Ontario uranium miner cohort: Linkage with national mortality and cancer incidence files

Status: in progress

Purpose:

To update the cancer experience of an Ontario uranium miner cohort by extending follow-up over 20 years for mortality and, for the first time, examining cancer incidence.

Background:

Over 30,000 men were employed to extract uranium from deep underground mines in Ontario from 1954 through 1996. Despite economic benefits, mining uranium is a dangerous occupation with potentially fatal long-term consequences. One example is the excess of lung cancer mortality associated with radon decay products that has been well demonstrated in uranium miners worldwide.

In the past, surveillance of Ontario uranium miners played an important international role in radiation protection, providing information on the magnitude of cancer risks associated with radon exposure. The most recent information resulted from studies done more than 20 years ago. Although uranium mining no longer occurs in Ontario, this large cohort remains a valuable source of information relevant to radiation protection.

Methods:

Statistics Canada will link national mortality and cancer incidence data with the cohort file. The mortality and cancer incidence experience of this cohort will be compared to the general Canadian population by calculating standardized mortality (SMR) and incidence (SIR) ratios. The next step will be to examine cancer risks associated with different levels of cumulative radon exposure experienced by these miners. This includes an examination of factors that could potentially modify the relationship between radon exposure and lung cancer risk. Gamma radiation exposure will also be estimated based on information available from the cohort, which includes area measurements in the various mines at different points in time, employment data collected during routine annual chest x-rays, as well as badge readings recorded in the National Dose Registry for exposures after 1980.

Implications:

The findings from this project will contribute to our understanding of uranium mining, radon and gamma radiation exposure, and cancer risk with potential implications for radiation protection. This project will also shed light on the uncertainties in the low-dose linearity assumption, non-lung cancer risks, cancers with long latency periods, incident cancer risks and risk of non-cancer endpoints (e.g. cardiovascular diseases).

Progress:

Linkage with Canadian mortality and cancer incidence databases was completed at Statistics Canada. Major analyses have been completed and additional analyses are underway.

Funding:

This study is funded by the Canadian Nuclear Safety Commission.

Investigators:

Loraine Marrett (Occupational Cancer Research Centre and Cancer Care Ontario) (co-PI)
John McLaughlin (Occupational Cancer Research Centre and Cancer Care Ontario) (co-PI)
Minh Do (Occupational Cancer Research Centre)
Paul Demers (Occupational Cancer Research Centre and Cancer Care Ontario)
Shelley Harris (Occupational Cancer Research Centre and Cancer Care Ontario)
Paul Villeneuve (Health Canada, University of Toronto)
Garthika Navaranjan (Occupational Cancer Research Centre)
Colin Berriault (Occupational Cancer Research Centre)
Anna Koné (Occupational Cancer Research Centre)
National Uranium Miners Working Group (Doug Chambers, Rachel Lane, Ron Stager, Robert Kusiak, Willem Sont)