The two principal concerns for radon are stomach cancer from ingesting radon (e.g. from drinking water) and lung cancer from inhalation. The health risk of radon inhalation is believed to be many times greater than the risk resulting from direct ingestion of radon contained in water. Radon in water is emitted to the air, especially where water is agitated or sprayed (shower, washing machine). The EPA has not set a Maximum Contaminant Level (MCL) for radon in public drinking water at this time but recommends that public water suppliers reduce radon in their system's drinking water to 300 pCi/L; or develop a comprehensive local radon mitigation program that includes addressing the risk from radon in indoor air and reducing levels in drinking water to 4000 pCi/L. Any level of radon in a private drinking water supply above 300 pCi/L should be a concern.

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