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DOE-STD-1121-98
For exposures to the short-lived progeny of radon and thoron, Hlung,50 may be calculated as HE,50
divided by the tissue weighting factor for lung, wlung = 0.12.
7.1.3 Total Effective Dose Equivalent
Total effective dose equivalent should be calculated in cooperation with the site's external dosimetry
program and records program pursuant to 10 CFR 835. Total effective dose equivalent includes all
occupational doses: internal, external, and those received at other sites.
7.1.4 Cumulative Total Effective Dose Equivalent
Committed doses from intakes prior to January 1, 1989, may be included in lifetime dose
calculations. Including such doses gives a more accurate estimate of the lifetime accumulation and is
consistent with the recommendations of NCRP Reports 91 and 116 (1987 and 1993). However, to
demonstrate compliance with 10 CFR 835 requirements, these doses should be kept separate from the
cumulative total effective dose equivalent from intakes occurring after January 1, 1989.
7.2 DATA NEEDS AND DEFAULT ASSUMPTIONS
Generally, the more data available, the more precise the dose determination. However, practical
considerations generally limit the amount of data available. Internal dosimetry programs should commit
resources in proportion to the magnitude of potential doses. For doses below the IL, it is acceptable to use
default assumptions as described in the technical basis documentation.
7.3 INTERPRETATION OF BIOASSAY DATA
Selection of methods for bioassay interpretation plays an important role in the design of the bioassay
program. For example, in cases where either the intake scenario or the biological retention cannot be well
known, more bioassay data are needed to adequately arrive at the dose estimation. Conversely, if the
intake, uptake, and retention models are well characterized and apply to the exposure scenario, one
bioassay measurement which confirms a previous result may be sufficient for dose assessment. Since
there is normally sufficient uncertainty in both the bioassay data and the biokinetic models, the use of
multiple data points and fitting to the model may be necessary. Facility-specific and radionuclide-specific
decisions about bioassay interpretation methods should be documented and should dictate a significant
part of the overall bioassay and internal dosimetry program.
The derivation of intakes and retained quantities from bioassay data may be the critical step in the
dose assessment process. Evaluations of exposure to internal radionuclides should account for all
possible sites of retention and their associated retention times (if known) in the body. Generalized
biokinetic models, suitably modified to account for experience or studies at the facility, may provide a
starting point for the initial assessment of an intake and for determining the specific needs for follow-up
bioassay measurements. All organs contributing to the effective dose equivalent, calculated with the
weighting factors given in 10 CFR 835, should be considered rather than only those organs in which the
radionuclide can be readily measured.
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