Radiological Safety Aspects of Indian Watches Containing Tritium

In recent years tritium activated radioluminous paint has become the preferred compound in dial painting by wrist watch industries. Tritium activity in metallic wrist watches has been found to be in the range of 5.5-18.8 MBq. The release rates of tritium from different watches showed considerable variation in the range of 0.2-15 kBq.d-1 under humid conditions and indicate dependence on the gross activity level present in the watch. The mean tritium life in watches is 5 ± 2 years based on gross activity estimated and release rate measured. The annual effective dose to the wrist watch wearer works out to be about 2.5 µSv from air concentration through inhalation and precutaneous absorption through skin and assuming the highest release rate and continuous watch wearing conditions. In the worst possible imagined situation, the maximum possible annual skin dose equivalent rate is estimated to be in the range of 6.7 mSv-67 mSv over a 10 cm2 area. Both the dose estimates are far less than the respective limits recommended by ICRP for the public at large.