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Since soil-adsorbed plutonium contamination exists as discrete
particles of various sizes, analysis of
larger soil volumes (25–100 g) is recommended (EPA 1976a). Commonly, soil samples with high
amounts of carbonate are difficult to analyze. More rapid, efficient, and economical procedures have
been developed to sequentially analyze a number of radioactive actinides (Hindman 1986).
The U.S. Department of Energy Environmental Measurement Laboratory provides techniques for the
determination of plutonium in various biological and environmental samples using alpha spectroscopy.
EPA methods are available for the determination of plutonium in air, soil, coal fly ash, ores, vegetation,
biota, and water. APHA has standard methods for determination of gross alpha and
beta radioactivity and
gamma-emitting radionuclides in water, Methods 7110 and 7120, respectively; however, no methods that
are specific to plutonium isotopes are reported (APHA 1998a, 1998b). No methods were reported by the
AOAC for the determination of plutonium (AOAC 1990).
Anderson et al. (2001) reported that the U.S. Food and Drug Administration determines
239
Pu
concentration using electroplating and alpha-spectroscopy, following sequential nitric acid/hydrofluoric
acid and nitric acid/hydrofluoric acid/hydrochloric acid digestions of ashed food samples.
A detection
limit of 0.004 Bq/kg for
239
Pu is reported for this method.
Alpha spectrometry is the most common analytical method for measuring plutonium concentrations in
environmental samples. Other measurement techniques available are liquid scintillation, mass
spectrometry (MS), and gamma spectrometry. ICP-MS has been used increasingly for the determination
of plutonium in environmental samples (Muramatsu et al. 2001a). Low concentrations of plutonium in
environmental samples with high salt and organic matter content cause signal suppression and make it
difficult to obtain an accurate plutonium determination. Preconcentration and matrix separation are
typically required in these analyses (Epov et al. 2005; Figg et al. 2000).
MS is used by some research laboratories to determine the concentration of each plutonium isotope,
including the naturally-occurring
244
Pu. MS determines the number of atoms of a given mass number
and, therefore, can measure the concentration of all of the plutonium isotopes, not only the alpha-particle
emitters as in alpha spectrometry. MS is several orders of magnitude more sensitive than alpha
spectrometry in determining the quantities of plutonium isotopes with long half-lives,
which also tend to
be the heavier isotopes.
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Quantities of
241
Pu, a beta-particle emitter, can be quantified from assumed isotopic abundance ratios;
estimated in-growth of its progeny
241
Am by gamma spectrometry; or MS (EPA 1976a).
241
Am is
produced from the beta decay of
241
Pu and, therefore, can be used to indirectly measure
the concentration
of
241
Pu (Metz and Waterbury 1962). Direct determination of
241
Pu by measurement of its low energy
beta-particle decay has been reported using liquid scintillation analysis (Martin 1986).
7.3 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
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.
7.3.1
Identification of Data Needs
Analytical methods are available and are adequately sensitive to detect plutonium isotopes
in biological
materials (e.g., blood, urine, and bone) and in environmental samples (e.g., water, soil, air, and food). No
data needs are identified at this time.
Methods for Determining Biomarkers of Exposure and Effect.
Exposure.
There are methods available for measuring the isotopes of plutonium in biological samples.
The measurement of plutonium in the urine is considered a biomarker of exposure to plutonium. Methods
are available to detect plutonium in the urine. However, no information was available concerning the
reliability of these methods for determining plutonium levels in the urine. Plutonium can be determined
sensitively and selectively by alpha spectrometry and ICP-MS in urine and tissues (DOE 1997; Epov et
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al. 2005). Analytical methods with satisfactory sensitivity and precision are available to determine
levels
of plutonium in human tissues and body fluids.
Effect.
Existing methods are sensitive enough to measure background levels for plutonium in the
population and levels at which biological effects occur.
Methods for Determining Parent Compounds and Degradation Products in Environmental
Media.
Environmental media are analyzed to identify contaminated areas and to determine if
contaminant levels constitute a concern for human health. The detection of plutonium in air, water, and
soil is of concern due to the potential for human exposure. There are many steps involved in the analysis
of plutonium in environmental media. Alpha spectrometry a satisfactory method available for the
determination
of plutonium in water, air, and solid waste samples (DOE 1997, 1999c).
7.3.2
Ongoing Studies
No ongoing studies pertaining to analytical methods for plutonium were identified in a search of the
Federal Research in Progress database (FEDRIP 2007).