Experience with a routine fecal sampling program for plutonium workers

A quarterly fecal sampling program was conducted at the U. S. Department of Energy's Hanford site for congruent to 100 workers at risk for an intake of plutonium oxide and other forms of plutonium. To our surprise, we discovered that essentially all of the workers were excreting detectable activities of plutonium. Further investigation showed that the source was frequent, intermittent intakes at levels below detectability by normal workplace monitoring, indicating the extraordinary sensitivity of fecal sampling. However, the experience of this study also indicated that the increased sensitivity of routine fecal sampling relative to more common bioassay methods is offset by many problems. These include poor worker cooperation; difficulty in distinguishing low-level chronic intakes from a more significant, acute intake; difficulty in eliminating interference from ingested plutonium; and difficulty in interpreting what a single void means in terms of 24-h excretion. Recommendations for a routine fecal program include providing good communication to workers and management about reasons and logistics of fecal sampling prior to starting, using annual (instead of quarterly) fecal sampling for class Y plutonium, collecting samples after workers have been away from plutonium exposure for a least 3 d, and giving serious consideration to improving urinalysis sensitivity rather than going to routine fecal sampling.