United States
Environmental Protection
Office of Health and
Environmental Assessment
Washington DC 20460
Research and Development
EPA/600/S6-86/002 June 1987
Project Summary
Development of Advisory Levels
for Polychlorinated Biphenyls
(PCBs) Cleanup
Polychlorinated biphenyls (PCBs),
commercially known as Aroclors, con-
sist of mixtures of chlorinated biphenyl
compounds. Many sites contaminated
by PCBs remain contaminated because
of PCB persistence in the environment.
Although commercial PCB production
in the United States has been banned
by the Toxic Substances Control Act,
continued use in previously existing
commercial equipment can result in
spills which require cleanup. The En-
vironmental Protection Agency (EPA)
has become increasingly involved in the
discovery, assessment, and cleanup of
these sites.
The purpose of this study is to provide
advisory levels for PCB cleanup, and to
describe the technical and scientific
rationale and methods used in develop-
ing these advisory levels for PCBs in
contaminated soil. This required the
development of exposure and risk as-
sessment methodology related to haz-
ardous waste and spill sites, and
analyses of health effects data.
The currently available modeling tech-
niques considered most appropriate are
used to estimate exposures. PCBs ad-
visory 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.
This Project Summary was developed
by EPA's Office of Health and Environ-
mental Assessment, Washington, D.C.,
to announce key findings of the research
project that Is fully documented In a
separate report of the same title (see
Project Report ordering Information at
back).
Introduction
The full report of this project summary
was prepared in response to a request
from the Office of Emergency and
Remedial Response (OERR), that the
Office of Health and Environmental As-
sessment (OHEA) develop advisory levels
for polychlorinated biphenyls (PCBs) which
can be used as guidelines for initiating
removal action for sites contaminated
with PCBs. Interested offices within EPA,
including OERR, have advised OHEA that
these advisory levels for PCBs cleanup
should be developed based on considera-
tions of public health protection from
short-term and long-term exposures. The
advisories presented include permissible
levels of PCBs in soil corresponding to
10-day and lifetime acceptable intakes.
Exposure routes considered in develop-
ing 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 bioaccumulated PCBs,
are considered in relation to their im-
portance and their relevance to this pro-
ject. In view of the high bioaccumulation
factor for PCBs, the consideration of bio-
accumulation 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 ex-
posure route or human intake considered,
the advisories need to be reevaluated.
Chemical Composition
Commercial-grade PCBs, consisting of
mixtures of different composition, are
sold under the trade name Aroclors.
Impurities such as chlorinated dibenzo-
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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 numbers represent
the type of molecule (12 = biphenyl-based;
54 = terphenyl-based; 25 or 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.
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
using high-resolution gas chromatog-
raphy. No compounds which can be
formed by addition of chlorine rather than
substitution were found in a detailed
study of PCBs published in 1976. It is
suspected that the conditions prevailing
during industrial manufacturing of PCBs
do not favor the formation of addition
compounds, or that these latter com-
pounds might have been destroyed in the
step used to purify the Aroclor. The
literature data show that even for the
same type of Aroclor, the compositions
of individual biphenyls vary slightly.
Major PCB components in foreign pro-
ducts bearing the names of Kanechlor
and Phenoclor for Japanese and Franch
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.
Exposure Assessment
It is likely that not all of the PCBs
ingested or inhaled by humans are ab-
sorbed. 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 param-
eters needed in the pharmacokinetics
models has prevented their applications
to the analysis for PCB absorptions
through human exchange boundaries.
Future work should consider these
models. Although most animal studies
(in rats and mice) on the extent of absorp-
tion 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 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 ab-
sorption rate for humans after ingestion
of PCB-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 in-
formation is available for the quantitative
evaluation of dermal absorption rates.
Five percent dermal absorption is as-
sumed for soil contaminants in contact
with human skin.
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 distri-
bution: (1) Exposure occurs onsite. This
can be further subdivided into: (a) sites
that are readily accessible to children,
and, hence, the soil from which will be
subject to ingestion, dermal 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
OXa) 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 dis-
tances of 0.1 km or 1 km from the site, as
in Classes (2) and (3) above, it is assumed
that no ingestion of contaminated soil
occurs and the exposure route is that of
inhalation.
Emission Evaluation
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 concentra-
tions 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-con-
taminated material is covered with low-
permeability material of appropriate thick-
ness. 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 dif-
fusional 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 assumption. Since the
depletion rate varies over time, it is
averaged over the exposure period. Deple-
tion 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 initially
exposed to the atmosphere and the soil is
contaminated up to the conditions ex-
hibiting saturation vapor pressure. A
constant emission rate can be assumed if
the vapor-phase concentration maintains
a constant value at the surface of soil
contamination for time-varying emission
rates. Calculations corresponding to
Classes (1), (2), and (3) for exposure
possibilities with surface contamination
are repeated at an assumed 25-cm thick-
ness of a soil cover initially free from PCB
contamination. Among many factors af-
fecting the emission rate (including 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 cmVg.
PCB Levels In Soil
The method for determining the per-
missible 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 calcu-
lations are summarized in Tables 1 and
2, which have been prepared using
different combinations of the following
variables:
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Table 1. Permissible PCB Soil Contamination Levels (Uncovered Surface Contamination)
Permissible Levels (ug PCB/g soil) Corresponding to
On the contaminated site
-Soil ingestionc,
inhalation*
-Soil ingestion".
inhalation*
-Inhalation only',
0.1 km from
contaminated site
-Inhalation only*
1 km from
contaminated site
-Inhalation only*
Noncancer Short-Term*
Acceptable Intake fug/day)"
Cancer Risk Specific Doses (fig/day)
Location and
Route of Human
Exposure
100
for Child
700
for Adult
0.00175
HO'7 Risk)
0.0175
(10'* Risk)
0.175
(10'"Risk)
1.75
(10'4Risk)
25-100
42-420
47-vs"
vs*
510-730
2100-3000
vs
0.008-0.01
0.01-0.06
.08-O.I
0.1-0.6
0.8-2
1-6
220-1.3X103 2.2x10*-1.3x10s
8-17
35-61
vs 0.01-0.2 0.1-2.0 1-20 77-470
vs 2.0-220 90-2.2x10* 7.7xW3-vs 8.7xW*-vs
vs
'Short-term ss 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).
'Inhalation rates are assumed to be 20 rrr/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.
avs denotes no theoretical upper-bound limit. Practical reasons require no free-flowing PCB liquids for the limit.
(1) Surface contamination represent-
ing a situation where the con-
taminated 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 (1) (a),
corresponding to sites accessible to
children.
(4) Different acceptable intake (Al)
levels (short-term Al, and Als at
different cancer risk levels).
(5) Four Aroclors (Aroclor 1242, 1248,
1254, and 1260).
(6) Two selected values of the soil-air
partition coefficient, representing
the high and low values.
(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 atmosphere
and is left uncovered. Table 2 represents
the case where the contaminated 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.
Results
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 concentration of PCBs at
the contaminated soil surface is main-
tained 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 equilibrium with the air phase being
emitted. Therefore, the concentration of
PCBs in the initially clean soil material
cannot exceed the concentration in equili-
brium 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 in the ex-
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Table 2. Permissible PCB Soil Contamination Levels (25-cm-Thick Clean Cover)
Permissible Levels (fjg PCB/g soil) Corresponding to
Location and
Route of Human
Exposure
Noncancer Short-Term*
Acceptable Intake (ug/day)°
Cancer Risk Specific Doses (ug/day)
100
for Child
700
for Adult
000175
(10~7 Risk)
00175
(10~eRisk)
0 175
(W5 Risk)
1.75
f10~' Risk)
On the contaminated site
-Soil mgestionc,
inhalation'
-Soil ingest/on",
inhalation"
-Inhalation on/y°
0.1 km from
contaminated site
-Inhalation only"
1 km from
contaminated site
-Inhalation only"
110-200' 800-1400
450-vsa
3100-vs
001-0.2
0.02-0 6
0.02-1 0
1-vs
0 1 -2.0
02-60
0.2-vs
620-vs
1-17
1 0-48
20-vs
22-vs
93-vs
770-vs
"Short-term = 10-day intake.
t'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).
'Inhalation 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 soil-air partition coefficient are used in the calculations
gvs denotes no theoretical upper-bound limit Practical reasons require no free-flowing PCB liquids for the limit.
posure 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, the first
assumption is tantamount to requiring
the presence of no free liquids in the soil,
which may otherwise result in the
phenomenon of "wicking " Since the
ranges shown in Tables 1 and 2 are
dependent upon the type of Aroclors and
the values of the soil-air partition coef-
ficient, site-specific or Aroclor-specific
information should be used to establish
an appropriate level of PCBs for that
particular condition. Computer outputs
for the selected Aroclors under the ranges
and conditions of common environmental
concern can be used to find the permis-
sible concentrations in soil suitable to
particular situations
Table 1, for example, can be inter-
preted 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 occur-
ring to the children by inhalation and
dermal contact is accounted for, the per-
missible PCB levels in soil should range
from 25 to 100 /ng/g and 42 to 420 M9/9
for prevention of noncancer effects from
10-day exposure for a child with an
average weight of 10 kg ingesting soil at
the rates of 3 and 0 6 g/day, respectively
For cancer effects, permissible levels m
soil for a lifetime exposure to PCBs re-
sulting from ingestion of and dermal
contact with contaminated soil and in-
halation of contaminated air should range
from 008 to 0.1 ng/g and 0.1 to 0.6
jug/g, corresponding to an upper-bound
risk estimate of 106 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
possibility of soil ingestion, PCB levels in
soil, based on the inhalation route only,
should range from 47 M9/9 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 M9/9. corresponding to a
lifetime Al at a risk factor of 10 6. Again,
the level will be dictated by the types of
Aroclor present and the specific char-
acteristics of the site involved
(2) If there is no possibility of a popula-
tion entering the contaminated site within
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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 M9/9, without exceed-
ing 10-day Al and lifetime Al 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 104, 10'5and107.
Conclusion
The short-term Al levels (100 M9/9 day
for a child and 700 ng/g day for an adult)
used to develop 10-day advisories based
on noncancer effects are derived from
animal studies, which collectively indicate
that the experimental threshold for ad-
verse effects of Aroclor 1254 is at or near
a dose of 1.0 jug/kg body weight. Using
this dose as a No Observed Adverse
Effect Level and a safety factor of 100,
the 10-day Al levels for noncancer effects
described above (100 and 700 M9/daY)
were computed. The permissible con-
centrations of PCBs in soil are calculated
from multimedia exposure assessments
by requiring that the total PCBs intake
rate from pertinent exposure "pathways
do not exceed these Als. Advisory levels
for 1 -day and lifetime noncancer effects
cannot be derived at this time because of
the insufficiency of available data. How-
ever, in view of the experimental duration,
the 10-day advisories may well be used
for the 1 -day advisories.
The EPA authors Seong T. Hwang (also the EPA Project Officer, see below),
James W. Falco. and Charles H. Nauman are with the Office of Health and
Environmental Assessment. Washington, DC 20460.
The complete report, entitled "Development of Advisory Levels forPolychlorinated
Biphenyls (PCBs) Cleanup." (Order No. PB 86-232 774/AS; Cost: $22.95,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Office of Health and Environmental Assessment (RD-689)
U.S. Environmental Protection Agency
Washington, DC 20460
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S6-86/002
OC00329
60604
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