Experimental animal studies have clearly demonstrated that radon is a lung carcinogen. They have 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. The following is a summary of relevant findings to date from animals studies:
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 repiratory tract tumors were found to increase as cumulative radon exposure increased. Decreased exposure rate was also found to increase the incidence of respiratory tract tumors.
Rats exposed to radon progency 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.