Fecal Sample Results - doe-std-1128-98

DOE-STD-1128-98

Once an intake is confirmed, sufficient samples must be obtained to establish a

reasonably anticipated baseline against which future measurements can be compared.

This is important both to provide future verification of the accuracy of the assessment

and to identify potential additional intakes.

The statistical fluctuation of low-level measurements can be particularly troublesome

for long-term excretion patterns. Factors of 2 can be easily expected due to day-to-

day variability and imprecise adherence by the worker to urine collection protocols.

5.7.3

Fecal Sample Results

Fecal samples are much more sensitive to detection of intakes than are urine samples

and, consequently, are an important part of follow-up bioassay monitoring for

potential intakes initially identified by workplace indications. Pitfalls to the data

interpretation include highly variable individual fecal voiding patterns, ranging from

more than one per day to one every few days. This makes it extremely important to

know what time interval is represented by a collected fecal sample. While

normalizing a single set of fecal data to reference man daily excretion rate can be

done, it is not likely to improve the quality of assessment.

The preferred fecal sampling protocol following an intake is to collect all the early

fecal clearance (meaning total feces for the first five-to-seven days). This method will

allow a good estimation of inhalation or ingestion intake, but does not readily permit

discrimination of inhalation from ingestion, or identify whether inhaled material

exhibits class D, W, or Y clearance patterns. For optimum interpretation, total fecal

collection should be interpreted in light of early urine and in vivo data for

preliminary estimates. The urine data is likely to be particularly valuable in

conjunction with fecal data to classify an intake as class W or Y. Longer-term follow-

up fecal samples at nominally 30, 60, and 90 days post intake should substantially

improve the classification of material as class W or Y.

Fecal sampling can also be applied to monitor excretion at long times post-intake.

One caveat in such sampling is that a worker still active in a plutonium facility may

be incurring very minor chronic exposure, which can significantly interfere with

long-term interpretation of acute exposure data. Bihl et al. (1993) have discussed

experience with a routine fecal sampling program.

5.7.4

Use of Air Sample Data in Internal Dosimetry

Results of air sampling and continuous air monitoring implying more than 40 DAC-

hours exposure should be used to initiate special bioassay to assess intakes of

plutonium. Although bioassay data are the preferred method for assessing intakes and

internal doses, air sample data can be used for assessing internal doses if bioassay

data are unavailable or determined to be inadequate or nonrepresentative. Air sample

data can be used to calculate an exposure to airborne material either in terms of

DAC-hours or potential radioactivity intake as follows:

5-28