Updated Eldorado Workers Study

50 Years of Health Monitoring of Uranium Workers Exposed to Radon Gas

The Canadian Nuclear Safety Commission (CNSC), in partnership with provincial, federal and industry stakeholders, participated in the updated historic Eldorado Study, which followed the health of uranium miners over the past fifty years, from mines in Beaverlodge in Northern Saskatchewan, Port Radium in the North West Territories, and the uranium processing plant in Port Hope, Ontario.

The original study concluded that radon gas exposure in high concentrations causes lung cancer. This updated study adds important new information to our understanding of the relationship between exposure to radon gas and the risk of lung cancer. It is also worth noting that today's exposures to radon gas in Canadian mines do not pose the same risk to miners, due to enhanced and rigorous health and safety standards.

The call for health studies came from the 1993 Joint Federal-Provincial Panel on Uranium Mining Developments in Northern Saskatchewan. It was initiated in part on research that found that past uranium miners suffered from lung cancer because of high levels of exposure to radon gas in the mines. In addition, knowledge that the uranium ore extracted in today's uranium mines in northern Saskatchewan is extremely rich – typically containing an average of 20% uranium, compared to much lower grades of uranium ore mined in Saskatchewan in the past – led to concerns about the health of miners now employed in these mines.

The initial study looked at causes of death among workers from 1950-1980. In 1995, a working group was formed to update the initial study, with representatives from the CNSC, the government of Saskatchewan, and two uranium mining companies in Saskatchewan – AREVA Resources Inc. and Cameco Corporation – with representation from management and the mine worker's occupational health and safety committees.

This updated study included a total of 17,660 workers, the majority of them (> 90%) male, who worked for Eldorado Nuclear sometime between 1930 and 1982. It provided 19 additional years of data related to causes of death among workers since 1980 (49 years in total) and 30 years of data on cancer incidence information from 1969 to 1999.

The implementation of stringent health and safety standards has resulted in significantly lowering radon levels in today's uranium processing mines, and thus the health risks to uranium miners in Canadian mines. Today's uranium miners are exposed to very low levels of radon, with an average exposure of about one half a Working Level Month (0.5 WLM) per year, as opposed to 400 WLMs per year for past miners in Port Radium.

In other words, workers in modern Canadian mines are exposed to 800 times less radon gas than in the past, and therefore have a very low risk of lung cancer from occupational exposure to radon. In fact, uranium workers today and Canadian citizens in general face a comparable risk of getting lung cancer from exposure to radon gas.

The results of the updated Eldorado Study are very consistent. They show proportionate increases in lung cancer risk with increasing radon exposure, but no increase in any other disease from radon exposure. The updated study further supports the conclusions that radon gas is not linked to any other type of cancer, or to other causes of death.

To view the full report: http://www.nuclearsafety.gc.ca/eng/media/facts/eldorado_study.cfm