COHERE - strengthening cooperation within the Canadian government on radiation research

PURPOSE

Canadian Organization on Health Effects from Radiation Exposure (COHERE) is a government initiative to better understand biological and human health risks from ionizing radiation exposures relevant to occupational and environmental settings (<100 mGy, <6 mGy/h). It is currently a partnership between two federal agencies, Health Canada (HC) and the Canadian Nuclear Safety Commission (CNSC). COHERE's vision is to contribute knowledge to reduce scientific uncertainties from low dose and dose-rate exposures. COHERE will advance our understanding by bridging the knowledge gap between human health risks and linkages to molecular- and cellular-level responses to radiation. Research focuses on identifying sensitive, early, and key molecular events of relevance to risk assessment.

CONCLUSIONS

The initiative will address questions of relevance to better apprize Canadians, including radiation workers and members of the public and Indigenous peoples, on health risks from low dose radiation exposure and inform radiation protection frameworks at a national and international level. Furthermore, it will support global efforts to conduct collaborative undertakings and better coordinate research. Here, we describe a historical overview of the research conducted, the strategic research agenda that outlines the scientific framework, stakeholders, opportunities to harmonize internationally, and how research outcomes will better inform communication of risk to Canadians.

An ecological study of cancer incidence in Port Hope, Ontario from 1992 to 2007

A plant processing radium and uranium ores has been operating in the town of Port Hope since 1932. Given the nuclear industry located in the community and ongoing public health concerns, cancer incidence rates in Port Hope were studied for a recent 16 year period (1992-2007) for continued periodic cancer incidence surveillance of the community. The cancer incidence in the local community for all cancers combined was similar to the Ontario population, health regions with similar socio-economic characteristics in Ontario and in Canada, and the Canadian population. No statistically significant differences in childhood cancer, leukaemia or other radiosensitive cancer incidence were observed, with the exception of statistically significant elevated lung cancer incidence among women. However, the statistical significance was reduced or disappeared when the comparison was made to populations with similar socio-economic characteristics. These findings are consistent with previous ecological, case-control and cohort studies conducted in Port Hope, environmental assessments, and epidemiological studies conducted elsewhere on populations living around similar facilities or exposed to similar environmental contaminants. Although the current study covered an extended period of time, the power to detect risk at the sub-regional level of analysis was limited since the Port Hope population is small (16,500). The study nevertheless indicated that large differences in cancer incidence are not occurring in Port Hope compared to other similar communities and the general population.

Bioaccessibility of uranium in soil samples from Port Hope, Ontario, Canada

Adequate assessment of human health risk of uranium contamination at hazardous waste sites, which is an important step in determining the cleanup strategy, is based on bioavailability data. Bioavailability of uranium from contaminated soil has not been properly determined yet. Bioaccessibility is an in vitro conservative estimate of bioavailability and is thus frequently used for site-specific risk assessment. Bioaccessibility of uranium was measured in 33 soil samples from the Port Hope area in Ontario, Canada, by the physiologically based extraction test (PBET). Higher bioaccessibility values in the gastric plus intestinal phase, 48.4% ± 16.8%, than in the gastric phase, 20.8% ± 11.7%, are very probably the result of more efficient extraction of uranium from soil by intestinal fluid rich in carbonate ions. The observed variability of measured bioaccessibility values is discussed in light of the results of scanning electron microscope examination of the soil samples. Uranium bioaccessibility values in both gastric (acidic) and gastric plus intestinal (neutral) phases are higher in soil samples with smaller uranium-bearing particles and lower in samples where the uranium-bearing particles are larger. We postulate that the most important reason for variability of measured bioaccessibility values in Port Hope soil samples may be the difference in particle size of uranium-bearing particles.