARCINOGENESIS, INITIATION, AND PROMOTION
OiGiovanni et al. (1978) demonstrated that Aroclor 1254 had weak tumor
initiating activity in the mouse two-stage tumorigenesis models. Promoting
activity was not indicated for this Aroclor in a study by Berry et al. (1978).
Using other experimental systems, Ito et al. (1973) observed an increased inci-
dence of liver tumors in rats co-administered PCBs and benzene hexachloride as
compared with benzene hexachloride treatment alone. Co-administration of other
potent live carcinogens, 3'-methyl-4-dimethyl aminoazobenzene, N-2-fluorenylace-
temide and diethylm'trosamine, with PCBs, however, has resulted in the inhibi-
tion of the tumorigenic response (Ito et al., 1973). Similarly, antineoplastic
effects were reported by Nishizumi (1980) for pups of dams administered
Kanechlor-500 and diethylnitrosamine. These studies make it apparent that expo-
sure to PCBs can affect the carcinogen!city of other xenobiotics.
SUMMARY
For the purposes of setting advisory levels for PCBs contaminating soils,
acceptable intake (Al) levels have been developed which are based on both the
toxicity and the carcinogenicity of PCBs. The 10-day health advisories (HA)
for toxicity other than cancer have been developed. The 1-day and lifetime HAs
could not be evaluated. Advisories for the cancer end point are expressed in
terms of 10~4 to 10"7 lifetime individual excess risk levels. See Table 0-3 for
a summary of these AIs and risk-specific doses.
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TABLE U-3. SUMMARY UF RISK SPECIFIC, UUSES (RSDs) FOR CANCER
RISKS UF PCBs, OR OF ACCEPTABLE INTAKES FOR PROTECTION
AGAINST THE NONCARCINOGEMC EFFECTS OF PCBs
Description
Value (py/day)
11T4 RSU
11T5 RSU
11T6 RSU
Short-term AI (1-day)
Longer-term AI (10-day)
Lifetime AI
1.75
U.175
U.0175
Not estimated
10U for a child
7UO for an adult
Not estimated
U-21
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The toxicity and carcinogenicity of PCBs have recently been critically
evaluated in a number of EPA documents (U.S. EPA, 1980, 1983, 1984b, 1985b).
The approach taken here in developing a 10-day exposure advisory for non-
cancer toxicity has been to select from the available literature the animal
study that addresses the critical toxic effect and yields the most appropriate
no observed effect, no observed adverse effect, lowest observed effect, or
lowest observed adverse effect level. This dose was then divided by an appro-
priate uncertainty factor to obtain the 10-day HA.
The calculation of a 10-day HA for noncarcinogenic toxicity should make
use of animal data derived after an exposure period ranging from 10 to 30 days.
The literature contains several animal studies which address this length of
exposure. The studies chosen as a basis for the 10-day HA (Villeneuve et al.,
1971; Grant and Phillips, 1974; Collins and Capen, 1980a, b, c; Carter, 1983)
yield a No Observed Adverse Effect Level (NOAEL). These studies involved the
feeding of Aroclor 1254 to rabbits and rats. Collectively, in these studies, a
NOAEL can be ascribed to a dose of 1 mg/kg/day). Dividing this NOAEL by an
uncertainty factor of 100 yields a 10-day HA of 100 wg/kg/day for a child,
and 700 ug/day for a 70-kg adult.
The 1-day HA could not be estimated based on animal data derived from
studies with an exposure duration of 1 to 5 days. The lifetime HA noncancer
%
toxicity, likewise, could not be estimated.
The cancer risk specific doses (intake levels) have been calculated by
solving for exposure in the equation
Risk = Potency x Exposure
and multiplying by 70 kg. A cancer potency factor of 4.0 (mg/kg/day)~1 was
D-22
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adopted for use in these calculations. This value is the mean of the values
determined by OTS (3.57 (mg/kg/day)"1) and by ORD (4.34 (mg/kg/day)-1) for
PCBs.
0-23
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REFERENCES (APPENDIX D)
Allen, J.R. (1975) Response of the non-human primate to polychlorinated
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