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The City of Portland, Oregon

Portland Water Bureau

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Radon in Portland’s drinking water does not pose a significant health concern. The risk associated with radon comes from exposure to breathing air with high levels of radon, such as from indoor air where radon released from soils can accumulate.

Radon is a naturally occurring radioactive gas that is a health concern when inhaled. It is not generally a health concern when present in low concentrations in drinking water and is not currently regulated by the Environmental Protection Agency (EPA) or State of Oregon.

Radon has been detected at varying levels in Portland’s groundwater wells from the Columbia South Shore Well Field, Portland’s secondary source of drinking water. The Water Bureau turns to groundwater during annual maintenance, when heavy winter storms prevent use of the Bull Run source and during particularly hot, dry summers and during emergencies to supplement the Bull Run water supply.

Overall exposure to radon in Portland’s drinking water is very low.  Radon is rarely detected from the Bull Run source and only then, at extremely low levels. Radon from the Groundwater Pump Station outlet ranges from 131-370 pCi/L (picocuries per liter). In February 2017, radon was detected at the Groundwater Pump Station outlet at 330 pCi/L. Although no standard has been adopted, the Environmental Protection Agency has proposed regulating radon in drinking water at 4,000 pCi/L if a multi-media mitigation program is in place. This level is approximately 10-30 times higher than what the Water Bureau has detected at the Groundwater Pump Station outlet.  

Radon decays as it travels through the distribution system by approximately 50% every 3.8 days. Therefore, it is expected that radon levels are lower by the time it reaches customers.  Radon is not currently a regulated contaminant in drinking water, and therefore monitoring is not required. However, the Portland Water Bureau has been proactively monitoring radon for many years. The Water Bureau also reports radon results in the Annual Drinking Water Quality Report when radon is tested for and detected.

In Portland, the greatest source of radon exposure is from naturally occurring radon gas that enters homes and buildings through the foundation. Customers are encouraged to test their home for radon. The EPA, Surgeon General, and the Oregon Health Authority all recommend testing your home for radon gas.  The American Lung Association of Oregon offers test kits at:

Additional information about radon can be found at the Oregon Health Authority’s radon webpage or from the EPA’s radon webpage or Radon Hotline at 800-SOS-RADON.