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6. POTENTIAL FOR HUMAN EXPOSURE
6.7 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES
Total plutonium deposition in five Manhattan Project workers exposed to plutonium in 1944–1945 ranged
from 98 to 3,300 Bq (2,600–89,000 pCi) according to autopsy data (Voelz et al. 1997).
Individuals living near facilities which utilize plutonium in their operations may have higher exposure
potential due to regular releases through stack-emissions or waste water. In addition, atmospheric fallout
to the soil can result in secondary releases due to dust generation while farming or due to uptake by crops
and subsequent ingestion of contaminated crops (Corey et al. 1982).
Individuals living in Palomares, Spain, were exposed to plutonium after the dispersal of the plutonium in
two bombs released during the midair collision of two airplanes (Iranzo et al. 1987). Exposure via
inhalation due to the resuspension of contaminated soil was studied for 15 years following the release.
Those individuals living near cultivated lands with the highest contamination received a cumulative total
of 52.3 mrem (5.2x10
-1
mSv) from 1966 to 1980 while those in the urban area of Palomares, farther away
from the source, received 5.4 mrem (5.4x10
-2
mSv) (Iranzo et al. 1987).
Kathren et al. (1987) determined levels of
239
Pu at autopsy in bones of an individual known to have had
occupational exposure to plutonium. Values ranged from 1.9x10
-4
to 1.14x10
-2
pCi/g ash (7.0x10
-6
–
5.0x10
-5
Bq/g ash), with the highest value detected in the scapula.
Kawamura (1987) estimated the
239,240
Pu inhalation intake of visitors to Kiev after the Chernobyl accident
to be 0.8 pCi/day (0.03 Bq/day) during peak fallout exposure.
6.8 ADEQUACY OF THE DATABASE
Section 104(i)(5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with the
Administrator of EPA and agencies and programs of the Public Health Service) to assess whether
adequate information on the health effects of plutonium is available. Where adequate information is not
available, ATSDR, in conjunction with NTP, is required to assure the initiation of a program of research
designed to determine the health effects (and techniques for developing methods to determine such health
effects) of plutonium.
The following categories of possible data needs have been identified by a joint team of scientists from
ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that if met would
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6. POTENTIAL FOR HUMAN EXPOSURE
reduce the uncertainties of human health assessment. This definition should not be interpreted to mean
that all data needs discussed in this section must be filled. In the future, the identified data needs will be
evaluated and prioritized, and a substance-specific research agenda will be proposed.
6.8.1
Identification of Data Needs
Physical and Chemical Properties.
Table 4-2 summarizes many of the relevant physical and
chemical properties of plutonium and selected plutonium compounds. Table 4-3 summarizes the
radiological properties of selected plutonium isotopes. There are adequate data for the physical,
chemical, and radiological properties of plutonium and plutonium compounds. No data needs are
identified.
Production, Import/Export, Use, Release, and Disposal.
According to the Emergency
Planning and Community Right-to-Know Act of 1986, 42 U.S.C. Section 11023, industries are required
to submit substance release and off-site transfer information to the EPA. The TRI, which contains this
information for 2004, became available in May of 2006. This database is updated yearly and should
provide a list of industrial production facilities and emissions.
The potential for human exposure to plutonium is great due to its ubiquitous presence in the environment,
resulting from releases from production facilities and from weapons testing, and its radiological half-life.
However, the level of exposure to plutonium will generally be small. The production and use of
plutonium 238–243 are well documented. There is little information regarding the production of
237
Pu.
The amounts of these plutonium isotopes produced for various applications have been documented;
however, the most current information is from 1974. More recent data are needed in order to compare
past and present production and to project future production. The majority of information on the
production and use of plutonium is classified in the nation's defense program. Information on past major
releases of plutonium from weapons testing and from the explosion of a navigational satellite is available.
However, current information on releases from production facilities is unavailable and is needed in order
to monitor populations that might be exposed. The disposal of plutonium prior to 1970 is documented,
but again, more recent information regarding amounts being held for mandated disposal in the proposed
high-level disposal facility is needed. Rules and regulations for the disposal of plutonium have been
established and these are reported in Chapter 8.
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6. POTENTIAL FOR HUMAN EXPOSURE
Environmental Fate.
The major transport processes involved in the environmental fate of plutonium,
as it relates to potential human exposure, have been fairly well defined. These processes include transport
in the atmosphere when adsorbed to particulate matter and dry or wet deposition on land and water.
Information on environmental compartments, such as flux rates, and the mechanisms and rates of several
processes involved in the biogeochemical cycling of plutonium are still undefined. The data available
regarding uptake of plutonium by plants are limited. There is some information regarding the conversion
of the oxidized forms of plutonium to reduced forms followed by uptake into plants. Information
regarding the influence of inorganic complexes on transport and regarding the media-specific effects of
pH on the oxidation states of plutonium would be useful in order to more fully understand transport
processes. The persistence of plutonium isotopes is well documented. Transformation of plutonium is
through radioactive decay or chemical oxidation/reduction reactions. These processes have been well
characterized.
Bioavailability from Environmental Media.
Plutonium is known to be absorbed following
inhalation exposure. Bioavailability following oral and dermal exposure is very low; however, plutonium
can be absorbed from contaminated wounds. Bioassay data are available on absorption from
contaminated air and water.
Food Chain Bioaccumulation.
Plutonium has been shown to bioconcentrate in aquatic organisms at
the lower end of the food chain (WHO 1983). However, data do not indicate that plutonium is
bioconcentrated in plants, higher aquatic organisms, or animals. In addition, there is no indication that
plutonium is biomagnified in terrestrial or aquatic food chains. No additional information on
bioaccumulation appears to be necessary at this time.
Exposure Levels in Environmental Media.
Reliable monitoring data for the levels of plutonium
in contaminated media at hazardous waste sites are needed so that the information obtained on levels of
plutonium in the environment can be used in combination with the known body burden of plutonium to
assess the potential risk of adverse health effects in populations living in the vicinity of hazardous waste
sites.
A number of studies have been performed throughout the years on the fallout associated with the testing
of nuclear weapons. Information is available on levels in air, water, soil, plant materials, and foodstuffs
(Ahier and Tracy 1995; Arimoto et al. 2005; Dai et al. 2002; DOE 1999a, 2005a, 2005c, 2005d, 2005e,
2005f, 2006a; Hirose and Aoyama 2003; Ibrahim et al. 1997; Lee and Clark 2005; Lehto et al. 2006;
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