For their entire lives in a German laboratory, 101 lab mice lapped up water containing extraordinary amounts of a metallic compound.
It was 1968, and scientists were trying to figure out whether chromium--widely used in industrial paints and plating materials--was dangerous in drinking water. Two of the mice developed stomach tumors so big that the mounds protruded from their bellies. All the others remained healthy.
The scientists concluded that the tumors were insignificant--perhaps just random chance--and that the cancer connection was equivocal.
Yet more than 30 years later, the fate of those two mice is the prime evidence that has been used by state health officials to recommend a stringent goal for chromium in drinking water. If enforced, that recommendation could shut down hundreds of wells across the Los Angeles area, especially in the San Fernando Valley, at a cost of tens of millions of dollars.
George Alexeeff, chief scientist at the state's Office of Environmental Health Hazard Assessment, said the state goal may be "over-erring on the side of public health." But that, he said, is exactly what public health officials must do--legally and morally--in the face of scientific uncertainty.
"The spirit of the law is when there's a controversy, we're to err on the side of being health protective," he said.
Others disagree. The federal Environmental Protection Agency has dismissed the German study. And one of the world's leading chromium experts, Max Costa of New York University, called it "totally stupid and scary" for California to calculate its health goal based on the fate of two mice.
Costa suspects that water containing even small amounts of chromium, particularly the most hazardous form, chromium 6, may be dangerous to people who are genetically susceptible to cancer. But he said the mouse study is so problematic that calculations derived from it are no more credible than pulling a number out of a hat.
To scientists, chromium 6, also known as hexavalent chromium, is an enigma. It alters DNA. It mutates cells. And it is among only a handful of chemicals proved to cause cancer in human beings.
But the danger, at least so far, has been proved only when chromium 6 particles are inhaled. There are no published studies that have found a significant cancer increase from drinking it, even in lab animals consuming extremely high concentrations. Published studies--one of people in China and several involving lab animals--have found no cancer link.
