Much-Needed Guidance

State agencies took two significant steps last week to address concerns about chromium 6 in drinking water. The California Department of Health Services and the Office of Environmental Health Hazard Assessment announced that they will develop a standard specifically for chromium 6 to replace the standard in effect now for total chromium. And the California Environmental Protection Agency said it has asked the University of California to convene a panel of expert scientists from throughout the country to review the health risk posed by chromium 6 when ingested in drinking water.

Chromium, a metal that is not considered dangerous, is used in aircraft manufacturing, electroplating and other industries. Chemical reactions can transform chromium into chromium 6, which can cause cancer when inhaled.

What is not known for certain is whether chromium 6 can cause cancer by another route of exposure, such as being swallowed in water.

Based on its review of scientific studies, the federal government set a standard of 100 parts per billion for total chromium--an indirect way of limiting chromium 6. Based on its review of studies, one state agency, the Department of Health Services, set a standard of 50 ppb for total chromium. And most recently, the state Office of Environmental Health Hazard Assessment, based on its review of studies, recommended that that standard be lowered to 2.5 ppb.

In tests mandated by the city of Thousand Oaks, Calleguas Municipal Water District found its water to contain a tiny fraction of state-mandated maximum. Calleguas serves Thousands Oaks and much of Ventura County.

When tests of Los Angeles County wells and tap water turned up concentrations lower than state and federal standards but higher than the newer, advisory public health goal, consumers were understandably confused to find there were three different “standards” out there. Which should they trust?

The question became even murkier when further tests revealed that chromium 6 made up a higher percentage of total chromium than had been assumed when the standards for total chromium were set.

We nonscientists want our science to be black and white: Does chromium 6 in water cause cancer, yes or no? Does it cause other health risks? If so, at what concentrations?

But answers are seldom that straightforward. We have to make decisions on the best information available. Setting a direct standard for chromium 6 alone, rather than an indirect standard, and convening a panel of scientists to address what is and is not known may not give us clear answers but will surely make things less murky than they are now. These actions will provide much needed guidance to water agencies--and consumers.

Two significant steps to address concerns about chromium 6 in drinking water may not give us clear answers but will surely make things less murky than they are now, for water agencies and for consumers.