A state agency withdrew its effort Friday to limit chromium in drinking water, acknowledging that its initial risk assessment was flawed and said a future recommendation will focus on the chemical's toxic byproduct, chromium 6.
Officials of the California Office of Environmental Health Hazard Assessment said they acted on advice from a University of California panel. The UC Chromate Toxicity Review Committee found in September that questionable data was used in a 1968 German study that provided the basis for the agency's position on chromium.
"Given that, it seemed appropriate to withdraw it," said Allan Hirsch, a spokesman for the state agency.
The review committee disputed a 1999 recommendation by the state agency that the amount of chromium allowed in drinking water be lowered to 2.5 parts per billion from 50 ppb as a way to limit chromium 6.
Chromium 6 is a chemical used in paint, chrome plating and other manufacturing processes, and it is known to cause cancer in humans when inhaled. It has been detected in water systems throughout the state, including industrial areas of Los Angeles and the San Fernando and San Gabriel valleys, Davis, Los Banos and Daly City.
The state and federal governments limit chromium as an indirect means of regulating chromium 6. Federal guidelines limit total chromium to 100 ppb, twice the state limit.
The state agency was criticized two years ago for proposing that the Department of Health Services, which sets chemical limits in drinking water, reduce total chromium to 2.5 ppb. In turn, that would have limited chromium 6 to 0.2 ppb.
Scientists argued that the carcinogenic qualities of chromium 6 were documented for inhalation but proved inconclusive for ingestion.
Other critics, including local water agencies, argued that adopting such a strict standard would cost Burbank, Los Angeles and the city of San Fernando more than $50 million to replace affected water sources with imported supplies.