Investigation of monitoring for internal exposure by urine bioassay in a biomedical research facility

A simple monitoring programme by urine bioassay was carried out to assess internal doses for workers in a biomedical research facility. Urine samples were measured without chemical treatment using a liquid scintillation counter or sodium iodide (NaI (Tl)) scintillation detector. The detection limits for the committed effective doses were below 1 mSv for 125I and 131I and below 1 x 10-1 mSv for 3H, 14C, 32P, 35S and 51Cr, in the case that samples were collected within 3 d after handling. All of the urinary concentrations were below the detection limit, suggesting that no significant intake was detected during the investigation. The present results suggest that personal monitoring, such as the urine bioassay, is not necessary in many cases as a routine monitoring for workers engaged in tracer experiments using the above nuclides. (authors)