That ionising radiation increases cancer risks is well known from studies of people exposed to relatively high doses including atomic bomb survivors from Japan or patients receiving radiation therapy. But what about the more common low doses of radiation to which the population at large is exposed to such as natural background radiation or diagnostic radiology; do these also contribute to cancer risk and, if yes, do similar dose-response relationship apply?
This week, a study by Ben Spycher, Claudia Kuehni and other researchers from the ISPM together with colleagues from Basel, Zürich and Lucerne was published in Environmental Health Perspectives suggesting that the answer to the first of these questions is yes. The researchers included all children in the Swiss National Cohort aged less than 16 years - over 2 million children – and used a geographic radiation model to estimate levels of terrestrial and cosmic radiation at the children’s homes. Diagnoses of cancers were identified from the Swiss Childhood Cancer Registry. A two-fold higher risk for leukaemia and brain tumours was seen among children exposed to dose rates of ≥200 nSv/h compared to those exposed to <100 nSv/h. The researchers estimated that an increase in 1 mSv cumulative dose received since birth was associated with and 4% increase in risk both for leukaemia and brain tumours. However, statistical uncertainty was large and more large studies will be needed to establish reliable dose response relationships for low-dose ionising radiation.