Age-dependent lung doses from ingested 222Rn in drinking water.

The U.S. Environmental Protection Agency currently is considering regulatory standards limiting the concentration of 222Rn in public drinking water supplies. As part of this effort, a criteria document has been prepared detailing the health risks expected to occur from the presence of 222Rn in water used in homes. The present report examines the dose equivalent delivered to lung tissue following direct ingestion of 222Rn in water. Irradiation from both in-situ decay of 222Rn in lung tissue and the decay of 222Rn in lung air passages following exhalation are examined and results presented for ages from neonate through adult. These results indicate that the risk of lung cancer from inhalation of airborne progeny following emanation of 222Rn from water into home air is significantly greater than the risk from both irradiation pathways considered in ingestion at all ages.