Highlights of Noteworthy Decisions
- Exposure (radiation)
- Mining (uranium)
The worker was a uranium miner from 1968 to 1992. He was diagnosed with acute myeloid leukemia in 2005 and died in 2006. The worker's estate appealed a decision of the Appeals Resolution Officer denying the worker entitlement for the leukemia. At the request of the Board's Occupational Disease and Survivor Benefits Program (ODSBP), the Board's Occupational Disease Policy and Research Branch prepared a research memo on Risk of Leukemia in Uranium Miners. Ionizing radiation is the type of radiation that has enough energy to produce charged particles (ions) when contacting matter, which can cause changes in cells, leading to cancer. Ionizing radiation is produced by unstable atoms that are referred to as radioactive. There are primarily three types of ionizing radiation: high energy electromagnetic radiation, such as x-rays and gamma radiation, which travels many metres in air and many centimetres in human tissue; beta radiation, consisting of high energy electrons, which can penetrate a few millimetres of human tissue, but has little impact on miners; alpha radiation, consisting of high energy helium nuclei, which has no ability to penetrate even outer layers of dead skin but which can be harmful if the unstable atoms are ingested or inhaled. There are primarily two types of ionizing radiation that could affect miners: external gamma rays, which comes from surrounding rock and can pass right through the body; internal alpha emitters from radon decay products, which can be inhaled. Levels of gamma radiation in a mine are relatively low and constant, while radon and radon progeny levels are greatly affected by ventilation. The memo then reviewed and summarized the scientific and medical literature: there is positive evidence of elevated lung cancer risk due to radon progeny; there is positive evidence that high external gamma radiation (500 mSv) increases the risk of leukemia; there is evidence suggesting no association between radon and radon progeny exposure and risk of leukemia. The evidence in this case was that the worker's exposure to ionizing radiation was too low for it to be considered a significant risk of leukemia. The worker's whole body external gamma radiation dose was only 30.8 mSv. The appeal was dismissed.