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Summary of the Public Health Goal for Uranium

A Public Health Goal (PHG) of 1 ppb is developed for natural uranium in drinking water based on carcinogenicity. The U.S. Environmental Protection Agency (U.S. EPA) has not established a Maximum Contaminant Level (MCL) for natural uranium. Uranium is a naturally occurring radioactive element that is ubiquitous in the earth’s crust. Uranium is found in ground and surface waters due to its natural occurrence in geological formations. The average uranium concentration in surface, ground and domestic water is 1, 3 and 2 pCi/L, respectively. The uranium intake from water is about equal to the total from other dietary components. Natural uranium contains 99.27% 238U, 0.72% 235U and 0.006% 234U. The primary noncarcinogenic toxic effect of uranium is on the kidneys. Uranium is an emitter of ionizing radiation, and ionizing radiation is carcinogenic. On the basis of carcinogenic risks, a PHG of 2 pCi/L is calculated for natural uranium, equivalent to 0.001 mg/L or 1 ppb.

June 29, 1998
Pursuant to Health and Safety Code Section 116365(e)(1), the Office of Environmental Health Hazard Assessment (OEHHA) is revising the public health goal (PHG) for uranium in drinking water established December 31, 1997. Based on new information, OEHHA hereby withdraws the previously established PHG for uranium of 2 picocuries per liter of water. OEHHA is in the process of reviewing the relevant scientific data in order to propose a revised PHG.