UC Toxics News: Summer 2001
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Chromium
6 and Our Drinking Water by Mika Pringle Tolson |
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With the current public controversy over chromium in drinking water, California's Office of Environmental Health Hazard Assessment (OEHHA) has been charged with developing standards for acceptable levels of chromium in water.
The TSR&TP was asked to convene a review panel of expert scientists to examine the methods and assumptions used by OEHHA in their draft public health guideline. The panel is chaired by TSR&TP Director Dr. Jerry Last. Members of the panel include University of California scientists Russell Flegal, analytical chemistry and environmental fate of chromium, Marc Schenker, epidemiology, and Hanspeter Witschi, pathology and toxicology, and consulting scientist Gene McConnell, animal pathology.
At issue is the question of whether chromium 6 is a carcinogen in drinking water. The current federal and State of California guidelines for drinking water do not regulate chromium as a carcinogen. OEHHA's proposed standards are 250 times lower than the current standards because they do consider chromium as a carcinogen. The difference between the federal standards and the proposed California standards is based on OEHHA's use of data from a 1968 study that other agencies have chosen not to accept.
Scientists do not agree on whether the 1968 study proves the carcinogenicity of chromium 6 when ingested. Chromium 6 has been demonstrated to be a carcinogen in studies of occupational exposure through inhalation, but the carcinogenicity of chromium may not necessarily be extrapolated from inhalation to ingestion. For example, the stomach is the first organ encountered in ingestion, and the stomach contains acid which has been shown to quickly reduce chromium 6 to a nontoxic form, chromium 3 (which is an essential nutrient in the diet).
The panel has met and reviewed the proposed guidelines. A public meeting to give interested members of the public a chance to inform the panel was held at UC Davis on July 25, 2001. The panel issued its final report to OEHHA at the end of August 2001. OEHHA will take the report into consideration when revising the public health guideline, and this revised guideline will be reviewed once again by the UC panel in the spring of 2002. Once OEHHA completes its risk assessment, the public health guideline will be given to the California Department of Health Services to devise a maximum contaminant level for public drinking water.
The TSR&TP's involvement in the review of the chromium 6 guidelines adds quality to the process by bringing in objective scientists who aren't involved in setting standards or carrying them out. "It minimizes the possibility of conflict of interest," says Director Jerry Last, "which can occur not only from industries (and their consultants) with a financial stake in the outcome, but also those with a financial stake in litigation and lobbying in the public interest." California's Environmental Protection Agency was comfortable in asking UC for assistance in evaluating a controversial topic. And the TSR&TP was glad to help.
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