San Francisco health officials are demanding answers from the U.S. Navy after learning that elevated radiation levels were detected at the decommissioned Hunters Point Naval Shipyard in November 2024.

Plutonium-239 was found in an air filter at the site during asphalt grinding, with levels more than double the EPA’s “action level,” but the city was not notified until nearly a year later.

Health experts warn inhaling plutonium can lodge radioactive particles in the lungs for years, increasing cancer risk, the San Francisco Gate has reported.

The contamination was detected in Parcel C, an uninhabited area still under environmental cleanup, while parts of the shipyard have been transferred to the city for residential use.