Radiation and Incidence of Cancer Around Ontario Nuclear Power Plants From 1990 to 2008 (The RADICON Study)

Executive summary

The Canadian Nuclear Safety Commission (CNSC) has completed a groundbreaking ecological study on populations living near Ontario's three nuclear power plants (NPPs). The purpose of the Radiation and Incidence of Cancer Around Ontario Nuclear Power Plants from 1990 to 2008 study (the "RADICON" study) was to determine the radiation doses to members of the public living within 25 km of the Pickering, Darlington, and Bruce NPPs and to compare cancer cases among these people with the general population of Ontario from 1990 to 2008. The study was conducted using data from the Canadian and Ontario Cancer Registries and the Census of Canada.

The most important finding of the RADICON study is that there is no evidence of childhood leukemia clusters around the three Ontario NPPs. The rates of cancer incidence for children aged 0–4 and aged 0–14 were similar to the general Ontario population.

Overall, for all ages, there is no consistent pattern of cancer across the populations in question living near the three facilities studied. Some types of cancer in the communities studied were higher than expected (excess cancer); however, many types of cancer were lower than expected.

While this type of study cannot determine the causes of the cancer, excess cancers (increase in cancer above what's expected in Ontario) are unlikely to be due to radiation. Radiation doses from NPPs to members of the public are extremely low – at least 100 to 1,000 times lower than natural background radiation and public dose limits. As such, doses are a minor risk factor compared to the high prevalence of major risk factors like tobacco, poor diet, obesity and physical inactivity, which account for about 60 percent of all cancer deaths in developed countries. These factors represent a public health concern throughout Ontario, including the communities located near NPPs. Other important Ontario studies found that once these main risk factors were taken into account, there was no evidence of a cancer risk due to environmental factors like radiation. Given the high frequency of these factors, the current scientific understanding of radiation risk, and the minuscule public doses, it is not realistic to attribute any excess cancers to the radiation doses from NPPs found in these communities.

The main strength of the RADICON study is the use of detailed public dose information around each NPP that was generated from radiological releases and environmental monitoring data. The data collected for this study takes into account any emission spikes from the NPPs. This methodology improves on recent epidemiological studies of childhood cancer that have used distance from an NPP as a substitute for radiation dose. Doses closest to the NPPs were not consistently higher than doses further away. Many factors influence doses to the public as a result of the operation of an NPP, including prevailing wind directions and lifestyle characteristics (i.e., diet and lifestyle habits) of the surrounding communities. Therefore, distance is not a good substitute for dose.

To conclude, public radiation doses resulting from the operation of the NPPs are 100 to 1,000 times lower than natural background radiation and there is no evidence of childhood leukemia clusters around the three Ontario NPPs. All cancers for all age groups are well within the natural variation of the disease in Ontario. Thus, radiation is not a plausible explanation for any excess cancers observed within 25 km of any Ontario NPP.

Read the article in the Journal of Environmental Protection. (refer to Volume 9, 2013).