Introduction
Although exposure to high-dose ionising radiation is rare outside of radiotherapy, repeated or protracted low-dose exposure has become increasingly common over the past 25 years.1 Occupational and environmental sources of radiation exposure are important; however, the largest contributor to this trend is medical radiation exposure. In 1982, the average yearly dose of ionising radiation from medical exposures was about 0·5 mGy per person in the USA; by 2006, it had increased to 3·0 mGy.2 A similar pattern exists in other high-income countries: use of diagnostic procedures involving radiation in the UK more than doubled over that period3 and more than tripled in Australia.4 Because ionising radiation is a carcinogen,5 its use in medical practice must be balanced against the risks associated with patient exposure.6
The primary basis for estimating cancer risks from ionising radiation exposures are epidemiological studies of Japanese survivors of the atomic bombings of
Hiroshima and Nagasaki in August, 1945.7 Within a few years of the bombings there was evidence of an excess of leukaemia, predominantly myeloid subtypes, among the survivors.8–12 These findings helped to establish that ionising radiation causes leukaemia.13 However, this evidence mostly relates to acute high-dose exposure. The risks associated with protracted or repeated low-dose exposures are more relevant to the public and health practitioners.
The International Nuclear WORKers Study (INWORKS) was done to strengthen the scientific basis for protecting people from low-dose protracted or intermittent radiation exposure. It included workers from France,14 the UK,15 and the USA16 who have been monitored for external exposure to radiation with personal dosimeters and followed up for up to 60 years after exposure. Here, we report data for leukaemia, lymphoma, and multiple myeloma mortality among participants of INWORKS.