Contents Chapter 5
Acronyms S. J. Cotter, F. R. O Donnell, and P. A. Scofield
The interaction of radiation emitted by radionuclides with human tissue accounts for most of the doses from radionuclides in the environment. Radionuclides can be taken into the body through ingestion, inhalation, and skin absorption. Humans can also be exposed directly to radiation sources outside the body, which can include radionuclides. Radiation dose can be estimated based on type of radiation, route and length of exposure, and organs exposed. This section presents estimates of radiation doses due to small quantities of radionuclides released to air and water as a result of operations at the ORR facilities during 1995 and describes the methods used to make these estimates.
Small quantities of radionuclides were released to the environment from operations at the ORR facilities during 1995. Those releases are quantified and characterized in Sects. 4, 5, and 7. This section presents estimates of the potential radiation doses to the public from the releases and describes the methods used to make the estimates.
6.1.1 Terminology
Most doses associated with radionuclide releases to the environment are
caused by interactions between radiation emitted by the radionuclides
and human tissue. These interactions involve the transfer of energy from
the radiation to tissue, a process that may damage the tissue. The
radiation may come from radionuclides located outside the body (in or on
environmental media or objects) or from radionuclides deposited inside
the body (by inhalation, ingestion, and, in a few cases, absorption
through the skin).
Exposures to radiation from nuclides located outside the body are called external exposures; exposures to radiation from nuclides deposited inside the body are called internal exposures. This distinction is important because external exposures occur only when a person is near or in a radionuclide-containing medium; internal exposures continue as long as the radionuclides remain inside the person. Also, external exposures may result in uniform irradiation of the entire body and all its components; internal exposures usually result in nonuniform irradiation of the body. (When taken into the body, most radionuclides deposit preferentially in specific organs or tissues and thus do not irradiate the body uniformly.)
A number of the specialized terms and units used to characterize exposures to ionizing radiation are defined in Appendix A. One of these is used repeatedly in this section and is defined as the EDE, a risk-based dose equivalent that can be used to estimate health-effects risks to exposed persons. It is a weighted sum of dose equivalents to specified organs, expressed in rem or sieverts (1 rem = 0.01 Sv).
6.1.2 Methods of Evaluation
6.1.2.1 Airborne Radionuclides
Characterization of the radiological consequences of radionuclides
released to the atmosphere from ORR operations during 1995 was
accomplished by calculating, for each plant and for the entire ORR, EDEs
to maximally exposed off-site individuals and to the entire population
residing within 80 km (50 miles) of the center of the ORR. The
dose calculations were made using the CAP-88 package of computer codes
(Beres 1990
), which was developed under
EPA sponsorship to demonstrate
compliance with Rad-NESHAP
40 CFR 61, Subpart H. This package contains the most recent,
approved version of the AIRDOS-EPA and DARTAB computer codes and the
ALLRAD88 radionuclide data file. The AIRDOS-EPA computer code implements
a steady-state Gaussian plume atmospheric dispersion model to calculate
concentrations of radionuclides in the air and on the ground. It also
uses Regulatory Guide 1.109
(NRC 1977
) food chain models to calculate radionuclide concentrations in
foodstuffs (vegetables, meat, and milk) and subsequent intakes by
humans.
The concentrations and human intakes are used by EPA's latest version of the DARTAB computer code to calculate EDEs from radionuclides released to the atmosphere. The dose calculations use the dose conversion factors (DCFs) contained in the ALLRAD88 data file (Beres 1990 ).
Three types of radionuclide releases were reported in the ORR Rad-NESHAP report for 1995: monitored, sampled, and calculated. Monitored releases are quantified using data from continuous sampling systems. Monitored sources during 1995 included the combined monitored stacks at the Y-12 Plant; stacks associated with buildings 2026, 2523, 3020, 3039, 7830, 7877, and Stack 7911 at ORNL; and the K-25 Site TSCA Incinerator (K-1435) stack.
Sampled releases are calculated from measured radionuclide contents of various media (e.g., grab samples of room air concentrations and sections of filters) and measured flow rates through the sampled media. Sampled sources during 1995 include room exhausts at the Y-12 Plant; stacks associated with buildings 2000, 3018, 3074, 3544, 7025, and 7512 at ORNL; and discharge points associated with the K-1015 laundry, K-31/K-33, and K-1037 at the K-25 Site.
Calculated releases are determined from source inventories (e.g., hot cell, hood, and storage area) using EPA-approved emission factors. Therefore, these calculated releases are conservative and largely hypothetical. Their purpose is to determine whether source monitoring or sampling is required. All doses (including those derived from these hypothetical releases) must be reported in the Annual Site Environmental Report and in the Rad-NESHAP report; however, it is important to realize that radiation doses associated with calculated releases, which may be hypothetical, are added to the doses associated with monitored and sampled releases.
Monitored and sampled radionuclide releases were modeled for 1 combined
release point at the Y-12 Plant, for 13 release points at
ORNL, and for 3 release points at the K-25 Site. Table 6.1
lists the source parameter values used in the calculations.
Meteorological data used in the calculations were in the form of joint
frequency distributions of wind direction, wind speed class, and
atmospheric stability category. These data were derived from data
collected during 1995 at the 60-m height on MT6 for the Y-12 Plant;
at the 100-m height on meteorological tower 2 (MT2) for stacks
2000, 2026, 2523, 3018, 3020, 3039, 3074, 3544, and 7025 and at the
30-m height on MT4 for stacks 7512, 7830, 7877, and 7911 at ORNL;
and at the 60-m height on MT1 for the K-25 Site. Rainfall on the
ORR during 1995 was 120 cm (47 in.), the average air temperature was
14�C (56�F), and the average mixing layer height was 1000 m
(3280 ft).
The dose calculations are based on the assumption that each person
remained at home (actually, outside the house), unprotected, during the
entire year and obtained food according to the rural pattern defined in
the NESHAP background documents
(EPA 1989
). This pattern specifies that 70% of the vegetables and produce,
44.2% of the meat, and 39.9% of the milk consumed by each
person are produced in the local area (e.g., a home garden). The
remaining portion of each food is assumed to be produced within
80 km (50 miles) of the ORR. For collective EDE estimates,
production of beef, milk, and crops within 80 km of the ORR was
calculated using the state-specific production rates provided with
CAP-88.
The EDE received by the hypothetical, maximally exposed individual for
the Y-12 Plant was calculated to be 0.46 mrem
(0.0046 mSv). This individual is located about 1080 m
(0.7 miles) north-northeast of the Y-12 Plant release point.
Essentially, all ( is similar to 96%) of this dose is from ingestion and
inhalation of uranium, primarily 234U, 235U, and
238U and about 1% of the dose is due to
239Pu. The contribution of Y-12 Plant emissions to the
50-year committed collective EDE to the population residing within
80 km of the ORR was calculated to be about 6 person-rem
(0.06 person-Sv), which is approximately 51% of the collective
EDE for the ORR.
The EDE received by the hypothetical, maximally exposed individual for
ORNL was calculated to be 0.2 mrem (0.002 mSv). This
individual is located 4060 m (2.5 miles) south-southwest of
the 3039 stack and 3720 m (2.3 miles) southwest of the 7911
stack. About 54% of this dose is from ingestion and inhalation of
212Pb, about 21% is from immersion in noble gases
(primarily 41Ar), and about 14% is from ingestion and
inhalation of 138Cs. Other nuclides contributing is similar
to 1% or more to the dose are 3H (2.4%) and thorium
nuclides ( is similar to 1%). Calculated source terms account for about
20% of the dose. The contribution of ORNL emissions to the
collective EDE to the population residing within 80 km of the ORR
was calculated to be about 3 person-rem (0.03 person-Sv),
which is approximately 25% of the collective EDE for the ORR.
The EDE received by the hypothetical, maximally exposed individual for
the K-25 Site was calculated to be 0.05 mrem
(0.0005 mSv). This individual is located about 5180 m
(3.2 miles) west-southwest of the TSCA Incinerator (K-1435) stack.
About 93% of this dose is from ingestion and inhalation of uranium,
about 5.6% is from 40K, and about 1% is from
99Tc. The contribution of K-25 Site emissions to the
collective EDE to the population residing within 80 km of the ORR
was calculated to be about 3 person-rem (0.03 person-Sv),
which is approximately 24% of the collective EDE for the
reservation.
The reasonableness of the calculated radiation doses can be inferred by
examining the radiation doses that could be received from measured air
concentrations of radionuclides at the ORR
PAMs and
RAMs (Fig. 5.3). Hypothetical individuals assumed to reside at the
PAMs could have received EDEs between 0.089 and 4.7 mrem/year
(0.00089 and 0.047 mSv/year); these EDEs include contributions from
naturally occurring (background) radionuclides, from radionuclides
released from the ORR, and radionuclides released from any other
sources. The highest calculated potential dose rate, 4.7 mrem/year
at PAM 35, is due to tritium of unknown origin. An indication of
doses from sources other than those on the ORR can be obtained from the
EDEs calculated at the two RAMs, which averaged 0.062 mrem/year
(0.00062 mSv/year). Between 30 and 90% of the calculated EDEs
at the PAMs are attributable to tritium, some of which was produced
naturally.
Of particular interest is a comparison of doses calculated using
measured air concentrations at PAMs located near the maximally exposed
individuals for each plant and doses calculated to those individuals
using CAP-88 and measured emissions. PAM 46 is located near the
maximally exposed individual for the Y-12 Plant and the entire ORR.
The EDE calculated at PAM 46 was 0.09 mrem/year
(0.0009 mSv/year), which is 20% of the 0.46 mrem/year
(0.046 mSv/year) to the maximally exposed individual modeled by the
CAP-88 code. PAM 39 is located near the maximally exposed individual for
ORNL. The EDE calculated at PAM 39 was 0.11 mrem/year
(0.0011 mSv/year), which is about half the 0.20 mrem/year
(0.0020 mSv/year) based on CAP-88 code modeling. PAM 35 is located
near the maximally exposed individual for the K-25 Site. The EDE
calculated at PAM 35 was 4.7 mrem/year (0.047 mSv/year), which
is much higher than the 0.052 mrem/year (0.00052 mSv/year)
modeled value to the maximally exposed individual.
Measured, annual-average concentrations of radionuclides in water
samples taken at the K-25 Site (Gallaher) water plant and at the
Kingston municipal water plant were used to calculate potential maximum
individual EDEs from drinking water. A worker who drank 365 L (half
of the worker's total water consumption) of K-25 Site water during
1995 could have received an EDE of about 0.10 mrem
(0.0010 mSv); a person who drank 730 L of Kingston water could
have received about 0.15 mrem (0.0015 mSv).
There are other unsampled water treatment plants along the
Clinch-Tennessee River system. Three plants are located above Melton
Hill Dam, and others are located on tributaries of Watts Bar and
Chicamauga Lakes. The three upstream plants are located near sampling
points CRK 84, CRK 66, and CRK 58. Persons drinking
730 L of sampled water per year could receive EDEs of 0.16, 0.28,
and 0.31 mrem (0.0016, 0.0028, and 0.0031 mSv), respectively.
(These dose estimates may be high because they are based on water
samples taken before processing in the plants.) Persons drinking water
from the Watts Bar and Chicamauga plants should receive EDEs lower than
the 0.15 mrem calculated for the Kingston water treatment plant.
A program initiated during 1993 involves collecting samples of water and
fish at selected locations along the Clinch River, Poplar Creek, and
near the intake of the Kingston city water plant on the Tennessee River
(Fig. 5.21). The results of this sampling program were used to illustrate
potential radiation doses from radionuclides found in waters above and
below inputs from the ORR.
Measured concentrations of radionuclides in water at the selected
locations were input to the LADTAP XL computer code to calculate
potential EDEs to maximally exposed individuals who are assumed to eat
21 kg of fish/year, to swim or wade for 27 hours/year, to boat
for 63 hours/year, and to use the shoreline for 67 hours/year
at the sampled location. Also, fish sampling data were used to calculate
maximum individual EDEs from eating 21 kg of fish. Table 6.4
is a summary of the potential EDEs. Eating fish and shoreline usage
are the only significant contributors to potential EDEs. Doses
attributable to swimming or wading and boating are negligibly small.
EDEs from eating fish also are estimated using measured concentrations
of radionuclides in fish. Because of differences in the radionuclides
reported as present, doses calculated using concentrations in water
exceeded those calculated using concentrations in fish tissue. The
results are presented in Table 6.4.
Calculated EDEs ranged from 0.2 to 1.1 mrem (0.002 to
0.011 mSv) per year. High and low dose estimates are found both
above and below DOE inputs.
Doses that result from eating fish range from 0.002 to 0.93 mrem
(0.00002 to 0.0093 mSv) per year, and doses resulting from
shoreline exposures ranged from negligible to 0.2 mrem
(0.002 mSv) per year. The highest EDEs were calculated at a
location (CRK 80) upstream from almost all DOE inputs.
When all pathways are considered, the maximum EDE resulting from
waterborne radionuclide discharges could have been about 1.2 mrem
(0.012 mSv): 1.1 mrem (0.011 mSv) from use of off-site
waters plus 0.1 mrem (0.001 mSv) from drinking K-25 or
Kingston water. The collective EDE to the 50-mile population was
estimated to be about 9 person-rem (0.09 person-Sv). These are
small percentages of individual and collective doses attributable to
natural background radiation, 0.4% and 0.003%, respectively.
To calculate potential EDEs from eating the sampled vegetables, it was
assumed that a person ate 32 kg (70.56 lb) of homegrown
tomatoes, 10 kg (22.05 lb) of leafy vegetables, and 37 kg
(81.58 lb) of root vegetables during the year. These consumption
rates, which differ from those used in 1994, were obtained from
Exposure Factors Handbook-Draft
(EPA 1995
). It provides a thorough summation of U.S. vegetation consumption
rates (EPA 1996). Based on these assumptions, the average individual's
EDE from eating all three vegetable types could be about 5.3 mrem
(0.053 mSv), about 1.4 mrem (0.014 mSv) from
fruit-bearing vegetables, about 2.0 mrem (0.02 mSv) from leafy
vegetables, and about 1.9 mrem (0.019 mSv) from root
vegetables (Table 6.5).
If the contribution (about 99%) of 40K, which is strictly a
naturally occurring radionuclide, to this dose is excluded, the maximum
individual EDE could have been about 0.047 mrem (4.7E-4 mSv).
This 0.047 mrem was from the other radionuclides detected in the
vegetables. Detected isotopes include 238U, 137Cs,
and 60Co. Although these radionuclides are measured in
emissions from the ORR, uranium isotopes occur naturally in soil and
fertilizers that are spread on gardens. Therefore, most of the
radioactivity found in the vegetables and the associated radiation doses
are not attributable to ORR operations. The estimated EDEs for
ingesting vegetables grown at the ORR monitoring sites are summarized in
Table 6.5.
Hay samples were collected from one background location and from six ORR
locations. The six ORR samples were combined into three samples.
Statistically significant concentrations were found for 7Be
and 40K, both of which are naturally occurring radionuclides.
Essentially all of the dose to humans (about 99%) from eating beef and
drinking milk from cattle that eat hay was from the naturally occurring
40K. Including the contribution from 40K, the EDE
from drinking milk and eating beef was estimated to be about
20 mrem (0.2 mSv); excluding 40K, the EDE was
estimated to be about 1.4E-03 mrem (1.4E-05 mSv).
All deer were surveyed at the
TWRA inspection station to
determine the 137Cs content in tissue and total strontium in
bone. Based on field measurements, the average 137Cs
concentration in the 481 released deer was 0.18 pCi/g
(0.0067 Bq/g). The EDE for an individual consuming one deer with
the average concentration of 137Cs was estimated to be
0.2 mrem (0.002 mSv). The collective EDE from eating all the
harvested deer meat with an average 137Cs concentration of
0.18 pCi/g could have been about 0.09 person-rem
(9E-4 person-Sv).
EDEs were estimated for hunters with the highest potential intake (in
terms of concentration and field dress weight) who harvested two deer.
Using actual field-derived 137Cs concentrations and
field-dressed weights, and assuming that one individual consumed all the
deer meat, the highest EDE was about 1 mrem (0.037 mSv).
In 1994, random muscle, liver, bone, and/or thyroid samples were
collected from 36 nonconfiscated deer. In 1995, samples were
collected from 25 nonconfiscated deer. The 1994 average
90Sr concentration in nonconfiscated deer muscle was
0.96 pCi/g (0.036 Bq/g). Assuming that the 1994 tissue
analyses are representative of 1995 90Sr concentrations in
deer, and the 137Cs concentration is 0.18 pCi/g
(0.0067 Bq/g), the average EDE from consuming a deer [edible tissue
weight of 21.5 kg (47.3 lb)] is estimated to be about
3 mrem (0.03 mSv).
Four deer were collected from Chuck Swan State Park in 1994; these are
considered to represent background tissue samples. In the limited number
of background deer tissue (muscle and liver) samples, the average
137Cs concentration was is similar to 0.2 pCi/g
(7.4E-03 Bq/g) and the average 90Sr concentration was
is similar to 0.96 pCi/g (0.036 Bq/g). Essentially, similar
average 137Cs concentrations were found in deer harvested on
the ORR in 1995, and similar average 90Sr concentrations were
found in deer harvested on the ORR in 1994.
The average weight of the Canada geese scanned during the roundup was
about 3.8 kg (8.4 lb), half of which is assumed to be edible.
A person eating a Canada goose with the average field
137Cs concentration could have received an EDE of about
0.008 mrem (0.00008 mSv). A person eating a Canada goose
with the maximum 137Cs concentration and the maximum weight
of a goose surveyed [5.2 kg (11 lb)], could receive an EDE of
about 0.03 mrem (0.0003 mSv). If a person consumed
8 geese [this number is based on 2.15 geese, the average number of
geese harvested per hunter in the East Tennessee Zone during the
September hunt,
(Warr 1996
)], each with an average 137Cs concentration
[0.084 pCi/g 0.003 Bq/g)], the estimated EDE would be
0.06 mrem (0.0006 mSv). This is a conservative assumption,
since most hunters harvest on average 1 to 2 geese per hunting
season (Warr 1996
; USFWS 1995
.)
Of the geese harvested in the four surrounding counties Anderson, Knox,
Loudon, and Roane), it is estimated that about 160 of these geese could
have spent time on the ORR. Therefore, the collective EDE from eating
160 geese harvested in 1995 could have been about
1.9E-04 person-rem (1.9E-06 person-Sv), assuming all were
contaminated at the average concentration.
Eleven geese were sacrificed and tissue, bone, and thyroid samples were
collected and analyzed. In addition, six background geese also were
sacrificed and samples were collected and analyzed. The average tissue
137Cs concentration derived from laboratory analyses was
0.013 pCi/g (4.8E-4 Bq/g), which was lower than the average
137Cs concentration estimated at the deer counting station.
The average 90Sr concentration in tissue was 6.8 pCi/g
(0.25 Bq/g). Taking into account these analytical results, if an
individual consumed one goose with these average concentrations of
137Cs and 90Sr, the EDE is estimated to be
2 mrem (0.02 mSv). Taking into account the maximum
concentration of 137Cs and 90Sr detected in the
goose samples, 0.54 pCi/g (0.02 Bq/g) and 11 pCi/g
(0.41 Bq/g), respectively, and the maximum goose weight of
5.2 kg (11 lb), the EDE is estimated to be 4.5 mrem
(0.045 mSv).
During 1987, external exposure rate measurements were taken along a
1.7-km (1.1-mile) length of Clinch River bank. Measured exposure rates
along this stretch of bank averaged 13 �R/hour and ranged between
3.5 and 18 �R/hour. These measured exposure rates are attributable
to radiation emanating from a nearby field that contains the remnants of
a 137Cs seeding experiment. The experimental plots were
remediated during 1994, but measurements to confirm that the exposure
rate along the Clinch River has decreased were not performed. Therefore,
we assume the exposure rate along the Clinch River caused by the cesium
plots was the same as reported last year, about 8 �R/hour
(0.006 mrem/hour) above background.
A potential maximally exposed individual is a hypothetical fisherman who
was assumed to spend 5 hours/week (250 hours/year) near the
point of average exposure. This hypothetical, maximally exposed
individual could have received an EDE of about 1 mrem
(0.01 mSv) during 1995. This dose estimate is high because most of
the 137Cs was removed from the experimental fields in
1994.
The radiation field along Poplar Creek emanates from storage areas
within the K-25 Site. The section of the creek affected by this
area runs through the plant and is used at times by fishermen. Exposure
rate measurements, corrected for background, taken along the creek
during 1995 ranged between 3.9 and 8.3 �R/hour, which is equivalent
to an EDE rate from 0.003 to 0.006 mrem/hour (between 0.00003 and
0.00006 mSv/hour). The average exposure rate was about
5.1 �R/hour, which corresponds to an EDE rate of
0.004 mrem/hour. A 4-hour fishing trip could have resulted in
reception of an EDE between 0.01 to 0.02 mrem (0.0001 to
0.0002 mSv). If the hypothetical Clinch River fisherman is used,
the 250-hour/year exposure time could have resulted in reception of an
EDE of about 1 mrem (0.01 mSv). It is extremely unlikely that
anyone would fish this stretch of Poplar Creek for
250 hours/year.
Table 6.6
lists average and maximum total dose rates to aquatic organisms from
waterways at the Y-12 Plant, ORNL, and the K-25 Site. The
doses for ORNL are based on water concentrations associated with nine
different sampling locations: Melton Branch (Outfalls X-13 and 2), WOC
(Outfall X-14), WOD (Outfall
X-15), First Creek, Fifth Creek, Raccoon Creek, Northwest Tributary, and
at the 7500 Bridge. The results from these calculations indicate that
absorbed dose rates to aquatic biota are much less than 1 rad/day
(0.01 Gy/day).
At ORNL the highest dose rates, which were associated with maximum
concentrations of radionuclides in water, occurred at WOC (X14):
0.0022 rad/day (2.2E-5 Gy/day) to fish, and at Melton Branch
(X-13): 0.013 rad/day (1.3E-4 Gy/day) to crustacea, and
0.004 rad/day (4E-5 Gy/day) to muskrats. Even with maximum
radionuclide concentrations at these locations, the absorbed doses were
significantly less than the limit of 1 rad/day
(0.01 Gy/day).
At the Y-12 Plant, aquatic organism doses were estimated from
radionuclide water concentrations obtained at EFPC (Station 17),
Bear Creek (Outfall 304), and Rogers Quarry (Outfall 302). At
East Fork Poplar Creek the maximum dose rates to fish, crustacea, and
muskrats were ascertained: 5.5E-4 rad/day (5.5E-6 Gy/day) and
0.0058 rad/day (5.8E-5 Gy/day), and 0.069 rad/day
(6.9E-4 Gy/day), respectively. In 1995, the sampling periods were
split into two 6-month increments (1/1 to 6/30 and 7/1 to 12/31) at Bear
Creek (Outfall 304) and Rogers Quarry (Outfall 302).
Similar analyses were conducted at the K-25 Site. The waterways
evaluated were Mitchell Branch (K-1700), Poplar Creek at the sewage
treatment plant (K-1203), outfall K-1007B, and outfall K-901A. At Poplar
Creek (K-1007B) the maximum dose rates to fish and crustacea were
calculated: 5.1E-4 rad/day (5.1E-6 Gy/day) and
5.1E-3 rad/day (5.1E-5 rad/day), respectively. The maximum
dose rates to a muskrat were estimated at Mitchell Branch (K-1700) and
at Poplar Creek: 2.5E-4 rad/day (2.5E-6 Gy/day) and
2.6E-4 rad/day (2.6E-6 Gy/day), respectively. Absorbed doses
estimated from maximum radionuclide water concentrations determined on
the ORR resulted in doses significantly less than the 1 rad/day
(0.01 Gy/day) limit prescribed in DOE Order 5400.5.
DOE Order 5400.5 limits to no more than 100 mrem (1 mSv)
the EDE that an individual may receive from all exposure pathways from
all radionuclides released from the ORR during 1 year. As described
in the preceding paragraph, the 1995 maximum EDE could have been about
6 mrem (0.06 mSv), or about 6% of the limit given in DOE
Order 5400.5. For further information, see Table A.2, which
provides a summary of dose levels associated with a wide range of
activities.
Airborne emissions from these facilities (based on information supplied
by the facilities) should not cause any individual to receive an EDE
greater than 1.7 mrem (0.017 mSv). When combined with impacts
caused by emissions from the ORR, no individual should receive an EDE in
excess of EPA or DOE limits. No information was obtained about
waterborne releases, if any, from these facilities.
RfDs, which are used to evaluate potential health effects from
noncarcinogens, are derived from doses of chemicals that result in no
adverse effect or the lowest dose that showed an adverse effect on
humans or laboratory animals (See Appendix B). The EPA maintains
the Integrated Risk Information System
(IRIS) data base, which
contains verified RfDs and SFs and up-to-date health risk and EPA
regulatory information for numerous chemicals.
For chemicals for which RfDs are not available, national primary (MCL)
and secondary drinking water regulation (SMCL) concentrations, expressed
in milligrams per liter, are converted to RfD values by multiplying by
2 L (the average daily adult water intake) and dividing by 70 kg
(the reference adult body weight). The result is a dose expressed in
mg kg-1 day-1. Table 6.9
lists the RfDs SFs used in this analysis.
SFs are used to evaluate carcinogenic impacts. The SF converts the
estimated daily intake averaged over a lifetime exposure to the
incremental risk of an individual developing cancer. Because it is
unknown whether a threshold (a dose below which no adverse effect
occurs) exists for carcinogens, units for carcinogens are set in terms
of risk. For potential carcinogens at the
ORR, a risk of developing
cancer over a human lifetime of 1 in 100,000 (10-5) was used
to establish acceptable levels of exposure. That is, the EPA estimates
that a certain concentration of a chemical, if ingested, could cause a
risk of one additional cancer case for every 100,000 exposed
persons.
To evaluate the drinking water pathway, HQs and I/CDIs were estimated at
current drinking water supply locations
(CRK 23 and 58) both
below and above the ORR. The Gallaher Water Station (CRK 23) is
located near the water intake for the K-25 Site and is below the
ORNL effluent discharge point. The Knox county water supply intake
(CRK 58) is located above the ORR discharge points. In addition,
the drinking water pathway was evaluated at the Anderson County
Filtration Plant (CRK 84) which is above all
DOE inputs, and at
CRK 16, which is a location downstream of all DOE inputs.
With the exception of aluminum, arsenic, and iron, the HQ values were
less than 1. Elevated aluminum and iron HQs were estimated both upstream
and downstream of the ORR. At CRK 58, upstream of ORR discharge
points, an HQ greater than 1 was estimated for arsenic.
For carcinogens, I/CDI ratios greater than 1 indicate a risk
greater than 10-5. Chemicals for which I/CDIs were greater
than 1 were PCBs (Aroclor 1248, 1254, and 1260), 4,4\math{\prime
}-DDE, and dieldrin. I/CDIs greater than 1 for these PCBs and
pesticides were found in both sunfish and catfish collected up and
downstream of the ORR. In many cases, the tissue concentrations of PCBs,
4,4\math{\prime }-DDE, and dieldrin were estimated at or below the
analytical detection limit. Because of analytical detection limitations,
the actual fish tissue concentrations are unknown (an exception is the
average Aroclor-1260 concentration in the catfish tissue samples
collected at CRK 16).
Results
Calculated EDEs from radionuclides emitted to the atmosphere from the
ORR are listed in Tables 6.2
(maximum individual) and 6.3
(collective). The EDE received by the hypothetical, maximally exposed
individual for the ORR was calculated to be about 0.5 mrem
(0.005 mSv), which is below the NESHAP standard of 10 mrem
(0.10 mSv) and well below the 300 mrem (3 mSv) that the
average individual receives from natural sources of radiation. About
0.1 mrem (0.01 mSv) of the 0.5 mrem is from calculated
emissions. The maximally exposed individual is located about 9300 m
(5.8 miles) northeast of the 3039 stack at ORNL, about
13,000 m (8.1 miles) east-northeast of the K-1435 (TSCA
Incinerator) stack at the K-25 Site, and about 1080 m
(0.7 miles) north-northeast of the Y-12 Plant release point.
The calculated collective EDE to the entire population within 80 km
(50 miles) of the ORR (about 879,546 persons) was about
11 person-rem (0.11 person-Sv), which is 0.004% of the
264,000 person-rem that this population could have received from
natural sources of radiation. About 2 of the 11 person-rem are from
calculated emissions.6.1.2.2 Waterborne Radionuclides
Radionuclides discharged to surface waters from the ORR enter the
Tennessee River system by way of the Clinch River and various feeder
streams. Discharges from the Y-12 Plant enter the Clinch River by
way of Bear Creek and EFPC,
both of which enter Poplar Creek before it enters the Clinch River.
Discharges from ORNL enter the Clinch River by way of
WOC and
WOL. Discharges from the
K-25 Site enter the Clinch River by way of Poplar Creek. This
section discusses the potential radiological impacts of these discharges
to persons who drink water, eat fish, swim, boat, and use the shoreline
at various locations along the Clinch and Tennessee rivers.6.1.2.3 Radionuclides in Other Environmental
Media
The CAP-88 computer codes calculate radiation doses from ingestion of
meat, milk, and vegetables that contain radionuclides released to the
atmosphere. The doses are included in the dose calculations for airborne
radionuclides. Milk
One environmental pathway for ingestion, drinking milk, also was
evaluated using concentrations of strontium, tritium, and
131I measured in milk collected from nearby farms. If, during
the year, an individual drank 310 L of milk containing the highest
detectable quantity of strontium, the individual could have received an
EDE of about 0.1 mrem (0.001 mSv) or less. The average EDE
associated with drinking milk in EPA Region 4 is about
0.09 mrem (0.0009 mSv)
(EPA 1993a
). Neither tritium nor 131I were detected in milk samples
during 1995. Honey
Three bee colonies are located on the ORR. The honey produced in these
hives was sampled, and the sampling results are used to give an
indication of potential EDEs to persons who eat honey produced by bees
that may have collected pollen on the ORR . If an adult consumed
1 kg (2.2 lb) of the sampled honey during the year, the
resulting EDE could be no higher than 0.09 mrem (0.0009 mSv).
The average adult likely consumes less than 1 kg of honey per year.
The total production of honey in Anderson, Loudon, and Roane counties
during 1992 (the latest available data) was approximately 1500 kg
(3200 lb). In the extremely unlikely event that all the honey
produced in the three counties contained the sampled concentrations of
radionuclides, the resulting collective dose could be
0.3 person-rem. Crops
Another environmental pathway for ingestion that was evaluated
separately is eating vegetables. In 1995, three types of vegetables were
sampled: tomatoes, lettuce, and turnips. These vegetable types were
chosen as representative of fruit-bearing, leafy, and root vegetables.
Tomatoes and turnips were sampled from eight plots, and lettuce was
sampled from nine plots, located at the ORR PAMs. Hay grown on the ORR
also was sampled, as was hay from one reference location. White-Tailed Deer
Several deer hunts were held on the ORR during 1995. A total of 489 deer
were killed, of which 8 were confiscated because their radionuclide
content potentially exceeded the release limit (20 pCi/g
90Sr in bone). The remaining 481 deer had an average
field-dressed weight of about 39 kg (86 lb). Assuming
55% of the dressed weight is edible, the average deer would yield
about 21.5 kg (47.3 lb) of meat. Therefore, based on the
average weight, the total harvest of edible meat was about
10,320 kg (22,750 lb). Canada Geese
During the annual roundup of Canada geese, whole-body gamma scans were
conducted on 86 geese at the deer-checking station. The geese were
collected from the Y-12 Plant (15 geese), ORNL
(10 geese), the K-25 Site (20 geese), Melton Hill Dam
(20 geese), and the Oak Ridge Marina (21 geese). The average
field 137Cs concentration was 0.084 pCi/g
(0.003 Bq/g). The maximum field 137Cs concentration,
surveyed in a goose collected from the K-25 Site, was
0.21 pCi/g (0.008 Bq/g). Eastern Wild Turkey
Twelve live eastern wild turkeys were collected on the ORR during
February 1995. These turkeys were whole-body counted at the deer
counting station and released in an off-site wildlife management area.
Cesium-137 was detected in 1 of the 12 turkeys that were counted. The
estimated 137Cs concentration was 0.09 pCi/g
(0.0033 Bq/g). The average weight of a male wild turkey is about
24 lb (10.9 kg) and the female wild turkey weighs about
12 lb (5.4 kg). If a turkey [average weight 18 lb
(8.16 kg)] was consumed by one individual and the edible portion
was 4.08 kg (9 lb) (50% of the total weight of the
turkey), the estimated EDE would be about 0.02 mrem
(2E-4 mSv). Two turkeys are the bag limit in a wildlife management
area per season. If one individual consumed two birds collected from a
wildlife management area at the aforementioned 137Cs
concentration, the estimated EDE would be about 0.04 mrem
(4E-4 mSv). Direct Radiation
External exposure rates from background sources in the state of
Tennessee average about 6.4 �R/hour and range from 2.9 to
11 �R/hour. These exposure rates translate into annual EDE rates
that average 42 mrem/year (0.42 mSv/year) and range between 19
and 72 mrem/year, or 0.19 and 0.72 mSv/year
(Myrick
et al. 1981
). External radiation exposure rates are measured at a number of
locations on and off the ORR. The average exposure rate at PAMs around
the ORR during 1995 was about 7.8 �R/hour. This equals a dose rate
of about 51 mrem/year (0.51 mSv/year). Except for two
locations, all measured exposure rates beyond the ORR boundaries are
near background levels. The two exceptions are a stretch of bank along
the Clinch River and a section of Poplar Creek that flows through the
K-25 Site.6.1.3 Doses to Aquatic Biota
DOE Order 5400.5, Chapter II, sets an interim absorbed dose rate limit
of 1 rad/day (0.01 Gy/day) to native aquatic organisms. To
demonstrate compliance with this limit, absorbed dose rates to fish,
crustacea (e.g., crayfish), and muskrats were calculated using the
computer code CRITR2 (Baker
and Soldat 1993
). Fish and crustacea are considered to be primary aquatic organisms,
those that reside in the aquatic ecosystem. Muskrats are considered to
be secondary organisms, those that subsist on aquatic plants. Maximum
and average concentrations of radionuclides measured in surface waters
on and around the ORR are used to estimate dose rates from internal and
external exposures. Internal dose rates are calculated using organism-
and nuclide-specific bioaccumulation factors and absorbed energy
fractions. External dose rates are calculated for submersion in water
and irradiation from bottom sediments. Exposure to sediments is
particularly meaningful for crawling or fixed organisms (such as
crayfish and mollusks). Direct radiation doses from sediment are
estimated from water concentrations using factors such as a geometry
roughness factor, sediment deposition transfer factor, and
nuclide-specific ground-surface irradiation dose factors.6.1.4 Current-Year Summary
A summary of the maximum EDEs to individuals by several pathways of
exposure is given in Table 6.7.
It is unlikely (if not impossible) that any real person could have been
irradiated by all of these sources and pathways for a period of 1 year;
however, if the resident who received the highest EDE [0.5 mrem
(0.005 mSv)] from gaseous effluents, also drank water from the
Kingston plant [0.15 mrem (0.0015 mSv)], ate fish from
CRK 80 [0.93 mrem (0.0093 mSv), and fished the Clinch
River near the cesium field or Poplar Creek inside the K-25 Site
[1 mrem (0.01 mSv), he or she could have received a total EDE
of about 2.6 mrem (0.026 mSv), or about 0.9% of the
annual dose [300 mrem (3 mSv)] from background radiation. If a
person ate a deer harvested on the ORR, that person could have received
a committed EDE of about 3 mrem (0.03 mSv).6.1.5 Five-Year Trends
Dose equivalents associated with selected exposure pathways for the
years from 1990 to 1995 are given in Table 6.8.
The variations in values over this 5-year period likely are not
statistically significant. The dose estimates for direct irradiation
along the Clinch River have been corrected for background.6.1.6 Potential Contributions from Off-Site Sources
Four off-site facilities were identified as potential contributors to
radiation exposure of the public around the ORR. These facilities
include a waste processing facility located on Bear Creek Road, a
depleted uranium processing facility located on Illinois Avenue, a
decontamination facility located on Flint Road in Oak Ridge, and a waste
processing facility located on Gallaher Road in Kingston.6.1.7 Findings
The maximally exposed off-site individual could have received a 50-year
committed EDE of about 0.5 mrem (0.005 mSv) from airborne
effluents from the ORR. This dose is within the limit specified in the
CAA for DOE facilities. The
estimated collective committed EDE to the about 880,000 persons
living within 80 km (50 miles) of the ORR was about
11 person-rem (0.11 person-Sv) for 1995 airborne emissions.
This represents about 0.004% of the 264,000 person-rem
(2,640 person-Sv) that the surrounding population would receive
from all sources of natural radiation.6.2.1 Terminology
The following terms are pertinent to the understanding of chemical
exposure. See Appendix B for further explanation of terms and
methodology. 6.2.2 Methods of Evaluation
6.2.2.1 Airborne Chemicals
Air permits issued by TDEC
allow release of permitted quantities of chemicals. Sampling or
monitoring is required only at the
ORNL Steam Plant. No air
monitoring data amenable to human exposure analysis were available. (See
Sect. 4, ``Airborne Discharges.'')6.2.2.2 Waterborne Chemicals
Current risk assessment methodologies use the term
HQ to evaluate
noncarcinogenic health effects. Intakes, calculated in
mg kg-1 day-1 in the HQ methodology, are
expressed in terms of dose. For carcinogens, the estimated dose (I) from
ingestion of water or fish is divided by the chronic daily intake
(CDI), which corresponds to a
10-5 lifetime risk of developing cancer. See Appendix B
for a more detailed discussion.6.2.2.3 Drinking Water
HQs and I/CDI ratios for chemicals concentrations found in surface water
are summarized in Table 6.10.
The tilde ( is similar to ) indicates that estimated values and/or
detection limits were used in estimating the average concentration of a
chemical. This symbol is listed beside the estimated HQ or intake
(estimated dose)/calculated daily intake
(I/CDI) ratios to indicate
the type of data used.6.2.2.4 Fish Consumption
Chemicals in water can be accumulated by aquatic organisms that may be
eaten by humans. Bluegill (sunfish) and catfish (at two locations)
collected from the Clinch River and Poplar Creek were analyzed for a
number of metals, pesticides, and
PCBs. Table 6.11
summarizes the HQ and I/CDI ratios derived on average chemical
concentrations in fish samples found both upstream and downstream
locations from the ORR. Arsenic, lead, and mercury concentrations in
fish tissue resulted in HQs greater than 1. HQs greater
than 1 for arsenic and mercury were found in sunfish upstream
and downstream of the ORR, catfish downstream of the ORR, and in sunfish
found in Poplar Creek (PCK
2.2). An HQ greater than 1 for lead also was calculated for sunfish
collected from CRK 16; however, estimated values and/or the
detection limit were used in estimating the average concentration.