Animal Studies

Although human epidemiological data provides the most important basis for assessing risks of radon exposure, additional animal studies have clearly demonstrated that radon is a lung carcinogen. The animal studies provided important information on the exposure-response relationship, the effect of exposure rate on cancer risk, and the potential effect of simultaneous exposure to radon and other contaminants on the radon-lung cancer relationship.  Experimental animal studies conducted on rats in mines for more than 50 years yielded the following results:

• Health effects observed in animals exposed to radon include lung carcinomas, pulmonary fibrosis, emphysema, and a shortening of life span.
• Rats exposed to low levels of radon (as low as 20 WLM) were found to have an increased number of respiratory tract tumors.
• The number of respiratory tract tumors was found to increase as cumulative radon exposure increased.  Decreased exposure rate was also found to decrease the incidence of respiratory tract tumors.
• Rats exposed to radon progeny and uranium dust simultaneously were found to have elevated lung cancer risk at exposure levels similar to those found in homes. The risk decreased as radon exposure decreased.

Exposure to ore dust or diesel fumes simultaneously with radon did not increase the incidence of lung tumors above that produced by radon exposures alone.