Example 5.1. Baseline Bioassay Scenarios
A new employee in a plutonium facility would not require a baseline bioassay measurement
if there was no prior potential occupational exposure to plutonium. However, a new
employee at a plutonium facility who came from another facility where plutonium was a
nuclide of concern should undergo baseline measurements if a termination bioassay was not
performed by the former employer or work history information is absent.
Workers with potential exposure to uranium should receive baseline uranium urinalyses due
to the ubiquitous and highly variable occurrence of uranium naturally and its possible
presence in urine.
Workers with potential exposure to 137Cs should receive baseline whole body counts because
of environmental 137Cs, present from worldwide atmospheric fallout, can be present in low-
levels in certain food products.
5.3 PARTICIPATION IN ROUTINE INDIVIDUAL MONITORING PROGRAMS:
BIOASSAY AND/OR PERSONAL AIR SAMPLING
Workers considered likely to receive intakes which could result in HE,50 values in excess of 100
mrem or who are at risk for such intakes should participate in a routine individual monitoring program
that includes bioassay and/or personal air sampling. Those workers are identified using criteria based on
knowledge of the radionuclides, facilities, processes, and anticipated work. Criteria may be expressed in
many forms, including quantity and form of material handled, type of work, or category of worker. There
is no single method that is most cost-effective and technically correct for identifying those workers.
Example 5.2 presents criteria for determining the need for routine participation in a bioassay and/or
personal air sampling program and sample applications of those criteria. Example 5.3 gives instances in
which personal monitoring is not needed..
The ICRP (1988) recommends the order of preference for bioassay program data interpretation to be
(1) direct in vivo measurement of body content, (2) excreta analysis, and (3) personal air sampling.
However, the radionuclide or element being monitored and its characteristic radiations usually establish
the type of monitoring performed.
Participation in routine individual monitoring programs may be discontinued when sufficient facility
history and experience is available to indicate that there is no need for a routine program. However, in
such cases, a confirmatory monitoring program (see Section 5.7) may be of value.
5.3.1 Exposure Monitoring Thresholds for Radon and Thoron Progeny
Since there is no practical bioassay for radon and thoron, exposure monitoring is required when
individuals have the potential to be exposed in excess of the dose levels given in 10 CFR 835.402(c)
requiring monitoring. It is important to emphasize that the radon and thoron exposure monitoring
thresholds are exposure-based (WLM or DAC-h) versus concentration-based thresholds because of the
dynamic nature of radon concentrations.