Baseline measurements

DOE-STD-1128-98

-- Baseline measurements are used to establish a pre-exposure condition, either for

a new employee or as a result of a new work assignment. The standard,

Radiological Control, Ch. 1. (DOE, 2004), recommends baseline measurements

if workers are considered likely to receive intakes resulting in greater than 100-

mrem CEDE. It is a good practice to perform such measurements for newly hired

employees, intra-company transferees, or workers transferred from facilities

where bioassay measurements may not have been required. In addition, baseline

measurements can verify workers' status for special work assignments. For

plutonium bioassay, baseline measurements made before any occupational

exposure can be expected to yield no detectable results using current technology.

Exempting workers from baseline bioassay implies accepting any detectable

results as likely attributable to current occupational exposure. However, requiring

baseline measurements can potentially impact the schedule of short-term jobs;

the time required to obtain a chest count and a large-volume urine sample may

add a day or two delay to entry procedures. Moreover, missing a baseline for a

long-term employee who will be placed on a routine bioassay program is not

likely to be as troublesome as not obtaining a baseline for a short-term worker

who provides a termination sample that shows detection of plutonium after the

worker has left the site and is difficult to reach for follow-up.

-- Routine, or periodic, measurements are performed on a predetermined

schedule (e.g., an annual or quarterly frequency).

-- Special bioassay measurements are performed as follow-up to unusual

routine results or suspected intakes (See Section 5.9 for recommended

internal dosimetry indicator and action levels).

-- End of assignment or termination measurements are performed following

completion of specific work or at the time of termination of employment.

The standard, Radiological Control, Ch. 1. (DOE, 2004), recommends that

workers who participate in bioassay programs have appropriate termination

measurements.

Bioassay classification is important because the purpose of a sample may affect

the collection and analysis or monitoring method chosen. For example, single-

void urine samples are not adequate for routine monitoring of potential

plutonium exposure, but can provide important information for dose-reduction

therapy following a suspected intake; samples representative of excretion over a

24-hour period should be collected for quantitative intake and dose assessment.

The date of sample collection (and possibly the time of collection) can be very

important to special monitoring performed to assess intake. However, these are

much less important with regard to periodic monitoring, for which measurements

are not expected to show detectable activity and when any detection whatsoever

is likely to initiate investigation and special bioassay.

5-11