Bioassay Compared to and Contracted With Workplace Air Monitoring

DOE-STD-1121-98

progeny, as well as radionuclides such as 227Th, 223Ra, 225Ra, and 225Ac when separated from their long-

lived parents. It may also include routine bioassay for isotopes with high dose per intake coefficients,

such as many of the transuranics.

As defined in the IDG, a technology shortfall, such as for routine bioassay monitoring for Pu, does

not preclude the use of routine bioassay monitoring nor force the use of air sample data for dose

calculations. Rather, the IDG suggests that the capabilities of the bioassay program be stretched as far as

reasonable, that workplace monitoring be enhanced, and that state-of-the-art techniques be used in

general. Reliance should be placed on prompt detection of possible intakes in the workplace, and that

special bioassay should be promptly initiated (usually the same day) when intakes are suspected. In vivo

count times should be as long as reasonable, and MDAs should be as low as reasonably achievable, with

an emphasis in both cases on "reasonable" as explained in the IDG. Air sample data may be used for

initiating special bioassay without being used for dose assessment.

The DOE Office of Worker Protection Policy and Programs (previously the Office of Worker

Protection and Hazards Management) prepared a "Radiological Control Technical Position" entitled

"Technology Shortfalls and Dose Determinations for Radioactive Material Intakes" (Office of Worker

Protection Programs and Hazards Management 1995a). This document states,

By performing air sampling and documenting the results, in combination with an effective access

control program, worker exposure measured in DAC-h can be tracked. Internal dosimetry programs

typically base bioassay frequency and type on levels of actual or anticipated exposures to

individuals. By tracking DAC-h for individuals, the type and frequency of needed bioassay

measurements can be determined. For example, if a radiological worker receives less than 40 DAC-

h (2 percent of an ALI) in a year with no respiratory protection, the individual would not be

scheduled to participate in the bioassay monitoring program for that year. Additionally,

participation of the individual in the bioassay monitoring program for the next year should be

considered.

In the case where bioassay measurements may not be available or their validity is questionable,

internal dose assessments can be determined from the number of DAC-h tracked for that individual.

When DAC-h are used for this purpose, any adjustments, such as protection factors for respiratory

protection, must be documented.

Air sampling and monitoring play an integral role in dose assessment for all isotopes, including

those where the DIL is less than the detection capability. By tracking DAC-h, the expected

magnitude of the exposure can be determined. DAC-h can be used to determine an individual's dose

when necessary. Air monitoring provides early warning of an immediate and significant exposure

hazard and provides indications of the need for special bioassay monitoring.

The monitoring criteria contained in 10 CFR 835.402(c) do not establish required levels of detection

capability, that is, the minimum detectable dose. For example, it may not be feasible to actually confirm

intakes that will result in 100-mrem HE,50, particularly for bioassay measurements of some alpha-emitting

radionuclides. Therefore, monitoring thresholds should not be considered requirements on the sensitivity

of a particular measurement. Furthermore, workplace monitoring and occupancy factors should be

considered, as appropriate, in evaluating potential exposures and monitoring needs.

10 CFR 835.402(d) requires that "internal dose evaluation programs" be capable of demonstrating

compliance with the dose limits stated in 10 CFR 835.202 (e.g., 5 rems committed effective dose