Rn
Radon
radionuclideSDWA code: 4200
EPA Limit (MCL)
No MCL
Health Goal (MCLG)
Zero (0)
No level is considered safe
Unit of Measure
pCi/L
How concentrations are reported
EPA proposed an MCL of 300 pCi/L but it was never finalized. No enforceable federal MCL currently exists for radon in drinking water.
Health Effects
Increased risk of lung cancer (from inhaling radon released from tap water). Stomach cancer risk from ingestion.
The EPA has set the health goal (MCLG) at zero, meaning no level of exposure is considered risk-free.
How It Gets Into Water
Decay of naturally occurring uranium deposits in rock and soil; enters water from groundwater sources
Official EPA Guidance
For authoritative information on Radonin drinking water, visit the EPA's official resource page.
View EPA Guidance ↗