EPA 520/4-77-016
PROPOSED GUIDANCE
ON
DOSE LIMITS FOR PERSONS EXPOSED
TO
TRANSURANIUM ELEMENTS
IN THE
GENERAL ENVIRONMENT
\
*Z i ^ - - J "Z-
S
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RADIATION PROGRAMS
CRITERIA AND STANDARDS DIVISION
WASHINGTON, D.C. 20460
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PROPOSED GUIDANCE
on
DOSE LIMITS FOR PERSONS EXPOSED TO TRANSURANIUM ELEMENTS
In the
GENERAL ENVIRONMENT
SUMMARY REPORT
September 1977
U. S. Environmental Protection Agency
Office of Radiation Programs
Criteria and Standards Division
Washington, D.C. 20460
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Guidance on Dose Limits
for the Transuranium Elements in the General Envrionment
Table of Contents
Page
1. Background Information on the Transuranium Elements
1.1 Introduction 1
1.2 Current Sources of the Transuranium Elements 3
1.3 Movement Through the Biosphere 4
1.4 Potential Health Effects 7
2. Federal Guidance
2.1 Agency Action and Authorities 11
2.2 Involvement of other Federal Agencies 12
2.3 Existing Standards and Guides 13
2.4 Criteria and Rationale for Proposed
Guidance 14
2.5 Text of Proposed Guidance 20
2.5.1 Definitions 21
3. Implications of Guidance
3.1 Scope of Sources and Population Groups 23
3.2 Risk Perspectives 24
3.3 Implementation , 28
3.4 Remedial Measures and Economic Evaluation 30
References 32
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Annex
Annex I Transuranium Elements in the Environment
Annex II Environmental Transport and Pathways
Annex III The Dose and Risk to Health Due to the Inhalation and
Ingestion of Transuranium Elements
Annex IV Risk Perspective
Annex V Guidance Implementation
Annex VI Environmental Assessment
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Section 1
Background Information on the Transuranium Elements
1.1 Introduction
The transuranium elements include, all of the elements with atomic
number greater than that of uranium. Only extremely small quantities
of these elements occur naturally and nearly all of the existing
inventory has been created from other elements. Nuclides of the
transuranium elements are radioactive and are considered to be toxic in
humans. From the viewpoint of protecting the public health, the trans-
uranium elements of primary interest are those which undergo slow
radioactive decay with the emission of alpha particles and with
half-lives greater than 1 year. When present in the environment, trans-
uranium elements may be available for intake by humans over very long
periods of time. Table 1.1 is a listing of such transuranium radio-
nuclides of major interest, their mode of decay, half-life, and daughter
products.
Plutonium is the most abundant, most studied, and most publicized
of the transuranium elements. It is a metallic, radioactive element
with atomic number 94, and was the first man-made element to be produced
in relatively large quantities. Its primary use to date has been as
fissile material in nuclear weapons, but an important potential use may
be nuclear electric power generation. It is produced in all nuclear
reactors and is a significant component of spent uranium fuels.
At present, americium and curium are the only other transuranium
elements produced in sufficiently large quantities to be of interest as
a potential environmental hazard.
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Table 1.1
Nuclear Properties of Environmentally Significant Transuranium Nuclides
Radionuclide
Pu-238
Pu-239
Pu-240
Pu-241
Pu-242
Am-241
Am-243
*Cm-242
Cm-244
Mode of
Decay
a
a
a
3
a
a
a
a
a
Physical
Half-life
87.4 y
2.4xl04 y
6.6xl03 y
14.3 y
3.9xl05 y
433 y
7.4xl03 y
0.45 y
18.1 y
Daughter
Product
U-234
U-235
U-236
Am-241
U-238
Np-237
Np-239
Pu-238
Pu-240
* Included for reference because of potential quantities available
for release. Not significant for environmental exposure con-
siderations because of short persistence.
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1.2 Current Sources of the Transuranium Elements
Present levels of the transuranium elements in the environment have
resulted from several sources - regional and worldwide fallout from the
testing of nuclear weapons in the atmosphere, accidents involving
military and related operations, and local releases from nuclear facil-
ities. The major portion of the transuranium elements in the environ-
ment is the result of surface and atmospheric nuclear weapons tests
during the period 1945-1963. Atmospheric tests injected .radioactivity
into the stratosphere which has since then been slowly deposited more
or less uniformly over the lands and oceans of the earth. As a result
of these earlier weapons tests, the existing level of transuranium
element contamination in soils of the United States is about 0.002
2
microcurie per square meter (yCi/m ). More recent weapon tests have not
added significant amounts to this level. Isolated sites used by the
United States to test nuclear devices, such as those in Nevada and the
Bikini and Enewetak atolls, often have significantly higher amounts of
the transuranium elements in small areas near the detonation point.
Underground nuclear tests also have produced localized radioactive
contamination, but this is contained below the eartjh's surface and is
not expected to be readily available for uptake by humans.
Areas where there is substantial localized contamination above the
general background level are well documented and extensive environmental
analyses have been carried out at all these sites. Areas of highest
contamination are, for the most part, on Federally owned property
and therefore are under the direct control of the Federal government
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and access to these areas may be restricted. Table 1.2 shows estimates
of the amount of plutonium in the environment at known United States
locations. More detailed information on the sources and current levels
of the transuranium elements in the general environment is given in
Annex I.
1.3 Movement through the Biosphere
Plutonium and other transuranium elements can move through the
environment by a,variety of transport mechanisms and pathways. These
are determined by the chemical and physical form of the deposited
material, the characteristics of the surface, local land use patterns,
and other parameters such as wind or rainfall. Principal environmental
pathways to humans are indicated in Fig. 1.
The principal modes of transport of these elements from a source
to man are by direct airborne movement from the source (source-air-
humans) or by resuspension of previously deposited small particles by
the action of wind or other disturbance (soil-air-humans). Transuranium
elements released to the environment may exist as discrete particles
or they may become attached to soil particles. Resuspension is a
complex phenomenon affected by a number of factors, including the
characteristics of the surface, vegetative cover, meteorological con-
ditions, and age of the deposit. The resuspension factor is defined as
o
the ratio of the concentration in air (yCi/m ) at a given height above
the surface to the average immediately adjacent surface contamination
2
level (pCi/m ). Observed resuspension factor values range from about
10 to 10 per meter for a variety of conditions and sites. In
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TABLE 1.2
Inventory and Levels of Plutonium for Selected U.S. Sites*
Location Approximate
Inventory
U.S. (Fallout) ~ 20,000 Ci
Nevada Test Site > 155 Ci
(near Las Vegas, NV)
Rocky Flats Plant 8-10 Ci
(Jefferson County near
Denver, CO)
Mound Laboratory Pu-238 = 5-6 Ci
(Miamisburg near
Dayton, Ohio)
Savannah River Plant 3-5 Ci
(SW part S. Carolina
near Augusta, GA.).
Soil Concentration**
(above background)
ave. =0.06 pCi/g
Area 13: to 18,000 pCi/g
Area 5: to 12,000 pCi/g
off -site: 0.1-10 pCi/g
on-site max > 1,000 pCi/g
boundary: 0.1-4 pCi/g
off-site
sediments max > 1000 pCi/g
soils: 0.003-2 pCi/g
N area: 30 pCi/g
F area: 3 pCi/g
perimeter: 0.02 pCi/g
Remarks
Surface and
subsurface
tests
Limited
cleanup
in progress
Sediments
under water
in canals
Plutonium
and higher
isotopes
production
Los Alamos Scientific 1-2 Ci
Lab (NW of Santa Fe, NM)
on-site: 0.02-5 pCi/g
off-site: 0.005-1 pCi/g
High local
levels above
100 pCi/g
in remote
canyons
Hanford Site
(Central Washington
near Richland)
perimeter: 0.01-0.04 pCi/g
High levels
in trenches
on site
Oak Ridge Facilities
(East Tennessee near
Knoxville)
perimeter: 0.01-0.08 pCi/g
Research &
Development
facility
Trinity Site
(near Alamogordo, NM)
45 Ci
perimeter: <\» 55 pCi/g
off-site: 0.1-4 pCi/g
Site of
first atomic
bomb test
* See Annex I for details and references
2 3
** 1 pCi/gram of soil = 0.015 uCi/m for an assumed soil density of 1.5 g/cm
and a depth of 1 cm.
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PRINCIPAL PATHWAYS OF THE TRANSURANIUM ELEMENTS
THROUGH THE ENVIRONMENT TO MAN
Figure 1
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general, the resuspension factor will be relatively high immediately
after initial deposition, gradually decrease with time, and approach
a long-term constant within about one year after deposition.
Transport of plutonium and other transuranium elements through the
food chain and subsequent ingestion is generally of lesser importance
than the air pathway. Environmentally distributed transuranium
elements may be deposited on plant surfaces or assimilated through
the plant root system. The uptake by plants is relatively small and
most animals, including humans, have a high discrimination factor
against transfer of these elements into body tissues. The solubility of
plutonium in water is very low and nearly all plutonium released into
lakes and streams is ultimately deposited and sorbed onto sediments.
Direct ingestion of contaminated soils and contamination of wounds are
other possible routes of entry into humans, but are generally of minor
importance relative to the inhalation and food pathways.
The environmental transport of the transuranium elements is
discussed in more detail in Annex II.
1.4 Potential Health Effects
The potential health effects caused by a specific nuclide of a
transuranium element are a function of several biological and physical
parameters including the biological retention time in tissue, the type of
radioactive emission, and the half-life of the nuclide. For the more
important transuranium nuclides, such as Pu-238 or Pu-239, biological
retention times are very long and radioactive decay occurs at such a
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slow rate that uptake of these materials in the humans body will result
in prolonged exposure of body organs. Many of the transuranium nuclides
decay by emission of an alpha particle (ionized helium atom), in a
manner similar to radium and other naturally occurring alpha emitting
nuclides. Alpha particles are highly ionizing, and damaging, but their
penetration in tissue is very small (about 40 urn). Thus, biological
damage is limited to tissue in the immediate vicinity of the radioactive
material, and a potential health hazard from transuranium elements in
the environment can only result when these materials are inhaled or
ingested into the body. Exposure of the unbroken skin from external
alpha emitting sources is not a health problem.
Even though there is no direct evidence of cancer induction in
humans due to the inhalation of transuranum elements, data from animal
studies with these radionuclides and from human experience with other
alpha-emitting elements such as radon daughters indicate that the in-
halation of transuranium elements could cause lung cancer and other
forms of cancer in humans. Cancer induction is not the inevitable
result of such inhalation, but rather the result of this intake is an
increase in the probability that a cancer may occur in the individual.
Inhaled particles are initially deposited in various regions of the
respiratory tract, where they remain until either cleared or translocated
to other body organs. Much of the material deposited in the lungs is
cleared within a few days, but some of the smaller particles which
diffuse into the pulmonary regions of the lung are removed much more
slowly and have a biological half-life of a year or more. Estimates of
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the risk of lung cancer due to the inhalation of transuranium elements
are based on the alpha particle dose delivered to the pulmonary tissue,
which is the portion of the lung receiving the highest dose as a result
of inhalation. This is likely to overestimate the risk because the pul-
monary region is not considered a probable site for induction of cancers
in humans. In a recent study the National Academy of Sciences has con-
cluded that the probability of cancer induction increases in proportion
to the dose delivered to various lung tissues and that the incidence of
cancer will not be underestimated by averaging the total alpha energy
Imparted over the mass of the pulmonary region (1).
Inhaled transuranium elements may also transfer and be retained
in other body organs, and cause cancers of the bone and liver. For the
less soluble transuranium compounds, such as plutonium oxide, this will
contribute only marginally to the total risk for the inhalation pathway.
Inhaled radioactivity is also concentrated in the respiratory lymph
nodes. The dose delivered to the lymph nodes exceeds that to pulmonary
tissues but, if a risk exists, animal studies indicate that it is small
compared to the risk due to cancer in pulmonary tissue.
Ingestion of transuranium elements generally represents a smaller
environmental risk to humans than inhalation. A relatively small
fraction of any ingested transuranium element will be transferred by the
bloodstream from the digestive tract and deposited in bone, liver,
gonadal tissue, and other organs. In most cases, less than one-tenth of
a percent of the ingested material is absorbed by the body, with the
remainder excreted. The cancer risk to individuals as a result of
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ingestion of transuranium elements is mainly due to potential bone and
liver cancers.
Because of possible accumulation in gonadal tissues a potential
risk of genetic damage to the progeny of exposed individuals exists
as a result of exposure to transuranium elements. At the dose limits
recommended in this guidance, this risk is very small compared to the
natural incidence of genetic damage.
Preferred models for calculating the dose to pulmonary tissue,
bone, gonadal tissue, and to the other organs as a result of inhalation
or ingestion of transuranium elements are described in Annex III. In
general, these dose models are based on publications prepared by the
International Commission on Radiological Protection (ICRP) (2-4), sup-
plemented by more recent data. In conjunction with estimates of the
cancer risk due to alpha particle irradiation, these models are used
to estimate the risk from radiation doses to specified body organs.
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Section 2
Federal Guidance
2.1 Agency Action and Authorities
The Agency announced in the Federal Register on September 23, 1974,
that it intended to review the current and projected environmental
impact of the transuranium elements and consider whether guidelines or
standards under its statutory authorities were needed to assure adequate
protection of the health and safety of the general public (5).
Subsequently, public hearings were held in Washington, D.C., on
December 10-11, 1974, and in Denver, Colorado, on January 20, 1975, to
permit interested citizens and organizations to present both technical
evidence and opinions pertinent to this subject (6). Prior to this
action the Agency had been considering the control of plutonium in soil
as a result of a specific request during 1972 from the State of Colorado
in regard to utilization of land in the vicinity of the ERDA Rocky Flats
Plant. As an interim measure, Colorado adopted in 1973 a plutonium
activity limit of 2 dpm/g in the top 1/8 inch of soil as a guide for
protection of construction workers engaged in home building.
The Agency concluded that Federal Radiation Guidance was needed to
control the potential health impact of plutonium and other alpha-emitting
transuranium elements in the environment and that promulgating Federal
Guides under the authority of the former Federal Radiation Council was
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the appropriate procedure. This authority was transferred to the
Administrator of the Environmental Protection Agency (EPA) by the
President's Reorganization Plan No. 3 of 1970, (7) and included all the
functions of the Federal Radiation Council, as specified in the Atomic
Energy Act. Section 274(h) of this Act provides that "the Administrator
shall advise the President with respect to radiation matters, directly
or indirectly affecting health, including guidance for all Federal
agencies in the formulation of radiation standards and in the establish-
ment and execution of programs of cooperation within States." Federal
Guides developed under this authority and approved by the President are
considered to be an adequate means to limit any problems of environ-
mental contamination by the transuranium elements, since all sources of
transuranium elements are under direct control of the Federal government.
These Guides are therefore directed to all Federal agencies having
regulatory or administrative control of transuranium elements. However,
the Guides can also be viewed as advice by State and local governments.
2.2 Involvement of Other Federal Agencies
The implementation of these Federal recommendations is the
responsibility of those agencies having regulatory and administrative
responsibilities for the production, utilization, and control of
transuranium elements, especially plutonium. Therefore, the
Administrator established an Interagency Working Group to insure the
availability of technical expertise and interagency coordination in the
development of the Guides. This Interagency Working Group consisted of
representatives from the Energy Research and Development Administration,
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Nuclear Regulatory Commission, National Aeronautics and Space Adminis-
tration, and the Departments of Defense, State, Commerce, Interior, and
Health Education and Welfare. Although EPA has been primarily respon-
sible for the development of these recommendations and supporting
documents, this group has provided valuable assistance and has made
available to the EPA both the expertise and viewpoints of these agencies.
2.3 Existing Standards and Guides
Several specific standards or guides have been published (8-12)
pertaining to the presence of the transuranium elements in soil, to the
controlled release of such materials into the environment (e.g., the EPA
standard for the uranium fuel cycle*), and the decontamination of
equipment surfaces. With the exception of EPA's uranium fuel cycle
standards, such guides are based for the most part, on recommendations
on numerical limits by the International Commission on Radiological
Protection (ICRP) and by the National Council on Radiation Protection
and Measurements (NCRP). Recomendations by the ICRP and the NCRP
include numerical limits on air and water concentrations applicable to
individuals in the general population.
Department of Defense guidelines have been developed to deal with
instances of accidental surface contamination and represent ad hoc
guidance for accidents involving nuclear weapons. The decontamination
* Note: EPA published (F.R. 42:2858, Jan. 13, 1977) as title 40;
Part 190, Environmental Standards for the Uranium Fuel Cycle, normal
operations, a limit of 0.5 millicuries combined of plutonium-239 and
other alpha-emitting transuranium radionuclides with half-lives
greater than one year entering the environment as planned releases
per gigawatt-year of electrical energy produced by the fuel cycle.
13
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o
guidance prescribes that surface levels of less than 1000 ug/m plutonium
2
(numerically equal to 61 vCi/m for Pu-239) shall be achieved where such
reduction is possible and is consistent with reasonable cost and effort.
Each of the Armed Services has also developed more detailed
implementation manuals.
For case of surface contamination of materials for shipment and of
transport vehicles, the Department of Transportation specifies as "not
significant", a level of 220 dpm/100 cm2 (0.01 uCi/m2) of removable
alpha contamination. There is also a recommendation by the Nuclear
Regulatory Commission that the average level of alpha contamination for
reactor equipment to be released to the general public be no more than
100 dpm/100 cm2.
Recommendations have also been published by individuals for the
specific situation of soil contamination by transuranium elements, but
none of these have been adopted by government agencies (13-15).
2.4 Criteria and Rationale for the Proposed Guidance
The purpose of the proposed guidance is to establish maximum dose
rates for persons in the general population who might receive radiation
exposure to transuranium elements in the environment, which considers
all possible pathways to humans and which the Agency judges to be
protective of the public health. The two primary criteria used in
determining the guidance recommendations were: that the added risk to
an individual from exposure to the transuranium elements be very small,
and that implementation of the guidance be feasible in terms of overall
economic impacts. The Agency has also determined that the costs of
remedial actions and the benefits of risk reduction differ so greatly
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between sites, both for those where excess contamination already exists
and for those where accidents might occur in the future, that generic
guidance applicable to all sites cannot be provided by formal benefit-
cost procedures.
The primary purpose of the guidance is to achieve a level of
public health protection which will minimize the risk to exposed
individuals. Radiation induced risks can be estimated in a number of
ways, but the most prudent methods assume that there is some finite risk
to humans no matter how small the amount of absorbed radiation might be
and that this risk at any given dose level is directly proportional to
the damage actually observed at much higher dose levels. Such a cal-
culation, in the absence of data to the contrary, must be considered as
the method appropriate for a regulatory or guidance function. On this
basis, there is no level of radiation exposure which is absolutely safe
and any radiation dose carries with it some degree of risk. Balanced
against this is the realization that all persons are exposed to a large
number of competing risks (including natural background radiation) and
the reduction of a single risk must be viewed from the overall per-
spective of the costs and benefits to society.
The guidance recommendations are intended to achieve adequate
health protection for the small fraction of the total population at
greatest risk from exposure to transuranium nuclides in the environment,
and will therefore offer much greater protection to the vast majority of
the population at lesser risk. The numerical guidance can be related to
a maximum risk level to an individual which is-comparable to that used
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for other carcinogens and lower than that for many other competing
risks. The level of risk at the proposed guidance level, estimated
by the above method, is less than one chance per million per year
and less than ten chances per hundred thousand in a lifetime that an
individual would develop a cancer from continuous exposure at the stated
dose rates. Actual exposures and risks to individuals are expected to
be well below this level. It must be recognized that these risk
estimates are not precise but represent the best judgment of the
Agency. There may be differences in reputable scientific opinions on
their accuracy.
Other regulatory actions have considered lifetime risk levels for
carcinogens but there is, at this time, no uniformity of approach to
the regulation of carcinogens. The Food and Drug Administration (FDA)
uses a lifetime risk level of one per million as "virtually safe," and
has proposed to ban saccharin because, for an average consumption, the
lifetime cancer risk was estimated to be 10/100,000. EPA has recom-
mended an action level for kepone in fish for which the associated
lifetime cancer risk is 30/100,000. Differences in the action levels
reflect different regulatory requirements, constraints associated with
remedial actions for a particular carcinogen, uncertainties in the
calculations, differences in methods used to derive lifetime risks, and
economic considerations. The proposed guidance is intended to be viewed
from the perspective of providing a limit applicable to remedial and
restorative actions, and must be distinguished from other risk levels
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which provide for a routine level of acceptability.
The Agency has also considered the costs which may be involved
in implementing the proposed guidance. These costs were estimated
from soil contamination levels at existing sites of contamination.
The magnitude of areas which might require remedial actions at each site
has been estimated for a soil concentration contour which can with a
very high probability be expected to result in an inhalation dose rate
to an individual not to exceed 1 mrad/year, as well as for soil
concentration contours higher and lower than the reference case by
factors of ten. Changes by factors of ten are judged to represent the
limit of precision available for such calculations and are considered
sufficient for purposes of a generic assessment. However, in order to
attempt to more closely define where costs of implementation would begin
to rise rapidly, an intermediate contour of one-third the reference
level was also considered. The costs of implementing the guidance can
be expected to vary by location, contamination level, and other factors.
A minimum cost of $500 per acre has been assumed for estimating the
costs which may be incurred in bringing all areas above the designated
level into compliance. Such costs include dilution or removal of
contamination by plowing or scraping as required and restorative actions
needed to prevent erosion and assist ecological recovery. Costs
necessarily increase as the difference between the existing contamina-
tion levels and those sought becomes greater. On this basis, costs of
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remedial actions have been estimated for those few sites in the United
States where some environmental contamination extends beyond the
boundaries of the source from where it originated, and are shown in
Table 2.1. It must be recognized that there are large uncertainties
associated with both the areas involved and in the estimates of costs.
Nonetheless, the calculations serve a useful purpose of comparison on
a common basis. It can be concluded that the costs of implementing
the guidance at the reference level would be reasonable and achievable,
but that the cumulative costs increase rapidly when more restrictive
limits are considered.
The Agency has recognized a difference between those sites
presently contaminated and sites that may be accidentally contaminated
in the future, and has considered whether separate numerical guides
should be developed for these two cases. In the first case the judgment
is between continued exposure to these elements at some given level and
the cost of remedial action to reduce exposures. In the second case,
the risk of possible future accidental contamination events must be
taken into account in the initial decision to perform any activity
where there is risk of accidental contamination, and include the entire
cost of possible future remedial actions that might be required in
event of an accidental release. However, no specific rationale is known
that would justify different guidance based on health risk considera-
tions. Therefore, the Agency recommends that the same numerical guide
be used in both cases, but that all future contamination be cleaned up
as soon as possible after occurrence to a level as low as reasonably
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Table 2.1
Comparison of Costs of Remedial Actions At Various Sites
of Existing Plutonium Contamination For Several Possible
Levels of Maximum Soil Concentrations (Areas are Estimated
from Contour Maps and Costs Are Arbitrarily Assumed as $500/acre)
Rocky
Flats
Plant
Nevada
Test
Site
Trinity
Site
Mound
Lab.
Reference Level
0.2 yCi/m2
Area
0
0
0
•v* 0.01 mi2
Cost
0
0
0
*
10 x Ref: Level
2 yCi/m2
Area
0
0
0
* 0.01 mi2
Cost
0
0
0
*
1/3 Ref. Level
0.07 yCi/m2
Area
0.3 mi2
<80 mi2
<20 mi2
* 0.01 mi2
Cost
100K
25M
<6M
*
1/10 x Ref. Level
0.02 yCi/m2
Area
2
^ 1.6 mi
< 165 mi2
* 300 mi2
% 0.01 mi2
Cost
500K
50M
100M
*
* Most of the existing contamination is in sediments of canals, and
does not represent a hazard to humans. Costs of eventual remedial
actions are indeterminate.
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achievable and with the numerical guide as an upper limit.
In summary, the Agency has recognized that any radiation exposure
is potentially harmful and has concluded that the guidance recommenda-
tions should limit the risk to those persons in the critical segment of
the population to a level as low as reasonably achievable within the
constraints of economic considerations. There is at present no
uniformity of approach to the regulation of carcinogens among the
various Federal agencies. It is the judgment of the Agency that for
presently existing sites of contamination, the proposed guidance
recommendations will provide the necessary protection of the public
health and be achievable at reasonable costs. It is also the judgment
of this Agency that, in some cases of accidental contamination of the
environment by the transuranium elements, cost considerations will
permit reduction of residual contamination to levels below those
specified in this guidance. In all cases, the guidance recommendations
represent a maximum value and further reduction should be sought when
this can be accomplished at a cost judged to be reasonable in terms of
alternatives available.
2.5 Text of Proposed Guidance
The Environmental Protection Agency proposes that the following
recommendations be submitted by the Administrator to the President for
issuance as Federal Radiation Guidance:
1. The annual alpha radiation dose rate to members of the
critical segment of the exposed population as the result of exposure to
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transuranium elements in the general environment should not exceed
either:
a. 1 millirad per year to the pulmonary lung, or
b. 3 millirad per year to the bone.
2. For newly contaminated areas, control measures should be
taken to minimize both residual levels and radiation exposures of
the general public. The control measures are expected to result in
levels well below those specified in paragraph one. Compliance with
the guidance recommendations should be achieved within a reasonable
period of time.
3. The recommendations are to be used only for guidance on
possible remedial actions for the protection of the public health in
instances of presently existing contamination or of possible future
unplanned releases of transuranium elements. They are not to be used by
Federal agencies as limits for planned releases of transuranium elements
into the general environment.
2.5.1 Definitions
a. "critical segment of the exposed population" means that group of
persons within the exposed population receiving the highest radiation
dose to the pulmonary region of the lung or to the bone.
b. "rad" is the unit of absorbed dose, defined as the energy imparted
to tissue due to ionizing radiation divided by the mass of the tissue.
One rad is equal to the absorption of 100 ergs of radiation energy
per gram of matter.
c. "pulmonary lung" means that region of the lung consisting of
respiratory bronchioles, alveolar ducts, atria, alveoli, and alveolar
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sacs. The average total weight of this tissue, including the capillary
blood, is assumed to be 570 gins.
d. "millirad per year to the pulmonary lung" means the equilibrium
dose rate following chronic inhalation. This dose rate is calculated by
dividing the alpha energy absorbed per year in the pulmonary lung by its
mass.
e. "bone" means osseous tissue. The average total weight of this
tissue is assumed to be 5000 gms.
f. "millirad per year to the bone" means the dose rate attained after
70 years of chronic exposure. This dose rate is calculated by dividing
the alpha energy absorbed in the bone during the 70th year by the bone
mass.
g. "general environment" means the total terrestrial, atmospheric
and aquatic environments outside the boundaries of Federally licensed
facilities or outside the boundaries of sites which-are under the
direct control of a Federal agency.
h. "curie (Ci)" is the basic unit to describe the intensity of radio-
activity in a material. It is equal to 37 billion disintegrations per
second.
1 millicurie (mCi) = 10~3 Ci
1 femtocurie (fCi) - 10~15 Ci
22
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Section 3
Implications of Guidance
3.1 Scope of Sources and Population Groups Included
The objective of the proposed guidance is to assure that the
public health and welfare will be adequately protected from the con-
sequences of environmental contamination by the transuranium elements.
The proposed guidance is not intended to supersede existing rad-
iation protection guides, such as the individual and population limits
established by the Federal Radiation Council in 1960 (17), but rather to
supplement these by specifying limits for one type of source and for one
group of radionuclides within these broader limits. The scope of the
proposed guidance includes all transuranium element contamination in the
general environment from all sources. The recommendations are applicable
to all individuals in the general population outside the boundaries of a
Federal facility, Federally licenced facility, or other site under the
direct control of a Federal agency.
The recommendations are expressed in terms of an annual limiting
dose commitment to the pulmonary region of the lung or to the bone. It
should be noted that, although the proposed guidance specifies dose rate
limits to only certain organs, this also limits the potential accum-
ulajtion in gonadal tissues and the attendant genetic risk. The limits
apply to the critical segment of the exposed population, which is that
group of persons in the general population who, because of residency,
occupation, or other factors can on the average be expected to receive
23
-------
the highest lifetime radiation dose from a specified source of
transuranium elements.* The annual dose rate to the designated organs
can be estimated from representative measurements of air concentrations
or soil contamination levels, either by use of site-specific data or by
use of calculations based on reasonable procedures and assumptions.
3.2 Risk Perspectives
Exposure to radiation may increase somatic risks, primarily that of
cancer, as well as genetic risks to future generations. The somatic
risks to persons caused by exposure to small amounts of radiation can
best be viewed in terms of the probability of death to an individual
when he is considered as a member of a large exposed population group.
Although the gejietic risks to humans as a result of the assimilation of
transuranium elements cannot be quantified with exactness, these risks
may be estimated in terms of the number of expected genetic defects
per 100,000 live births where both parents are assumed to have accumu-
lated a given gonadal dose. The development of this guidance is based
on suitable models chosen by the Agency that relate environmental levels
to the dose to internal organs. Health risks resulting from radiation
exposure were estimated using models and recommendations of the Advisory
Committee on the Biological Effects of Ionizing Radiation of the National
Academy of Sciences (NAS-BEIR Committee) in its reports entitled "The
Effects on Populations of Exposure to Low Levels of Ionizing Radiation"
* The dose received during childhood, and any differences in radio-
sensitivity between children and adults assumed by the NAS, have
been taken account of in the derivation of these guides. Because
a lifetime radiation dose is, for the most part, received during
maturity, adults are defined in this guidance as the critical
population group.
24
-------
(1972), and "Health Effects of the Alpha-Emitting Particles in the
Respiratory Tract" (1976) as well as information in other technical
reports.
The radiation risk due to inhalation of transuranium elements is
primarily lung cancer. Additional risks may result from translocation
of a small fraction of the transuranium elements from the lung to other
body organs, especially to the liver, hone, and gonadal tissues. On the
basis of models, it was estimated that, for a cohort of 100,000 persons*
followed through their entire lifetimes, the continuous inhalation over
their lifetimes of transuranium aerosols leading to an average annual
dose rate to the pulmonary tissue of 1 mrad/year per person could
potentially result in 10 premature deaths. For an average lifespan of
71 years, the annual risk to each person from lifetime exposure at this
level is about 1x10 per year, and the estimated number of additional
premature deaths would represent an increase of less than 0.1 percent of
the current risk of death due to all cancers.
The lifetime risk due to ingestion of transuranium elements is due
both to cancer mortality and an increased genetic risk. In a cohort of
100,000 persons, continuous ingestion over a lifetime of a transuranium
radionuclide at a level causing an average skeletal (bone) dose rate of
1 mrad per year 70 years after the start of ingestion is estimated to
result in less than 2 premature deaths from bone and liver cancer. In
* Epidemiological studies are generally based on results for a cohort
of 100,000 persons. This number is arbitrarily large and bears no
relation to the number of individuals expected to be exposed to the
maximum recommended dose rates of this guidance.
25
-------
order to approximate the same risk for the ingestion pathway as was
estimated for the inhalation pathway, the equivalent bone dose rate
limit would be about 6 mrad per year after 70 years. However, as noted
below, ingestion at this rate entails a greater genetic risk than that
resulting from the proposed inhalation limit. Therefore, in order to
have more comparable risks for either pathway, the recommended limiting
dose rate to bone is proposed as 3 mrad per year in the 70th year after
the start of ingestion. This could potentially result in 5 premature
cancer deaths in the cohort under consideration.
Genetic damage is possible as a result of assimilation of trans-
uranium elements in gonadal tissue. There is considerable uncertainty
in the estimated dose to gonadal tissue and resultant genetic risk. On
the basis of very limited data it can be estimated that, for continuous
ingestion at the limits set by this guidance, the total dose to gonadal
tissue over 30 years of chronic exposure would be about 10 millirad.
Such a gonadal dose to each of the parents is estimated to produce 1 to
20 genetic effects per 100,000 live births in the first generation.
This number can be compared to the approximately 6000 congenital
abnormalities normally observed in 100,000 live births. Potential
genetic risk to succeeding generations is not well known but, if the
guidance dose rate limit were maintained, may range as high as 5 to 150
impaired individuals per 100,000 live births. The dose rate to gonadal
tissue and the resultant genetic risk from continuous inhalation leading
to the guidance limit is estimated to be about six times smaller than
that estimated for continuous ingestion.
26
-------
In practice, very few, if any, individuals are expected to be
subjected to the recommended guidance limits and the total number of
individuals exposed above the level of worldwide fallout will be small.
The Agency also considered the total impact on population groups but,
because the exposed population groups are small and are likely to remain
so, it was deemed unnecessary to separately consider the environmental
radiation dose commitment in developing this guidance.
The estimated lifetime risk from exposure to transuranium elements
at levels equivalent to the guidance recommendations can be put in
perspective by comparison with other presently experienced risks of
death. These comparative risks have been derived from Life Table for
the U.S. Population for 1970 (18) and specific mortality rates as
published in Vital Statistics of the United States (19), both published
by the National Center for Health Statistics. Risk estimates are based
on a hypothetical cohort of 100,000 individuals with the race and sex
distribution of the U.S. population. Cohort members are subjected to
the same age specific mortality rates as are observed in the U.S.
population, and followed from birth until all members of the cohort are
dead. Impacts are derived in terms of number of premature deaths and
ages at death. The number of adverse health effects attributed to
radiation doses from transuranium elements are projected from models
which assume a linear non-threshold hypothesis for the dose effect
relationship. Therefore, the calculated risks may be overestimated,
and no deaths from exposure to transuranium elements in the environment
have been identified. In contrast, the number of deaths resulting from
27
-------
diseases are based on actual data taken from existing mortality records.
On the basis of these analyses, the Agency has concluded that the
added risks imposed on those persons who might be exposed to environ-
mental transuranium concentrations at the guidance recommendation levels
over a prolonged period of time are of the same order of magnitude as
those for relatively rare events, such as fatalities from bites and
stings and from electric current in home wiring and appliances. On the
basis of comparative life shortening, however, the potential risk from
transuranium elements in the environment would be smaller. Complete
results of life table models and data for other causes of death in-
vestigated are given in Annex IV.
3.3 Implementation
Implementation of this guidance will require measurement of the
ambient concentration level of transuranium elements in air, soil, food,
or water. In most cases the critical pathway for exposure to trans-
uranium elements is through inhalation of airborne particulates derived
from resuspension of soil particles and compliance with this dose
guidance can be demonstrated by measurements of air and/or soil con-
centration. Air concentration may be related to the dose guidance using
dosimetry models that include consideration of particle size distri-
bution and other parameters appropriate to the specific site of con-
tamination. Because of short-term and seasonal meteorological variations,
results of air concentration measurements are best based on the average
of consecutive weekly samples over a period of at least one year.
Air measurements may not indicate the specific source of
contamination, nor provide data for particular land areas of concern.
28
-------
Therefore soil measurements may be more advantageous in certain cases.
Such soil measurements are warranted when the air concentrations
indicate that the dose guidance limits are exceeded. Air concentration
measurements can be related to a corresponding soil contamination level
by use of a resuspension factor, which is obtained either by experi-
mental determination or by calculational techniques based on the mass-
loading concept as described in Annex II.
For practical reasons of facilitating implementation of this
guidance the Agency has derived a numerical value for a level of soil
contamination which can reasonably be predicted to result in dose rates
less than the guidance recommendations. On the basis of limited data
available for several existing sites, the Agency suggests that a soil
2
contamination level of 0.2 yCi/m , for samples collected at the surface
to a depth of 1 cm and for particle sizes under 2 mm, would establish a
reasonable "screening level" for this purpose. Use of such a numerical
value can serve to reduce the land area requiring evaluation and
minimize the number of measurements needed.
In some cases it may be prudent to specifically evaluate exposure
from ingestion, although this is not normally expected to be the
critical exposure pathway. The procedure suggested above does not
explicitly consider such alternative pathways. However, if these are
considered to be of sufficient importance from the viewpoint of human
exposures, they must be included in the evaluation of a specific site.
Further information on implementation of these guides, and on the
application of environmental measurements to demonstrate compliance with
the recommendations, are discussed in Annex V.
29
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3.4 Remedial Actions and Economic Evaluation
The recommendations of this guidance are primarily intended to
serve as an indicator of the need for possible remedial actions to
protect the public health. The guidance is stated in terms of a
maximum allowable dose to a critical segment of the population
occupying lands freely accessible to members of the general public.
Remedial action may be required at any site that fails to meet these
criteria. Economic evaluation is needed to determine the least cost
method of achieving the recommendations.
Where a need for the use of remedial measures arises, two
alternatives are available: 1) reduction or elimination of the source
term or 2) establishing restricted access or use of the area in question.
Remedial measures which reduce or remove existing surface contamination,
in order to minimize the source term and subsequent transport of plu-
tonium to humans, Include:
1. In-place stabilization by the application of a relatively
impermeable cover, such as oil, polymerized plastics, or
asphalt
2. Dilution by plowing or other similar techniques
3. Disposal by removal of surface soils and burial either
on-site or in a designated waste storage repository.
It can generally be expected that a variety of techniques can be
used to achieve the guidance level at any site. The objective of an
economic evaluation is to identify the technique or combination of
techniques that attains the guidance level at the least total cost.
Monetary costs, environmental costs, and other nonmonetary costs should
30
-------
all be considered in the evaluation of each alternative combination of
possible remedial actions.
Monetary costs include those for removal, stabilization and
dilution of contaminated soils, radiological monitoring, protective
measures for workers, and the maintenance of restricted areas if they
are used. Generally these costs can be readily evaluated. Environ-
mental costs, especially those of long-term degradation, must be
evaluated to the extent possible. Nonmonetary costs, including such
intangible factors as disruption of living patterns must be weighed in
the evaluation. Whenever feasible, costs of alternative remedial
actions should be evaluated monetarily or quantified in the best
available nonmonetary units.
31
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References
1. National Academy of Sciences - National Research Council: Health
Effects of Alpha-Emitting Particles in the Respiratory Tract;
Report of Ad Hoc Committee on "Hot Particles" of the Advisory
Committee on the Biological Effects of Ionizing Radiation. Published
by the Office of Radiation Programs, U.S. Environmental Protection
Agency, Washington, D.C., Report No. EPA 520/4-76-013 (October 1976).
2. ICRU Report 25, 1976. Conceptual Basis for The Determination
of Dose Equivalent, International Commission on Radiation Units
and Measures, Washington, B.C.
3. ICRP Publication 19, 1972. The Metabolism of Compounds of
Plutonium arid Other Actinides, Pergamon Press, New York.
4. ICRP Publication 23, 1975. Report of the Task Group on Reference
Man, Pergamon Press, New York.
5. U.S. Environmental Protection Agency: Plutonium and the Transuranium
Elements - Contamination Limits: Intent to Review the Need for
Establishing New Rules. Federal Register Vol. 38, p. 24098, Sept. 23,
1974.
6. U.S. Environmental Protection Agency - Office of Radiation Programs:
Proceedings of Public Hearings: Plutonium and the Other Transuranium
Elements (3 Volumes). ORP/CSD-75-1 (1975).
7. Presidential Documents. Federal Register Vol. 35, pp 15623-6
(Oct. 6, 1970).
8. International Commission on Radiological Protection: Report of
Committee II on Permissible Dose for Internal Radiation - ICRP
Publication 2 (1959).
9. National Committee on Radiation Protection and Measurements:
Maximum Permissible Body Burdens and Maximum Permissible Concen-
trations of Radionuclides in Air and Water for Occupational
Exposure - NCRP Report 22 (June 1959).
10. Atomic Energy Commission - Defense Atomic Support Agency:
Plutonium Contamination Standards. AEC - DASA Publication
TP 20-5 (May 22, 1968).
11. Department of Transportation: Chapter 49, Code of Federal
Regulations 173.397 (1970).
32
-------
12. U.S. Nuclear Regulatory Commission: Regulatory Guide 1.86:
Termination of Operating Licences for Nuclear Reactors (June 1974).
13. C.E. Guthrie and J.P. Nichols: Theoretical Possibilities and
Consequences of Major Accidents in U-233 and Pu-239 Fuel Fabrica-
tion and Radioisotope Processing Plants: Oak Ridge National Lab-
oratory Document ORNL-3441 (April 1964).
14. R.L. Kathren: Toward Interim Acceptable Surface Contamination
Levels for Environmental PuQ2: Battelle Northwest Laboratories
Document BNWL-SA-1510 (1968)7
15. J.W. Healy: A Proposed Interim Standard for Plutonium in Soils:
Los Alamos Laboratory Document LA-5483-MS (January 1974).
16. International Commission on Radiological Protection: Implications
of Commission Recommendations that Doses be kept as Low as Readily
Achievable. ICRP Publication 22 (April 1973).
17. Federal Radiation Council: Radiation Protection Guidance for
Federal Agencies. Federal Register Vol. 25, pp 4402-3 (May 18,
1960).
18. U.S. Department of Health, Education, and Welfare, Public Health
Service, U.S. Decennial Life Tables for 1969-71. Volume 1,
Number 1, May 1975.
19. U.S. Department of Health, Education, and Welfare, Public Health
Service, National Center for Health Statistics. Excerpt from
Vital Statistics of the United States 1969. Volume H-Mortality.
33
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Annex 1
TRANSURANIUM ELEMENTS IN THE ENVIRONMENT
U. S. Environmental Protection Agency
Office Radiation Programs
Washington, D.C. 20460
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Annex 1
Table of Contents
1. Introduction 1
2. The Nevada Test Site (NTS) 9
3. Rocky Flats Plant (RFP) 12
4. Mound Laboratory (ML) 23
5. Savannah River Plant (SRP) 28
6. Los Alamos Scientific Laboratory (LASL) 38
7. The Trinity Site 42
8. Sites of Underground Nuclear Detonations.. 42
9. Enewetak Atoll '. 42
10. Other Sites 46
REFERENCES 58
Tables
A 1-1 Cumulative Deposit of Fallout Pu-239 at Selected
Locations in the United States (3) 3
A 1-2 Concentration of Fallout Pu-239 with Depth at North
Eastham, Massachusetts (4) 4
A 1-3 Fallout Pu-239 in New York City (6) 5
A 1-4 Nuclear Properties of Environmentally Significant
Transuranium Radionuclides (7) 6
A 1-5 Inventories and Concentration Levels of Plutonium at
Contaminated Sites 8
A 1-6 Estimated Inventory of Plutonium in Surface Soil (0-5
cm depth) at Specific Areas within the National Test
Site and Tonopah Test Range (11) 11
A 1-7 Pu-239 in Air Samples - Near the NTS (7) 15
A 1-8 Plutonium Concentration in Ambient Air at Selective
Locations - Rocky Flats Site (11) 22
A 1-9 Concentrations of Plutonium and Americium in Water
Supplies and in Finished Drinking Water - Rocky Flats
Site (10) 24
A 1-10 Concentration of Pu-238 in Environmental Media Mound
Laboratory (10) 29
A 1-11 Mound Laboratory U.S. Environmental Protection Agency
1974 Survey 33
A 1-12 Plutonium Concentration in Environmental Media Around
the Savannah River Plant (10) 37
A 1-13 Plutonium in Sediments in the Liquid Waste Receiving
Canyons (20) - cy 1975 39
A 1-14 Plutonium and Americium in Environmental Media - LASL
Site - (10) - CY 1975 - 40
A 1-15 Underground Testing Conducted Off the Nevada Test Site
(10) 44
A 1-16 Plutonium Concentration in Soil on Enewetak Atoll
(22) 47
-------
A 1-17 Plutonium and Americium Concentration in Surface Air
on Enewetak Atoll (14) 48
A 1-18 Plutonium and Americium Concentrations in Various
Environmental Media on Enewetok Atoll (14) 49
A 1-19 Environmental Monitoring for the Transuranium Elements
at the Pantex Plant Site 50
A 1-20 Environmental Monitoring for the Transuranium Elements
at Argonne National Laboratory 52
A 1-21 Environmental Monitoring for the Transuranium Elements
at Battelle-Columbus Laboratories (West Jefferson
(Site) 53
A 1-22 Environmental Monitoring for the Transuranium Elements
at the Idaho Engineering Laboratory 54
A 1-23 Environmental Monitoring for the Transuranium Elements
at the Oak Ridge Facilities 55
A 1-24 Environmental Monitoring for the Transuranium Elements
at Hanford 56
A 1-25 Environmental Monitoring for the Transuranium Elements
at the Lawrence Livermore Laboratory 57
Figures
Page
A 1-1 Population Distribution by Azimuth and Distance 10
A 1-2 Cumulative Deposit of Pu-239, 240 (mCi per km2) 13
A 1-3 Cumulative Global Fallout Deposit of Pu-239, 240 (mCi
per km2) 14
A 1-4 Wind Rose for the Rocky Flats Site (10) 16
A 1-5 Population Distribution Around Rocky Flats 18
A 1-6 Rocky Flats 1974 Plutonium Concentrations in Soil
(Values in Picocures Per Gram. (10) 20
A 1-7 Rocky Flats Plutonium-239 Contours mCi/km2 (11) 21
A 1-8 Population Distribution Around Mound Laboratory (0 to
10 km) LAT 39.6305 LONG 84.2897) 25
A 1-9 Mound Laboratory Preliminary Estimate of Plutonium-238
Airborne Deposition (mCi/km2) (10) 27
A 1-10 Mound Laboratory 32
A 1-11 Savannah River Plant Plutonium Deposition (10) 36
A 1-12 Trinity Site 1973-1974 Plutonium Soil Sampling Results
(n Ci/m2) (14) 43
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Annex 1
TRANSURANIUM ELEMENTS IN THE ENVIRONMENT
1. Introduction
Plutonium and other transuranium elements have been released into
the general environment primarily from four sources. In order of
quantities released from most to least, these are:
a. Aboveground testing of nuclear weapons
b. Accidents involving nuclear weapons and satellite power sources
c. Accidents at nuclear facilities
d. Planned discharges of effluents from nuclear facilities
The aboveground testing of nuclear weapons during 1945-1963 is
responsible for a worldwide dispersal of plutonium and americium. For
the most part, this radioactivity was injected into the stratosphere and
has been redeposited more or less uniformly over the earth's lands and
waters. This redeposited plutonium and americium is available to
people through inhalation and ingestion pathways and exists as a
ubiquitqus source in the general environment upon which is superimposed
the releases of transuranic elements from other sources.
Fallout plutonium is primarily a mixture of Pu-239 and Pu-240 with
lesser amounts of Pu-238, Pu-241 and Pu-242. About 58% is Pu-239 and
39% Pu-240; because these two radionuclides are essentially identical
with respect to chemical behavior and alpha energies, the sum of their
activities in the environment is will be referred to in this Annex as
"Pu-239" (1). The daughter of Pu-241 (t1/2 - 12y) is Am-241, so that as
the Pu-241 continues to decay, the concentration of Am-241 in the
-------
environment increases relative to the amount of Pu-239. The Am-241/
Pu-239 activity ratio in soil is now about 0.25 and will eventually
increase to 0.40 (2).
Aboveground nuclear weapons testing produced approximately
430 kilocuries of Pu-239 over the period 1945 to 1974. About 105
kilocuries deposited quickly near the various detonation sites. Of
the 325 kilocuries injected into the stratosphere, 250 kilocuries have
deposited in the mid latitudes of the northern hemisphere, 70 kilocuries
have deposited in other latitudes and about 5 kilocuries still remained
in the stratosphere as of 1974. This has led to cumulative depositions
of Pu-239 on ground surfaces in the United States that range from 0.001
2
to 0.003 yCi/m . Since 1967, sporadic aboveground nuclear tests have
held the air concentration level of plutonium to relatively constant
o
values, currently ranging from 0.01 to 0.1 fCi/m in ground level air.
These levels are not believed to be the result of resuspension from soil
surfaces (1, 3).
Table A 1-1 gives the cumulative deposition of fallout Pu-239 at
selected locations in the United States (3). Table A 1-2 shows how it
is distributed in soil with respect to depth at both an undisturbed site
and a cultivated site (4,5). Table A 1-3 is a summary of fallout Pu-239
levels in New York City for both air and ground deposition as a function
of time from 1954 to 1975 (6). Table A 1-4 is a listing of the nuclear
properties of the more significant transuranium nuclides (7).
The total amount of Pu-238 injected into the stratosphere from
aboveground nuclear tests is about 9 kilocuries (3). In addition, 17
-------
Table A 1-1
Cumulative Deposit of Fallout Pu-239 at Selected
Locations in the United States (3)
Approximate Location
Richland, Washington
San Francisco, California
Los Angeles, California
National Test Site, Montana
Rapid City, South Dakota
Topeka, Kansas
Tulsa, Oklahoma
Corpus Christi, Texas
Chicago, Illinois
Augusta, Maine
Cape Cod, Massachusetts
Long Island, New York
Raleigh, North Carolina
Miami, Florida
Pu-239 Concentration (a)
(yCi/m2)
0.0014
0.0009
0.0007
0.0019
0.0025
0.0024
0.0022
0.0010
0.0021
0.0017
0.0023
0.0024
0.0024
0.0010
Average (± 2a)
0.0018 ± 0.0006
(a) Top 30 cms of soil
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Table A 1-2
Concentration of Fallout Pu-239 In Soil as a
Function of Depth at North Eastham, Massachusetts (4)
0-2 (Includes Vegetation) (a)
2-4
4-6
6-8
8-10
10-12
12-14
14-16
16-21
21-26
Depth
Undisturbed Site
Concentration of Pu-239 % of Total
(yCi/m2)
0.91xlO~3 52 (a)
0.37 21
0.15 8
0.12 7
0.052 3
0.035 2
0.028 2
0.027 1
0.047 3
<0.004 <1
Cultivated Site
(5)
Concentration of Pu-239 % of Total
(yCi/in )
0-5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
0.42^10
0.45
0.34
0.37
0.32
0.20
0.02 ± 0.
0.02
0.02
0.02
0.02
03
19
20
16
17
15
10
0.01
0.01
0.01
0.01
0.01
(a) 12% of the total plutonium was associated with vegetation
-------
Table A 1-3
Fallout Pu-239 in New York City (6)
Deposition
Cumulative deposit
Surface air concentration
Year
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
(yCi/m2)
0.07xlO~3
0.09
0.12
0.12
0.16
0.23
0.04
0.06
0.32
0.62
0.41
0.14
0.05
0.04
0.04
0.06
0.03
0.03
0.02
0.01
0.02
0.01
(yCi/m2)
0.00007
0.00016
0.00028
0.00040
0.00056
0.00078
0.00082
0.00089
0.0012
0.0018
0.0022
0.0024
0.00245
0.0025
0.0025
0.0026
0.0026
0.0026
0.0027
0.0027
0.0027
0.0027
(fCi/m3)
0.14
0.18
0.23
0.23
0.32
0.45
0.081
0.13
0.63
1.68
0.91
0.33
0.12
0.051
0.08
0.06
0.068
0.06
0.027
0.013
0.039
0.02
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Table A 1-4
Nuclear Properties of Environmentally Significant Transuranium Radionuclides (7)
Radiological
Energy of
Radionuclide
Pu-238
Pu-239
Pu-240
Pu-241
Pu-242
Am-241
Am- 243
Cm-242
Cm-244
nail-life
Cy)
87.4
2.4xl04
6.6xl03
14.3
3.9xl05
443.
7.4xl03
0.45
18.1
Mode of
Decay
alpha
alpha
alpha
beta
alpha
alpha
alpha
alpha
alpha
t>^
Major Radiations
(MeV)
5.50; 5.46
5.16; 5.11
5.17; 5.12
0.021 (max)
4.90; 4.86
5.49; 5.44
5.28; 5.23
6.12; 6.07
5.81; 5.77
Daughter
TJ-234
U-235
U-236
Am-241
U-238
Np-237
Np-239
Pu-238
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kilocuries of Pu-238 were released in 'the high stratosphere of the
southern hemisphere when a satellite containing a nuclear power source
(SNAP-9A) failed to orbit and disintegrated (9). As a result, there are
measurable amounts of Pu-238 in most environmental media. Also, an
estimated 90 curies of curium (Cm-245 and Cm-246) have been produced as
the result of weapons tests (1).
The principal additional potential source for future release of
the transuranium elements to the general environment are operations
associated with the Light-Water Reactor Fuel Cycle. About 250 kg of
Plutonium, which is inside the spent fuel rods, is removed per year
from a 1000 Mw(e) light-water reactor. The isotopic composition of
this plutonium is typically 59% Pu-239, 29% Pu-240, 11% Pu-241, 4%
Pu-242 and 2% Pu-238 (9).
Sections that follow briefly discuss specific controlled sites and
other areas in the general environment which have become contaminated
with transuranium elements significantly above levels attributed to
stratospheric fallout. There are several possible reasons: local
fallout from aboveground nuclear tests, accidents at nuclear facilities
or effluent releases from nuclear facilities. Data was selected to be
representative of conditions at these sites as of 1973 to 1975; the
years for which the most recent reports on environmental monitoring
have been published. Much additional information is available in the
documents that have been referenced.
Table A 1-5 provides a summary of these sites, their locations,
inventories, and approximate onsite and offsite maximum soil concentra-
tion levels.
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INVENTORIES
Table A 1-5
AND CONCENTRATION LEVELS OF PLUTONIUM IN THE ENVIRONMENT
Location
Nevada Test Site
Nevada
Rocky Flats Plant
Denver, Colorado
Hound Laboratory
Miaalaburg, Ohio
Savannah Rlvar Plant
South Carolina
Los Alanos Scientific
Laboratory
Los Alaoos, New Mexico
Trinity Site
New Mexico
Enevetak Atoll
Micronesia
Continental United States
Approximate Inventory of
Plutonium released to Soils
(curies)
> 155 (Pu-239)
11 (Pu-239)
1 (Ao-241)
5 to 6 (Pu-238)
2 (Pu-239)
> 1 (Pu-239 and
Pu-238)
•»• 45 (Pu-239)
Not published
16,000 (Pu-239)
4,000 (Pu-238)
Maximum Soil Concentration Levels
Onsite Offsite
6,000 uCi/m2 2xlO"3 yCi/n2
10 pCi/g
> 1000 pCi/g2 « pci/g
M
> 10 jiCi/nr
4,600 pCi/g
0.001 uCi/m2 0.01 yCi/m2
220 pCi/g < 1 pci/g
0.1 uCt/m2
530 pCi/g 0.3 pCi/gm
0.07 pCl/m
0.001 to 0.003 vCl/m2
Comments v>aft*f *****+*,.,
"**"Siih° — _,- Ket erences
Onsite levels refer to small 1,11,12
subregions of the site
It is estimated that 8 curies 14,15,17
of plutonium are onsite; 3 are
offsite. Inventory of Am-241
will double due to ingrowth.
Soil samples are taken 5 cm
deep.
Most of the plutonium is 18,19
associated with buried sedi-
ments in waterways' adjacent
to the site.
Offsite plutonium is located 1,10
in a swamp area of the
Savannah River in the top
8 cms of sediment.
Plutonium is associated with 10
soils iix dry canyons (top 5 cms)
22
Offsite value refers to 23
islands most likely to be
resettled (top 15 cm of soil)
(top 30 cm of soil) 3
-------
1. The Nevada Test Site (NTS)
2
The Nevada Test Site (10) is an area of about 3500 km located in
Nye County, Nevada, 90 kilometers northwest of Las Vegas. It is
surrounded by an exclusion area 25 to 100 kms wide between the test site
itself and public lands. The climate is for the most part arid, with
insufficient rainfall (10 to 25 cm/y precipitation) to support trees or
crops without irrigation. Winds blow primarily from the north, except
for May through August when they are predominantly from the south-
southwest. Fig. A 1-1 shows the population distribution around this
site by azimuth and by distance.
Major programs conducted at NTS have included nuclear weapons
tests, tests for peaceful uses of nuclear explosives, nuclear reactor
engine development, basic high energy nuclear'physics research, and
seismic studies. As the result of these activities, the test site,
exclusion area and, to a much lesser extent, large areas outside the
exclusion areas have become contaminated with plutonium.
Although the total inventory of plutonium in soils within the NTS
is not known, detailed surveys have been made of certain specific loca-
tions in the site and the Tonopah Test Range (TTR) which are believed to
be the areas most highly contaminated with plutonium and americium (11).
As shown in Table A 1-6, the inventory of plutonium in these areas is
about 155 curies.
Estimates of offsite plutonium concentration -in soil as the result
2
of activities at NTS have been made (12). In units of mCi/km
-------
A • AOUIT5
C • CHItOKN
0 - 0»I«T COWS
I • FAMI1Y COW)
A- MO JUHVIT CONOUCTIO
POPULATION DISTRIBUTION BY AZIMUTH AND DISTANCE
AROUND NTS (10)
FIGURE A1-1
10
-------
Table A 1-6
Estimated Inventory of Plutonium in Surface Soil at Specific
Areas within the National Test Site and Tonopah Test Range (11)
Area
13
5 (GMX)
Double Track
Clean Slate 1
Clean Slate 2
Clean Slate 3
Plutonium Valley
Size of Estimated Range of Soil b
Area Inventory Concentrations
(m2) (curies Pu-239) (yCi/m2) Pu/Am Activity Ratios
3.6xl06 44 ± 9 2 to 840 9
2.4xl05 3 ± 0.3 3 to 530 10
3-OxlO5 5 ± 1 7 to 2,800"
2.2xl05 5 ± 2 15 to 120 22 to 26
7.9xl05 29 ± 6 4 to 260
1.3xl05 30 ± 5 12 to 370 .
4.8xl06 39 ± 4 1 to 6,200 5 to 8
Total 155
(a) Inventory as measured to 5 cm soil depth.
(b) Soil concentration range values refer to concentrations within sub regions of each site
as selected by stratified random sampling.
-------
2 2
(1 mCi/km = 0.001 pCi/m ) Fig. A 1-2 shows isopleths for this material;
Fig. A 1-3 shows, for comparison, the additional amounts of plutonium at
the same locations due to fallout. Offsite levels of plutonium in soil
2
are less than 0.1 yCi/m , most areas being far lower.
A limited special study was made of plutonium concentrations in air
at locations close to the NTS (13). Results are shown in Table A 1-7
and indicate that, while resuspended plutonium from NTS has probably
been detected at three locations, the air concentration level has not
o
exceeded 0.5 fCi/m . Long term air surveillance from 1966 to 1972 at
eight major centers of population in western states was performed for
ambient plutonium levels in ground level air (13). Within annual
cycles, these levels, which are ascribed entirely to fallout plutonium
3
from the stratosphere, varied from 0.01 to 0.5 fCi/m with mean annual
3
values of approximately 0.1 fCi/m .
The milk surveillance network around the NTS does not analyze
samples for plutonium. Water samples from wells both onsite and offsite
in surrounding communities were analyzed for Pu-239 and Pu-238. Plu-
tonium was not detected, indicating levels less than about 0.1 pCi/A
Pu-239 or Pu-238.
3. Rocky Flats Plant (RFP)
The Rocky Flats Plant (10) is located in Jefferson County,
Colorado, 26 kilometers northwest of Denver. Currently, the site
consists of 6,500 areas of Federally owned land of which 385 acres is
enclosed within a security fence. The area is arid (40 cm/y precipita-
tion) with predominant winds from the northwest. Figure A 1-4 is a
12
-------
I __UTAH ,°
I' ARIZONA" I —
CUMULATIVE NTS DEPOSIT OF Pu-239,240 (12)
(mCi per km2)
FIGURE A1-2
13
-------
/
*/'
§1 •1.1*03
o/
I . «.
|
1
/ 3. 3tO."2 •"""--/
1 j o
o2.1*0.2
'•8*0-3
03.3,0.3 /
20±0.2l __ •1.9*0.2
«1.7to.5
ol.5i0.4 °
n n , «
• 2.8*1.0
o2.1*0.4
ol.4*0.3
1.0*0.2*1
, 7 n -J '
•1.7*0.3 /
•/1. 7±0.8
»2.6*0.3
«1.2±0.4
• 2
0*0.7
•1.1*0.5
•1.5*0.5
»1.1*0.1
"I
I
I
2.2±0.1Q I
2.0±0.1° I
2.3*0.1°
1
l
!-,
•1.5*0.7
/
/
/
•1.7*0.1
»1.8±0.2
,g
'
I »O
I «r / """* *"" """" *"" """" """ ••» O
"**T p""" Q | "™" ^~" "™* "** "*"• — - — ^. ^_ U t AH IW
-------
Table A 1-7 Pu-239 in Air Samples - Near the NTS (13)
Downwind Pu-239
Concentration
Upwind Pu-239
Concentration
Pu-239
Concentration
Downwind
Location
Furnace Creek, CA
Death Valley Jet.
CA
Beatty, NV
Diablo, NV
Hiko, NV
Indian Springs, NV
Lathrop Wells, NV
Pahrunp, NV
Scotty's Jet., NV
V/»rn Springs, NV
Date
2/20/71
10/30/72
2/20/71
3/31/71
10/24/72
10/28/72
12/13/72
2/3/71
2/25/71
3/1/71
3/17/71
10/28/71
A/25/72
A/20/71
5/4/71
5/26/71
3/26/71
4/25/71
6/26/71
9/25/71
3/13/71
4/25/72
3/18/70
9/25/70
3/18/71
10/24/72
5/17/71
10/30/72
2/19/70
3/31/71
10/24/72
10/29/72
12/13/72
3/12/71
3/26/71
4/25/71
(fCi/m3)
<0.05
<0.04
0.20
0.12
0.10
<0.07
<0.03
0.09
0.08
<0.06
0.19
<0.08
0.088
0.20
0.20
0.40
0.20
0.20
0.20
<0.70
0.10
0.087
<0.06
0.17
0.20
0.04
0.30
<0.12
0.15
0.20
0.068
0.15
<0.059
0.14
<0.08
0.13
Date
4/20/71
12/7/72
5/2/71
5/3/71
10/2/72
12/6/72
12/7/72
6/28/70
ft/20/71
5/2/71
5/20/71
10/16/71
4/16/72
2/20/71
3/1/71
3/31/71
9/25/70
2/20/71
3/18/71
10/28/71
4/20/71
.4/16/72
ft/20/71
6/26/71
9/25/71
10/2/72
4/20/71
10/2/72
4/20/71
5/3/71
5/27/71
12/4/72
12/6/72
12/7/72
2/19/70
3/18/70
3/31/70
2/3/71
2/20/71
3/17/71
3/31/71
(fCi/m3
0.20
0.051
0.20
0.20
<0.065
<0.048
0.055
0.40
0.17
0.20
0.12
0.20
0.075
<0.06
<0.07
0.30
<0.07
<0.07
0.09
<0.06
0.15
0.19
0.20
0.30
0.20
0.042
<0.10
<0.044
0.17
0.20
0.20
<0.036
0.056
<0.042
<0.09
0.23
0.10
<0.60
<0.60
0.20
0.12
vs Upwind
No difference
No difference
Significant
difference
No difference
Significant
difference
Probable
difference
No difference
No difference
No difference
No difference
15
-------
A = frequency for a direction (%)
B = average velocity (meters per
second) for a direction from
which the wind blows
C = calms (%)
D = variable direction (%)
A/
10
20
30
40
Scale for length of wind frequency lines (%)
FIGURE A1-4
WIND ROSE FOR THE ROCKY RATS SITE (10)
-------
wind rose for the site; Fig. A 1-5 provides population densities around
the site by azimuth and distance. Less than 10 yCi of plutonium was
released from plant stacks and vents to the atmosphere in 1975 (10).
Data on the total amount of plutonium released to surface waters from
1973 to 1975 have not been published.
The plant produces components for nuclear weapons, which involves
the processing of plutonium. As the result of leakage from barrels of
plutonium-contaminated cutting oil, parts of the site and, to a lesser
degree, the general environment around the site have been contaminated
with plutonium and americium. The total amount of plutonium released to
the environment is estimated to be 11 curies of which 3.4 ± 0.9 curies
is estimated to be offsite (14). Of the approximately 8 curies onsite,
more than half is believed to be stabilized by coverage with an asphalt
pad and remedial measures are being taken to control the remainder to
the extent practicable.
Figures A 1-6 and A 1-7 show values for Pu-239 concentrations
in soils (5 cm depth) around the site (15, 16). Concentrations of
Am-241 within the site boundaries are about 10% of Pu-239 values (17).
Table A 1-8 provides selected yearly average plutonium
concentrations in ambient air within the plant boundary, at distances
of 3 to 6 kilometers from the plant and in nearby communities (10).
Liquid effluents released from the plant may eventually reach the
Great Western Reservoir, while storm water runoff from the site tends to
collect both there and in Standley Lake. Both reservoirs are sources of
17
-------
FIGURE A1-5
POPULATION DISTRIBUTION AROUND ROCKY FLATS
<• Tfl 10 tan)
18
-------
MltZ
HBURE A1-5
POPULATION DISTRIBUTION AROUND ROCKY FLATS
(10 TO 80 km)
19
-------
0 0A ROCKY
' FLATS
PLANT
FIGURE A1-6
ROCKY FLATS 1974
PLUTONIUM CONCENTRATIONS IN SOIL.
(VALUES IN PICOCURIES PER GRAM. (15)
20
-------
FIGURE A1-7
ROCKY FLATS
PLUTONIUM-239 CONTOURS mCi/km12 (16),
21
-------
Table A 1-8
Plutonium Concentration in Ambient Air at Selective
Locations - Rocky Flats Site, 1975 (10)
Average Plutonium
Concentration
Station Location with
Location
Onsite
Three to six
Kilometers Distant
from Plant
Boulder
Marshall
Superior
Walnut Creek
Wagner
Leyden
Station
S-14
S-16
S-4
S-6
S-ll
S-31
S-34a
S-3?a
S-41
-
-
-
-
-
—
(fCi/m3)
< 0.02
< 0.06
0.1
1.
0.01
< 0.03
< 0.04
0.06
< 0.03
< 0.03
< 0.03
< 0.04
< 0.03
< 0.04
0.04
Respect to the Plant
West
Northwest
North
East
South
West
North
East
South
Northwest
North
North
East
East
South
(a) Site Boundary
22
-------
drinking water. Table A 1-9 gives estimates of plutonium and americium
concentrations in these water supplies as well as in finished drinking
water for nearby communities (10). Modifications of the Rocky Flats
plant operations have been proposed that will eventually halt all of its
liquid effluent discharges.
In summary, in offsite areas around the Rocky Flats plant, the
o
plutonium concentration in ambient air is < 0.06 fCi/m , plutonium in
finished drinking water is < 0.03 pCi/Jl, and plutonium in soil is
< 0.1 yCi/m2 (5 cm deep samples) (17).
A. Mound Laboratory (ML)
Mound Laboratory (10) is located in Miamisburg, Ohio, 16
kilometers southwest of Dayton. The 180 acre site is within an indus-
trialized river valley in a region that is predominantly agricultural.
Corn and soy beans are major crops and livestock is pastured. Winds are
predominantly from the south or west; average precipitation is 91 cm/yr.
The population distribution around the site is given in Fig. A 1-8.
The mission of the laboratory includes research, development and
production of components for the nuclear weapons program and fabrica-
tion of radioisotopic heat sources for medical applications and space
operations. This latter operation involves processing large quantities
of Pu-238 which has become the plutonium radionuclide of primary
concern associated with this site.
Pu-238 in airborne effluent discharges from the plant has, over
the years, contaminated the site and, to a lesser degree, offsite areas.
Figure A 1-9 shows preliminary estimates of the levels of Pu-238 in
23
-------
Table A 1-9
Concentrations of Plutonium and Americium in Water Supplies
and in Finished Drinking Water - Rocky Flats Site, 1975 (10)
Location
Indiana Street)
Water Supply
Great Western
Reservoir)
Concentration
Plutonium Americium
(pCi/A)
Great Western
Stand ley Lake
Boulder
Broomfield
Denver
Golden
Lafayette
Westminister
(Walnut Creek at
Reservoir
Reservoir
Drinking Water
it
ti
n
it
n
(Discharge to
< 0.1
< 0.04
< 0.007
< 0.04
< 0.008
< 0.009
< 0.007
< 0.04
(0.6)
< 0.03
< 0.03
< 0.006
< 0.03
< 0.04
< 0.009
< 0.007
< 0.03
(0.2)
24
-------
HGUREA1-8
POPULATION DISTRIBUTION AROUND MOUND LABORATORY
(0 to 10 km) (LAT 39.6305 LONG 842897)
25
-------
TOTAL POPULATION IN SECTOR
RGURE A1-8
POPULATION DISTRIBUTION AROUND MOUND LABORATORY
(10 to 80 Km) LAT 39,6305 LONG 84,2897)
TOTAL P-2,903,384
26
-------
RGURE A1-9
MOUND LABORATORY
PRELIMINARY ESTIMATE OF PLUTONIUM - 238 AIRBORNE DEPOSITION
(m Ci/km2)(iO)
27
-------
soil around the site. Approximately 0.5 curies of Pu-238 have been
released to the offsite environment in this manner.
The concentration of Pu-238 in various environmental media around
the Mound Laboratory is given in Table A 1-10 for 1975 (10). The
annual average concentration of Pu-238 in offsite ambient air did not
o
exceed 0.03 fCi/m ; in surface waters it was as high as 1.4 pCi/£ in an
off-site pond but in water supplies it did not exceed 0.05 pCi/£.
In 1969, an underground pipe carrying acid radioactive waste
solutions ruptured. During repair work on this pipe, heavy rains
eroded the radioactive soil, and carried about 5 curies of Pu-238 off-
site into waterways adjacent to the Laboratory. This plutonium now is
in sediments that are mostly buried under approximately 1 to 3 feet of
additional non-contaminated sediments added by normal processes later
in time (18). A special study of this incident was also conducted by
the U.S. Environmental Protection Agency; results are given in Fig.
A 1-10 and Table A 1-11 (19).
5. Savannah River Plant (SRP)
2
The Savannah River Plant (10) is located on a 790 km Federally
owned site along the Savannah River in Aiken and Barnwell Counties,
South Carolina, about 100 kilometers southwest of Columbia. The sur-
rounding area is predominantly forested with some diversified fanning,
the main crops being cotton, soy beans, corn, and small grains, with the
production of beef cattle. The climate is mild, with an annual rainfall
of 115 cm/y. Population density around the site ranges from 10 to 400
people per square mile.
28
-------
Table A 1-10
Concentration of Pu-238 in Environmental Media
Mound Laboratory (10)
Ambient Air
Sample Location
(Location Number)
onsite (211)
(212)
(213)
(214)
North of Plant (101)
East of Plant (103)
South of Plant (104)
West of Plant (105)
Miamisburg (122)
Dayton (108)
(National Average from Fallout)
Average Concentration of Pu-238
(fCi/m3)
0.2
0.05
1.0
0.06
0.02
0.01
0.01
0.009
0.02
0.008
(0.003)
29
-------
Table A 1-10 (Continued)
Waters
Sample Location
(Location number)
Great Miami River
Above the Plant (1)
Below the Plant (A)
Canal/pond area
North Pond
South Pond
Miamisburg Drinking Water
Private Well J
Private Well B
Average Concentration of Pu-238
(PCI/A)
0.019 ± 0.0022
0.052 ± 0.004
0.22
1.4
0.043 ± 0.003
0.020 ± 0.002
0.006 ± 0.00003
30
-------
Table A 1-10 (Continued)
Foodstuff Collected Close to the Plant
Sample
Milk
Fruits & Vegetables
Grass
Field Crops
Aquatic life
Average Concentration of Pu-238
(pCi/g)
2x10
-4
< 6x10
-4
1x10
-2
1x10
-3
< 3x10
,-4
31
-------
FIGURE A1-10
U.S. ENVIRONMENTAL PROTECTION AGENCY SAMPLING SITES
MOUND LABORATORY (19)
32
-------
Tafele A.1-11
MOUND LABORATORY
U.S. ENVIRONMENTAL PROTECTION AGENCY
1974 SURVEY (19)
Plutonium in Samples from the Vicinity of Mound Laboratory
I.D. t
EA-1
EB-1
EC-1
ED-1
EE-1
£ EF-1
EG-1
EH-1
EI-1
EJ-1
FA-1
FE-1
Location 238Pu
Core sediment samples collected by Mound Laboratory, pCi/g dried weight
North Canal at south end of South Pond 0.13
0.09
" 0.13
0.11
4.8
1.1
440
1170
1090
" 10.8
" 26
" 0.98
0.89
1.30
North end of North Canal 8.9
7.5
9.1
16.9
19.2
Concentration
239pu
< 0.02
< 0.02
< 0.02
< 0.02
0.07
< 0.02
2.3
15.4
7.9
0.18
0.16
0.06
0.05
0.06
0.51
0.44
0.18
0.05
GA-1 North end of North Pond 0.48 < 0.02
-------
Table A 1-11 (Continued)
CO
Concentration
I.D. tf
HA-1
IA-L
JA-1
KA-1
LA-1
CE-1
QE-1
EPA-1
EPA-20
EPA-17
EPA-18
Location
Middle of North Pond
South end of North Pond
North end of South Pond
Middle of South Pond
South end of South Pond
South Canal at west drainage ditch
South Canal where it crosses US 25
Sediment samples, top 1 inch, pCi/g dried weight
South Canal at west drainage ditch
East drainage ditch, ~200 ft south of Mound Rd culvert
South drainage ditch, 15 ft from junction with South Canal
South Canal, 10 ft from junction with south drainage ditch
238pu
5.1
2.5
0.70
27
10.9
24
920
230
1.9
47
60
239PU
0.07
0.06
0.02
0.27
0.30
0.46
10.9
3.54
0.06
0.84
0.77
Surface soil and mud samples, top 1 inch, pCi/g dried weight
EPA-2
EPA-3
EPA-6
EPA-7
EPA-13
EPA- 14
EPA-15
EPA-12
Railroad cut south of control box
Railroad cut north of control box
Run-off hollow
At shelter house SE of South Pond
NE of Lab, at fence between tennis court and Harmon Field
SE of Lab, at SU corner of Mound Park
SW of Lab, at junction of US 25 with^ South Canal
NW of Lab, at alley south of Mound Rd
0.12
0.39
3.8
0.44
0.10
0.44
0.96
0.19
0.17
0.02
0.13
0.11
0.07
0.02
0.04
0.04
0.05
0.05
-------
SRP produces plutonium, tritium and other special nuclear materials.
Facilities include nuclear reactors, nuclear fuel and target fabrica-
tion plants, nuclear fuel reprocessing plants, a heavy water production
plant and various supporting laboratories.
Two airborne releases, in 1955 and 1969, from fuel reprocessing
plant operations are believed to have caused the detectable plutonium
contamination of soil that is found within a 2 km radius around those
facilities within the site perimeter. Approximately 1 curie of plu-
tonium is estimated to be within the isopleths shown in Fig. A 1-11 (20)
During the 1960's, radioactive liquid effluents were released
from SRP such that radioactive materials, including Cs-137, Co-60 and
plutonium deposite'd in off site swamp areas. In these areas plutonium
—3 2 -3
concentrations range from 3 to 11x10 yCi/m Pu-239 and 0.3 to 6x10
2
viCi/m Pu-238. The amount attributed to fallout sources is approxi-
mately IxlO"3 yCi/m2 Pu-239 and O.lxlO"3 yCi/m2 Pu-238 (10).
Levels of plutonium in various environmental media in the general
environment around SRP are given in Table A 1-12 for 1975 (10). Resu-
spended plutonium from the contaminated areas within the site was not
detected in offsite ambient air. Values for plutonium concentration
levels in ambient air at onsite locations have not been published. In
1975, the plant released 2 mCi Pu-238 and 0.5 mCi Pu-239 to the atmo-
sphere; the plant released 8 mCi Np-239 and 19 mCi Pu-239 in liquid
effluents.
35
-------
QUANTITIES:
ON ISOPLETHS (3) - mCl/km2
IM ZONES (1.0) - CURIES
DEPOSITED IN ENTIRE ZONE
FIGURE AMI
SAVANNAH RIVER PLANT PLUTONIUM DEPOSITION (10)
36
-------
Table A 1-12
Plutonium Concentration in Environmental Media
Around the Savannah River Plant - 1975 (10)
Ambient Air.
Sample Location
Plant Perimeter
(Locations not specified)
25 mile radius
(Locations not specified)
Rain Water,
Sample Location
Plant Perimeter
25 mile radius
Soil (0-5 cm depth?
Location
Plant Perimeter
NW quadrant
NE
SE
SW
Sprinfield, SC
Aiken Airport, SC
Clinton, SC
Savannah, GA
Average Plutonium Concentration
Pu-239 Pu-238
(fCi/m3) (fCi/m3)
0.02
0.02
0.001
0.001
Average Plutonium Concentration
Pu-239 Pu-238
(pCi/m2) (pCi/m2)
2.2
1.9
0.11
0.15
Average Plutonium Concentration
Pu-239 Pu-238
(yCi/m2) (uCi/m2)
0.0009
0.0014
0.0010
0.0012
0.0003
0.0010
0.0008
0.0005
5x10
8
6
8
4x10
7
3
2
-5
-5
37
-------
6. Los Alamos Scientific Laboratory (LASL)
The Los Alamos Scientific Laboratory (10) is located on a 110 km2
site in Los Alamos County in North Central New Mexico about 40 kilo-
meters northwest of Santa Fe. The site is on a series of mesas
separated by canyons that run eastward from the Jemez Mountains to the
Rio Grande Valley. The climate is semi-arid with rainfall of 46 cm/y.
While the land around the site is undeveloped, about 16,000 people
reside in the immediate area.
The primary mission of LASL is associated with nuclear weapons
research and development. Industrial effluents from these operations
have for some time been discharged onsite into canyons, where the
transuranium nuclides in these effluents soon become attached to soil
particles. It is estimated that less than 1 Ci of transuranic waste
has been disposed of, in this fashion, to Pueblo, DP-Los Alamos, and
Montandad canyons. Liquid effluents are usually absorbed in the
soil so they do not flow beyond the site boundaries, but, during periods
of heavy runoff, storm waters have carried detectable amounts of trans-
uranium elements down the canyons and offsite. Plutonium concentrations
in sediments in the canyons receiving; liquid waste are given in Table
A 1-13 (21).
Concentration levels of plutonium and americium in various
environmental media around the LASL site are given in Table A 1-14
for 1975 (10). During the same year, the Laboratory discharged less
than 0.3 mCi of plutonium to the air; the amount of transuranium ele-
ments discharged in liquid effluents was not published.
38
-------
Table A 1-13
Plutonium in Sediments in the Liquid Waste Receiving
Canyons on the LASL Site - 1975 (20)
Average Plutonium Concentration in dry soil
(a)
Distance from
outfall
(kms)
0
0.6
1.3
2.6
5.1
10.2
Acid Pueblo
Canyon
(pCi/g)
3
10
2
0.4
1
0.2
(Estimated
Canyon Inventory)
(Average Regional Plutonium
Concentration in Dry Soil)
DP - Los Alamos
* Canyon
(pCi/g)
40
1
-
0.2
0.4
-
Mortandad
Canyon
(PCi/g)
220
20
9
11
0.1
0.03
(0.1 to 0.3
curies)
(0.01)
(a) top 5 cm of soil
39
-------
Table A 1-14
Plutonium and Americium Concentrations in Environmental
Media at the LASL Site - 1975 (10)
Ambient Air
Station Location
(Station Number)
On Site
Perimeter
Off Site
22
23
24
25
26
12
14
18
20
1
4
8
(Santa Fe) 11
Pu-239.
(fCi/in )
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
Average Radionuclide Concentration
Surface Water and Water Supplies
Pu-238,
(fCi/in )
1x10
5x10
5x10
-3
-4
-4
5x10
6x10
9x10
r*
-4
1x10
5x10
6x10
-4
7x10
9x10
4x10
.-*
-4
-4
-4
Am-241_
(fCi/in )
3x10
-3
7x10
-3
0.02
1x10
-3
4x10
4x10
4x10
,-3
-3
-3
Average Radionuclide Concentration
Sample Location
Regional Surface Waters
Perimeter Surface and
Ground Waters
Pu-239
(pCi/&)
9xlO~4
8x10"
Los Alamos Water Supply* ' -3x10
.(a)
Pu-238
(pCi/A)
6xlO"4
2xlO~3
-3xlO~4
(a) Negative values are due to statistical fluctuations in the measurement.
40
-------
Table A 1-14 (Continued).
Soils
(a)
Average Radlonucllde Concentration
Pu-239 Pu-238
Sample Location (pCl/g) (pCl/e)
On site 40xlO~3 lxlO~3
-3 -3
Site Perimeter and Regional areas 12x10 0.5x10
(a) Top 5 cms of soil.
41
-------
7. The Trinity Site
The first nuclear device was tested at the Trinity Site, 100
kilometers northwest of Alamogordo, New Mexico, on July 16, 1945.
During 1973 and 1974, the site was surveyed by the U.S. Environmental
Protection Agency to determine the extent of resulting plutonium con-
tamination (22). Figure A 1-12 shows plutonium contours based on
this study. Highest soil activity levels were 0.05, 0.09 and 0.02
2
yCi/m found along arcs 1A, 2 and 3, respectively. The total amount of
o o
plutonium estimated to be within the 3 nCi/m contour (1 nCi/m =
2
0.001 yCi/m ) is approximately 45 curies.
8. Sites of Underground Nuclear Detonations (4)
Table A 1-15 is a listing of underground tests conducted off the
Nevada Test Site (10). Nuclear devices containing plutonium may have
been used but all transuranium elements are believed to be contained.
9. Enewetak Atoll
The Enewetak atoll (23) consists of 40 islands on an elliptical
coral reef-about 3800 km southwest of Honolulu in the northern part of
Micronesia. It was the site of 43 nuclear weapons tests during the
2
period 1948-1958. The total land area is about 7 km , the largest
2
island of which is 1.5 km with land heights above sea level of
3 to 5 meters. There are plans for future rehabilitation and resettle-
ment of the atoll by the Enewetak people who were displaced in 1948.
The soil of many of the islands is highly contaminated with Sr-90,
Cs-137, Co-60 and Pu-239. Plutonium concentrations vary considerably
from island to island, depending upon the locations of the detonations
42
-------
TRINITY SITE
1973-1974 PLUTONIUM
SOIL SAMPLING RESULTS
(nCi/m2)(14)
FIGURE AM 2
43
-------
Table A 1-15
Underground Testing Conducted Off the Nevada Test Site (10)
Name of Test,
Operation or
Project
Project Gnome/
Coach3
b
Project Shoal
Project Dribble
(Salmon Event)
Date Location
12/10/61 48 km (30 mi) SE of
Carlsbad, N.M.
10/26/63 45 kni (28 mi) SK of
Fallen, Nev.
10/22/64 34 km (21 mi) SW of
Hattiesburg, Miss.
Yieldd
(kc)
3.1f
12
5.3
Depth
m
(ft)
360
(1184)
166
(1200)
823
(2700)
Purpose o£
the Event *e
Multi-purpose
experiment.
Nuclear test
detection re-
search experi-
ment
Nuclear test
detection re-
search experi-
ment .
Opergtion Long 10/29/65 Amchicka Island,
Shot Alaska
Project Dribble 12/03/66 34 km (21 mi) SW of
(Sterling Event) Hattiesburg, Miss.
Project Gasbuggy 12/10/67 88 km (55 mi) E of
Farmington, N.M.
Faultless Event0 01/19/68 Central Nevada Test
Area 96 km (60 mi) E
of Tonopah, Nev.
Project Miracle . 02/02/69 34 km (21 mi) SW of
Play (Diode Tube) Hattiesburg, Miss.
Project Rulison 09/10/69 19 km (12 ml) SW of
Rifle, Colorado
Operation Milrow0 10/02/69 Amchitka Island,
Alaska
Project Miracle O/t/19/70 J4 km (21 ml) SW of
Play (Humid Hattiesburg, Miss.
Water)
•v-80 716
(2350)
0.38 823
(2700)
29
200-
1000
1292
(4240)
914
(3000)
Non- 823
mu-lear (2700)
explnti ion
40
^1000
2568
(8425)
1219
(4000)
Non- 823
nuclear (2700)
explosion
DOD nuclear
test detection
experiment.
Nuclear test
detection re-
search experi-
ment .
Joint Government-
Industry gas
stimulation ex-
periment.
Calibration
test.
Detonated in
Salmon/Sterling
cavity. Seismic
studies.
Gas stimulation
experiment.
Calibration test.
DeloiKit i'd In
SaJmuii/Sterl Ing
cavity. Seismic
stud les.
44
-------
Table A 1-15 (continued)
Name of Test,
Operation or
Prolect
Operation
Cannikin
Project Rio
Blanco
Yieldd
Date . Location (kt)
11/06/71 Amchitka Island, < 3000
Alaska
05/17/73 48 km (30 mi) SW of 3x30
Meeker, Colorado
Depth
m
(ft)
1829
(6000)
1780
to
2040
(5840
to
6690)
Purpose of
the Event >e
Test of war-
head for
Spartan
missle.
Gas stimula-
tion experi-
ment.
Plowshare Events
Vela Uniform Events
cWeapons Tests
dlnformation from "Revised Nuclear Test Statistics," distributed on September 20, 1974,
by David C. Jackson, Director, Office of Information Services, U.S. Atomic Energy
Commission, Las Vegas, Nevada.
News release AL-62-50, A£C Albuquerque Operations Office, Albuquerque, New Mexico.
December 1, 1961
"The Effects of Nuclear Weapons" Rev. Ed. 1964.
45
-------
and the fallout patterns that followed. Table A 1-16 gives data on
Enewetak soils (23); the islands most likely to be reoccupied are Fred,
Elmer, David, and eventually Janet. The average plutonium contamination
level in surface soils on Fred, Elmer, and David which were not as
-3 2
heavily contaminated as the northern islands, is 9x10 yCi/m , with a
-3 2 2
range of 0.9 to 70x10 yCi/m ; on Janet the average is 2 yCi/m , with
2
a range of 0.2 to 4 yCi/m .
A limited number of measurements have been made on plutonium and
americium concentrations in surface air and in other environmental
media. These are given in Tables A 1-17 and A 1-18 (23).
10. Other Sites
The following tables show levels of the transuranium elements in
the general environment around other facilities known to use the
transuranium elements in their operations. At this time, the total
amount of the transuranium radionuclides in soils both on and off
such nuclear facility sites is believed to be less than 1 curie.
-------
Table A 1-16
Plutonium Concentration in Soil on Enewetak atoll (23)
Island
(U.S. Occupational Designation)
Pu-239 in top 15 cm of soil
Mean . Range
(pCi/g)'
a. "dense" and "light" refer to vegetation cover
(pCi/g)
Alice
«
Belle dense
light3
Clara
Daisy dense
light
Edna
Irene
Janet
Kate dense
light
Lucy
Mary
Nancy
Percy
Olive dense
light
Pearl hot spot
remainder
Ruby
Sally
Tilda dense
light
Ursula
Vera
Wilma
Yvonne southern
northern beaches
David, Elmer, Fred
Leroy
All others
^ r- •-• — w ^ j
12
26
11
22
41
15
18
11
9
17
2
8
8
9
4
8
3
51
11.
7
4
8
3
1
3
1
3.2
3
0.04
0.6
0.07
xjr***™/ f* J
4-68
7-130
6-26
4-88
22-98
4-33
13-24
2-280
0.08-170
9-50
0.2-14
2-22
2-5
2-28
2-23
2-30
2-4
15-530
1-100
3-24
0.2-130
1-17
1-34
0.3-7
0.6-25
0.1-5
0.02-50
0.3-18
0.004-0.3
0.02-2
0.004-1.1
b.
1 pCi/g in the top 15 cm of soil is approximately equivalent to
0.23 yCi/m2 or 0.045 yCi/m2 if only the top 1 cm of soil is
considered and 20% of the total activity is assumed to be in the
top 1 cm of soil.
47
-------
Table A 1-17
Plutonium and Americium Concentration in Surface Air
on Enewetak Atoll (23)
Radionuclide
Pu-239
Pu-238
Am-241
Location
Runit (Yvonne)
Other islands
Reunlt (Yvonne)
Other islands
Runit (Yvonne)
Other islands
Concentration
fCi/m3
0.03-3
0.001-0.03
0.04-0.13
0.003-0.008
< 0.3-0.3
Not Detected
48
-------
Table A 1-18
Plutonium and Americium Concentrations in Various
Environmental Media on Enewetak Atoll (23)
Media
Sediments
Surface Waters
Coconuts
Birds
Muscle
Liver
Eggs
Coconut Crabs
Location
Lagoon
Lagoon
Ocean (East)
As Found
As Found
As Found
Radionuclide
Pu-239
Am-241
Pu-239
Pu-239
Pu-239
Pu-239
Pu-239
Activity
460 mCi/km^
170 mCi/km2
9-40 fCi/£
0.3 fCi/X,
< 0.022
0.001-0.1 pCi/ga
0.004-0.07 pCi/ga
0.0005-0.02 pCi/g£
0.001-0.01 pCi/ga
(a) dry weight
49
-------
Table Al-19
Environmental Monitoring for the Transuranium Elements
at the Pantex Plant Site
Site: Pantex Plant (10,13,24)
Location: 25 kilometers northeast of Amarillo, Texas
Mission: Atomic Weapons Assembly involving significant quantities
of uranium, plutonium, tritium
Transuranium Elements Released to the Environment
No releases during
Location of
Media Sample Collection
(a)
Air 10 kilometers from
plant in various
directions
25 kilometers from plant
Soil^ ' Off site in various
directions from
the plant
Jackrabbits Onsite
the period
Sample
Station
1
2
3
4
5
6
8
9
10
11
12
31
Different
Stations
11
samples
1973-1975
Average Plutonium
Concentrations - CY 1975
0.03 fCi/m3
0.07
0.03
0.02
0.00 ± 0.01
0.01
0.4
0.00 ± 0.01
0.09
0.5 (1 sample only)
0.00 (1 sample only)
0.00 ± 0.02
to
0.05 ± 0.02 pCi/g
0.00 ± 0.02 pCi/g
(wet) in kidney,
liver, lung, flesh,
and bone
50
-------
Table Al-19 (continued)
(a)
v 'Average air concentrations of plutonium in 1973 ranged from
0.4 to 2 fCi/m3 (10), which is higher than any other site. These high
levels are believed to have been caused by analytical errors.
Soil samples collected to a depth of 5 cm.
51
-------
Table Al-20
Environmental Monitoring for the Transuranium Elements
at Argonne National Laboratory
Site: Argonne National Laboratory (10,13,24)
Location: DuPage County, Illinois, 43 kilometers southwest of Chicago
Mission: Research and Development including chemical and
metallurgical plutonium laboratories
Transuranium Elements Released to the Environment (CY 1975)
To air
To surface waters (Sawmill Creek)
- not published
- 0.1 mCi Pu-239;
0.5 mCi Np-237;
0.05 mCi Am-241;
<0.05 mCi Curium and
Californium
Surface Water
(Sawmill Creek)
Sawmill Creek
Phytoplankton
Des Plains
River
Illinois
River
Soil
(a)
Location of
Sample Collection
Site Perimeter
Offsite
Downstream
from
Outfall
Upstream from Outfall
Downstream from Outfall
Upstream from Sawmill Creek
Downstream from Sawmill Creek
McKinley Woods State Park
Below Dresden Power Station
Site Perimeter
Offsite
Number of
Stations
Av. of 2 Stations
1 station
Av. of 10
Locations
Av. of 10
Locations
Average Plutonium
Concentrations - CY 1975
0.02 fCi/ra3
0.02
5 x 10~* pCi/1 Pu-239
< 3 x 10
4 x 10
4 x 10
< 1
5
10
10
-3
-2
'-3
-3
Pu-238
Am-241
Np-237
Cu-242
Cu-244
2.4 x 10 " PCi/g Pu-239
1.5 x 10 Pu-239
5 x 10~ pCi/1
8 x 10
2 x
3 x 10
2 x 10
1 x 10
2 x W
2 x 10
pCi/1
Pu-239
Pu-239
Pu-239
Pu-239
Pu-239
Pu-238
Pu-239
Pu-238
(a)
Soil samples collected to depth of 30 cm.
52
-------
Table A 1-21
Environmental Monitoring for the Transuranium Elements at
Battelle-Columbus Laboratories (West Jefferson Site)
Site: Battelle Laboratories (West Jefferson Site) (10,13,24)
Location: Columbus, Ohio
Mission; Reactor Fuel Research (Plutonium Laboratory)
Transuranium Elements Released to the Environment (CY 1975)
To air - 1.5 yCi Pu-239
To surface waters - not published
Media
Air
Silt
Grass
Food Crops
Sample Collection Location
(Site Boundary concentration as
calculated using atmospheric
dispersion equations)
Above and Below Outfall
Onsite and Various Locations
Onsite, 3-8 kilometers
Average Plutonium
Concentrations - CY 1975
(4xlO~3 fCi/m3)
<2xlO~2 pCi/g (dry)
<2xlO~2 pCi/g (dry)
_o
Corn, Soybeans, Rye, Vegetables <2xlO pCi/g (dry)
0.4 to 8 kilometers in Various
Directions around Site
53
-------
Site
Location
Mission
Table Al-22
Environmental Monitoring for the Transuranium Elements at
the Idaho National Engineering Laboratory
Idaho National Engineering Laboratory (10,13,24)
Southeastern Idaho; 35 kilometers west of Idaho Falls
Includes - Fuel reprocessing, calcining liquid radio-
active waste,and storage and surveillance of solid
transuranic waste
Transuranium Elements Released to the Environment (CY 1975)
To air - 2 mCi Pu-238, Pu-239, and Np-237
To disposal well - "very small amounts"
Media
Air
Surface Soils
Sample Collection Location
Boundary Stations
Boundary Stations
18 Samples
Distant Location
12 Samples
Average Plutonium
Concentrations-CY 1975
0.02 fCi/m3 Pu-239
0.01 fCi/m3 Am-241
2 ± 2xlO
3 ±
~2
pCi/g
(a)
Samples Collected to Depth of 5 cm.
54
-------
Site
Location
Mission
Table Al-23
Environmental Monitoring for the Transuranium Elements
at the Oak Ridge Facilities
Oak Ridge Facilities (10,13,23)
Oak Ridge, Tennessee
Multipurpose Research Laboratory, Gaseous Diffusion Plant,
and Nuclear Weapons Operations (Y-12 Plant)
Transuranium Elements Released to the Environment (CY 1975)
To air - 4 yCi sum of all transuranium elements
To Clinch River - 20 mCi sum of all transuranium elements
(CY 1973 - 80 mCi; CY 1974 - 20 mCi)
Media
Air
Soil
Water
Sample Collection Location
Perimeter Stations
Remote Stations
Perimeter Stations(a)
White Oak Creek
Clinch River
Average Plutonium
Concentrations-CY 1975
0.014 fCi/m3 Pu-239
< 0.001 fCi/m3 Pu-238
0.013 fCi/m3 Pu-239
< 0.001 fCi/m3 Pu-238
4xlO~2 pCi/g Pu-239
Not published
Not published
(a)
Soil Samples Collected to Depth of 1 cm.
55
-------
Site
Location
Mission
Table Al-24
Environmental Monitoring for the Transuranium Elements
at Hanford
Hanford
Southeastern Washington, 320 kilometers east of Portland, Oregon
Includes Fuel fabrication, liquid waste solidification and
radioactive waste burial. Originally, plutonium for nuclear
weapons was produced here.
Transuranium Elements Released to the Environment (CY 1975)
To air 1 mCi sum of all plutonium elements
To surface waters - 0.9 mCi sum of all plutonium elements
Media Sample Collection Location
Air Perimeter Stations
Distant Stations
Soil Perimeter Stations
Water Columbia River-Upstream
-Downstream
Vegetation Perimeter Stations
Average Plutonium
Concentrations-CY 1975
<0.03 fCi/m3 Total Pu
<0.04 Total Pu
<7xlO~3 pCi/g (dry) Pu-239
<4xlO~4 Pu-238
<0.03 pCi/1 Pu-239
<0.02 Pu-239
<2xlO"3 pCi/g (dry) Pu-239
56
-------
Table A 1-25
Environmental Monitoring for the Transuranium Elements at
the Lawrence Livermore Laboratory
Site Lawrence Livermore Laboratory
Location Alameda County, California, 64 kilometers east of
San Francisco
Mission Research and development on nuclear weapons
Transuranium Elements Released to the Environment (CY 1975)
to air - not published
To surface waters - not published
Average Plutonium
Media Sample Collection Locations Concentrations-CY 1975
Site 300 0.28 fCi/m3 Pu-239
9.0x15" £Ci/mJ Pu-238
Air Perimeter Locations (6) 0.019-0.034,fCi/m3 Pu-239
1.9-9.5x10 Pu-238
Soil(a) Site 300 (11) 0.001-0.03 pCi/g (dry) Pu-239
Livermore Valley (20) 0.001-0.1 Pu-239
Water Reclamation Plant 0.6 pCi/1 Pu-239
Effluents
(a) Soil Samples Collected to Depth of 1 cm.
57
-------
Annex 1
References
1. Wrenn, McD. E., "Environmental Levels of Plutonium and the
Transuranium Elements", in Proceeding of Public Hearings:
Plutonium and the Other Transuranium Elements, Vol 1 (ORP/CSD-
75-2), U.S. Environmental Protectioh Agency, Office of Radiation
Programs, Washington, D.C. (December 1974).
2. Krey, P.W. et.al., "Mass Istopopic Composition of Global Fail-Out
Plutonium In Soil", IAEA-SM/199-39, International Atomic Energy
Agency, Vienna, (1976).
3. Hardy Jr., E. R., "Worldwide Distribution of Plutonium", in
Proceedings of Public Hearings: Plutonium and the Other Trans-
uranium Elements, Vol 1 (ORP/CSD-75-2), U.S. Environmental
Protection Agency, Office of Radiation Programs, Washington, D.C.
(December 1974).
4. Hardy, E., "Depth Distribution of Global Fallout Sr-90, Cs-137 and
Pu-239 (240) in Sandy Loan Soil" in Fallout Program Quarterly
Summary Report (HASL-286) U.S. Atomic Energy Commission, New York,
N.Y. (October 1974).
5. Bennett, B. G. HASL, U.S. Energy Research and Development Adminis-
tration, New York, N.Y., Personnel Communication, (December 1976).
6. Bennett, Burton G., "Transfer of Plutonium From the Environment
to Man" in Transuranium Nuclides in the Environment (IAEA-SM-
199/40).
International Atomic Energy Agency, Vienna (1976).
7. Chart of the Nuclides. Knolls Atomic Power Laboratory Naval Reactor,
U.S. AEC (operated by the General Electric Company) llth Ed,
Revised to April 1972.
8. Krey, P. "Atmospheric Burn-up of a Plutonium-238 Generator, Science,
158 No. 3802 pp. 769771 (Nov. 10, 1967).
9. Erdman, C. A. and A. B. Regnolds, Nuclear Safety 16 43 (1975).
10. "Environmental Monitoring at Major U.S. Energy Research and
Development Administration Contractor Sites - Calendar Year 1975"
(ERDA-76-104) Energy Research and Development Administration,
Division of Safety, Standards and Compliance, Washington, D. C.
(August 1976) 2 Vols.
58
-------
11. Gilbert, R. 0. et. al., "Statistical Analysis of Pu-239(240) and
Am-241 Contamination of Soil and Vegetation on NAEG Study Sites"
in the Radioecology of Plutonium and Other Transuranics in
Desert Environments (NVO-153) U.S. Energy Research and Develop-
ment Administration, Nevada Operation Office, Las Vegas, Nevada
(June 1975).
12. Hardy, E., "Plutonium in Soil Northeast of the Nevada Test Site",
in Health and Safety Laboratory - Environmental Quarterly,
(HASL-306) Energy Research and Development Administration,
New York, N.Y. (July 1976).
13. "Environmental Monitoring Report for the Nevada Test Site and
Other Test Areas Used for Underground Nuclear Detonations -
Jan. through Dec. 1973" in Environmental Monitoring at Major
U.S. Atomic Energy Commission Contractor Sites - Calendar Year
1973, (WASH-1259 (73) U.S. Atomic Energy Commission, Division
of Operational Safety, Washington, D.C. (June 1973).
14. Krey, P. W. "Remote Plutonium Contamination and Total Inventories
from Rocky Flats", Health Physics _30, 209 (1976).
15. " Environmental Monitoring at Major U.S. Energy Research and
Development Administration Contractor Sites - Calendar Year 1974"
(ERDA-54) U.S. ERDA, Division of Operational Safety, Washington,
D.C. (August 1975).
16. Krey, P. W. and Hardy, E. P., "Plutonium in Soil around the Rocky
Flats Plant in Fallout Program Quanterly Summary Report (HASL 235)
U.S. Atomic Energy Commission, New York, N.Y. (1974).
17. Werkema, G. J. and M. A. Thompson, "Annual Environmental Monitoring
Report Rocky Flats Plant" in "Proceedings of Public Hearings:
Plutonium and the Other Transuranic Element, Vol. 2", ORP/CSD-75-1,
U.S. Environmental Protection Agency, Office of Radiation Programs,
Washington, D. C. (Jan. 10, 1975).
18. Rogers, D. R., Mound Laboratory Environmental Plutonium Study-1974,
(MLM-2249) Mound Laboratory, Miamisburg, Ohio (September 1975).
19. U.S. Environmental Protection Agency, National Environmental Research
Center, Cincinnati, Ohio. Letter to Mr. Gary Bramble, State of
Ohio, Environmental Protection Agency, from Bernd Kahn (Oct. 1, 1974).
20. McLandon, H. R., "Soil Monitoring for Plutonium at the Savannah
River Plant," Health Physics .28, 347 (1975).
21. "Annual Report of the Biomedical and Environmental Research Program
of the LASL Health Division - Jan. through Dec. 1974" (LA-5883-PR)
Los Alamos Scientific Laboratory, Los Alamos, New Mexico (Feb. 1975).
59
-------
22. Douglas, R. L. (Report in Press) U.S. Environmental Protection
Agency, Office of Radiation Programs, Las Vegas, Nevada.
23. "Cleanup, Rehabilitation, Resettlement of Enewetak Atoll - Marshall
Islands (Final EIS) Defense Nuclear Agency, Washington, D. C.,
4 Vols. (April 1975).
24. "Environmental Monitoring at Major U.S. Atomic Energy Commission
Contractor Sites - Calendar Year 1973" (WASH-1259) U.S. Atomic
Energy Commission, Division of Operational Safety, Washington,
D.C. (June 1973).
60
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ANNEX II
ENVIRONMENTAL TRANSPORT AND PATHWAYS
U. S. Environmental Protection Agency
Office of Radiation Programs
Washington, D.C. 20460
-------
Annex II
Contents
Page
1. Objective 1
2. Environmental Transport 2
2.1 Aerosol Transport 2
2.2 Soil Transport 8
2.3 Aqueous Transport 10
3. Exposure Pathways 11
3.1 Inhalation , 12
3.2 Ingestion 16
4. Methods of Relating Soil Concentration to
Airborne Activity 18
4.1 Resuspension Factor 18
4.2 Mass Loading 19
4.3 Resuspension Rate and Other Approaches 23
5. Derivation of the Screening Level for Soil 25
5.1 Enrichment Factor 26
5.2 Correction for Area Size 29
5.3 Calculation of the Soil Screening Level 30
REFERENCES 36
-------
1. Introduction
The purpose of this annex is to provide a brief overview of the
transport of the transuranium elements through the environment and the
subsequent exposure pathways which might occur as a result of their
release into the biosphere. Availability, uptake, and translocation
of the transuranium elements within the ecosystem depend upon many
factors. Included among these are: the mode of release (e.g.,
accidental fire or spillage), the physical form upon release (e.g.,
particulate or liquid), the chemical form (e.g., elemental, oxide, or
nitrate), and the nature of the environment being contaminated (e.g.,
desert soil or aqueous media). Also important is people's use of the
environment which can significantly affect the mobility of the trans-
uranium elements and, subsequently, their effect upon exposed popula-
tions. Because there are so many variables, potential pathways of
exposure should be evaluated on a site-by-site basis. However, some
general conclusions can be made based upon present knowledge of the
environmental behavior of these elements although it is limited.
For a terrestrial ecosystem, the major environmental transport
pathways are illustrated in Figure A 2-1. These pathways include:
1) exchange between air and soil, water, and vegetation as a result of
deposition and resuspension, 2) exchange between soil and water by
erosion, leaching, absorption, and precipitation and 3) uptake from air,
soil, and water by plants, animals, and man. Highlighted in Figure
A 2-1 are the pathways expected to produce the principal exposures to
people, which will be discussed in greater detail in the following
sections.
-------
PRINCIPAL PATHWAYS OF THE TRANSURANIUM ELEMENTS
THROUGH THE ENVIRONMENT TO MAN
RGURE A2-1
-------
2. Environmental Transport
2.1 Aerosol Transport
Airborne releases of the transuranium elements result from both
normal and accidental occurrences. Normal operational releases are
small and are expected to decrease in the future due to improvements in
containment. At present, doses from normal releases are below the
limits recommended in this guidance.
Accidental releases — such as those resulting from transportation
accidents and fires — can lead to localized contamination, and would
probably necessitate some form of protective and remedial action.
Generally accidental releases of the transuranium elements will be as
the element, the oxide, or in liquid form. When the release is in the
form of the element, it will convert rapidly to the oxide form, which is
relatively insoluble and stable thermodynamically. Airborne releases of
the transuranium elements will generally be as an oxide containing a
substantial percentage of particles with diameters less than 10 vim.
This is the size range roughly corresponding to the respirable range of
particle sizes. Because of the small settling velocities associated
with such particles they can be transported long distances by air
currents before depositing on the ground as a result of wet and dry
deposition. These particles then will become incorporated into soil and
aquatic systems. When deposited on soil, the aerosol particles can
attach themselves to the larger, less mobile soil particles. For
example, Mork (1) found that plutonium at test sites was usually
-------
bound to soil particles with a diameter greater than 44 ym. Likewise,
Tamura (2) has analyzed the plutonium bound to soil particles at the
Nevada Test Site and showed that the plutonium bound to coarse
particles (5-20 ym) was present as PuO^, while the plutonium bound
to fine particles (2-5 Mm) was present as hydrated PuO~.
Subsequent transport will be as a result of wind and mechanical
forces which transfer their energy to the surface particles causing them
to roll, slide or even become airborne. The smaller the particle dia-
meter the greater will be the tendency for the particle to stay airborne
and the greater will be the distance that it will travel before return-
ing to the surface. Some of the many factors which can influence the
redistribution of surface particles by wind are listed in Table A 2-1.
The multiplicity of factors and their complex interrelationship makes
the prediction of soil resuspension and transport a very complex
problem. Accordingly, the resuspension of soil particles has been the
focus of much research over the past several years.
One of the more commonly used indexes of resuspension has been
the concept of a resuspension factor which is defined as the ratio of
the air concentration to soil concentration (units; meters ). A
wide range of values has been reported for resuspension factors which
covers a variety of surfaces and modes of disturbance. Table A 2-2
is a summary of some values reported (3) for newly deposited PuO«
released during weapons testing. Such a wide range of values makes
the prediction of the resuspension factor for a particular set of
-------
Table A 2-1
Factors Influencing Wind Suspension
AIR GROUND SOIL
Velocity Roughness Structure affected by:
Turbulence Cover Organic Matter
Density affected by: Obstructions Lime Content
Temperature Temperature Texture
Pressure Topographic Features Specific Gravity
Viscosity Moisture
SURFACE PROPERTIES
Large-scale surface roughness
Mechanical turbulence
Overall sheltering
Small-scale surface roughness
Sheltering of individual particles
Area of credible surface
Vegetative cover
Live vegetation
Plant residue
Cohesiveness of individual particles
Moisture of surface
Binding acting of organic materials
PARTICLE PROPERTIES
Particle size frequency distribution
Ratio of credible to nonerodible fractions
Particle density
Particle shape
METEROLOGY FACTORS
Wind velocity distribution in the surface layer
Mean wind speed
Wind direction
Frequency, period, and intensity of gusts
Vertical turbulent exchange
Moisture content on ground surface
Precipitation
Dew and frost
Drying action of the air
-------
Table A 2-2
Short Summary of Experimental Results on Resuspension
of activity in the Air [After Stewart (1967)]
Measurement Conditions
Resuspension Factor, R-(i
Range Mean
Plutonium sampled at 1 ft above
ground (1)
Vehicle traffic
Pedestrian traffic
Particle size: Mainly 20-60 urn,
with 1% in hazardous range
(^ 3 ym for PuO_)
Uranium sampled downwind from a
crater (1)
At 1 ft. above ground (dust stirred up)
At 1 ft. above ground
At 2 ft. above ground
Brick/plaster dust sample contaminated
with 1-131 (2)
Enclosed space
Open space
Sample in cab of Landrover, after
a test (1)
Round 1 (H + 18 hr)
Round 2 (H + 5 hr)
Airborne material without artificial
disturbance of ground, consisting of
limestone rock and sand with coarse
grass and small bushes (3)
Random samples following a tower shot,
without artificial disturbance,
near crater (3)
On two roads formed by soil grading
-no artificial disturbance (3)
At back of a moving Landrover (3):
D-Day + 4 (21 results)
D-Day + 7 (21 results)
D-Day + 7 over tailboard
3xlO~£ to 7xlO~*
1.5xlO~° to 3xlO~4
2xlO~4 to 4xlO~5
lxlO~6 to 8xlO~5
(12 results)
IxlO"8 to lxlO~6
(9 results)
1x10
3x10
1x10
-3
-4
-5
2x10
-6
2.5x10
6.4x10
-5
-5
1x10
-5
2x10
-7
1.5xlO~6 to lxlO~8 2.5xlO~7
(14 results)
8xlO~7 to 3xlO~g 1.4x10
6xlO~ to 4x10 1.5x10
1.6 and 3.1x10 2.5x10
~5
(1) From nuclear weapon and other tests at Maralinga
(2) From Civil Defense trial at Falfield, Gloucester
(3) From Hurricane Trial
-------
conditions a difficult task. In general, however, values for newly
deposited material seem to fall in the range 10~ (m~ ) to 10 (m )
under conditions of low mechanical disturbance. In areas where the
surface is rocky or paved, the resuspension factor may range up to
-3 -1
10 (m ) due to these smoother, harder surfaces and because little
mixing with noncontaminated surfaces occurs (A). Mechanical disturb-
ances, such as vehicular traffic, will also increase the resuspension
factor by as much as a factor of 10 to 100 (5).
For planning purposes, Stewart (3) and others (6) have recommended
a resuspension factor of 10 (m ) for freshly deposited material under
quiescent conditions but recommended increasing this value to 10 (m )
if there is moderate vehicular or other disturbing activity. As the
freshly deposited material becomes aged, fixed to the soil or mixed with
the soil, the characteristics of the contaminant approach the resuspen-
sion characteristics of the soil itself. On the basis of empirical
information, a model has been proposed (7) in which the resuspension
-5 -1 -9 -1
factor decreases from 10 (m ) to 10 (m ) within two years. Bennett
has reportedly (8) estimated that in a humid eastern climate the
resuspension factor reaches 10~ (m~ ) to 10~ (m~ ) after the first good
-9 -1
rain or wet down and then rapidly decreases to 10 (m ). If the trans-
uranium material is released as a solution rather than as the oxide, its
resuspension will probably be in the low range (see Section 2.2).
Experiments (3) with yttrium chloride solution sorbed onto soil have
—9 —1
indicated a resuspension factor of 10 (m ), while measurements at
-------
Mound Laboratory (4) of Pu-238 released from a waste transfer line
produced resuspension factors in the range of 10 (nT1) to IcT^m"1).
Because of the propensity for greater mobility on the part of
freshly deposited material, stabilization of newly contaminated land
should be undertaken as soon as possible after the initial accident
in order to reduce the resuspension and inhalation exposure. In
addition to the benefit of reducing the hazard from inhalation, prompt
stabilization of the contamination should result in lower cleanup costs.
This lower cost arises from the fact that dispersion of the material is
being minimized through stabilization and, therefore, less land area
will be impacted and require cleanup.
2.2 Soil Transport
Soil contamination by plutonium has been the most prevalent
situation encountered and, therefore, is the most widely studied. Plu-
tonium dispersed onto soil has demonstrated a tendency to bond chemically
and/or physically with the soil rather than exist as a separate entity
(4,9,10,11,12). Plutonium oxide is relatively inert and initially
attaches itself to the soil matrix as a result of adhesive forces
established between the plutonium particle and the soil substrate. Over
a period of time, weathering processes such as freezing, thawing, and
precipitation, will begin to "solubilize" the oxide.
Although generally considered to be insoluble, plutonium oxide can
undergo dissolution in a neutral aqueous media. The plutonium oxide
particle dissolves producing plutonium ions until the formation of a
hydrated coating inhibits further dissolution. The rate and degree of
8
-------
dissolution depends on many factors including pH, temperature, the
presence of oxidizing, reducing, and complexing agents, as well as the
238
specific activity of the radionuclide. The dissolution rate of PuO.,
for example, has under certain circumstances been found (13) to be 100
239
times greater than that of PuO_. Plutonium ions formed during the
dissolution can undergo ion exchange reactions with the oxygenated
ligands commonly found in soil (e.g., silicates) and become sorbed
onto the soil, or react with other agents present in the aqueous phase-
and form soluble complexes. Chemicals that complex the plutonium
compete with the silicate particles for the plutonium and tend to reduce
the extent of plutonium sorptlon on soil.
When plutonium is released to soil as a solution (e.g., as a
nitrate) it will already be in ionic form and, in such situations, has
been shown (4) to react rapidly with soil. Plutonium ions are capable
of displacing most cations (e.g., calcium, magnesium, sodium, etc.)
generally found in soils and of forming strong chemical bands. Several
studies (2,14,15) have shown that, after sorption of plutonium has
occurred, it will not be readily displaced from the soil by natural
processes.
Once in the soil, the transuranium elements can be depleted through
the migration of particles down through the surface or through the
resuspension of a fraction of the material back into the air stream. Of
these two mechanisms, the resuspension of soil particles, with which
these nuclides have associated in one form or another, will be the
principal mode of further environmental transport. The resuspension of
-------
soil particles occurs as a result of wind action and more
intermittently as a result of mechanical forces; such as, plowing and
vehicular disturbances.
The size of the particle will determine its distance and mode of
\
transport. Particles with diameters greater than 1000 pm generally
slide or roll along the surface (creep), while particles with diameters
in the range of 50 pm to 1000 pm move in short hops along the surface,
usually at a small distance from the surface (saltation). The suspen-
sion of particles is generally restricted to those below 50 pm, which
will be carried along with the air stream.
2.3 Aqueous Transport
Studies have been conducted on various water bodies, streams,
rivers, lakes, estuaries and oceans to determine the final disposition
of plutonium in these environs. The following behaviors have been
noted:
(1) More than 90% of the plutonium becomes bound to
suspended sediments and carried to the sediment bed.
(2) Situations where reducing and complexing agents are both
present can lead to resolublization of the plutonium in the sediment
bed.
(3) Seaweeds generally have the ability to concentrate plu-
tonium with concentration factors of ^ 1000.
(4) Benthic biota can alter the plutonium concentration
profiles in the sediment beds.
Specifically, plutonium oxide exposed to an aqueous medium
undergoes slow dissolution, producing various complex ions of plu-
tonium as well as polymers in colloidal form and the hydrous oxide as a
precipitate (13). In 1972 Langham (16) studied the fate of PuO.
10
-------
following the Thule incident and found that the majority of the
plutonium agglomerated into inactive debris with only about 1% suspended
as fine particulates in the water. Further studies (17) after the Thule
incident showed 95% of the plutonium to be associated with the bottom
sediments to a depth of at least 10 cm. In addition, a study (18) of
nuclear waste discharged into the Irish Sea from Windscale has found
most of the Pu-239 and Am-241 to be associated with the sediments close
to the discharge area. Similar findings were observed (4) around Mound
Laboratory where plutonium was accidentally discharged into a freshwater
canal. Again the plutonium was found to be largely associated with the
bottom sediments. Therefore, although the movement of the transuranium
elements through aqueous systems is not yet well defined, the present
information available would indicate a limited mobility for environ-
mental transport via such systems.
3. Exposure Pathways
The principal hazard that arises as a consequence of soil being
contaminated with the transuranium elements is exposure to radiation
through the inhalation and ingestion pathways.
For a detailed discussion of the entry of plutonium and other
actinides into animals and man and the resultant biological behavior,
the reader is referred to ICRP Publication 19 (19) and Annex III of this
document. The following section will be limited to a description of
the environmental factors affecting the inhalation and ingestion
pathways.
11
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3.1 Inhalation
Inhalation exposures arise from direct injection of transuranium
radionuclides into the atmosphere (e.g., normal emissions and accidental
fires) and also from the resuspension of previously deposited material.
For the latter pathway, only a very small fraction of the material on
the surface actually becomes airborne and available to man. In general,
the respirable size is considered to be that range -of particles with
aerodynamic diameters less than 10 urn.
An assessment can be made, using dosimetry models, of the
potential health hazard resulting from the inhalation of airborne
particles. Such a model requires knowledge of the total airborne
activity and of the activity median aerodynamic diameter associated with
it. (Aerodynamic diameter is the diameter of a unit density sphere
having the same settling velocity as the particle in question of what-
ever shape and density.) The assumption made by most dosimetry models
is that the aerosol distribution is log normal and can, therefore, be
described through the use of two parameters - the activity median aero-
dynamic diameter (AMAD) and the geometric standard deviation of the
distribution, a . The PAID code used by EPA (see Annex III) assumes
o
0 to be 1.5 and, therefore, only the AMAD of the distribution need be
O
determined.
In determining the AMAD of the distribution, care should be
exercised to assure that the entire distribution is being measured.
Aerosol sampling is complicated by the fact that every sampler has its
12
-------
own characteristic upper size cut-off, which depends on its entry shape,
dimensions, and flow rate. When the aerosol being sampled contains
large particles with activity associated with them, the gross air
activity being measured may be underestimated. Likewise, sampling
techniques may be biased against the smaller particle sizes. If
particles from the resuspending soil have a disproportionate amount of
activity associated with them, the inhalation hazard could be under-
estimated. Therefore, sampling should be conducted so that (1) the
total airborne distribution is being measured, and (2) the AMAD
determined actually describes the corresponding distribution of
airborne activity.
Healy (20) and others (21) have emphasized the necessity of
considering the resuspension of soil by mechanisms other than normal
wind activity. The possibility exists that other mechanisms could,
under certain circumstances, produce exposures exceeding those normally
received via the resuspension pathway. Although this possibility has
been recognized, relatively little experimental data is currently avail-
able to determine quantitatively the importance of the many possible
secondary resuspension mechanisms. Two commonly encountered disturb-
ances (agricultural operations and vehicular disturbance) have recently
been investigated, however, and some conclusions can be drawn from these
studies.
For the agricultural situation, the vicinity of a field
contaminated over a period of twenty years was monitored. Increase in
airborne activity was measured during such activities as plowing,
13
-------
disking, and planting (22). During these operations, the air activity
was found to increase by a factor of approximately 30 at the location of
the tractor operator and by a factor of 6 at a distance 30 meters away
from the edge of the field. Assuming that these activities take place
30 days of the year for 8 hours each day (i.e., -rr- of the year), it can
be calculated that the average yearly air activity will increase by 80
percent for the tractor operator and 10 percent for an individual in the
vicinity of the field. For the individual at the edge of the field,
this is a conservative calculation, since it is doubtful that any one
individual would be standing at that location for the entire period of
time. Also, this level of increased air activity should occur for only
the first year. Subsequent agricultural activities should generate
lower air concentrations, because the activity originally on the sur-
face will be diluted through mixing with soil previously below it.
The conclusion that can be drawn from such an analysis is that
these agricultural operations would pose an increased inhalation hazard
to the vehicle operator during the first cultivation cycle, and some
protective action might be in order during that time. Subsequent
cultivation, however, should not lead to significant increases in the
inhalation hazard. For surrounding areas, no significant inhalation
hazard would be predicted during any of these operations.
Regarding vehicular disturbances, Sehmel (5) has examined the
importance of auto and truck traffic in increasing resuspension. It
was concluded that such disturbances, in the case of an asphalt surface
-------
with newly deposited material, will lead to increased resuspension,
with a fraction resuspended of the order of 10~5 to 10~2 per vehicle
passage. The higher rates occurred at speeds typical of freeway
driving; after the passage of about 100 cars only a small fraction of
the original contamination would remain on the road surface. The
material resuspended from the road surface deposited on the ground at
various distances from the road and was again available for resuspen-
sion, but at a much lower rate.
The potential for increased exposures from such situations will
depend upon many factors in addition to the quantity of contaminating
material, including the time of exposure, the frequency of vehicular
passage and the speeds, and the distance from the road to the receptor.
Based upon Sehmel's experiment, it can be expected that the integrated
inhalation exposure due to the vehicular disturbance will be smaller
than the chronic exposure received from just living within the generally
contaminated area. The material deposited on the road surface will be
depleted quickly and, once it is removed from there, its resuspension
will be orders of magnitude lower. Sehmel's results indicate that the
material transferred to the road parking strip resuspends at a rate only
one tenth of that on the road itself. In addition, the total quantity
of material resuspending at the higher rate would be small relative to
the surrounding area; once redistributed over the larger area, it should
show little increase in the average air concentration.
15
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3.2 Ingestion
Under normal circumstances, exposures via ingestion will arise from
the consumption of crops and animals grown on land contaminated by the
transuranium elements. Studies to date have assessed the ingestion
pathway from two directions. Some studies have looked at the uptake
factors for various plant species grown in contaminated soils, while
others have measured the residual amounts of fallout plutonium in
processed foods.
Two recent publications (23,24) have conveniently tabulated the
results of the many uptake studies performed on plutonium and other
transuranium elements. These studies have shown plant and animal
uptakes to be very small, with the concentration in plants (fresh
weight basis) being generally less than 10~ of that in dried soil
and the concentration in animal tissue (fresh weight) being about
10 of that in the plants they eat. Preliminary studies (23) of
transuranium elements other than plutonium produced uptake factors
somewhat higher than comparable studies with plutonium. Some initial
studies (25,26) seem to indicate an increase in uptake with time,
possibly as a result of bacterial action or increased solubilization.
The use of chelating agents as a part of agricultural practices may
also increase the uptake of the transuranium elements with time (27).
Measurements of plutonium in "market basket" food samples, in
which proportions of processed foods are chosen to represent the annual
total diet, can be used (28) as indicators of the quantity of plutonium
ingested. Such findings apply to a given soil contamination level when
16
-------
all consumed food is grown on contaminated lands. The methodology gives
an overestimate of activity ingested, because foods from other areas not
as highly contaminated will make up part of the diet. These studies
have observed uptake factors for plutonium in the range of 10 plus
or minus an order of magnitude. Based upon such uptake factors and food
consumption estimates, the annual estimated intake during 1972 of fall-
out plutonium was 1.6 pCi while the intake for 1965 was estimated to be
2.6 pCi. There is no reason to believe that the uptake factors for
crops grown on land with concentrations higher than fallout levels
should vary significantly from those obtained through this "market
basket" sampling technique. Some evidence indicates that americium is
concentrated in certain species of plants relative to plutonium.
However, preliminary analyses (29) of the "market basket" samples
indicate that the Am 241/Pu 239 ratios in diets are not greatly
different from current Am 241/Pu 239 ratios in soil.
The ingestion of plutonium through drinking water is another
possible pathway to humans. The concentration of fallout plutonium in
finished drinking water has been found (28) to be low (3 f Ci/Jl).
However, in areas of elevated levels, plutonium could migrate over-
time into cisterns and wells, thus increasing the activity in drinking
water. Likewise, it has been suggested (20) that a significant inges-
tion pathway could be the accidental ingestion of contaminated soil by
adults or the deliberate ingestion of soil by children. However, for
this pathway to be as significant as the inhalation pathway, extreme
assumptions of soil consumption rates would be required because of the
17
-------
low uptake factors and short residence time of plutonium in the
gastrointestinal tract.
4. Methods of Relating Soil Concentration to Airborne Activity
The relationship between soil and air concentrations is affected by
many complex factors (see Table A 2-1). Attempts to derive values for
them have resulted in many different approaches; each uses different
concepts and methods of measurement, selecting some physical factors as
important and tending to neglect others or include them as constants.
The purpose of this section is to describe briefly some of the more
commonly used approaches to relate soil contamination levels to airborne
radioactivity.
4.1 Resuspension Factor
One of the earliest and still most widely used methods of
predicting the relationship between soil and air contamination is the
resuspension factor. It is defined as the ratio of the plutonium
concentration in air, measured at some distance above the ground, to
that of plutonium in the soil:
K/m~l\ = concentration in air (activity/m ) Eq. 1.
concentration in soil (activity/m )
The resuspension factor, however, does have limitations in its
application. In the first place, it assumes that the air concentra-
tion above a contaminated surface is directly proportional to the
surface contamination level, rather than on the extent of ground con-
tamination upwind of the sampling site which is indeed the case. In
the second place, the resuspension factor is an empirically determined
18
-------
value which can be applied only to prevailing conditions at a given
site and at a given time. Most resuspension experiments have been
conducted for a relatively short duration of time and do not neces-
sarily represent the long-term average situation for a particular area.
Finally, applying a resuspension factor derived at one particular site
to predict airborne contamination levels at another site would be a
questionable extrapolation. However, for areas where the resuspension
factor has been measured over a period of time, sufficiently long to
average out the variability of the local meteorology, then this approach
can be useful in assessing the potential hazard from existing soil
contamination.
4.2 Mass Loading
One attempt to increase the capability of predicting soil
resuspension has been the mass loading approach. This technique
assumes the mass loading of the air with particulates to be an index of
resuspension and derives the airborne concentration of a specific radio-
nuclide by a comparison with its concentration on the adjacent surface.
Specifically,
Air Concentration (fCi/m3) = Soil Concentration (yC1/m2) x
Mass Loading (yg/m3) x C.F.* Eq. 2.
Airborne particulate mass loading Is one of the criteria for clean
air standards and measurements are widely available for urban and
* where C.F. is the units conversion factor based upon the depth of
sampling and the soil density.
19
-------
nonurban locations through the National Air Surveillance Network (NASN).
The data recorded at nonurban stations are a better indicator of the
levels of resuspended material than are urban measurements. In general,
annual mean mass concentrations of airborne particulate material at the
nonurban stations range from 5-50 micrograms per cubic meter (see Fig.
A 2-2); the mean arithmetic average for 1966 of all 30 nonurban NASN
stations was 38 ng/m3^30\
Anspaugh (30,31) employed this model to predict air concentrations
at a number of sites. Predicted values did not exceed measured values
by more than a factor of roughly five (Table A 2-3). This fallacy of
the model is in assuming that the resuspendible fraction of the soil
would carry with it an equal fraction of the activity, which implies
essentially that: 1) activity is distributed hpmogeneously in the top
soil and, 2) activity exists independently of particle size. For
instance, if the specific ground activity is associated mostly with
particles of size greater than 50 ym, a very small air concentration
would result, although the model would predict the same air concentra-
tion for this case as it would for all the activity being distributed
among particles of resuspendible size. In either case the model would
fail. Data obtained (2,4,15) at sites of present contamination have
shown a non-uniform distribution of activity with particle size,
probably caused by such factors as: 1) the chemical form of the plu-
tonium when released 2) the ion exchange capacity of the soil and
3) the surface area of the soil particles. It would seem reasonable,
however, that the error associated with using the mass loading
20
-------
.3° 20
'50
3O
ANNUAL MEAN MASS CONCENTRATIONS (jug/m3) OF AIRBORNE
PARTICLES FROM NON-URBAN STATIONS OF THE U.S. NATIONAL
AIR SAMPLING NETWORK. 1964 - 1965
FIGURE A2-2
21
-------
Table A 2-3
OBSERVED AIR CONCENTRATIONS COMPARED WITH CONCENTRATIONS PREDICTED
BY MASS LOADING MODEL [ADAPTED FROM ANSPAUGH ET AL. (1974) AND
ANSPAUGH ET AL. (1974)]
Air Contentration
Location, etc.
GMX site. USAEC Nevada
Test Site
NE, 1971-1972
GZ, 1972, 2 weeks
Lawrence Livermore
Radionuclide
Predicted£
239
239
Pu
Pu
7200 aCi/m"
120 fCi/m3
Measured
6600 aCi/m"
23 fCl/m3
Laboratory
1971
1972
1973
1973
Argonne National
Laboratory
1972
1972
Button, England
1967-1968
Q
Predicted value is
10~4 g/m3.
238U
238U
238U
40K
232Th
natu
Mtu
equal to the soil
150 Pg/m3
150 pg/m3
150 pg/m3
1000 aCi/m
320 pg/m3
215 pg/m3
110 pg/m3
concentration
52 pg/m3
0
100 pg/m
86 pg/m3
3 980 aCi/m3
240 pg/m3
170 pg/m3
62 pg/m3
(activity/g) x
Most values are annual averages.
22
-------
approach would be least for soils in which the contaminant has been
present for some time and in making predictions of average annual
air concentrations.
4.3 Resuspension Rate and Other Approaches
Other approaches of a more sophisticated nature have been
developed to describe the resuspension of particles from a soil
surface. These approaches have attempted to include in their for-
mulations as parameters some of the physical forces which control
the resuspension phenomenon. One such technique proposed by Healy
and Fuquay (32) is the resuspension rate approach. This model
combines atmospheric transport and diffusion along with particle
resuspension to calculate airborne concentration. This is achieved
by assuming that the rate of pickup of particles from a surface is
directly proportional to the ratio of wind forces to gravity forces
on individual particles. Taking the wind force on a particle as
proportional to the square of the wind velocity and to the particle
area exposed to wind, the model develops a formulation for the resu-
spension rate, i.e., the rate at which particles will be resuspended
by wind from a* soil surface. Once the resuspension rate has been
determined it can be used as the source term in a standard atmospheric
diffusion equation to predict the resultant air concentration at some
distance from the contaminated site. Recently, Healy (20) has refined
the model formulations to be capable of handling various geometric
configurations of the contaminated area and the variability of surface
concentration within the contaminated area. The advantages of a model
23
-------
of this type are that it recognizes some of the physical conditions
and processes which affect resuspension as well as providing a method
to calculate air concentration at various distances away from the
contaminated area.
One assumption by Healy in the original formulation of the
resuspension rate model (20) was that the pickup rate for particles is
a function of the square of the wind velocity. Presently, studies are
being conducted by Sehmel to establish the relationship between resu-
spension rate and wind velocity. One such study conducted by Sehmel
(33) at Rocky Flats, for short time periods and for one sampling
station, found the air concentration to be a function of the square of
the wind velocity implying that the pickup rate was a function of the
cubic power of the wind speed. However, other experiments by Sehmel
(34) have shown resuspension rates to increase with wlndspeed to the 6.5
power. Studies are continuing to better elucidate this functional
relationship.
Other approaches (35,36) are also under development which attempt
to relate particle resuspension to such factors as the soil erodibility
index, surface roughness factor, and quantity of vegetative cover-to
mention just a few. These models generally require the determination of
several empirical constants in their formulation. Although these
constants may be applicable for the conditions under which they have
been measured, the general applicability of these formulations in
predicting air concentration has not been demonstrated at this time.
24
-------
5. Derivation of the Screening Level for Soil
A screening level for soil has been derived to minimize the area
around a contaminated site which must be monitored as well as the number
of soil samples which must be collected and analyzed. When the trans-
uranium activity in soil is at or below this concentration, it is highly
unlikely that the exposure levels recommended in this Guide will be
exceeded. The screening level is not to be interpreted as a soil cleanup
standard to which all sites of transuranium contamination must be
decontaminated; instead, when correctly applied, it will identify land
areas where no additional monitoring is required. Because of the con-
servative assumptions that have been incorporated into the calculation
of the screening level, it is anticipated that present and future
contaminated sites will not require cleanup to the screening level.
The screening level was derived after careful consideration of all
currently contaminated sites, placing particular emphasis on areas for
which enough site-specific data is available covering factors as
particle size and soil activity distributions. After examing these
data, a hypothetical site was defined with a combination of parameters
chosen to be conservative, i.e., to produce an acceptable level of
transuranium activity more restrictive than that which would be derived
for any of the existing sites. This conservative approach has been
taken due to the uncertainties inherent in any calculational model,
and because of the limited experience with contamination by the trans-
uranium elements. Sites of future contamination are also likely to have
site characteristics which would permit levels of contamination higher
than the screening level.
25
-------
Of the various models that have been suggested for relating soil
contamination levels to airborne concentrations, the Agency has opted
to use the mass loading approach in deriving a soil screening level.
This approach has been shown (30,31) to provide some capability in
predicting air concentrations on an annual basis at existing con-
taminated sites and, since the objective of this Guidance is to
relate soil contamination levels to annual dose levels, annual average
air concentrations are required. Additionally, since the screening
level is a generic value with application at all sites, the Agency
chose not to use one of the more sophisticated resuspension models
requiring detailed site-specific parameters such as wind speed, atmo-
spheric stability class, soil erodibility index, etc. In applying
the mass loading model to calculating a soil screening level, some
modifications have been made, however, in an effort to overcome some
of the shortcomings which are fundamental to the approach and which
were discussed earlier (Sect. 4.2).
5.1 Enrichment Factor
In an effort to take into consideration the non-uniform
distribution of activity with soil particle size as well as the
non-uniform resuspension of particle sizes, the Agency has derived
an "enrichment factor" which is included in the mass loading
calculation. Potential exposure due to contaminated soil depends
largely on the amount of activity associated with particles in the
respirable size range (generally < 10 ym). It has been suggested by
Johnson (21) that sampling of only those particles in a soil sample
26
-------
which are within the inhalable size range would give the best measure of
risk to the public health. However, the weight fraction of particles in
the less than 10 ym range is small in most soils, and sampling, separa-
tion, and analysis techniques are correspondingly more difficult and
inaccurate. There is also considerable evidence that some of the larger
particles really consist of aggregates and are relatively easily broken
down into smaller ones, so that an instantaneous measurement of a single
size range may not give a good picture of long-term trends. Another
important objection to limited sampling is that larger particle sizes
may make a substantial contribution to other possible pathways (e.g.,
ingestion), and hence should be measured.
To assess the potential hazard of the inhalable fraction of soils,
while retaining the advantages and convenience of analyzing the entire
soil sample, the Agency has modified the mass loading approach by use of
an "enrichment factor". The proposed method weights the fraction of the
activity contained within the respirable range in terms of its deviation
from the activity to mass ratio for the entire sample and at the same
time addresses the problem of the nonuniform resuspension of particle
sizes mentioned in the previous section.
The inhalable fraction of the soil is weighted by considering the
relative distribution of activity and soil mass as a function of
particle size for representative samples of soil. To accomplish this,
the sample of contaminated soil is segregated into size increments and
the activity and mass contained within each size increment is
determined. The factor g± is then defined as the ratio of the fraction
27
-------
of the total activity contained within increment i to the fraction of
the total mass contained within that increment. A value greater than 1
for g± implies an enrichment of activity in relation to mass within that
incremental fraction, while a value less than 1 indicates a dilution of
the activity with respect to mass. For gi equal to 1, the fraction of
the activity and the mass contained with increment i are the same.
The nonuniform resuspension of particle sizes must also be con-
sidered. This is achieved in the modification of the mass loading
calculation by measuring the mass loading as a function of particle
size. The fraction of the airborne mass contained within each size
increment, i, is then calculated and designated as f . The factors of
fi and g± can then be incorporated into the mass loading formulation as
follows:
Air Concentration^^ = Air Mass Loading xf±x Soil Concentration xg± Eq.3.
Summation over all the size increments results in the total air
concentration:
Air Concentration = Air Mass Loading x Soil Concentration
X I fi*i Eq.4.
The term £ f g weights the contribution of the
i1 X
Plutonium from each soil size fraction to the total resuspended material,
thereby taking into account both the nonuniform resuspension of particle
sizes as well as the nonhomogeneous distribution of activity.
28
-------
For purposes of this guidance, E f g. will be referred to as the
i 1
"enrichment factor" where the f factor accounts for the distribution of
airborne mass as a function of particle size and the factor g accounts
for the variability of both soil activity and soil mass as a function of
particle size.
5.2 Correction for Area Size
Use of the mass loading approach implies that the air concentration
is at equilibrium with the ground surface, i.e., a steady state situa-
tion exists in which the amount of material coming up from the surface
is balanced by the amount of material depositing back onto the surface.
In the strictest since this limit can only be achieved for source areas
approaching infinite dimensions. For source areas of finite dimensions
a fraction of the airborne mass loading can be arising from an uncon-
taminated area upwind which, although contributing dust to the atmo-
spheric, contributes no radioactivity. The smaller the size of the
contaminated area the less it will contribute to the mass loading level
and the greater the uncertainties involved in applying the mass loading
model.
Healy (37) has recently attempted to quantify the relationship
between the size of the contaminated area and the air concentration
that would result from it. His calculations show that, for a contam-
inated area which is 50 meters in horizontal depth, the air concentra-
tion would be approximately a factor of one hundred smaller than from
an area 5000 meters in depth (based upon certain assumptions regarding
prevailing meteorology). Obviously, a correction for area size
becomes necessary when applying the mass loading approach to small
29
-------
areas of contamination.
In deriving the screening level for soil, the Agency has assumed
the area contaminated to be sufficiently large that a correction for
area size is not necessary. It is recognized that this is a con-
servative assumption and that areas of actual contamination will
require a correction for area size; however, since one cannot predict
a priori the extent of a contamination incident nor the prevalent
meteorology, the conservative case has been assumed.-
5-3 Calculation of the Screening Level
The following assumptions were made in deriving the screening
level: 1) the mass loading for the hypothetical site was taken to be
2
100 pg/m and to have a particle size distribution similar to that
reported by Chepil (38) for resuspended dust, 2) the soil is enriched
with activity in the respirable size range relative to the soil as a
whole, 3) the contamination is widely dispersed and a correction for
area size is not appropriate and 4) there are no restrictions as to
land use.
An annual average mass loading of 100 pg/m3 is higher than the
annual average for any non-urban site reported by the NASN (Fig. A2-2)
and is indicative of higher resuspension for the hypothetical site.
Anspaugh (30) has examined the data from the NASN stations and has
concluded that 100 yg/m3 is a sufficiently conservative value to use
in mass loading calculations. This level of mass loading is also
consistent with the value of 120 pg/m3 arrived at by Healy (20) in
proposing an interim standard for plutonium in soil. In addition,
30
-------
3
100 yg/m was considered to be a sufficiently conservative mass loading
value and was applied in assessing the potential inhalation hazard
from plutonium contamination around Mound Laboratory (4).
The particle size distribution of the resuspended soil, for use
in calculating the screening level, is from Chepil's (38) data obtained
from fields undergoing wind erosion in Colorado and Kansas. The
results of his findings have been plotted by Slinn (35) and adapted as
Figure A 2-3. Comparision of Chepil's data with other studies sub-
stantiates the applicability of his results to other areas. For
example, Chepil found 30% of the airborne mass to be below 10 ym
versus a study by Sehmel (39) around the Hanford site where 28% of the
mass was below 10 ym (under mass loading conditions of approximately
3
30 yg/m ) and a study by Willeke (40) in the area around Denver where
33% of the measured airborne mass was below 10 ym (mass loading
< 100 yg/m3).
Currently, soil particle size and activity distribution data are
available for five sites with plutonium contamination: Mound Labora-
tory, Oak Ridge National Laboratory, and the Nevada Test Site (analyses
by Tamura [15]), and the Trinity Test Site and the Rocky Flats Plant
(analysis by the USEPA). Of these sites, the greatest enrichment of
activity within the fine particle size range is found in samples from
the Rocky Flats area. For this reason, the Rocky Flats soil distribu-
tion (see Table A 2-3) was used in calculating the screening level.
Since the size of the contaminated area varies greatly from site
to site, and because of the inability to predict the extent of future
31
-------
.100
u>
to
m
I
D
m
m
-10 S
J»
5
m
I
5
K
(0
fe
I I I I I I
30 40 60 60 70 80
99.8
12 5 10 20 30 40 SO 60 70 80 90 95 9p 99
PERCENT OF MASS ASSOCIATED WITH PARTICLES OF LESS THAN EQUIVALENT DIAMETER
PARTICLE SIZE DISTRIBUTION OF RESUSPENDED SOIL
FIGURE A2-3
,99.99
-------
contaminated areas, no reduction for area size was incorporated into the
calculation of the screening level. Likewise, the conservative assump-
tions of free access to the contaminated site with no limitations on
land usage were made in determining the screening level.
Finally, the air concentration which corresponds to the pulmonary
—15 3
dose rate limit of 1 mrad/yr is equal to 2.6x10 Ci/m . This con-
centration was obtained from Table A 3-4 of Annex III by assuming an
activity median aerodynamic diameter of 1 urn.
The above assumptions have been incorporated into the modified
mass loading formula (Eq. 4) and the screening level calculated as
follows:
Screening Level (yC1/m2) = Air Concentration (fCi/m3) Eq. 5
Mass Loading (yg/m3) x I f±g± x C.F.*
Screening Level (yCi/m2) = 2.6 fCi/m3 Eq. 6
100 yg/m3 x 1.5x6.6xlO~2
Screening Level = .26 yCi/m2 Eq. 7
As discussed earlier, it is highly unlikely that any present or
future site would have a combination of site-specific factors which
would produce an acceptable soil concentration more restrictive than
n
* C.F. is the units correction factor and is equal to 6.6x10 when
a soil density of 1.5 g/cm3 is assumed for a 1 cm dry soil sample.
33
-------
Table A 2-3
u>
Sample
RF 1A
RF IB
RF 1C
RF 2A
Size Increment (pm)
2000-105
105-10
<10
2000-105
105-10
<10
2000-105
105-10
<10
2000-105
105-10
<10
Wet. Fract.
.62
.18
.20
.63
.17
.20
.64
.16
.20
.46
.34
.20
Act. Fract.
.07
.40
.53
.39
.06
.55
.43
.07
.49
.13
<37
.50
el
.12
2.21
2.65
.63
• V J
.34
2.74
.68
.46
2.47
.28
1.10
2.48
fl
.7
.3
.7
.3
.7
.3
.7
.3
1 fl*l
2.34
1.06
1.06
1.51
av. 1.49
'Sampling and analysis by USEPA, Office of Radiation Programs, Las Vegas Facility.
-------
this screening level. To illustrate this, the resuspension factor for
this hypothetical site can be calculated:
R. F. (nf1) - 2.6xlO~15 Ci/m3 Eq. 8
2.6xlO~7 Ci/m2
R. F. - l.OxlO"8 m""1 Eq. 9
This value for the resuspension factor is a factor of 5-10 higher than
values reported for any of the existing sites. Sites of future con-
tamination, after stabilization, should have resuspension factors no
higher than the present unstabilized sites and, therefore, the screening
level value has applicability to sites of future contamination as well.
35
-------
References
1. H. M. Mork, Redistribution of Plutonium in the Environs of the
Nevada Test Site. UCLA-12-590, University of California Press,
Los Angeles (1970).
2. T. Tamura, "Distribution and Characterization of Plutonium in
Soils from Nevada Test Site," in The Dynamics of Plutonium in
Desert Environments. NVO-142, USAEC, Las Vegas, Nevada (1974).
3. K. Stewart, "The Resuspension of Particulate Material from Surfaces,"
in jmrface Contamination. B. R. Fish (ed.), Pergamon Press, New
York, N. Y. (1964), pp. 63-64.
4. D. R. Rogers, Mound Laboratory Environmental Plutonium Study 1974.
.MLM-2249, Mound Laboratory (1975).
5. G. A. Sehmel, "Particle Resuspension from an Asphalt Road Caused by
Car and Truck Traffic," Atm. Env.. _7_, P- 291 (1975).
6. W. H. Langham, Biological Considerations of Nonnuclear Incidents
Involving Nuclear Warheads. UCRL-50639, Lawrence Livermore
Laboratory (1969).
7- Environmental Statement for LMFBR. WASH-1535, Appendix 11.G, USAEC,
Washington, D. C. (1974).
8. B. L. Cohen, The Hazards in Plutonium Dispersal. GE2-6521, General
Electric (1975).
9. J. A. Hayden, "Characterization of Environmental Plutonium by
Nuclear Track Techniques," in Atmospheric-Surface Exchange of Partic-
ulate and Gaseous Pollutants. CONF-740921, ERDA, Washington, D. C.
(1974).
10. M. W. Nathans, R. Reinhart, and W. D. Holland, "Methods of Analysis
Useful in the Study of Alpha-Emitting and Fissionable Material
Containing Particles," in Atmospheric-Surface Exchange of Particlate
and Gaseous Pollutants. CONF 740921, ERDA, Washington, D. C. (1974).
11. G. A. Sehmel, "A Possible Explanation of Apparent Anomalous Airborne
Concentration Profiles of Plutonium at Rocky Flats," Pacific
Northwest Laboratory Annual Report for 1974. to the USAEC Division
of Biomedical and Environmental Research. BNWL-1950, Pt. 3, Atmos.
Sci., p. 221 (1975).
12. M. W. Nathans, The Size Distribution and Plutonium Concentration of
Particles from the Rocky Flats Area. TLW-6111. LFE Corporation (1972).
36
-------
13. J. H. Patterson, G. B. Nelson, G. M. Matlock, The Dissolution of
239Pu in Environmental and Biological Systems, LA 5624, Los Alamos
Laboratory (1974).
14. M. Sakanoue and T. Tsuji, "Plutonium Content of Soil at Nagasaki,"
Nature. 234. p. 92 (1971).
15. T. Tamura, "Physical and Chemical Characteristics of Plutonium in
Existing Contaminated Soils and Sediments," in Proceedings of the
International Symposium on Transuranium Nuclides in the Environ
ment (Nov. 1975), IAEA, Vienna.
16. W. H. Langham, "Biological Implications of the Transuranium
Elements for Man," Health Physics, 22_, p. 943 (1972).
17. A. Aarkrog, "Radioecological Investigation of Plutonium in an Artie
Marine Environment," Health Physics, 2(3, p. 30 (1971).
18. A. Preston and N. Mitchell, "Evaluation of Public Radiation
Exposure from the Controlled Marine Disposal of Radioactive
Waste," in Radioactive Contamination of the Marine Environment,
IAEA STI/PUB/313, International Atomic Energy Agency, Vienna,
p. 575 (1973).
19. ICRP Publication 19, 1972. The Metabolism of Compounds of Plutonium
and Other Actinides, Pergaman Press.
20. J. W. Healy, A Proposed Interim Standard for Plutonium in Soil,
LA 5483-MS, Los Alamos Scientific Laboratory (1974).
21. C. J. Johnson, R. R. Tidball, and R. C. Severson, "Plutonium
Hazard in Respirable Dust on the Surface of Soil," Science. 19_3,
p. 488 (1976).
22. R. C. Milham, J. F. Schubert, J. R. Watts, A. L. Boni, and J. C.
Corey, "Measured Plutonium Resuspension and Resulting Dose from
Agricultural Operations on an Old Field at the Savannah River
Plant in the Southeastern U. S.," in Proceedings of the Inter-
national Symposium on Transuranium Nuclides in the Environment,
(Nov. 1975), IAEA, Vienna.
23. R. L. Thomas and J. W. Healy, An Apprasial of Available Information
on Uptake by Plants of Transplutonium Elements and Neptunium.
LA 6460-MS, Los Alamos Scientific Laboratory (1976).
24. R. A. Bulman, Concentration of Actinides in the Food Chain. NRPB-R44,
National Radiological Protection Board, Harwell, England (1976).
25. E. M. Romney, H. M. Mark, and K. H. Larson, "Persistence of
Plutonium in Soil, Plants, and Small Mammals," Health Physics, 19^.
p. 487 (1970).
37
-------
26. P. Neubold, Absorption of Plutonium-239 by Plants. ARCRL-8,
St. Brit. Agr. Res. Council (1962).
27. W. V. Lipton and A. S. Goldin, "Some Factors Influencing the Uptake
of Plutonium-239 by Pea Plants," Health Physics. 31, p.425 (1976).
28. B. G. Bennett, "Environmental Pathways of Transuranic Elements,"
in Proceedings of Public Hearings; Phttonium and the Other
Transuranium Elements. Vol. 1, ORP-CSD-75-1, USEPA, Washington,
D.C., (1974).
29. B. G. Bennett, private communication.
30. L. R. Anspaugh, "The Use of NTS DATA and Experience to Predict
Air Concentration of Plutonium Due to Resuspension on the Enewetak
Atoll," in The Dynamics of Plutonium in Desert Environment,
NVO-142, USAEC, Las Vegas, Nevada (1974).
31. L. R. Anspaugh, J. H. Slinn, D. W. Wilson, "Evaluation of the
Resuspension Pathway Toward Protection Guidelines for Soil Con-
tamination with Radioactivity," in Proceedings of the Inter-
national Symposium on Transuranium Nuclides in the Environment
(Nov. 1975), IAEA, Vienna.
32. J. W. Healy and J. J. Fuquay, "Wind Pickup' of Radioactive Particles
from the Ground," Progress in Nuclear Energy Series XII, Health
Physics. V.I, Pergamon Press, Oxford, (1959).
33. G. A. Sehmel atid M. M. Orgill, "Resuspension by Wind at Rocky
Flats," Annual Report for 1972. BNWL-1751, pt. 1, Battelle Pacific
Northwest Laboratory, Richland (1973).
34. G. A. Sehmel and F. D. Lloyd, "Particle Resuspension Rates" in
Atmospheric-Surface Exchange of Particulate and Gaseous Pollutants,
CONF 740921, ERDA, Washington, D.C., (1974).
35. W. G. N. Slinn, "Dry Deposition and Resuspension of Aerosol
Particles - A New Look at Some Old Problems," ibid.
36. J. H. Shinn, N. C. Kennedy, J. S. Koval, B. R. Clegg, and
W. M. Porch, "Observations of Dust Flux in the Surface Boundary
Layer for Steady and Non-Steady Cases," ibid.
37. J. W. Healy, An Examination of the Pathways from Soil to Man for
Plutonium. LA-6741-MS, Los Alamos Scientific Laboratory (1977).
38. W. S. Chepil, "Sedimentary Characteristic of Dust Storms: III
Composition of Suspended Dust," Am. J_. Sci., 225, p. 206 (1957).
38
-------
39. G. A. Sehmel, Radioactive Particle Resuspension Research Experi-
ments on the Hanford Reservation. BNWL-2081, Battelle Pacific
Northwest Laboratory, Richland (1977).
40. K. Willeke, K. Whitby, W. Clark, and V. Marple, "Size Distribu-
tion of Denver Aerosols-A Comparison of Two Sites," Atm. Env.,
8, p. 609 (1974).
39
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Annex III
THE DOSE AND RISK TO HEALTH DUE TO THE
INHALATION AND INGESTION OF TRANSURANIUM NUCLIDES
U. S. Environmental Protection Agency
Office of Radiation Programs
Washington, D.C. 20460
-------
CONTENTS
3.1 Introduction
3.2 Risks
3.3 Exposure Pathways
3.4 Dosimetry of Inhaled and Ingested Plutonium, Americaurn, and
Curium
3.1.1 The Dose to Lung Tissues
3.4.2 The Dose to Bone, Liver, and the Total Body
3.4.3 The Dose to Gonadal Tissue
3.4.4 Dose Models for the Ingestion Pathway
3.5 The Risk of Lung Cancer from Inhaled Transuranics
3.6 The Risk of Bone Cancer
3.6.1 Inhalation Risk Estimates
3.6.2 .Ingestion Risk Estimates
3.7 The Risk of Inducing Cancer of the Liver
3.7.1 Inhalation Risk Estimates
3.7.2 Inyestion Risk Estimates
3.8 The Risk of Genetic Damage
3.8.1 Genetic Risk Estimates
3.9 Other Risks Due to the Inhalation and Ingestion of
Plutonium
3.9.1 Leukemia due to Bone Marrow Irradiation
3.10 Summary of Health Risks
3.10.1 Inhalation Pathway
3.10.2 Ingestion Pathway
References
Tables
Figures
-------
Annex 3
The Dose and Risk to Health Due to the
Inhalation and Ingestion of Transuranium Nuclides
May 23, 1977
3.1. INTRODUCTION
The purpose of this -chapter is to outline the methods recommended
by the Agency to estimate the dose and potential health effects from
some of the transuranium elements in the environment. An attempt has
been made to balance the discussion between scientific details and
understandability by laymen. Where it is impossible to satisfy both
needs, the documentation cited should supply more details for the
interested reader.
Information on the biological properties of transuranium elements
is reviewed in "Selected Topics: Plutonium in the Environment" which
includes an extensive bibliography (1) . The amount known about the
metabolisms of each of the transuranic elements varies depending on
their commercial importance as well as other factors. Considerable
information is available on the distribution of plutonium in most
human tissues, the gonads being a notable exception. The biological
data base for the dosimetry of americium and curium is not as
extensive, which limits the accuracy of estimates of the dose due to
these radionuclides.
3.2. Risks
Although much information is available on the somatic effects of
Plutonium inhalation and ingestion by laboratory animals, no relevant
epidemiological information is available on the effects of plutonium
-------
or other transuranium elements on humans via these exposure pathways
(1). When human data is available, the Environmental Protection
Agency prefers to base estimates of health risk due to radiation on
the results of human epidemiological studies rather than animal
experiments. To derive estimates of the cancer risk due to plutonium
and other transuranium elements, the Agency relies on human experience
with other alpha particle emitters. (In a few cases transuranics emit
radiation other than alpha particles but such emissions make
relatively unimportant contributions to the dose.) Estimates of
genetic risk are not based directly on human studies. Assumed
doubling doses for genetic injury are based almost exclusively on
irradiated animal populations.
Data oh human experience following alpha particle irradiation is
largely confined to occupational and medical exposures. The Agency's
chief reference documents for the effects of ionizing radiation on
health is the 1972 BEIR Report prepared by the National Academy of
Sciences (2), and the NAS Report, "Health Effects of Alpha-Emitting
Particles in the Respiratory Tract" (3), the latter document being used
to estimate lung cancer risk. Following the procedure used by the
BEIR Committee in arriving at its "best estimate" of radiation risk,
it is the practice of the Agency to average results obtained by the
two types of risk models utilized in the NAS-BEIR Report (2), absolute*
»Probability of cancer per organ rad.
-------
and relative risk*, respectively. These two models can yield results
differing by as much as a factor of about seven depending on the
particular cancer being considered, duration of risk following
exposure, etc. (2). Therefore, in addition to other uncertainties in
the risk estimates there is a residual uncertainty of a factor of
three or more in the average of the risk estimates listed below,
depending pn which of these models is appropriate for a particular
organ system.
The Agency*s risk estimates are based on an assumed linear
relationship between dose and the probability that a cancer is
induced. No threshold dose for effects is hypothesized and no
allowance is made for enhanced or reduced effects due to the
relatively low dose and dose rates realized from alpha particle
exposures. It should be noted that the Agency does not consider the
risks due to ionizing radiation hypothetical and that for highly
ionizing radiation such as alpha particles from plutonium, the linear
non-threshold hypothesis is unlikely to overestimate the actual risks.
In the case of estimating genetic risks, the overall uncertainty
is larger than for estimating the risk of cancer induction. The
NAS-BEIR Committee report (2) indicates that this uncertainty has two
components: an estimated uncertainty of a factor of ten in the dose
required to double the human mutation rate and for common diseases
*Percent increase of cancer per organ rad.
-------
thought to have a invitational component, an additional uncertainty of a
factor of ten. Obviously, only a broadly defined range of genetic
risk due to transuranium radionuclides can be estimated at the present
time.
Risk estimates for ionizing radiation are often expressed in
terms of the rem, a unit ~of dose equivalence used in radiation
protection practice to provide at least some degree of equality
between the biological damage produced by different kinds of
radiation. Since this guidance is limited to alpha particle emitters,
both dose and risk estimates are expressed in a more fundamental
physical unit, the rad, the specific energy imparted. The advantages
of this approach are that it is more straightforward and that the
guidance will not need periodic revision to account for differences
between various kinds of radiation that may be proposed. Future
information on health effects will, however, be factored into these
guides as the need arises.
An air concentration yielding 1 mrad per annum to adults will
result in children receiving a somewhat larger dose rate. The dose
rate to children cannot be calculated as accurately as for adults
because the necessary lung model parameters are not known. As a first
approximation to the dose rate as a function of age, the reduced
breathing rate (minute volume) and smaller organ mass of children have
been Used to estimate their increased annual dose. This provides a
conservative estimate of childhood dose since deposition and retention
in the lung should be less for children due to their smaller lung
-------
area. A more detailed treatment of the dose to children is not likely
to result in appreciable difference in the risk since most of a
person's body burden is accumulated during adult life, not childhood.
Specific information on the carcinogenic effects of alpha
particle or other highly ionizing radiations on children's lungs is
not available. No lung cancer deaths have been reported as yet in
children irradiated at Hiroshima. Nevertheless, as mentioned in
sections 3.5 and 3.6f the risk estimate of excess lung and liver
cancer mortality allow for observed differences in the
radiosensitivity of children and adults, based on data for other
radiogenic cancers (2). In the case of lung cancer, these differences
have a large effect on the estimated risks. Estimates based on the
BEIR absolute risk model include an assumption that children are less
sensitive to radiation than adults. Estimates based on the relative
risk model assume children are ten times more sensitive.
Unfortunately, there is paucity of information which can lead to a
choice between these two models on scientific grounds. It should be
noted that the Agency's use of a logarithmic averaging of the results
obtained by the absolute and relative risk models results in a bias in
favor of the former. However other assumptions in the risk model are
somewhat conservative so that on balance it is unlikely that the true
risks are not underestimated.
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3.3. EXPOSURE PATHWAYS
In general, the most important pathway for human exposure from
Plutonium oxide and other transuranium radionuclides in the
environment is expected to be inhalation. This route provides a
direct pathway for alpha particles to enter a sensitive organ, the
pulmonary lung. Subsequently, a fraction of the inhaled material is
redistributed via the blood to such important organs as the bone,
liver and gonadal tissues. This is in contrast to the ingestion
pathway, where the gut walls act as a barrier to plutonium absorption
by blood. The dose to the gut wall itself is not a major cause of
concern because, unlike other radiations, plutonium alpha particles
have a short.finite range in tissue, «1 microns (u) , i.e., less than
two-thousandths of an inch. Radiosensitive dividing cells in the qut
wall are over 100 u distant from the gut contents and are effectively
isolated from the alpha radiation.
The dose to various tissues from inhaled plutonium is highly time
dependent. Insoluble materials deposited in the pulmonary lung are
removed fairly rapidly; half is assumed to be cleared within 500 days.
Clearance from other organs is much slower; the estimated biological
half-life* in the liver is assumed to be 40 years, and in the case of
bone, 100 years (U). The dose delivered to an organ is directly
related to the residence time of the radioactive material. Following
»The -time required to eliminate one-half of the initial organ burden.
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a single acute exposure to airborne plutonium, the lung (pulmonary)
dose rate decreases due to the clearance of particles from the lunar so
that almost all of the dose is received in a few years. In contrast,
the dose rates to the liver and bone are relatively constant over this
time span.
In the case of chronic environmental contamination leading to a
constant annual intake, the temporal pattern of the dose rate to
various organs due to inhalation is different. For pulmonary tissues,
a constant (eguiliorium) dose rate is realized within a relatively few
years of the start of exposure. The dose rate to liver increases more
slowly and does not equal that to lung tissue until after about 70
years of exposure. The dose rate to bone never approaches that in the
lung and liver (Figure A3-1). Therefore, the total risk from chronic
inhalation will vary with the duration of exposure. In setting guides
for the dose due to inhalation, the Agency has selected the annual
dose rate to Jtung (pulmonary tissue) as the appropriate limit. This
choice is warranted because administrative controls for the inhalation
pathway can be more easily instituted on the basis of an annual dose
limit to lung rather than a lifetime dose limit for lung and other
tissues. This does not mean the risks from exposure to organs other
than lung have been overlooked. The estimates of the total risk from
inhaled radionuclides of transuranium elements made below account for
the dose to all important organ systems and are, necessarily, a
function of the duration of exposure so as to reflect the varying dose
rate for liver and bone shown in Figure A3-1. For highly insoluble
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transuranics, the additional risks due to liver and bone irradiation
due to inhalation are believed to be small compared to the risk of
lung cancer, as outlined below.
Use of lands contaminated with low concentrations of plutonium or
other transuranium radionuclides are expected to be strictly
controlled, unless the resulting doses are below the level specified
in this guidance. Uncontrolled land utilization implies that such
ordinary uses of land as farming, residency, industrial use, etc. are
not precluded. All of these activities and particularly residential
use could lead to exposures extending over several decades and in some
cases lifetime exposure. In the section below, the lung cancer risk
from plutonium inhalation is calculated on the basis of an annual
limiting dose rate of one mrad per annum occurring throughout a
persons life. In many cases of environmental contamination, the
concentration of plutonium in air would be expected to decrease with
time so that the life time dose, and risk, would be smaller.
3.4. DOSIMETRY OF INHALED AND INGESTED PLUTONIUM. AMERICIUM, AND
CURIUM
3.4.1 The Dose to Lung Tissues
Dosimetric models for projecting the average distribution of
ionizing radiation within body organs due to the inhalation of
radioactive aerosols are still somewhat crude (1). The most promising
general model is diat developed and published in ICRP Report f!9, "The
Metabolism of Compounds of Plutonium and Other Actinides" (4) , as an
amended version of a model developed earlier for the ICRP (5). In
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general, ICRP report 119 is the basis for the estimates of dose made
in this section. Where it has been supplemented by more recent data,
specific reference is made. Since the inhalation model is documented
in ICRP §19 <«) and in reference 5, only its basic outline is
described here.
Inhaled aerosols are considered on the basis of particle size and
other aerodynamic parameters. The fraction of inhaled materials
initially retained or exhaled, and the deposition in various portions
of the respiratory tract, is a given function of a particle's activity
median aerodynamic diameter (AMAD). The physiological parameters used
in this study were taken from reference 5. A diagram of the ICRP Task
Group Lung Model is shown in Figure A3-2. The rate at which deposited
material is removed from the lungs is considered to be a function only
of the chemical state of the inhaled material, and not of size or
radioactive' content. Environmental sources of plutonium and other
transuranium elements are likely to be in the oxide or hydroxide form.
Actinides in either form are currently classified as Class Y
(insoluble) materials by the ICRP (U). Such materials take years to
be cleared from the lung; their estimated biological half life in
pulmonary tissue being 500 days (4). The dose estimates made below
apply only to Class Y compounds. Dose estimates for the inhalation of
more soluble. Class W, materials are given in reference 6. The
breathing rate, retention half-time and fraction of material handled
by the various elimination pathways for relatively insoluble material
deposited in the lung that are assumed in this model are shown in
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Table A3-1, from ICRP §19 (U). A critique of the ICRP model is
included in (1) .
In assessing the dose and risk due to the inhalation of
transuranium elements only retention in the pulmonary region is of
primary importance. Residence time of inhaled materials in the
nasopharyngeal and tracheobronchial regions is short compared to that
in pulmonary tissues.
Radioactivity is assumed to leave the pulmonary tissues by three
routes: elevation up the tracheobronchial tree via the mucus elevator
into the gut by way of the esophagus and stomach, transport of
particulate materials into the lymphatic system and lymph nodes anci
most important by dissolution into the blood stream. Most of the
activity in blood is redeposited into the liver and bone.
The dose to different organs from inhaled aerosols of various
sizes has been considered by a number of workers who have written
computer codes to quantify the ICRP model (7,9). Since the ICRP model
is not described in the form of unambigious equations, there are minor
differences between the results obtained with various codes. The EPA
code PAID (9) has been used to calculate the annual dose rates due to
isotopes of plutonium, americium, and curium for a number of particle
sizes. Typical results tor five micron, one micron, and five
one-hundredths micron, AMAD plutonium-239 aerosols (1 fCi/m3) are
shown in Table A3-2 for the various compartments in the lung for the
case of lifetime exposure (70 years). It is seen from the Table that
most of the radiation insult is delivered to pulmonary tissue. Given
10
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equal concentrations in air, the dose to the pulmonary lung is not
very sensitive to particle size. For example, the size range from
0.05 to 5.0 micron (AMAD), the pulmonary dose decreases by a factor of
about five, as shown in Figure A3-3.
Doses calculated by the PAID code are obtained by averaging the
energy deposited by alpha particles throughout the entire organ mass
(570 grams in the case of pulmonary tissues) (10). While some have
argued (11) that the energy imparted from deposited aerosols should
not be averaged in such a manner, current scientific opinion holds
that it is a sufficiently conservative.way to estimate the radiation
damage even though some cells receive more or less dose than the
average for all cells (3) .
The ICRP model assumes that 10% of the radioactive material
transferred to the. lymph nodes from pulmonary lung is retained
permanently, and 90* is retained for a half time of 1000 days before
being released as soluble material into the bloodstream. As a result,
the dose rate to these nodes is high compared to that received by
pulmonary tissue, as shown in Table A3-3. This is not believed to be
an important consideration in estimating risk, since the frequency of
radiation induced cancers in respiratory lymph nodes appears to be
very small if not zero. Prom animal studies, it is certain that this
risk is small compared to the frequency of radiogenic cancers at other
sites (12,13).
11
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3.
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bone is from material in the lungs and lymph nodes that has been
dissolved and transferred via the blood. Transfer to blood of
swallowed materials is much less important. For example, depending on
particle size, only 0.06X to 0.35% of the annual dose to bone shown in
Table A3-3 is due to inhaled plutonium oxide crossing the gut wall.
Lifetime dose rates ^for plutonium-238, plutonium-239,
Plutonium-240, and the two member radionuclide chains, Pu-24I/Am-241,
Am-241/Np-237, and Cm-244/Pu-240 have been calculated to aid
implementation of this guidance (6, 9) . Table A3-4 lists the
concentration in air of transuranium element aerosols that should
deliver an annual alpha dose rate ot one mrad per year to adult
pulmonary tissues. Particle sizes in Table A3-4 range from 0.05 u to
5u.(AMAO) . Over this range of particle sizes the limiting
concentrations varies by a factor of about five.
3.4.3. The Dose to Gonadal Tissue
The degree to which transuranium elements are translocated from
human blood to gonadal tissues is not well known due to the analytical
difficulty of making reasonably precise measurements at the low
activity levels usually involved, and the high variability between
various individuals. Besides limited information from studies of
laboratory animals, there are three sources of post-mortem human data;
the general population exposed to fallout plutonium, industrially
exposed radiation workers, and a few clinical studies with hospital
patients. Richmond and Thomas reported that for the five animal
species considered in their 1974 review, an average of 0.03* of the
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Plutonium in blood was transferred to gonadal tissue (15). The data
on which this average is based varied by a factor of about ten. A
review of clinical data, based on only four persons, also leads to an
estimate of about .03% for transfer from blood to gonadal tissue (1U).
The Medical Research Council (MRC) also reviewed this problem in
their 1975 analysis of plutonium toxicity and concluded that 0.05* of
the plutonium in blood would be transferred to gonadal tissue (16).
Since the mass of the ovary is 11 grams, the MRC estimate on transfer
from blood is equivalent to 0.005* per gram of o*'ary. The mass of
testes is greater than that of the ovary by a factor of about 3. The
MRC assumed equal quantities of plutonium in each, so that the
concentration (percent per gram) in the testes would be about
one-third of that in ovarian tissue i.e., 0.002% per gram. Richmond
and Thomas estimated that the amount of plutonium in the smaller
female gonad was a factor of five to ten less than males, a somewhat
less conservative assumption. Recent data reported for plutonium in
beagle gonads indicates that the concentration per gram is about
0.0055% in ovaries and 0.0012% in testes which supports the MRC
viewpoint (17).
For calculational purposes it is convient to relate concentration
per gram of transuranics in gonodal tissue to that in bone. According
to the ICRP model, 0.09% of the plutonium in blood is concentrated in
one gram of bone (4). Based on the MRC study and the results cited
above this is about twice the concentration (% per gram) of plutonium
in the female gonads; and for testes .about five times greater.
19
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Autoradiographic studies in mouse testes indicate that because of the
deposition of plutonium near the spermatogonial stem cells, the
effective dose to these cells is about 2 to 3 times greater than that
to the testes as a whole. (No comparable study of the pattern of
deposition for the ovary has been reported). To account for this
factor, it is assumed that the effective genetic dose due to
transuranium elements in male gonads will be the same as in the
female.
The turnover rate of transuranium elements in gonadal tissues is
known to be small compared to that of other soft tissues (H, 18, 19).
For these calculations the biological half-life in gonadal tissue is
assumed to be the same as in bone, 100 years. As in bone, the buildup
of transuranium elements in gonadal tissue will occur rather slowly in
the case of chronic ingestion or inhalation. The significant gonadal
dose in terms of genetic risk is that received during the first 30
years of life (1). From Figure A3-1 it is seen that the dose rate to
gonadal tissue* over a 30-year period is considerably less than that
received by pulmonary tissue. For an equilibrium pulmonary dose rate
of 1 mrad per year, the dose to gonadal tissue in the first 30 years
of life is calculated to be 1.4. mrad (15). The dose to gonads and
other organs due to ingestion is considered below.
15
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3.4.1. Dose Models for the Ingestion Pathway
The magnitude of calculated doses due to the ingestion of
transuranic materials is directly proportional to the fraction of the
ingested material that is assumed to cross the gut wall and enter the
blood stream. This fraction is not well known and it is reasonable to
assume that it varies considerably depending on the solubility of the
ingested material. Animal experiments to measure gut transfer that
have used highly insoluble laboratory prepared materials in the oxide
form yield transfers in the parts per million range (U). However,
Plutonium oxide found in the environment has been shown to be much
more soluble than the refractory oxides utilized in animal experiments
(20) . This is in agreement with recent experiments showing plutonium
oxides formed at low temeratures are more soluble than those formed at
high temperatures (21) . Therefore it is reasonable to assume that
Plutonium oxidized in the environment will not be as in soluble as the
materials whioh have been used to determine plutonium gut transfer in
animals. Moreover, because the quantitative applicability of animal
data to man is unknown, conservative estimates that will not
underestimate the dose to humans are required. Information on the
transfer of transuranium elements across the gut wall, as reported in
references U and 22 as well as in the reports of more recent studies
(23, 2U, 25, 26) were reviewed and the transfer coefficients shown in
Table A3-5 adopted for use in the dose calculations for this Guidance.
The fractional transfers listed are much higher than currently assumed
16
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by the ICRP (4) and are thought to be conservative estimates
applicable to public health problems.
The degree of conservatism in these transfer fractions varies
depending on how much is known about a particular material, more
conservatism being applied to materials for which information is less
available. The lowest transfer, 10-*, is assumed to occur for low
specific activity plutonium oxides, which have been utilized in many
experimental situations with several species. Oxides of some of the
other transuranium elements may behave similarly but have been studied
less extensively. Transuranium elements in non oxide form, and the
oxide of high specific activity transuranium elements such as Pu-238,
are somewhat more soluble than plutonium-239 oxide. Present evidence
indicates the transfer to blood may increase by an order of magnitude
or even more if the element is incorporated into organic materials
(1). It should be noted that the fractions listed in Table A3-5 are
applicable to adults and children over one year of age. The special
case of infants is discussed in Section 3.6.
The estimates shown in Table A3-5 have been used in the dose
calculations described below. Most of the plutonium-239 and
plutonium-2to in the environment is assumed to be in the oxide form.
Dose calculations for these radionuclides assume one pCi in 10* pci
ingested is transferred to blood; for all other transuranium elements;
ten pCi per 10* pCi ingested. No allowance was made for transuranium
elements "biologically" incorporated into ingested materials. This is
assumed to happen when transuranium elements are incorporated into
17
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plant and animal tissues at the molecular level in contrast to the
surface contamination of foodstuffs. Where the fraction of such
material in the diet can be estimated, the dose estimates made below
should be increased in proportion to the increased amount transferred
to blood. For example, if 10X is incorporated into biological
material, the dose (and risk) would be increased by 40%.
Subsequent to their transfer across the gut wall, ingested
radionuclides enter the blood stream and are deposited primarily in
liver and bone and to a lesser extent gonadal tissue, as outlined
above in the description of the lung model. As stated in Section 3.2,
the dose to the intestinal walls is not considered in this analysis
because of the low likelihood of alpha particle penetration to
sensitive cells in the intestines. An ICRP Task Group has suggested,
as surrogate for information on the dose to dividing cells, that
calculations of maximum permissible concentration of transuranium
elements in air and water be based on the assumption that IX of the
alpha energy is absorbed (27,28). However, this is highly unrealistic
for the purpose of predicting health effects and is not used here.
The transfer factors from gut to blood shown in Table A3-5 have
been utilized to calculate annual dose rates as functions of the
duration of ingestion. Dose rates to bone, liver, and the total body
of reference man (10) due to the chronic ingestion of 1000 pCi/annum
of plutonium-239 oxide, americium-241, and curium-2f» are shown in
Table A3-6. Pu-241, half life 14.8 years, and Cm-244, half life 17.9
years, are the most rapidly decaying transuranium elements capable of
18
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causing chronic exposures in a contaminated environment. Because of
their short half lives, the occurrence of lifetime ingestion of these
radionuclides is remote. This is even more true of curium-212, half
life 0.45 years, where only acute intake is a plausible mode of
exposure.
The dose rate to bone in the 70th year due to a constant rate of
ingestion of 10 nCi per year are listed in Table A3-7 for a number of
transuranium elements. To determine if the bone dose limit is being
exceeded, the total dose rate due to the ingestion of a combination of
transuranium elements can be calculated from these data.
Table A3-8 lists the cumulative 30-year dose to gonadal tissue
due to the chronic ingestion of several transuranium elements at an
annual intake of 1000 pCi per year. The gonadal dose has been
calculated as described above in Section 3.4.3.
The organ dose rates listed in Table A3-6 were calculated on the
basis of organ masses appropriate for reference man, not children.
However, there is enough proportionality between food intake and organ
mass as a function of age so that the results are applicable to a
lifetime exposure situation. Because there is some evidence from
animal studies that the newborn have a particularly high transfer of
transuranium elements across the gut walj. to blood, the transfer
fractions listed in Table A3-5 may not be applicable to infants, (less
than one year old) . The duration of this increased transfer is
unknown for humans, perhaps a few weeks or considerably longer. To
test for what effect this may have on lifetime doses, it has been
19
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assumed below that the GI tract to blood transfer factor during the
first year of life is one hundred times greater than the value shown
in Table A3-5, i.e., 10~2 in the case of plutonium oxide (26). Any
increased transfer due to the incorporation of the plutonium into food
is included in this factor of 100.
Ingestion of contaminated food by infants would cause a large
initial dose rate to body organs. After the first year, the dose rate
decreases due to organ growth, and possibly a more rapid turnover rate
of minerals in infant bone compared to adults. However, because
turnover rates for children are poorly known, this factor has not been
included in calculating the skeletal dose. As an example of enhanced
transfer of radioactivity across the infant gut. Table A3-9 compares
the skeletal dose rates when transfer is increased by a factor of 100
in the first year of life with the dose rate, pattern to refernce man.
Increased dose rate during the first year of life has less effect on
lifetime dose rates than might be expected. Risk analyses of the type
outlined in Section 3.6 indicate that the dose pattern shown for
enhanced transfer in Table 3.9 would result in 50% more bone cancers
than are estimated below, for reference man.
Because infant feeding in the U.S. relies heavily on a variety of
non-local foods, it is unrealistic to assume that 100* of the first
year's intake would be produced only in contaminated areas. A
possible exception, milk, would be less contaminated than other
locally produced food stuffs because the transfer of most transuranium
elements into milk (animal) following ingestion of the radioisotope is
20
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only about 0.0001 percent per liter (29, 30). Transfer of americium
and curium to milk is about 100 times greater than other transuranium
elements (31) but is still small.
3.5. THE RISK OF LUNG CANCER FROM INHALED TRANSURANICS
In most cases, the lung is the organ of primary concern when
assessing the risks from plutonium and other transuranium elements in
soil. Animal studies, particularly those with dogs (15), which have a
relatively long life span, indicate that lung cancer can result from
inhaled plutonium aerosols as do extensive experiments with rats (32).
Even so, the assessment of the risk to humans cannot be directly
inferred from animal evidence. Almost all lung cancers in dogs
exposed to plutonium occur in a different location than radiogenic
cancers in humans following exposure to radon daughters. The animal
cancers are in the peripheral parts of the lung and often of different
cell types than human lung cancers. They are histologically
classified as 'bronchiolar-alveolar carcinomas (a type of
adenocarcinoma) (3). In humans, the inhalation of alpha particle
emitters (but not transuranium elements) has usually resulted in
bronchial cancers (hilar bronchogenic carcinomas). These are
primarily epidermoid and anaplastic carcinomas, but include some
adenocarcinomas. Cancers histologically similar to those in animals
(peripheral adenocarcinomas) are found much less frequently (3) . This
difference may be due to differing exposure conditions but must, in
part, be due to differences in tissue sensitivity between species (3).
21
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Some insight into this problem is obtained by considering the
type of cancers resulting from highly ionizing radiation that have
occurred in survivors of the Hiroshima bombing. Examination of these
data show that, even though the dose to the pulmonary lung must have
been higher than that delivered to the bronchi (33), the significant
increases in observed cancer occurred in the bronchi rather than in
the region of higher dose (34).
An NAS committee recently concluded that "the risk from alpha
irradiation of the deep lung tissues would not be underestimated by
applying risk factors from human experience with cancer induced by
irradiation of the bronchial tree" (3). Therefore, the risk estimates
(Tables A3-10,11) are based on the highest dose rate received by any
lung tissues (pulmonary lung) and risk estimates appropriate for the
most sensitive tissues within the lung, the site of bronchial cancers.
It should be noted that the dose to bronchial tissues following
Plutonium inhalation is small compared to tnat received in the
pulmonary lung. Tables A3-2.
The number of lung cancers from alpha irradiation at a given dose
appears to be increasing as the years at risk in relevant
epidemiological studies are extended. The 1976 NAS report states that
the absolute risk (the number of cases that will result from exposure
of a given population) estimate for bronchial cancer in uranium miners
is twenty cases per million organ rad per year at risk, not ten as in
the 1972 BEIR Report. The relative risk (the ratio of the risk in
those exposed to the risk to those not exposed) estimate in the 1972
22
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BEIR Report is also likely to be low. Assuming that the relative risk
for D.S. miners has increased in a manner similar to their absolute
risk, it would be comparable to the 1972 BEIR estimate for Canadian
miners who have been similarly exposed, i.e. 6% increase in annual
incidence per rad. Because an updated analysis of the U.S. uranium
miner cancer experience is not available, this estimate has been
utilized in the life table analysis described below.
Tumors may occur at any time after a latent period during which
the affected cell or cells progress from the state of initial injury
to a tumor which can be identified clinically. The duration of this
period is, of course, variable depending on the kind of cancer and
host response. For many cancers it is estimated as 10 to 20 years.
The 1972 BEIR Report assumed a 15 year latent period for all solid
tumors induced in both children and adults.
Following the latent period, tumors occur with an increased
frequency in the groups irradiated. The temporal pattern of cancer
induction is poorly known for human populations exposed to radiation,
mainly because exposed groups have not, as yet, been followed for
sufficiently long enough times. The 1972 BEIR Committee made two
approximations of the temporal pattern for tumor occurrence. One
assumes a constant risk per year for the balance of a person's
lifetime following a 15-year latent period; the other, a constant risk
for a 30-year plateau following the latent period. This may not be
long enough, since 30 years is-the duration of most of the
epidemiclogical studies used to establish the risk estimate.
23
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Estimates of the risk of cancer.following irradiation in the 1972
BEIR Report are a function of two parameters: the type of risk model,
absolute or relative, and the duration of the plateau period. In the
case of absolute risk the estimates are relatively independent of the
plateau period, for either children or adults. However, results
obtained with a relative risk model are more sensitive to the plateau
period selected, particularly when children are included in the
population at risk. If a 30-year plateau, relative risk model is
assumed, the calculated risk of radiation carcinogenesis is small from
early exposure when a child1s sensitivity to radiation injury is high.
Only in the later years of life is the natural incidence of cancer an
important cause of death, and the plateau period does not extend into
these years.
The life table analysis used to estimate the risk of premature
death following irradiation is described in reference 35 and in Annex
4. Table A3-10 compares the risk models and Plateau periods discussed
above, for the case of lung cancer due to lifetime inhalation causing
a dose rate (to adults of 1 mrad per year. The absolute risk from
exposures before ten years of age was assumed to be one-fifth that of
adults; the relative risk ten times the adult value, as shown in Table
A3-2 of reference 2. In Table A3-10, the risks to the exposed
population are accounted for by three measures: (1) number of early
deaths per 100,000 exposed, (2) the total life-shortening for the
group as a whole and finally, (3) the average number of years of life
lost by an afflicted individual. The much larger number of lung
2«
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cancers expected to occur in a cohort of 100,000 persons not exposed
to this additional insult is estimated in Annex H (Table AU-1).
For the purpose of this report, an estimate of the lung cancer
risk is obtained by averaging the geometric means of the absolute and
relative risk for 30-year and lifetime plateaus, shown in Table A3-10.
The Agency recognizes that these risk estimates must be regarded as
tentative, because information on the radiocarcinogenicity of high LET
particles is being reassessed by several competent scientific groups.
The Agency has an ongoing contract with the NAS to have the BEIR
committee re-evaluate radiation risk, including the risk of lung
cancer. Pending completion of the new NAS study, the average risk of
early death from a one millirad annual dose to adult pulmonary tissue
has been used to assess the lung cancer risk from inhaled
transuranics. At this level, lifetime exposure experienced by 100,000
persons could induce about 8 premature deaths.
3.6 The Risk of Bone Cancer
Unlike radium-226, which is distributed throughout the bone
volume following long term ingestion, plutonium is preferentially
deposited and retained on endostial bone surfaces, principally in the
organic matrix. In some cases as much as 30-50% of the endostial
plutonium has been shown to be retained on osteogenic cells (36).
Americium and curium are also retained on bone surfaces. Alpha
particle emitters which are retained on bone surfaces have been shown
to be more tumorgenie than radium-226 and other bone volume seekers.
Surface seekers deliver a higher dose to osteogenic cells adjacent to
25
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bone surfaces, and such injury is thought to be the cause of
radiogenic bone sarcomas.
There is no clinical evidence of bone cancer being caused by
plutonium. The most relevant human data is for medical patients
treated with radium-224, which, because of its short half-life (3.6U
days), is retained mainly on bone surfaces. A large number of
patients (approximately 900) who were treated with radium-224 for
tuberculosis and ankylosing spondylitis have been followed for bone
cancer incidence by S pi ess and Mays (37) . The dose to these patients
has been calculated by the authors in terms of the average skeletal
dose, defined as total alpha energy emitted divided by bone mass, even
though the dose distribution is very nonuniform. On this basis Mays
has estimated that for chronic irradiation due to Pu-239, 200 bone
cancers will be produced per 10s rad to a 7 kg skeletal mass (38). In
terms of the dose to mineral bone, mass 5 kg, utilized in this
analysis, these results yield 140 bone cancers per rad to osseous
tissue. As noted below this estimate is likely to be too low.
Because of uncertainties in the redistribution of Ra-22U
following its initial deposition on bone surfaces. Mays1 estimate of
the average skeletal dose delivered in the Ra-224 cases may be too
high, leading to an underestimate of the risk per rad for radium-224.
While Mays assumes that half of the skeletal radium-224 decays on bone
surfaces and half in the bone volume, Marshall has stated that only
1.5X of the skeletal radium-224 decays within the bone volume away
from bone surfaces. This would increase the risk per rad by 174%.
26
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Furthermore, Marshall's model predicts that, for radium-22«* on bone
surfaces, the dose rate to osteogenic cells near the bone surface is
8.9 times the average skeletal dose rate; for plutonium-239, 12.8
times (39). In terms of average dose to osseous tissue as calculated
for these risk estimates, plutonium-239 would therefore deliver 1.14
times as much alpha particle dose to osteogenic cells as radium-22U.
This estimate is likely to be too high, since it assurr.es all the
Plutonium is retained on bone surfaces and none is buried in the
remodelling or bone growth process.
The residence time of plutonivun on bone surfaces depends on acre.
In rapidly growing animals, it is relatively short (40), while in
adults, as Jee, et al. have pointed out, "Not only is there a
prolonged «»Pu bone surface residence time in adult bone, but they
accumulate more *3«Pu with time (UO)." 'since almost all of the body
burden is assumed during adult life, the exposure regime due to
chronic plutonium inhalation and ingestion way favor a surface dose
distribution more analogous to Marshall's model than Mays'. After
giving due consideration to the smaller number of bone precursor cells
in adults, Jee, .et al. have characterized the plutonium-239 injury to
bone as low in rapidly growing beagles, moderate for young adults, and
high for adults (HO). A similar characterization for degrees of
insult would appear to hold for humans, particularly when subjedt to
chronic exposure.
27
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Based on these considerations, below is an upper bound estimate
of the risk from plutonium and other bone surface seekers in terms of
average skeletal dose:
140 x 1.7U x 1.4U = 350 bone cancers
10« rad 10* rad
Even though the redistribution of plutonium on adult bone
surfaces is expected to be very uneven on both macroscopic and
microscopic scales, it seems likely that the amount of retained
plutonium irradiating bone surfaces will be between 50» and 90* of
total bone burden. It should be noted that the extent of plutonium
redistribution affects only the factor of l.UU in the relationship
shown above.
It is assumed that an average of EPA's upper and lower bound
figures, 250 bone carcinomas per 10* average skeletal rad, is a
reasonable estimate of the actual bone cancer risk. The same risk is
applied to americium and curium, whose metabolism in bone tissue is
expected to be similar if not identical to plutonium1s.
The latent period observed for the radium-22U patients was five
years, with a plateau period of ten years. Therefore, the average
annual risk would be 25 sarcomas per 10* skeletal rsd per year at
risk. The same risk is assumed for both juveniles and adults, since
Mays' analysis of the radium-22«» results indicates little difference
between these two groups.
This risk estimate for bone cancer has been used to determine the
risk to a cohort of 100,000 persons receiving a lifetime exposure, as
28
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outlined in Annex <». A cohort analysis is essential for this risk
estimate since the correlation between accumulated dose and the
duration of exposure is an important factor. To provide input data
for this risk analysis, annual dose rates to bone have been calculated
using the PAID code, as a function of the duration of exposure from
inhaled and ingested transuranium elements (see Tables'A3-3 and A3-6).
3.6.1 Inhalation Risk Estimates
The risk of bone cancer due to the lifetime inhalation of
Plutonium causing a one mrad annual dose to pulmonary lung tissue is
shown in Table A3-11. The estimated excess risk is relatively small
compared to that for lung cancer cf. Table A3-10. Estimates of
relative risk has not been considered for the case of bone cancer. In
view of the short duration of the plateau period used in the current
model, tert years, and the small risk of naturally occurring bone
cancer, the Agency believes that the absolute risk provides a suitable
estimate to use for public health protection.
3.6.2 Ingestion Risk Estimates
The risk of bone cancer mortality occurring in a cohort due to
ingestion has been calculated by means of a life table analysis. It
has been assumed that the cohort is irradiated for a lifetime due to a
constant intake of plutonium-239 oxide, so that the bone dose in the
70th year is 3.0 mrad. The estimated risk of bone cancer is shown in
Table A3-12. Note that while the risk due to the ingestion of Am-2«»l
or Pu-239 in a non-oxide form would be the same, the annual intake
29
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needed to produce the limiting dose rate to bone would be ten times
smaller.
Included in Table A3-12 is the bone cancer risk due to the
chronic ingestion of Am-2Ul, Cm-244, and Pu-2Ul. The latter is a
short half life (14.8 years) beta emitter having an alpha emitting
daughter Am-241. The temporal pattern of the alpha dose to bone for
Pu-241 and Cm-244 differs from that due to Pu-239 and Am-241. Because
of the delay caused by the short half life parent, the alpha dose from
the Am-241 daughter is delivered relatively late in life and the
cancer risk is somewhat smaller. In contrast, Cm-244 (half life 17.9
years) approaches the equilibrium dose rate more rapidly than pu-2-39
with a larger dose delivered early in life and thus a greater cancer
risk (see Table A3-12).
3.7 THE RISK OF INDUCING CANCER OF THE LIVER
The magnitude of the potential risk of inducing liver cancer by
means of plutonium and other transuranium elements has been recognized
only recently. Existing governmental regulations are based on the
1959 NCRP-ICRP assumption that the critical organ for plutonium
deposited from blood is bone (28). More recently, it has been
recognized that deposition in liver is as likely as in bone. ICRP 19
assumes '45% of the plutonium and other transuranium elements dissolved
in blood is deposited in the liver and an equal amount in bone (4).
Based on the results of animal studies, other authorities have
estimated a somewhat lower deposition in liver for plutonium and
somewhat higher for americium and curium (41). The expected variation
30
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between the transuranium elements is not large enough to change, by an
appreciable extent, the overall risk estimate made below. Only the
type of cancer might differ.
The risk to humans from alpha emitters deposited in the liver can
be assessed on the basis of rather limited information obtained from
epidemiclogical studies af medical patients. Earlier in this century,
a low specific activity alpha particle emitting contrast medium called
Thorotrast, was utilized in some diagnostic x-ray procedures. In
subsequent years patients who were treated with it, mainly European,
have been followed clinically and shown to have a higher than expected
incidence of liver cancer. These data are pertinent although they do
have limitations. Because the amount of material injected into the
blood in these studies was quite large, its deposition in the liver
was uneven (42, U3). Liver cancer incidence in this group would not
necessarily be higher than might be expected for a more uniform
deposition. £n the contrary, there is a general concensus that highly
localized concentrations of alpha particle emitters are likely to be
less carcinogenic than a more uniform distribution (3) . Another
possible limitation of these data is that the relatively large
quantity of Thorotrast deposited in the liver could lead to a foreign
body response, which might in turn result in cancer. While the
quantitative applicability of the human experience with Thorotrast to
the prediction of plutonium risks to liver is tentative, there is an
abundance of experimental animal data showing that liver cancers can
be induced by plutonium. Liver cancers are seen less frequently than
31
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bone cancers in most experiments with animals, but since liver cancers
have a longer latent period than bone cancers, they may be more
important in a longer-lived species such as man. The primary source
of data on Thorotrast patients is Faber's review (U«) also cited by
the MRC as a basis for their assessment of plutonium toxicity (16).
Faber's estimates are: absolute risk, «.2 x 10-* liver cancer for each
organ rad per year at risk; relative risk, an 11% increase per rad.
3.7.1 Inhalation Risk Estimates
In Table A3-13, the risk of liver cancer has been evaluated for
the airborne concentration of a plutonium-239 oxide aerosol (1 u AKAD)
that will cause a pulmonary dose rate to adults of 1 mrad per year.
Unlike the case of ingested material discussed below, the risk of
liver cancer due to various inhaled long half-life transuranics is
nearly the same (for a given lung dose) as for plutonium oxide. This
is because gut transfer has little effect on the dose to liver due to
inhaled materials. For Cm-2*'» and other comparatively short half life
transuranium elements, the dose to liver relative to lung is mucli
smaller, cf. Table A3-3 and A3-4 so that the risk of inducing liver
cancer is less for such radionuclides than for plutonium. The average
dose rate to liver relative to lung is nearly independent of particle
size (15). In computing Table A3-13, the risk to children leas than
10 years of age was assumed to be different from adults. Since no
clinical data is available on the effect of Thorotrast on the young,
their risk was estimated from Table 3-2 in reference 2, as described
above for the case of lung cancer.
32
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The average of the estimated excess deaths shown in Table A3-13,
is 0.34 for a lifetime exposure to 100,000 persons. This is a much
smaller number of excess cancers than the estimated mortality due to
lung cancer from the same aerosol concentration, cf. Table A3-10.
3.7.2 Ingestion Risk Estimates
In contrast to inhalation, the ingestion dose to liver and the
resultant risk is a direct function of the amount of radioactivity
transferred to blood via the gastrointestinal tract. Table A3-14
lists the risk of liver cancer from a lifetime ingestion pattern that
results in a 3 mrad dose to bone after 70 years. The results shown
are for plutonium-239. For transuranium elements having a physical
half life comparable to the elements1 residence time in liver the risk
will be somewhat greater since the dose approaches the equilibrium
value earlier in life. Averaging the estimates of early death shown
in Table A3-1U yields an estimated risk of two deaths per 100,000
exposed persoeis, somewhat less than for cancer of the bone, cf Table
A3-12. For Am-2«l, Pu-241 and Cm-2«H» this average lifetime risk is
2.1, 1.2 and 3.2 per 100,000 exposed, respectively.
3.8 THE RISK OF GENETIC DAMAGE
Risks due to transuranium elements are not only to persons
directly exposed to the radiation but also to their progeny. Alpha
particles can damage the male progenitor cells producing sperm and the
egg cell (oocyte) in the female. The expression of this damage is.
either genetic impairment of the live-bom offspring or fetal death.
33
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Only the former has, as yet, been quantified in current risk estimates
of health effects due to radiation.
NAS-BEIR estimates of genetic risk are based on chronic
x-irradiation to males, not the dose to both sexes due to alpha
particles. For the reasons given below genetic damage from alpha
particles is expected to be about a factor of 100 greater than that
assumed in the BEIR report (2). Based on current recommendations of
the ICRP, alpha particles are 20 times more damaging than x-
irradiation for a number of biological end points, including genetic
effects. This is not necessarily overly conservative since an
increase of about 20 compared to x-irradiation has been reported for
genetic damage from highly ionizing neutron irradiations (16).
Alpha particle damage is believed to be independent of dose rate.
However BEIR estimates of genetic risk are based on low dose rate
x-ray exposures which had the effect of lowering genetic damage to
males by a factor of 3.U and eliminating this damage to females. The
.British Medical Radiation Council also assumed no damage to the oocyte
of females (16), an assumption based on Searle's evaluation (47) of
mouse experiments with fission neutrons, performed by Batchelor,
et al. (i»6). However, more recent analyses of the efficacy of chronic
irradiation in producing genetic damage indicate that it may not be
wise to disregard potential damage to the ocoytes of the fomale (48) .
Therefore, at this time it appears prudent to increase the BEIR risk
estimate for genetic damage due to chronic x-irradiation by a factor
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of 100 (5 x 20) when assessing the risk of genetic, damage due to alpha
emitting transuranics in the gonads.
The range of the BEIR estimates of genetic risk is quite large
Table 4, on page 57 of (2). They reflect the uncertainty in the
extent of the genetic component in diseases classified as having a
'•complex etiology", i.e., those with a mutational component among many
other causes, such as heart disease. One recent analysis indicates
that this type of genetic risk may be so small that the actual risk is
near the lower end of the range estimated by the BEIR Committee in
1972 (49). on the other hand, there are other analyses which indicate
that the 1972 BEIR report may have underestimated the amount of
multifactorial diseases having a genetic component (50).
In 1976 EPA contracted with the National Academy of Sciences to
provide it with guidance on genetic risk, as part of the BEIR
committee's reevaluation of radiation risk. The degree to which the
estimate made above may be high or low may be resolved when the BEIR
Committee's ongoing review of this problem is completed.
It is estimated here that a 30-year dose of one millirad due to
alpha-emitting transuranium elements in gonadal tissue may cause
between 0.1 and 2 genetic effects per 100,000 live births in the first
generation. If this gonadal dose were to continue indefinitely so
that a new equilibrium of genetic damage was established in the
population, the risk might increase to 0.6 to 1? per 100,000 live
births. Currently, the observed genetic effects in the U.S. are about
6000 per 100,000 live births.
35
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3.8.1 Genetic Risk Estimates
Risk estimates for genetic damage are based on the gonadal dose
received in a reproductive generation, i.e., the first 30 years of
life. Table A3-15 lists the 30-year gonadal doses due to chronic
ingestion of transuranium elements that would also cause a 3 millirad
per year dose rate to bone after 70 years. Except for cm-244, the
guidance's limitation on the annual dose rate to bone limits the
relevant gonadal dose to about 10 millirad. The estimated genetic
risks due to this 30 year dose is shown in Table A3-16. Chronic
ingestion of Cm-2tt4, would cause genetic risks about two times larger
which would cause genetic risks about two times larger than those
shown in Table A3-16. However, because of Cm-244's relatively short
half life circumstances that would lead to a constant rate of
ingestion for 30-years are difficult to imagine. For the limiting
dose rates permitted by this guidance, genetic effects due to
inhalation are substantially less important than those due to
ingestion. Where the gonadal dose is from chronically inhaled
transuranics causing a one millirad dose to lung, the gonadal dose is
l.U mrad in 30 years (Section 3.U.3) . and the estimated genetic
effects are a factor of seven smaller than the estimates shown in
Table A3-16.
36
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3.9 OTHER RISKS DUE TO THE INHALATION AND INGESTION OF PLUTONIUM
3.9.1 Leukemia due to Bone Harrow Irradiation
Recently, several authors have pointed out that leukemia is a
potential risk from plutonium incorporated into bone tissues (51).
Alpha particles originating in trabeculae may irradiate a significant
fraction of the bone marrow, and the plutonium in marrow itself will
act as a source. Based on autoradiographic studies of bone and ton*
marrow. Spiers and Vaughan have estimated that the dose to trabecular
marrow is 88 percent of the average skeletal dose due to plutonium-239
(52).
Using this factor and the skeletal dose rate from Pu-239, shown
in Figure A3-1, the risk of leukemia has been calculated in a cohort
of 100,000 persons exposed to plutonium-239 aerosol having a 1 u AMAD
and concentration of 2.6 f Ci/m3. This concentration results in the
limiting dose rate to pulmonary lung of one mrad per annum. Excess
leukemia deaths were estimated utilizing the risk coefficients given
in Table 3-2 of the 1972 BEIR Report (2) and a quality factor of 20
for alpha particle irradiation (US). Results are listed in Table
A3-17, which shows that the incremental risk due to leukemia is rather
small compared to the risk for other cancers associated with a dose of
1 mrad per annum to pulmonary tissue, cf. Table A3-10.
In the case ot ingested plutonium-239 the estimated risk of
leukemia induction is somewhat greater. For a 3 mrad limiting dose to
have in the 70th year, the leukemia risk ranges from O.ft to 1.6 case,s
per 100,000 exposed for absolute and relative risk models respectively
*
37
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and is therefore smaller but comparable to the estimated risk of liver
cancer due to the ingestion of transuranic elements.
Over a lifetime the average dose to the whole body (soft tissues)
due to the 7* of actinides distributed in the body tissues after
inhalation is about a factor of 100 less than the dose received by
skeletal tissues. Leukemia mortality due to excess radiation is about
one-fifth of all radiation induced cancers (2). Therefore, health
effects due to the plutonium burden in the whole body are expected to
be about 5% of the early deaths due to leukemia indicated in Table
A3-17. Inhalation of other transuranium elements at these limits set
by those guides would cause a similar risk relative to leukemia.
3.10 SUMMARY OF HEALTH RISKS
3.10.1 Inhalation Pathway
Table A3-18 below summarizes the somatic and genetic risk due to
the inhalation of transuranium element aerosols causing an annual dose
to the pulmonary region of 1 mrad per year. The estimated cancer risk
to a cohort of 100,000 is nine premature deaths, with an estimated
range of between 3 and 30 early deaths. Since the average lifespan of
this cohort would be about 71 years, the annual risk of cancer from
lifetime exposure is about 1 x 10-* per year. The estimated genetic
risk to the first generation is considerably smaller numerically than
the risk of cancer due to the inhalation of transuranium elements.
38
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3.10.2 Ingestion Pathway
The total risk due to the ingestion of transuranium elements may
include an appreciable genetic component as well as the risk of
cancer. Therefore, in this guidance the cancer risk due to ingestion
is less than that due to inhalation. Exact correspondence between the
risks from inhalation and ingestion is not possible, since it depends
on value judgements concerning the acceptability of risk to future
generations as compared to the present. Moreover, the uncertainty of
the genetic risk estimates makes such a comparison uncertain.
The guides are expressed in terms of the dose rate to bone after
70 years of chronic ingestion. Including the risk of leukemia
induction, this would result in an estimated incidence of about five
cases of fatal cancer in a cohort of 100,000 persons. The range of
estimated genetic effects for the same pattern of exposure are shown
in Table A3-16. The estimated genetic risk to first generation
progeny may be numerically comparable to the cancer risk to the
parents, while the genetic risk to succeeding generations may exceed
the risk of cancer.
39
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51. Vaughan, J., 1976. Plutonium a Possible Leukemia Risk, pp
691-705 in The Health Effects of Plutonium and Radium, W. S. S.
Jee, editor. The J. W. Press, Salt Lake City, Utah
52. Spiers, F. W. and Vaughan, J-, 1976. Hazards of Plutonium with
Special Reference to the Skeleton, Nature 259;531-534.
-------
Table A3-1
Retention Halflives, Clearance Patterns and
Breathing Rate for Class Y Aerosols
Inhaled by Referenced Man (4,10)
Lung Compart mental**
Compartment Half life (days)
Nasopharyngea 1
Tracheobronchia 1
T-B
Pulmonary
T-B lymph nodes
Breathing rate 2
8 hours restimr)
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
.3 x
*
0.01
0.4
0.01
0.2
500
1
500
500
1000
10* liters
Transfer Target
Fraction
0.01
0.99
0.01
0.99
0.05
0.4
0.4
0.15
0.9
0.1
per day (16
to blood
to GI tract
to blood
to QI tract
to blood
to GI tract
via T-B
to GI tract
via T-B
to lymph nodes
to blood
retained
hours lightwork;
**See Figure A3-2 for designation of compartmental pathways (a) ,
(b)f etc.
-------
Table A3-2
Annual Dose Rate to Various Lung Compartments from
Chronic Exposure to Plutonium-239 Aerosols
Concentration: 1.0 fCi/m' Particle AMAD: 0.05, 1.0 and 5.0 Microns
Duration of
Exposure Pulmonary Tracheobronchial Nasopharyngeal
mrad/yr. x 10-l mrad/yr. x 10-2 mrad/yr. x 10-«
O.OSu l.Ou 5.0u O.OSu l.Ou 5. Ou O.OSu l.Ou 5.Ou
1
5
10
70
3.9
9.1
9.8
9.9
1.5
3.5
3.8
3.8
.7
1.7
1.8
1.8
2.7
3.7
3.8
3.8
1.1
1.5
1.6
1.6
6.1
7.9
8.1
8.1
.OU
.04
.04
.04
11.
11.
11.
11.
30.
30.
30.
30.
-------
Table A3-3
Annual Dose Rates to Various Organs from Chronic
Exposure to Plutonium-239 and Americium-241
Aerosols AMAD=lu; Concentration 1 fci/mJ; class Y Clearance
Duration of
Exposure
(years) Liver
(mr ad/year)
Bone T-B Lymph
Am***
(millirad/year)
Liver Bone T-B Lymph
1
5
10
15
20
30
40
50
70
Duration
Exposure
(years)
1
5
10
15
20
30
40
50
70
.001
.018
.052
.089
.13
.19
.24
.29
.36
Of
Liver
~ .001?
.087
.46
1.1
1.8
3.4
5.0
6.4
8.7
.0005
.0065
.019
.034
.049
.078
.11
• 13
'.17
Puz*i/Am*»»*
.40
4.0
7.0
8.7
9.8
12
14
15
19
(microrad/year)
Bone T-B Lymph
Nodes
.0005
.032
.17
.41
.71
1.4
2.2
3.0
4.4
.396
17.1
45
64
75
92
110
120
150
.0015
.019
.055
.095
.13
.20
.26
.30
.37
Cm*
.0005
.007
.021
.036
.052
.082
.11
.14
.18
!««yT>.?«0
Noaes
.39
4.2
7. H
9.1
10
12
14
16
20
^IH " * w f w™ " """
(milliirad/year)
Liver Bone T-B Lymph
Norths
.0016
.018
.047
.073
.094
.12
.14
.15
.16
.0006
.0016 4
.017 7
.028 7
.037 8
.049 9
.057 9
.063 10
.068 11
.040
.0
.5
.8
.4
.3
.8
* a dose only - 70th year beta dose rates: liver, 0.11 urad; bone, 0.049 urad.
47
-------
Table A3-4
Aerosol Concentrations in fCi/m3 Producing a
1.0 mrad Annual Dose Rate to the Pulmonary Region
of Reference Man; Class Y Clearance
Aerosol
AMAO (u)
0.05
0.10
0.30
0.50
1.0
2.0
3.0
5.0
Aerosol
AMAD (u)
0.05
0.10
0.30
0.50
1.0
2.0
3.0
5.0 .
94
2 34JJ (a)
92
1.0
1.1
1.6
1.8
2.5
3.4
4.1
5.2
9S
237Np(a)
93
1.0
1.1
1.6
1.8
2.4
3.3
4.0
5.1
z«Pu(a)
94
92
1.0
1.2
1.7
1.9
2.6
3.5
4.3
5.4
2*»Cm(a)
9*
94
1.0
1.1
1.6
1.8
2.5
3.4
4.1
5.2
94
23«U(Ct)
92
1.0
1.2
1.7
1.9
2.6
3.5
4.3
5.4
94
z*»Am(a)
95
330
390
540
630
850
1,100
1,400
1,800
* 0 dose rate < 40* of o dose - only a dose is considered in setting limit.
48
-------
Table A3-5
Fraction of Ingestion Material Transferred to
Blood from the Gastrointestinal Tract
Transfer Fraction
Radionuclide Biologically
Non-oxide Oxide Incorporated
Plutonium-238 10-' 10-' 5 x 10-'
Plutonium-239 10-' 10~* 5 x 10-'
Plutonium-2«0 10-' 10-* 5 x 10-'
Plutonium-2Ul 10-' 10-' 5 x 10-'
Americium-2Ul 10-' 10-' 5 x 10-»
Curium-244 10-' 10-' 5 x 10-'
* Persons over one year of age (see text).
49
-------
Table A3-6
Annual Dose Rate Due to Chronic Ingestion of
Plutonium-239 Oxide, Americium-241, Plutonium-241 and Curium-2UU
Annual Intake 1000 pCi/Year*
Duration of Plutonium-239 Oxide
Ingest ion (urad/year)
Years Bone Liver Whole
Body
1
5
10
15
20
30
40
50
70
Duration of
Ingest ion
Years
1
5
10
15
10
30
40
50
70
0.9
4.3
8.4
1.2x101
1.6x101
2.4x101
3.0x101
3.7x101
4.8x101
1
Bone
.007
.17
.60
1.2
2.0
3.8
5.7
7.6
11
2.4
1.2x101
2.2x101
3.2xlOi
4.1x101
5.6x101
6.9x101
8.1x101
9.8x101
Pu2*i/Am2*i
(urad/year)
Liver
.020
.45
1.6
3.1
4.9
8.7
12
16
21
1.1x10-2
6.3x10-2
1.0xlO-i
1.5x10-1
2.0x10-1
3.0x10-1
3.7x10-1
4.4x10-1
6.1x10-1
**
Whole
Body
9.0xlO-»
2.1x10-3
7.5xlO~3
1.5x10-2
2.6x10-2
4.7x10-2
7.0x10-2
9.6x10-2
1.4x10-1
Americium-241
(urad/year)
Bone Liver
9.2
4.5x101
8.8x10*
1.3x102
1.7x102
2.4x102
3.1x102
3.8x102
4.9x102
2.5x101
1.2x102
2.3x102
3.4x102
4.3x102
5.9x102
7.2x102
8.3x102
9.9x102
(urad/year)
Bone Liver
9.5
4.4x101
7.8x101
1.1x162
1.3x10*
1.6x102
1.8x102
1.9x102
2.1x102
2.6x101
1.2x102
2.1x102
2.8x102
3.3x102
3.9x102
4.3x102
4.6x102
4.8x102
Whole
Body
l.lxlO-i
5.6x10-1
1-1
1.6
2.1
3.0
4.0
a. 7
6.1
Whole
Body
1.2x10-1
S.uxlO-t
9.8x10-1
1.3
6.8x10-1
2.0
2.2
2.3
2.6
•Reference Han (10).
**Alpha dose rate.
50
-------
Table A3-7
Average Skeletal Dose Rate in the 70th Year Due to
the Lifetime Ingestion by Reference Man of 10 nCi/yr.
Radionuclide Chain Millirad Per Year
Oxide Other Inorganics*
23epu(a)/23»u(a) H.O 4.0
Z3«pu(a)/Z3su(a) 0.18 U.8
2«opu(a)/«»U(a) 0.»8 U.8
z«ipu(e)/2*lAm(a) 0.11** 0.11**
**iAm(a)/«mp(a) a.9 H.9
2»*Cm(a)/2*»(o) 2.1 2.1
•Biologically incorporated transuranic multiply by 5.0.
**Only the alpha dose listed in applicable to this guide.
The beta dose rate is 1.5 urad/yr. in the 70th year.
51
-------
Table A3-8
Cumulative 30-year Alpha Particle Dose to
Gonadal Tissue
Annual Intake 1000 pCi/y
Radionuclide 30-year Dose
millirad
Pu-238 . 1.80
Pu-239 (oxide) 0.18
PU-2UO (oxide) 0.18
*Pu-2«l 0.02
Am-2«l 1.9
Cm-2«« 1.5
* adose only - the 6 dose is 1.2 x 10-* rads.
52
-------
Table A3-9
Average Skeletal Dose Rates Due to Chronic Ingestion of
Plutonium-239 Oxide with and Without Increased Infant Uptake
Annual Intake 1000 pCi/yr.
Age Average skeletal Dose Rate (uRad/yr.)
Without Enhanced With Enhanced
Infant Absorption* Infant Absorption**
1 0.86 86.H
5 4.26 37.7
10 8.37 32,6
15 12.1 21.6
20 16.2 23.7
30 23.5 30.5
40 30.3 36.9
50 36.fi 42.7
70 48.0 53.3
*GI tract to blood transfer 10-* all ages.
**GI tr'act to blood transfer 10-* first year of life.
53
-------
Table A3-10
Measures of the Lifetime Health Risk Due to Lung
Cancer Mortality Pulmonary Dose Rate to Adults
Imrad/yr. Cohort Size 100,000 Persons - Latent Period = 15 Years.
Measure of Risk Relative Risk Estimate Absolute Risk Estimate
30-Year Lifetime 30-year Lifetime
Plateau Plateau Plateau Plateau
Premature Deaths 7.02 25.0 2.15 2.80
Aggregate Years of
Life Lost to Cohort 129 368 H7 5<4
Average Years of Life
Lost to Premature Deaths 18.» l«.7 22.0 19.u
54
-------
Table A3-11
Estimated Risk of Bone Cancer Mortality Due to the Inhalation
of Plutonium-239 Oxide (AMAD=1.0 u)
Pulmonary Dose Rate = 1 mrad/yr.
Average Skeletal Dose Rate in the 70th Year . U6 mrad
Cohort Size = 100,000 Persons
Measure of risk Absolute Risk Estimate
10 Year Risk Plateau
Premature Deaths 0.37
Aggregate Years of Life
Lost to Cohort 8.0
Average Years of Life Lost
to Premature Deaths 23.3
55
-------
Table A3-12
Estimated Risk of Bone Cancer Due to a Lifetime Ingestion
Pattern that Results in a 3.0 mrad Alpha Particle Dose Pate Per Year
to Bone in the 70th Year
Absolute Risk
10-Year Risk Platue
Radtonuclide Premature Deaths per 100,000 Exposed
Pu-239 2.H
Am-2ttl 2.5
PU-2U1 1.9
Cm-2«4 3.2
Average years of life lost per premature death 2H years.
56
-------
Table A3-13
Measures of the Lifetime Health Risk of Liver Cancer Mortality
Due to Inhalation of Plutonium-239 Oxide
-------
Table A3-1U
Estimated Risk of Liver Cancer Due to A Lifetime Ingestion Pattern
That Results in a 3.0 mrad Alpha Particle Dose Rate Per Year
to Bone in the 70th Year for Long Half Life Transuranic Elements*
Deaths per 100,000 exposed
Risk Model 30-year Plateau Lifetime Plateau
Relative Risk 1.6 2.8
Absolute Risk 1.5 i.a
*T »/z 100 years.
58
-------
Table A3-15
Thirty-year Gonadal Dose Due to an Ingestion Pattern
Causing a 3 Millirad/yr. Alpha Particle Dose Rate to Bone in the 70th Year
(Chronic Lifetime Ingestion at a Constant Rate)
Transuranium Element Gonadal Dose
(millirad)
Pu-238 13
Pu-239 11
Pu-2UO 11
Pu-201 6
Am~2«»l 12
Cm-2U4 21
E9
-------
Table A3-16
Estimated Genetic Risk Due to an Alpha Particle Dose
of 10 Millirads to the Gonads in the First 30 Years of Life
Number of Effects Per
100,000 Live Births
Type of Genetic Disease 1st Generation All Generations
Dominant 1-10 5-50
Multifactorial 0.1 - 10 1 - 100
Total 1 20 6 150
60
-------
Table A3-17
Measures of the Lifetime Health Risk of Leukemia Due to
Inhalation of Plutonium-239 Oxide (AMAD = lu)
Pulmonary Dose Bate 1 mrad/yr.
Cohort Size 100,000 Persons
Measure of Risk Relative Risk Absolute Risk
Early deaths 0.24 0.06
Decrease in population 2.8 1.4
life expectancy (years)
Average years of life 11.8 23.1
lost per early death
61
-------
Table A3-18
Estimated Risk Due to the Inhalation of Transuranic
Aerosols for a 1 mrad/yr. Lifetime Exposure
Estimated Somatic Risk in a
Cohort of 100,000 Persons
Cause of early death Premature deaths Range
Lung Cancer 8 2-25
Bone Cancer 0.3 0.2-.7
Liver Cancer 0.3 0.2-0.6
Leukemia 6 other causes 0.12 0.06-0.25
Estimated total
premature deaths 9 3-20
Estimated Genetic Risk
per 100,000 Live Births
First generation 0.1-3
All generations — 1-20
62
-------
1.0-
I
cc
M
(9
CC
o
111
i
.001
.001
10
20 30 40 50
DURATION OF EXPOSURE - (YEARS)
60
70
DOSE RATE TO ORGANS AS A FUNCTION OF TIME DUE TO CHRONIC INHALATION
OF ONE MICRON (AMAD) PLUTONIUM PARTICLES AT A CONCENTRATION OF
2.6 fCi/m». EQUILIBRIUM DOSE RATE TO PULMONARY LUNG 1 MRAD PER YEAR
ADULT REFERENCE MAN - BREATHING RATE 2.3 x 104 LITERS PER DAY.
FIGURE A3-1
63
-------
Inhala-
tion
^ °1 -
1 J
B
1
0
0
O
.<•>
M
L>2
! NASOPHARYNGEAL
i (N-P)
D4
TRACI
i
1
i
DB
4EOBRONCHIAL
(T-B) j-"
i PULMONARY
! (P)
1 (h)
LYMPH
NODES (j)
f1
(
(b)
'
f) *
g) ^
^~>
Inges-
tion
Y
s
T
O
M
A
H
i
S 1
M N
A T
L E
L S
T
N
E
T
D' IS THE TOTAL AEROSOL INHALED; D2 IS THE AEROSOL IN THE EXHALED AIR; D3, D4, AND Ds
ARE THE AMOUNTS DEPOSITED IN THE NASOPHARYNGEAL, TRACHEOBRONCHIAL, AND PULMONARY
LUNG HbSPECTIVELY. THE LETTERS (a) THROUGH (j) INDICATE THE PROCESSES WHICH TRANSLOCATE
MATERIAL FROM ONE COMPARTMENT TO ANOTHER. VALUES FOR THESE PARAMETERS ARE LISTED
IN TABLE A3-1.
FIGURE A3-2
64
-------
13.0
-2.5
LZO
PARTICLE AMAD - (MICRONS)
RELATIVE DOSE RATES DUE TO CHRONIC INHALATION AS A FUNCTION OF PARTICLE SIZE (AMAD).
FOR THE PULMONARY LUNG, THE DOSE RATE AT EQUILIBRIUM; FOR LIVER AND BONE, IN THE 70th
YEAR. THE CASE SHOWN is Pu-239. THE CURVES ARE VIRTUALLY IDENTICAL FOR ALL THE
TRANSURANIUM ELEMENTS CONSIDERED IN THIS STUDY.
FIGURE A3-3
65
-------
Annex IV
RISK PERSPECTIVES
U. S. Environmental Protection Agency
Office of Radiation Programs
Washington, D.C. 20460
-------
Annex IV
Table of Contents
Page
1. Introduction 1
2. Life Table Methodology 1
3. Risk From Background Radiation 4
4. Other Risks Experienced By the General Population.... 7
-------
Annex IV
Risk Perspective
1. Introduction
The purpose of this annex is to provide a perspective for
evaluating the somatic component of the risk from transuranium
elements. Life table measures of .risk of death are developed for
some of the diseases and accidents presently experienced by the U.S.
population. They are comparable to the life table risk measures
provided in Annex III.
Before proceeding with the discussion of what has been done to
provide a perspective for evaluating this risk, the general character-
istics of life table models will be described.
2. Life Table Methodology
Life tables are a method for following hypothetical cohorts of
individuals through their life spans, from birth to death. The cohort
is assumed to be subject throughout its existence to the age specific
mortality rates observed for an actual population.
The National Center for Health Statistics (NCHS) publishes life
table models for the U.S. population, which incorporate age specific
mortality rates for the U.S. population (1,2). They are used to estimate
the life expectancy of the U.S. population.
EPA has developed life table models (based on the NCHS models)
~ ' • - C - . . • , "
for measuring the impact of changes in the rate of mortality. Changes
-------
are measured from the mortality rates incorporated into the NCHS tables.
These changes may represent increases or decreases in the mortality
rate. Increases result when people are exposed to additional risks not
a component of the U.S. population average. Exposure to the ionizing
radiation emitted by transuranium elements is an example of an
increased mortality risk.
Decreases in mortality would result from the elimination of one
or more of the causes of death presently experienced. An example
(which is used in this annex) is the hypothetical elimination of lung
cancer as a cause of death in the U.S. population. When these cal-
culated results from the EPA model are compared to the results of the
NCHS model, the impact of lung cancer mortality on the U.S. population
can be estimated.
Because of methodological differences, the discussion of the EPA
life tables will consider the case of increased and decreased mortality
separately.
The life table concept of life expectancy has attractive features
for measuring risk, for it is based on the years of life lived by the
members of the cohort. EPA's models rely on standard life table
methodology to determine the sum of the years of .life lived. The
difference in years of life lived in the EPA and NCHS models is the net
change in total years of life lived by the two cohorts.
For the case of increases in the rate of mortality caused by
exposure to transuranium elements, the net change is downward (the years
-------
of life lived by the cohort in the EPA model is less than that for the
NCHS model). The EPA model has been designed so that the numbers of
deaths attributable to the increased rate of mortality can be calcu-
lated. These are premature or early deaths because the individuals die
at an earlier age than they would have, had there been no increase in the
mortality rate (i.e. had they not been exposed to transuranium ele-
ments). The net decrease in years of life lived divided by the number
of premature deaths is the measure of the average years of life lost to
those dying prematurely as a result of the exposure.
Lung cancer will be used as an example for discussing decreased
mortality rates resulting from the elimination of a cause of death.
The elimination of other causes of death uses the same methodology. The
years of life lived increases when the mortality effects of lung cancer
are eliminated. The EPA model determines the numbers of lung cancer
deaths averted by eliminating lung cancer as a mortality risk. The net
increase in years of life lived divided by the number of lung cancer deaths
is the average years of life gained to those whose deaths by lung cancer
have been averted. This effect can also be interperted as a change in
the opposite direction, from a situation where there is no lung cancer
mortality to one where lung cancer mortality is the same as presently
experienced in the U.S. With this change in interpretation, the net
change in years of life lived is considered a decrease, for it measures
the years of life lost to the cohort because of lung cancer mortality.
This value divided by the number of lung cancer deaths gives the average
years of life lost to those dying of lung cancer. This change in
-------
interpretation facilitates the comparison of the risks from transuranium
elements with the risk of lung cancer. This is the interpretation to be
used in this Annex.
A discussion of life table methodology and the technique for
removing specified causes of death from the life table are discussed in
Chiang (3). Life tables similar to the EPA models, with specified
causes of death removed, are published by NCHS (4). The basic methodol-
ogy used here for developing life table estimates is similar to that
discussed in the technical report, "Life Table Methodology for Evalua-
ting Radiation Risk" (5).
The remainder of this annex is devoted to the estimation of the
risk of death from a variety of diseases and accidents. Results are
shown in Tables A 4-1 and A 4-2. These can be compared to the risk from
transuranium elements calculated in Annex III.
3. Risk From Background Radiation
The average annual background radiation equivalent dose received by
the U.S. population is approximately 100 mrem over the whole body.
It is assumed that on a per rem basis background radiation will have the
same impact on cancer incidence as other forms of radiation. Two sit-
uations can be evaluated: one where all risks of death are the same as
presently experienced and the other (a hypothetical situation) where the
risk of mortality from 100 mrem whole body dose is removed. The'results
are shown in Table A 4-1. l
All risk estimates for whole body dose are taken from the BEIR
report, Table 3-2, p. 171. Results of four models are shown, based on
-------
relative and absolute risk and on the 30 year and life plateaus for
cancer other than leukemia as defined in the BEIR report (6).
Four measures of risk are shown for each life table model shown
in Table 1. The first measure is the numbers of deaths attributed to
background radiation. Numbers of deaths furnishes no perspective on the
prematurity of the deaths, since it provides no measure of the years
of lifetime lost because of these deaths. The other values in Table
A 4-1 are measures of the lifetime lost.
The basic measure of prematurity of death is the aggregate years
of life lost. Values for each model are shown in Table A 4-1. This
aggregate can be used to measure the reduction in average length of life
for the cohort. This measure expresses the viewpoint at the beginning
of life when all members of the cohort face equal risk of death from
background radiation. The average reduction in years of life lived by
the cohort (reduction in life expectancy at birth) is calculated by
dividing aggregate years of life lost by 100,000 (the cohort size at
birth). This value is shown in the table. The aggregate years of life
lost can also be used to measure the average loss of life to those dying
of background radiation induced cancer. The members of the cohort can
be considered in two groups, those that die of background radiation
induced cancer and those that do not. The second group has the same
life expectancy as it would if there were no background radiation. Those
that do die from background radiation have a reduction in life expect-
ancy equal to the average years of life lost to premature deaths.
-------
The four models (for absolute and relative risk and for 30 year and
life plateaus) provide estimates of cancer deaths ranging from 69 to 490
over the life of the cohort. Aggregate loss of life ranges from 1700 to
6600 years. Reduction in life expectancy at birth ranges from .0017 to
.0066 years. The individuals suffering the deaths induced from the
background radiation suffer an average shortening of their lives ranging
from 14 to 25 years depending on the model.
These results can be compared with the measures of risk presented
in Tables A 3-10 through A 3-14 and A 3-17 and 18 in Annex III.
Table A 3-10 displays the estimated measures of lifetime risk of lung
cancer Induced by inhaled transuranium elements. Estimated numbers of
early deaths range from 2.15 to 25.0 with an aggregate years of life
lost ranging from 47 to 368 years. The average years of life lost to
those suffering early deaths ranges from 14.7 to 22.0 years. Exposure to
1 mrad per year is therfore estimated to have a much smaller lifetime
impact than does background radiation.
Measures of lifetime risk of liver cancer mortality from inhaled
Plutonium are shown in Table A 3-13. This impact is considerably
below that of lung cancer induced by inhaled transuranium elements,
and is therefore lower in comparison to background radiation.
Tables A 3-10,12,14 and 17 of Annex III display measures of risk to
other organs from inhaled and ingested transuranics. Results show that
lung cancer induced from inhaled plutonium is the major contributor to
the risk from exposure to transuranium elements. The cumulative risk
from all organs is not large in comparison to that from background
-------
radiation, as can be seen from the summary of premature deaths from
inhaled transuranic aerosols for a 1 mrad per year lifetime exposure
(Table A 3-18).
These life table models show that lost years of life have an
almost insignificant impact on life expectancy at birth, but that those
that die prematurely from the exposure suffer a substantial shortening
of their lives. The life shortening is approximately the same for both
forms of risk: exposure to transuranium elements and background radiation.
4. Other Risks Experienced By The General Population
Table A 4-2 illustrates a few of the risks of death the U.S.
population presently experiences from various causes. All estimates are
based on the life table model. Mortality rates are derived from 1969
mortality statistics for the U.S (2). The measures of risk are the same
as those used in Table A.4-1 and are interpreted in an analogous manner.
The first risk shown is that from malignant neoplasms. Risk is
measured by removing malignant neoplasms as a cause of death and com-
paring the situation that would then prevail against that for the case
' * '- *»
where it exists at the presently experienced level.
The Table shows that a cohort of 100,000 individuals suffers 2900
spontaneously occurring lung cancer deaths. These deaths take an
aggregate of 45,000 years of life from the cohort. Therefore, life
expectancy at birth is reduced .45 years due to lung cancer. The
average loss of life to those individuals that die of lung cancer is 15
years. These results can be compared to the results in Table A 3-10.
Although the impact of lung cancer is much greater than that for inhaled
-------
Plutonium or for background radiation, the years of life shortening to
those that die of lung cancer is approximately the same.
Other models presented in Table A 4-2 measure the impact of a
variety of non-cancerous causes of death.* The numbers of deaths range
from a high of 1000 to a low of 2, and the aggregate years of life lost
to the cohort ranges from 12000 to 80. These impacts are considerably
smaller than those for malignant neoplasms or for lung cancer.
Some well known diseases are represented in the table. All
incorporate some risk of death. Some, such as chicken pox, are not
normally believed to cause death. As can be seen chicken pox does
involve a small risk of death. The average of 56 years of life lost to
those dying of chicken pox reflects that its impact is primarily on the
young.
The table.also has measures of the impact of various accidental
causes of death. The accidental risks shown range from 1000 deaths due
to falls to 8 for deaths from accidents caused by electric current from
home wiring and appliances. The average years of life lost to those
that die of these accidents reveals that different forms of accidental
death impact at different ages.
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Table IV-1
Measure of Lifetime Risk of Mortality from Background Radiation*
(Cohort size - 100,000)
Risk Models
Relative Risk Estimate Absolute Risk Estimate
Measure of Risk
Premature Deaths
Aggregate Years of Life Lost
to Cohort
Reduction in Life Expectancy
at Birth (in years)
Average Years of Life Lost
to the Premature Deaths
30 Year
Plateau
150
2700
0.027
17
Life 30 Year
Plateau Plateau
490
6600
69
1700
0.066 0.017
14
25
Life
Plateau
84
1900
0.019
22
*A11 mortality effects shown are calculated as changes from the U.S. Life Tables for
1970 to life tables with the risk of mortality from, all forma of cancer reduced to
account for the removal of background radiation. These effects also can be interpreted
as changes in the opposite direction; from life tables with the cause of death removed
to the 1970 life table. Therefore, the premature deaths and years of life lost are
those that would be experienced in changing from an environment where there is no
background radiation to one where background radiation is present. Background
radiation is assumed to be equal 100 mrem per year. Risk estimates are based
on the NAS-BEIR Report. All values rounded to no more than two significant figures.
-------
Table IV-2
Measure of Lifetime Risk of Mortality from a Variety of Causes
(Cohort size - 100,000)
Cause of Death
Malignant Neoplasms (140-209)2
Malignant Neoplasms of Trachea
Bronchus and Lung (162)
Accidental Falls (E880-E887)
Accidents Caused by Fires and
Flames (E890-E899)
Tuberculosis, All Forms (010-019)
Accidental Drowning and Submersion
(E910)
Asthma (493)
Accidental Poisoning by Drugs and
Medicaments (E850-E859)
Appendicitis (540-543)
Accidents Caused by Cataclysm
(E908)3
Accidents Caused by Bites and Stings
of Venomous Animals and Insects, and
Other Accidents Caused by Animals
(E905, E906)1*
Premature Deaths
16,000
17
8
Reduction, in iife
Aggregate Years of Expectancy at Birth Average Years of Life
Life Lost to Cohort (in Years)
250,000
490
220
2.5
0.005
0.002
Lost to Premature Deaths
15
2,900
1,000
300
270
190
100
69
67
45,000
12,000
7,600
4,300
8,700
2,100
2,500
1,200
0.45
0.12
0.076
0.043
0.087
0.021
0.025
0.012
15
11
26
16
45
20
37
17
30
27
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Table IV-2
continued
Reduction In Life
Aggregate Years of Expectancy at Birth Average Years of Life
Cause of Death Premature Deaths Life Lost to Cohort (In Years) Lost to Premature Deaths
Accidents Caused by Electric Current
" lr±n8 "* APPlianCe8 37
925)
8 290 0.003
Tetanus (037) * 80 0.001 20
Chicken pox (052) 2 130 0.001 56
mortality effects shown are calculated as changes from the U.S. Life Tables for 1970 to life tables with the
cause of death under Investigation removed. These effects also can be interpreted as changes in the °PP^e
direction, from life tables with the cause of death removed to the 1970 Life Table. Therefore the Premature
dSns £d years of life lost are those that would be experienced in changing from an ^°"*£*»™ *J signif 4.
indicated cause of death is not present to one where it is present. All values rounded to no more than two signiri
cant figures.
2ICDA Codes, 8th Revision.
3Catacylysm is defined to include cloudburst, cyclone, earthquake, flood, hurricane, tidal waves, tornado, torrential
rain and volcanic eruption.
"Accidents by bite and sting of venomous animals and insects includes bites by
and spiders; stings of bees, insects, scorpions and wasps; and other venomous bites and stings
Caused by animals includes bites by any animal and non-venomous insect; fallen on by horse or "^ "^' *£!*'
kicked or stepped on by animal; ant bites; and run over by horse or other animal. It excludes transport accidents
involving ridden animals; and tripping, falling over an animal. Rabies is also excluded.
5Accident caused by electric current from home wiring and appliance includes burn by electric current, electric shock
or electrocution from exposed wires, faulty appliance, high voltage cable, live rail and open socket. It excludes
burn by heat from electrical appliance and lightning.
-------
References
1. U.S. Department of Health, Education, and Welfare, Public Health
Service. U.S. Decennial Life Tables for 1969-71. Volume 1,
Number 1, May 1975.
2. U.S. Department of Health, Education, and Welfare, Public Health
Service, National Center for Health Statistics. Excerpt from
Vital Statistics of the United States 1969. Volume II-Mortality.
3. Chiang, Chin Long. Introduction to Stochastic Processes in Bio-
statistics. John Wiley & Sons, Inc., New York, London, Syndney.
(A Wiley Publication in Applied Statistics).
4. U.S. Department of Health, Education, and Welfare, Public Health
Service, U.S. Decennial Life Tables for 1969-71. Volume 1, Number 5,
May 1975.
5. Hunger, Byron M., Barrick, Mary Kay, and Cook, John, "Life Table
Methodology for Evaluating Radiation Risk". Office of Radiation
Programs, U.S. Envrionmental Protection Agency, Technical Note
(in preparation).
6> The Effects on Populations of Exposure to Low Levels of Ionizing
Radiation. National Academy of Sciences, National Research Council
Washington, D. C., November 1972.
12
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ANNEX V
Guidance Implementation
U. S. Environmental Protection Agency
Office of Radiation Programs
Washington, D. C. 20460
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Contents
Page
1.0 Introduction 1
2.0 Implementation of Guidance by Estimating Dose Rates
to Lung and Bone 4
2.1 Dose Rate to the Lung 4
2.2 Dose Rate to the Bone 6
3.0 Implementation of Guidance by Use of a Soil
"Screening Level" 8
4.0 Implementation of Guidance by Means of Soil Data
Using Site-Specific Parameters 9
5.0 Sampling and Analysis Methods 11
5.1 Statistical Criteria 12
5.1.1 Soil Sampling 12
5.1.2 Area Acceptance Criteria 14
6.0 Remedial Actions 15
6.1 Costs of Remedial Actions 17
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1.0 Introduction
The Environmental Protection Agency is issuing guidance directed to
all Federal Agencies in response to the problem of environmental contam-
ination by the transuranium elements. The guidance recommends annual
dose rate limits to members of the public in the critical segment of
the exposed population for pulmonary lung and for bone. Implementation
procedures that may be used to determine compliance with this guidance
are discussed in this annex.
Implementation of these recommendations should include an evaluation
of the site, a projection of the radiation dose rate to determine whether
or not guidance values are being exceeded, and remedial actions if there
is indication that guidance values are, or may in the future be exceeded.
A reasonable evaluation of a contaminated site should include a descrip-
tion of the site and environmental measurements of contamination levels
in environmental media at a level of detail sufficient to convey
adequate information to the general public. All dosimetry and environ-
mental pathway models used in estimation of radiation doses to persons
should be described in sufficient detail to permit evaluation of the
procedures used. If projected dose rates are greater than the guides,
protective or remedial actions should be performed to the extent
necessary, so that guidance values are not exceeded and will not be
exceeded in the foreseeable future. The implementation of these
recommendations is the responsibility of those Agencies having
regulatory and administrative responsibilities for the site in question
and/or the materials in use at that site.
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The Agency believes that these recommendations can be implemented
by using one of three general procedures without requiring unreason-
able, unnecessary, and expensive regulatory actions. These procedures,
which are described in more detail in the following sections of this
annex, may be used for the entire site or for portions of the site as
appropriate:
a. dose rates can be calculated, using the appropriate dosimetry
models, from measurements of the concentration of the transuranium
elements in air, food, and water at the point of inhalation and/or
ingestion by people. This is the most direct and preferred method.
b. soil concentration levels of the transuranium elements can be
compared to a "screening level" for soil,- defined as that level below
which the concentration of the transuranium elements are not likely to
lead to dose rates in excess of guidance recommendations.
c. dose rates can be calculated from the soil contamination
levels of the transuranium elements using site-specific parameters for
transport models and the appropriate dosimetry models.
An implementation program for obtaining needed information at
minimum cost may best be designed according to statistical criteria
for sampling, measurements, and analysis. By selecting such criteria
appropriate to the site, adequate data can be obtained for making a
decision on any required action without unnecessary cost due to overly
restrictive conservatism or inefficient design.
In the context of this guidance, the objective of environmental
sampling and analysis is to derive information for the purpose of
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estimating dose rates to pulmonary lung and to bone of exposed
individuals. These dose estimates are derived on the basis of models
which depict the various pathways by which transuranium elements in the
environment may interact with man and produce exposure to radiation.
These models include parameters which describe the characteristics of
transuranium elements in the environment, the manner in which they may
be transported through the air or through food pathways, modes of
interaction with man (including inhalation or. ingest ion) and, finally,
factors related to the radiation energy deposition in organs and tissues.
In general, the best dose estimates are derived from data acquired from
measurements in the dose pathway as close as possible to the point where
transuranium elements interact with man, although it is sometimes
necessary to make measurements of the radionuclide concentrations at
points in the environment further from the receptor, followed by the use
of pathway models' to estimate doses to individuals or population groups.
A soil sampling program may be utilized to determine compliance
with the recommendations. Most sites where contamination of the soil
presently exists have been surveyed to determine levels of transuranium
elements. The data should be used to indicate areas which are clearly
much greater or much smaller than the limiting soil concentration
derived from the guidance recommendations. It is only for those land
areas in between, which may or may not exceed the guidance recommenda-
tions, that it will be necessary to conduct a sampling program.
The guidance is intended to be applicable to all sites and all
types of land utilization. Evaluation must be made on the basis of
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present and projected conditions and include recognition that
disturbance of the soil surface may change both the pathway to humans
and the magnitude of the accumulated dose. For the inhalation pathway,
most of the potential hazard is derived from contamination at, or near
the surface. Most man-made disturbance will reduce the concentration
in the top layer either by dilution or removal, but may increase the
resuspension rate. The overall effect of such activities must be
considered in the implementation plans.
2>0 ImPlementation of Guidance by Estimating Dose Rates to Lung and
Bone ~~ ~^
Federal Agencies may show compliance for a specific site, or for
sub-areas of a specific site, by certifying that guidance values for
dose rates to the lung and bone of members of the critical segment of
the exposed population are not being exceeded. The most direct method
is to measure transuranium element concentrations in environmental media
-such as air, food, and water at the point of interaction with man and to
then calculate the potential radiation dose rates using the appropriate
dose conversion factors and dose model parameters. When this procedure
is used, adequate documentation should be provided to demonstrate how
dose rates are calculated. The Agency favors the use of realistic
environmental measurements and realistic model .input parameters; con-
servative parameters should only be used to the extent necessary to
compensate for uncertainties.
2.1 Dose Rate to the Lung
Lung dose rates are calculated using appropriate dosimetry models,
which require knowledge of the annual average transuranium element
-------
concentration in air, aerosol particle size distributions, and
solubility class of the specific radionuclides present. Procedures for
the sampling and analysis of near-ground level air for the transuranium
elements have been published and have been used for many years. Pro-
cedures of sufficient sensitivity, .accuracy, and precision are available
for implementation of this guidance.
Judgment should be exercised in the design of an air sampling
program to ensure that air concentration levels are representative of
actual exposure conditions. Environmental measurements of airborne
particulates which bias the dose estimates by the collection of only
certain particle size ranges should be avoided or a suitable correction
should be made. It is preferable that the particle size distribution be
experimentally measured for a specific site. Reasonable values can be
assumed based on analogies with similar sites when projected lung dose
rates are small compared to the guidance level. The solubility class of
an aerosol can usually be determined from the history of the contam-
inating event and the subsequent environmental weathering mechanisms.
Dose conversion factors for lung dose rates that the Agency believes to
be reasonable for the purpose of implementation of the guidance are
presented in Annex III.
In certain cases, the determination of site-specific parameters
for use in the dosimetry models may be difficult or impossible with the
equipment available or within the time constraints allowed. Under these
circumstances, a derived air concentration limit, which will have a
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very large probability that the guidance recommendations will not be
exceeded, may be substituted for the site-specific value. The Agency
suggests that such a derived air concentration limit be based on an
activity median aerodynamic particle diameter (AMAD) not to exceed
0.1 ym, which is substantially smaller than observed values at all
known contamination sites. The calculated limiting concentration for
o
this procedure would be about 1 fCi/m of alpha emitting transuranium
nuclides, for air samples averaged over a period of one year or more.
Air concentrations above this value do not necessarily mean that the
guidance recommendations may be exceeded, but rather dictate that a
more thorough evaluation of existing conditions be made.
Elevated levels of transuranium elements in air indicate that
these elements may be found in nearby soils. When these levels approach
that of the guidance recommendation, implementation should include a
characterization of the environmental source term, to provide a means
of judgment with respect to the potential for future exposure levels and
the practicality of remedial measures.
2.2 Dose Rate to the Bone
Bone dose rates are calculated with appropriate dosimetry models
using a knowledge of the average amounts of transuranium elements that
are Ingested in a year, the chemical state of the transuranium elements
at the time of ingestion, and the proper dose conversion factor.
Inhalation of transuranium elements, especially in soluble forms, can
also lead to radiation doses to bone and should be considered where
appropriate.
-------
Sampling and measurements of transuranium elements in food and water
at the point of human consumption is the most direct and preferred
procedure for determining the annual average ingested amount of these
elements. Alternatively, the amounts of ingested radionuclides may be
estimated using environmental pathway models. The chemical state at the
time of ingestion is inferred from the medium into which the transuranium
elements are incorporated at the time of ingestion. In particular, trans-
uranium elements which are incorporated into biological tissue when
ingested should be considered as "organically complexed" and require a
special dose conversion factor. Dose conversion factors that the Agency
believes appropriate for the implementation of this guidance with
respect to bone dose rates are given in Annex III.
The Agency believes that suitable sampling and analytical procedures
are available for the analysis of the transuranium elements in food and
water and that they have the necessary sensitivity, accuracy, and pre-
cision for purposes of implementating of this guidance. Also, as with
the inhalation pathway, elevated levels of Plutonium and the trans-
uranium elements in food or water indicate that these elements may be
found in nearby soil or in sediments. Under such conditions, imple-
mentation of the guidance should include a characterization of the
environmental source term, to provide a means of judgment with respect
to the potential for future exposure levels and the practicality of
remedial measures.
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3.0 Implementation of Guidance by Use of a Soil "Screening Level"
Federal Agencies may show compliance for the total area of a site,
or for subareas of a site, by certifying that such areas have trans-
uranium element soil concentration levels less than a screening level
2
value of 0.2 yCi/m . The "screening level" is a total transuranium
element soil concentration level in the top 1 cm of soil such that, in
the Agency's opinion, dose rates will not exceed guidance recommenda-
tions under the vast majority of land use conditions. Its usefulness
is limited to the area in close proximity to the measurement, in that
a dynamic equilibrium between the surface and adjacent air column is
localized and only indirectly contributes to the adjacent areas.
Because of present uncertainties in the amount of plant uptake
for the more soluble transuranium nuclides, such as americium and
curium, and the resultant possibility of larger doses via the ingestion
pathway than calculated, the screening level concept may not be appli-
cable when the soils of a contaminated area contain these nuclides in
amounts greater than 20% of the total activity. Lands with concentra-
tion levels less than the screening level are judged to be suitable for
all normal activities including residential and agricultural uses. The
use of this screening level is intended to reduce the land areas
requiring extensive evaluation and to minimize the number of measure-
ments needed.
If land areas have transuranium element levels greater than the
screening level, it should not be presumed that guidance values are
necessarily exceeded, because conservative assumptions were used in the
8
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derivation of the screening level. Additional site specific evaluations
of potential dose rates to lung and bone (Section 4) should be made
before remedial actions are initiated.
Inherent in the application of the screening level is the assumption
that soil contamination by the transuranium elements will cause radia-
tion exposure through pathways such as the inhalation of resuspended
soil, the ingestion of foodstuffs grown on the soil, the ingestion of
soil by children, and the ingestion of drinking water contaminated by
soil runoff. In all cases the cumulative doses to the critical segment
of the population must be considered, with the admonition that the
accumulated doses from all pathways should not exceed those recommended
in this guidance.
4.0 Implementation of Guidance by Means of Soil Data Using
Site-Specific Parameters
Federal Agencies may show compliance with this guidance for a
specific site, or for subareas of a specific site, by means of soil
measurements and by using pathway and dosimetry models with parameters
determined for that specific site to certify that the resulting dose
rates do not exceed guidance values. This approach differs from the use
of a soil screening level because parameters such as the resuspension
factor are determined for a specific site. It is expected that use of
site-specific parameters will show that soil contamination levels higher
than the suggested screening level may correspond to organ doses well
below guidance level. Implementation by site-specific parameters is
appropriate where land areas have transuranium element levels greater
than the screening level and further evaluation is necessary to
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determine whether or not guidance dose limits are being exceeded.
The air concentration at the site of the receptor can be generally
correlated with the adjacent soil concentration by use of a resuspension
factor, and used to estimate the inhalation dose rate.
The site-specific resuspension factor may be either measured
directly or calculated from other data. Direct experimental determina-
tions are often difficult to make and not very reproducible. Therefore,
calculational techniques are sometimes preferred although their cor-
relation with measured values is subject to considerable uncertainty.
The Agency has developed a method, based on the concept of air mass
loading, which may be useful for this purpose (see Annex II). An
"effective" resuspension factor is derived, defined as the resuspen-
sion factor derived from the air mass loading for the given location
and modified by an "enrichment factor" which takes into account the
generally observed nonuniform distribution of the activity with size
of particles in calculating the amount of transuranium element activity
in the inhalable fraction of the resuspended material. The "enrichment
factor" is a theoretically derived parameter, and its correlation to
actually observed situations has not yet been established. The
resuspension factor derived in this manner is applicable only to an
infinite plane source, and must be further corrected for the dilution
by uncontaminated materials carried into the generally small contam-
inated area.
The ingestion pathway must be evaluated separately, using data
applicable to the specific site in terms of type of crops, plant uptake
10
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parameters, and pathway to a critical segment of the population. The
more unusual transfer mechanisms to people, such as the ingestion of
dirt by children and the contamination of drinking water wells, may
also need to be examined if shown to be of importance.
5.0 Sampling and Analysis Methods
Choice of Methods
The choice of suitable methods for sampling and analysis is the
responsibility of the Agency implementing the guidance. The implementing
Agency should demonstrate that the methods that are used have the
necessary sensitivity, accuracy and precision for purposes of implementing
this guidance. A description of the tools and techniques used to collect
the samples, the. procedures for preparing the samples for analysis, and
the method used for radiochemical analysis should be included.
Sample Collection
The Agency recommends that for undisturbed sites where soil
measurements are taken to evaluate the inhalation pathway, soil samples
should be taken to a depth of one centimeter and transuranium element
activity be measured in all soil particles less than two millimeters in
size. Several individual samples may be composited for a single measure-
ment. At some sampling points it may not be possible to collect samples
to a depth of one centimeter (for example, very stony soil or a thick
grassy area). In such cases, other means must be found so that repre-
sentative samples are collected.
Soil Particle Size Distribution Analy«ia
If a model for determining a transuranium element soil
concentration corresponding to the lung dose rate limit is chosen which
11
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involves the calculation of a soil particle resuspension factor,
measurement of the soil particle size distribution may need to be made.
The usual method for determining the distribution is by sedimentation
analysis (1). The standard sedimentation technique employs wetting
agents for dispersing agglomerated soil particles. Another method
uses an oscillating air column for the dry separation of particles down
to 5 ym. For purposes of this guidance, soil characteristics should be
altered as little as possible in the collection and preparation of the
soil sample and care should be taken to choose a method which does not
cause the breaking up of soil aggregates that were present when the
sample was taken.
Radiochemical Analysis
Techniques for the determination of transuranium elements in soil
have been published (2). Each of the more widely used techniques has
been shown to be accurate under certain conditions. The principal dif-
ferences between them are the techniques used to solublize the plutonium
in the sample. Three solubilization techniques are most commonly used:
acid leaching, acid dissolution, and fusion. The fusion method is
considered to be applicable to a wider variety of soils than the other
two methods.
5.1 Statistical Criteria
5.1.1 Soil Sampling
When planning a soil survey it is advisable to divide the total
area under investigation into units at the very beginning of the survey
rather than to collect samples more or less haphazardly. Then samples
12
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taken to determine the acceptability of the land by comparison of
measured concentration levels to the screening level may be collected
from sampling units in accordance with a sampling plan. If it is later
decided that more sampling is necessary, no change in the sampling plan
is necessary, and the location for additional samples will have already
been determined.
The number of samples to take within a sampling unit may be
estimated from the specific statistical approach used in the sampling
plan. An important factor affecting the number of samples to be taken
is the risk of making the wrong decision in deciding whether a sampling
unit is acceptable or requires remedial action. To reduce the risk of
making the wrong decision, larger numbers of samples must be taken.
Judgment must be used to strike a balance between the desirability of
making the right decision and the difficulties and expense involved in
taking large numbers of samples. An additional factor affecting the
number of samples is the variability of the transuranium element
concentration within a sampling unit. If detailed information is not
available on the variability, a simple approach is to take the same
number of samples within each unit. These could be taken on a grid
system to ensure that all subareas of the sampling unit are sampled. A
disadvantage of this approach is that if the variability is substantially
different in different units, then the probability of detecting con-
centration levels requiring remedial action will vary from unit to unit.
If estimates of variability are available from past studies, these can
be used to help determine the number of samples required within each
13
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unit so that the probability of making a correct decision will be the
same for all units.
5.1.2 Area Acceptance Criteria
After soil concentration levels have been determined, it must be
decided if the area under consideration complies with the guidance
recommendations or whether further evaluation will be needed. The
statistical methodology that is used must be such that few assumptions
regarding the form of the soil concentration distribution will be
necessary to ensure the validity of the statistical test. The method
should also ensure reasonably low bounds on the risk of making the wrong
decision, and the probability of not accepting an area which meets the
guidance, or accepting one which does not* should be small. Acceptance
criteria which allow a maximum chance of error of 5-10% are generally
considered appropriate.
Considerable variation generally occurs in environmental samples
taken even in closely adjacent locations. If one or more samples from
any sampling unit exceed the air or soil concentration limits corre-
sponding to the guidance recommendations, a decision must be made on
whether the sampling unit is acceptable. Such a decision is best based
on statistical tests which consider both the magnitude of the deviations
from the average and the number of samples which are involved. A number
of statistical methods are available for performing such an evaluation,
and the choice must be made on the basis of the data available and the
results desired.
14
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The number of samples collected and analyzed should be sufficient
to adequately guard against the errors of falsely failing to accept
a land area when the true fraction does not exceed a lower bound and of
falsely accepting an area when the true fraction is equal to or greater
than the upper bound. The upper bound is a measure of that portion of
the land area which would be considered reasonable to exceed the limiting
soil concentration. A small fraction would provide assurance that the
mean for the entire area, assuming a normal or known skewed distribu-
tion, would not exceed the screening level.
6.0 Remedial Actions
Remedial actions are required at a site when the projected
radiation dose exceeds the recommended guidance values. Choosing a
specific action is usually a complex decision affected by the physical
characteristics of the site, the variety of appropriate remedial actions
possible, and on monetary and non-monetary costs. The long half-lives
of the transuranium elements makes the decision more difficult because
consideration must be given to long-term care. The objective at a
specific site is the selection of remedial actions that best assure that
guidance recommendations will not be exceeded at the least possible
cost.
Most remedial actions can be categorized into one of five general
classifications: removal of the contamination for off-site disposal,
removal for on-site shallow burial, stabilization with no removal of
contamination, dilution of the contaminant with no removal, and measures
restricting the use of the site by members of the public.
15
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Methods of removing contamination include raking and grubbing out
vegetation, stripping the top layer of soil by scraping, vacuuming,
or other similar techniques. The contaminated soil and other material
can be transported to especially designated locations on site for
storage or shallow burial, or they can be shipped to off site
depositories with provision for long-term care.
Stabilization of a contaminated site includes actions such as
covering the land with an impermeable cover such as oil, polymerized
plastics or asphalt, or with soil and vegetation, or by applying
chemical stabilizers to the land area. The stabilization leaves the
contamination on site, but reduces its accessibility to wind and surface
water erosion and therefore reduces the potential exposure dose.
Plowing and cultivating are the principal methods of dilution of
contamination. The goal is to mix the surface contamination into the
top 20 cm or more of soil, attaining a form of stabilization in place.
Estimates of the amount of dilution achieved by cultivation are suggested
in Table A 1-2 of Annex I.
At some sites, it may be feasible to perform no cleanup, but rely
completely on restricting land use. Restrictions are applied to the
contaminated area itself, and may include a buffer zone bordering the
contamination site. Land-use restrictions serve two purposes; they
provide a means of controlling access to areas where the radiation
health risk is excessive and they help in preventing the disturbance
of the land surface. Land-use restrictions may limit or prohibit access
to an area, or they may be limited to prescribing the types of activities
carried out within an area.
16
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6.1 Costs of Remedial Actions
It is to be expected that a variety of remedial actions should be
effective in reducing the exposure dose. Under these conditions, the
least costly action or set of actions should be selected. When costs
are evaluated both monetary costs and nonmonetary costs, including the
environmental costs, are to be considered. Whenever possible, it is
desirable that all costs be quantitied monetarily. Costs that cannot
be quantified in monetary terms should, whenever possible, be quantified
in other ways, with narrative descriptions used when quantification is
not possible. A major difficult is likely to be that different com-
binations of decontamination procedures are expected to have somewhat
different combinations of monetarily and nonmonetarily, quantifiable
and nonquantifiable costs.
Although it probably is impossible to identify and measure all
costs in the evaluation of various remedial actions, it is desirable
that as many as possible of the larger costs be evaluated. One con-
straint on any attempt at measuring costs is the cost of acquiring the
information needed. Some costs may be easy to identify but expensive
to quantify. Other costs may be quantifiable in nonmonetary terms,
but it may be difficult or impossible to place a monetary value on
them. Models may be usefull in estimating the difference in costs of
some remedial procedures. It should be noted that the cost of any
radiological surveillance carried out to determine if a site exceeds the
guidance does not impact on the selection of the least cost remedial
action. However, all radiological surveillance costs necessary for the
17
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performance of a cleanup procedure are a cost to that particular
procedure.
Any general technique of remedial action is likely to incorporate
costs associated with some combination of the following actions or
procedures: (1) radiological surveillance, (2) protection of workers,
(3) stabilization of land surface, (4) dilution, (5) removal of con-
taminated material from surface, (6) packaging, (7) transportation of
contaminated materials, (8) ultimate disposal at storage site, (9)
restoration of site, and (10) maintenance of restricted access to site.
Costs for each must be evaluated as appropriate. When services are
needed indefinitely, these future costs should be expressed as present
worth.
Nonmonetary costs include all costs that are difficult or
impossible to quantify in monetary terms. They should be quantified
in nonmonetary terms to the extent possible. Descriptive discussion
is appropriate where quantification is not complete or is impossible.
Examples of such costs would include the increased health risk
to workers performing the remedial actions, the risk of health effects
to members of the general population that may result when land surfaces
are disturbed during remedial actions, and psychological costs resulting
from fears of a little understood environmental contaminant.
18
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References
1. Day, P.R., Particle Fractionation and Particle-Size Analysis,
*n Methods of Soil Analysis. Part- I. C. A. Black, Editor, Amer.
Soc. of Agronomy, Inc., Madison, Wisconsin 1965.
2. Bernhardt, D. E., "Evaluation of Sample Collection and Analysis
Techniques for Environmental Plutonium:" U.S. Environmental
Protection Agency, Technical Note, ORP/LV765.
3' JU"te1?!,?- 1971 Attribute Sampling; Tables and Explanation.
McGraw-Hill, New York.^ ~~
19
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ANNEX VI
ENVIRONMENTAL ASSESSMENT
U. S, Environmental Protection Agency
Office of Radiation Programs
Washington, B.C. 20460
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Annex VI
Table of Contents
Page
I. Introduction 1
II. Generic Impact Assessment 2
III. Alternatives to Proposed Action 4
IV. Projected Impact of Guidance at Existing Sites 8
V. Costs of Remedial Actions 13
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Annex VI
ENVIRONMENTAL ASSESSMENT
I. Introduction
Under the provisions of the National Environmental Policy Act of
1969, it is intended that every major Federal action be examined in
terms of projected impacts and that all available alternatives be
considered. The purpose of such an analysis is to compare the costs
and benefits of the recommended action with other options in terms of
the broad range of projected health, sociological, economic, and
environmental impacts.
The implementation of the proposed action would be site-specific.
The portion of the environment affected is that where present or
future transuranium element concentrations may exceed guidance values.
Such areas are likely to be those where the transuranium elements are
prepared, fabricated, used, stored, or transported. A number of such
areas currently exist within the limits of the continental United States.
Most such contamination is located on lands with restricted or limited
access, but a few instances exist where significant contamination has
spread to privately owned property.
The proposed guidance does not include recommendations on specific
methods of cleanup and restoration. Such methods are to be determined
for each contaminated site by consideration of the effectiveness of
the techniques, the cost-benefit evaluation, and the specific environ-
mental impacts. Therefore, the range of total impacts must be evaluated
separately and independently for each proposed'major remedial action in
terms of all available and applicable methods.
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II. Generic Impact Assessment
The probable impacts of Implementation of the proposed action will
vary according to the nature and scale of the method used for affecting
cleanup and restoration, and may be particularly sensitive to the
location of the proposed actions. The primary impacts of most methods
of effecting desired cleanup and restoration of contaminated areas will
result in some temporary disruption of normal activities on and near the
site, slight and temporary impairment of air and water quality, and
possibly significant effects on animals, flora, and fauna. The exact
nature of such environmental impact will be site specific and
dependent on the nature and extent of the site, the degree of contamina-
tion, and the procedures chosen for cleanup and restoration. Examples
of adverse environmental impacts are: loss of habitat of fish, birds
and mammals, increased mortality among displaced animals as well as
loss of trees and other vegetation. Run-offs from disturbed land can
lead to pronounced short-term aquatic impacts depending upon the amount
of the chemical and biotic components of the system. A detailed study
of such short- and long-term ecological impacts has been commissioned
by the Environmental Protection Agency and results are expected to be
available by late 1977.
Of special concern in the evaluation of potential environmental
impacts is the irreversible or irretrievable commitment of resources.
Such commitments range from permanent removal of the land from useful
productivity to loss of scenic beauty and other intangible values.
Cleanup and restoration inevitably involves a commitment of money,
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labor, and equipment and this must be taken into consideration in an
overall assessment. Both the temporary and permanent commitment of
resources can be expected to increase as the stringency of the regula-
tion becomes more severe, but not necessarily on a linear proportional
basis.
The principal expected effects of a land cleanup and restoration
action are those related to the anticipated benefit on the health and
safety of individuals in the general population, the short- and long-
term effects on the environment, the costs related to the total action,
and the sociological and political consequences of these changes. A
number of alternative levels of control need to be considered to gain
an overall perspective from which to evaluate the overall impact.
Under Section 102(2)0 of the National Environmental Policy Act of
1969, it is required to study, develop, and describe appropriate altema-
i
tives to the proposed or recommended courses of action. The purpose is
to analyze the environmental benefits, costs and risks so as not to fore-
close prematurely options which might better advance environmental
quality or have less detrimental effect. Examples of such alternatives
are those of taking no action, of postponing action pending further
study, of taking actions of a significantly different nature which could
provide similar benefits with less severe environmental impacts, or
the acquisition or condemnation of land and waters. The analysis of
each alternative should compare the environmental benefit, coats and
risks with the proposed action. In summary, alternatives to the pro-
posed action consist of (1) no action, (2) more stringent limits (3)
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less stringent limits (4) alternative ways of implementing guidance (5)
action which will achieve desired results by other means.
III. Alternatives to Proposed Action
A number of realistic alternatives were considered in the
development of this guidance. The lowest level of effort would be
that of maintainance of the status quo, with no remedial actions. This
would gain zero benefit in that committed adverse health effects would
not be reduced, have zero costs, and have no detrimental effect on the
environment. .The highest level of effort would be a uniform cleanup to
fallout level background. This would gain a benefit of reducing the
future number of adverse health effects to a very low number, but have a
potential for very large monetary cost and widespread disruption of the
environment. Such a level would be virtually impossible to achieve on a
uniform basis and difficult to enforce because of major variations in
the background level. Uniform cleanup to such a limit on a national
scale would be prohibitively expensive, involve significant relocation
of populations and disruption of activities, and result in major eco-
logical damage.
A reasonable range of numerical limits for environmental
contamination by the transuranium elements would appear to range from
a lower bound set at some reasonable multiple of the average background
level to an upper bound set at the limit required by consideration of
public health criteria. These limits, and the costs and benefits at
these levels, are considered below in more detail.
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The least restrictive available guidance for population exposures
resulting from soils contaminated by the transuranium elements is that
derived from the numerical guidelines of the International Commission on
Radiological Protection (ICRP) and given as recommended maximum
permissible concentrations in air and water for specific radionuclides.
For unrestricted occupancy this is 1 pCi/m3 for insoluble and 0.06 pCi/m3
for soluble plutonium-239 in air. Soil concentrations derived from these
recommendations are of the order of 1000 yCi/m2, or, higher than the
proposed "screening level" by a factor of 5000. Numerical values of
this magnitude would appear unacceptable for protection of an individual
in the general population, in that the total permissible radiation
exposure of that individual would be allocated to a single source or
activity. , Such numerical values could well be acceptable, however, for
remote or intermittently inhabited areas where the maximum cumulative
individual exposures would be considerable lower. Such relatively high
contamination limits may also be appropriate where the decontamination
costs are prohibitive and remedial actions must be limited to on-site
stabilization and restricted occupancy. The costs associated with
remedial actions only to this level could generally be expected to be
lower than for the more restrictive guidance proposed.
The lowest presently existing limit applicable to land use of
contaminated areas is the plutonium-in-soils standard of 2 dpm/g of dry
soil adopted by the State of Colorado in 1973. This value represents
approximately twenty times the average Plutonium fallout background for
Colorado, and also represents the threshold below which no increase in
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the adjacent airborne particulate concentration was reported observable.
The Colorado standard is intended as a worker protection level above
which some control action needs to take place before construction work
can proceed in a contaminated area. Because of the increased dust
loading created by such activities the actual inhalation dose to exposed
individuals could exceed the proposed guidance recommendation and no
direct comparison of long-term impacts is possible. Because it is
intended to achieve only a limited objective for a relatively short
period of time, the Colorado standard cannot be considered in the
context of long-term general public health protection.
On an administrative basis, a number of alternatives were available
to this Agency for promulgation of appropriate, guides or standards. The
President's Reorganization Plan No. 3 of 1970 transferred certain
functions from the Atomic Energy Commission to the Environmental Pro-
tection Agency"...to the extent that such functions of the Commission
consist of establishing generally applicable environmental standards
for the protection of the general environment from radioactive material."
As a result of this transfer, Section 161(b) of the Atomic Energy Act
provides that the Administrator may, within the above framework,
"establish by rule, regulation, or order, such standards to govern the
use of special nuclear material, source material, and by-product material
as (he) may deem necessary or desirable to... protect health or to
minimize changes of life or property."
The same Reorganization Plan also transferred all the functions of
the former Federal Radiation Council, as specified in the Atomic Energy
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Act, to the Agency. Section 274(h) provides that "the Administrator
shall advise the President with respect to radiation matters, directly
or indirectly affecting health, including guidance for all Federal
agencies in the formulation of radiation standards and in the
establishment and execution of programs of cooperation with States."
The Agency has considered both of the above options and decided
in this instance to promulgate Federal Radiation Guidance. The
decision was based, in part, on the realization that all transuranium
elements are currently under the direct or indirect control of the
Federal government, that the extent of current contamination is very
limited, and that considerable flexibility may be required in imple-
mentation because of substantial differences between sites.
Other applicable legislative authorities delegated to the Agency
include sections of the Clean Air Act, as amended, the Safe Drinking
.Water Act, and the Hazardous Materials Control Act. These other
authorities are generally considered to apply to effluent releases
rather than to existing environmental contamination, and therefore
have limited applicability to the problems addressed in this guide.
The above discussion is intended only to convey the basis for
the decision making process for a generic guidance. Application to
specific sites will necessarily require a more detailed consideration
of alternatives for possible remedial actions and/or land use restric-
tions where required. It is therefore important that a detailed impact
evaluation be made in every instance prior to implementation of these
guides. ,
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A further alternative considered would involve issuance of no
Federal guides, with remedial actions determined solely by State and
local authorities. Such a course of action could be expected to result
in a diversity of standards and regulations, not all of which may be
derived on a timely or rational technical basis. In general, .such
regulations tend to be unduly restrictive when viewed from the objective
of protecting the public health and reflect much of the fear of the
unknown. Because the exact scope and application of such regulations
cannot be predicted, no analysis of expected impacts can reasonably be
made.
Iv* Projected Impact of Guidance at Existing Sites
The proposed guidance is intended to provide a minimization of
health risk to that level where no individual is exposed to greater
than an equilibrium lung dose rate of 1 mrad per year, with an
attendant maximum risk of one additional fatality per million persons,
exposed to that level per year. In terms of environmental contamination
levels, this can be equated to approximately one hundred times the
current contamination levels derived from fallout. For a parametric
analysis of the effect of changing the proposed guidance in either the
positive or negative direction, a reference case of a deviation by a
factor of ten can be assumed. The lower bound will then be of the
order of magnitude of the Colorado standard and the upper bound at a
level currently exceeded in only a few instances on unrestricted lands.
There are four Federal sites in the United States that presently
have transuranium element contamination above ambient levels beyond
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their boundaries. These include the Rocky Flats Plant in Jefferson
County, Colorado, Mound Laboratory in Miamisburg, Ohio, Nevada Test
Site in southern Nevada, and Trinity Test Site near Alamogordo,
New Mexico. The majority of all contamination released is confined
within areas under the direct control of the Federal government, which
imposes restrictions on the access and use of these areas. Relatively
small amounts of transuranium element contamination exists outside the
boundaries of these sites on lands generally accessible to the public.
The following discussion is intended to supply a perspective of applying
the guidance recommendations to these sites in terms of a soil concen-
tration reference level derived on the basis of generic data, which with
a very high degree of probability would be expected to result in an
inhalation dose to an individual not to exceed the guidance recommendations.
Use of such a soil contamination level is intended solely to provide a
basis for comparisons and does not imply direct correlation with the
dose rate recommendations. A brief description is given for each site
and the general contamination pattern is indicated. Numerical compari-
sons to show the estimated areas of limiting contamination to one-third
and one-tenth the reference level, and of allowing ten times greater a
value are given in Table VI-1. Comparisons are made in terms of areas
outisde the boundaries of these sites.
The Rocky Flats Plant (RFP) produces components for nuclear
weapons. Barrels containing plutonium contaminated cutting oil slowly
corroded and some of the contents eventually leaked into the environment
and were dispersed. On the basis of soil concentration data, all
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Annex VI
Table VI-1
Comparison of Costs of Remedial Actions At Various Sites
of Existing Plutonium Contamination For Several Possible
Levels of Maximum Soil Concentrations (Areas are Estimated
from Contour Maps and Costs Are Arbitrarily Assumed as $500/acre)
Rocky
Flats
Plant
Nevada
Test
Site
Trinity
Site
found
Lab.
Reference Level
0.2 yCi/m2
Area
0
0
0
* 0.01 m2
Cost
0
0
0
*
10 x Ref. Leve
2 pCi/m2
Area
0
0
0
* 0.01 mi2
Cost
0
0
0
*
1/3 Ref. Leve
0.07 yCi/m2
Area
0.3 mi2
<80 mi2
<20 mi2
^ 0.01 mi2
Cost
100K
25M
<6M
*
1/10 x Ref. Level
0.02 uCi/m2
Area
*> 1.6 m2
< 165 mi2
^ 300 mi2
* 0.01 mi2
Cost
500K
50M
100M
*
* Most of the existing contamination is in sediments of canals, and
does not represent a hazard to humans. Costs of eventual remedial
actions are indeterminate.
10
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off-site areas at the Rocky Flats Plant would probably be in compliance
with guidance recommendations. However, more intensive evaluation may
be needed to determine the actual dose rates to the general population,
particularly in the most highly contaminated areas east of the plant.
The area is sparsely inhabited and there are few people living in the
particular area of concern. The off-site area contaminated to a level
2
one-tenth the screening level comprises about 1.6 mi with a current
population of less than 600. No uncontrolled areas are contaminated to
a level greater than ten times the screening level. All local water
supplies are expected to yield ingestion dose rates well below the
guidance recommendation.
Mound Laboratory is a major research and development site for
fabrication of radioisotopic heat sources used for space and terrestrial
applications. In 1969 a pipeline transporting a Pu-238 waste solution
ruptured, spilling the contaminated solution. The plutonium migrated
slowly into nearby waterways. The majority of the plutonium is now
sorbed and fixed on the sediments of the North and South Canals.
Maximum concentrations are 1 to 3 ft below the sediment surface and
currently do not pose any radiation problem, since very little of the
plutonium is in soluble form and the canal water is not used for
drinking purposes. Banks immediately adjacent to the canal and overflow
creek subject to occasional flooding have maximum plutonium concentra-
tions exceeding the reference level. The amount of land in question is
2
about .01 mi and there are no people living on this land. There are no
areas with transuranium element contamination 10 times the screening
11
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level. The amount of land contaminated to one-tenth the screening level
is the same as the amount of land above the screening level, because the
nature of the contaminating event limited the contamination to the
waterways and adjacent banks. No immediate cleanup is indicated for
this site, but continued surveillance will be required.
The Nevada Test Site (NTS) covers an area of 1400 mi2 with an
additional exclusion zone extending 16 to 48 miles. Major programs at
NTS have included nuclear weapons tests, testing for peaceful uses of
nuclear explosives, and nuclear reactor engine development. These
activities have resulted in plutonium contamination in certain areas
of the test site and exclusion areas and slight contamination (above
background levels) outside the exclusion areas. There are no known
uncontrolled areas which have transuranium element contamination
exceeding the reference level. Land contaminated to one-tenth the
reference level or less covers approximately 165 mi2 with a resident
population of less than 240 people.
The Trinity Test'Site was the location of the first nuclear
explosion. No other nuclear explosion tests were performed at Trinity.
A site survey was- performed by EPA during 1973-74 to determine residual
Plutonium concentration contours. The highest plutonium contamination
levels in uncontrolled areas ranged from .02 to .09 uCi/m2. The amount
of land contaminated to a level one-tenth the reference level covers
2
less than 300 mi , with fewer than 500 people living in the area in
small towns, ranches, and farms. On the basis of the limited available
12
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data, no major remedial actions would appear to be indicated for this
site.
V. Costs of Remedial Actions
The Agency has evaluated the available methods and costs for
cleanup and restoration of contaminated land areas. For soils with
transuranium element concentrations no higher than about 10-100 times
the guidance recommendations, remedial actions to bring such areas
into compliance would generally involve only plowing or surface removal
followed by restorative actions needed to prevent erosion and assist
ecological recovery. The most common recommended methods include
plowing, surface stabilization, soil cover, and soil removal. Specific
steps required for each of these methods, and the associated costs, are
summarized in Table VI-2. The costs of implementing the guidance can be
expected to vary by location, contamination level, and other factors.
Therefore, the numerical estimates shown can only be considered as a
general approximation and specific values must be established for each
site. Dollar values are given on a 1975 basis and must be adjusted by
suitable indicators.
V
The range of options available for bringing an area into compliance
with the guidance recommendations includes both the method(s) used for
dilution or removal of surface contamination, the stabilization dnd
restoration of the area, and the ultimate disposal of displaced soils.
Certain alternatives may have to be considered, including those of
changing land use or long-term restrictions. In all cases, the total
costs of remedial actions should be evaluated to the maximum extent
possible in the selection of alternatives.
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