P&S Journal: Winter 1998, Vol.18, No.1
Mutagenic Effects of Radon
A single radon alpha particle can produce a mutation in mammalian cells, according to a study by P&S researchers published in the April 1997 issue of Proceedings of the National Academy of Sciences.
Dr. Tom K. Hei, associate professor of radiation oncology and of public health in environmental health sciences, and colleagues studied the mutagenic effects of low level exposure to alpha particles, the positively charged high energy particles emitted as a decaying product of radon gas. Radon is,
ubiquitous in the environment and is the main source of radiation exposure for the general public. According to the Environmental Protection Agency, radon accounts for approximately 15,000 lung cancer deaths annually in the United States. But because data on the cancer-causing potential of radon comes mostly from epidemiological studies of miners exposed to high levels of alpha particles, scientists do not know with certainty the relative cancer risk from the low levels of radon typically found in homes.
Dr. Hei's team, using a microbeam irradiation fixture at the Radiological Research Accelerator facilities, measured the genetic effects of a single alpha particle on mammalian cells. They found that even at such a low level of exposure, the frequency of gene mutations was enhanced more than two-fold above the background. "Our findings provide the first direct evidence that exposure to radon at levels commonly found in the home is mutagenic to the target cells and provide a genetic basis for radon-induced lung cancer," says Dr. Hei.
Since only a small percentage of the target bronchial epithelial cells will be hit each year by a single alpha particle arising from residential radon exposure, the findings would indicate that this small population of cells is at significantly increased risk for cancer development. Another important implication of the study is that people who have high radon levels in their homes will be at higher risk for lung cancer. Dr. Hei and colleagues are now investigating the biological consequences of cytoplasmic and membrane damage induced by alpha particles.