Tritium exposure estimates of dial painters from bioassay measurements: case study and proposal for a simple methodology

In India, radioluminous dial painting industries consume about 60 TBq of tritium based compounds every year. In all, they employ nearly 100 dial painters who are occupationally exposed to tritium. These small scale industries are subjected to periodic surveillance and surprise checks regarding safe practices adopted in handling small quantities of radioactivity. Only random data on parameters such as air concentration or bioassay results will be available for any assessment by the regulatory agency. A mathematical model has been developed (i) to estimate urine concentration when there is a steady intake of tritium over a fixed period of work every year, and (ii) to correlate air concentration in the working environment with urine assay values of dial painters. The model-predicted mean urine concentration values, derived from mean air concentration measurements, have been found to be in reasonable agreement with the measured mean urine assay values in two different institutions over the period 1992-1995. The estimated CED for a painter is found to be typically 1.2 μSv.y-1 per g of the paint handled and the annual occupational exposures are less than 1 mSv which is the ICRP recommended limit for the public. (author)