The chemical that was found last week to be contaminating the drinking water of hundreds of thousands of West Virginians is used to clean coal. But very little is known about how toxic it is to people or to the environment when it spills.
The chemical is called 4-methyl-cyclohexane-methanol or MCHM. If you've never heard of it, you're in good company. Most chemists and toxicologists hadn't either nor had the water company, nor emergency responders in West Virginia who had to deal with thousands of gallons of it spilling from a tank into the Elk River, just a mile and a half upstream from the intake for the region's drinking water plant.
West Virginia officials say they looked to the Centers for Disease Control and Prevention to give them advice about when they could tell people the water was safe to drink again.
"There are unknowns," acknowledges Karen Bowling, West Virginia's secretary of health and human resources. "So we have to rely on what's already known about [it] and what's [been] tested about this particular chemical."
At the time of the accident, the CDC didn't have a standard for how much of this chemical in water is safe to drink.
So the agency had to come up with one.
The agency relied on the little research that had been done on the chemical an animal study that established the lethal dose for rats.
"And from that you would decrease the proposed level down further and further taking into account all the uncertainties," says Vikas Kapil, chief medical officer at the CDC's National Center for Environmental Health.
For instance, the CDC built a safety factor into the limits it set because health officials were uncertain if people are more sensitive than rats to the chemical. And they added an additional margin of safety to account for certain populations such as infants and the elderly that might be especially vulnerable.
Kapil acknowledges that there was very little data to go on. Still, he says, drinking water that meets the CDC guideline of one part per million, is "generally not likely to be associated with any adverse health effects."
West Virginia officials say they also turned to safety information companies, which are required to provide information on the chemicals they possess. But that so-called Material Safety Data Sheet included very little data, in this case.
"The entries were largely 'data not available' for this particular compound," says Sharon Meyer, a toxicologist from the University of Louisiana at Monroe.
Meyer looked at the one published study she could find on the chemical and analyzed the 4-methyl-cyclohexane-methanol's chemical structure. She says she saw nothing obvious that should present a concern to people who drank the water.
"I really think they were not exposed to extreme levels that would cause serious problems. But I don't have the data to definitively say this," Meyer says.
Experts weren't surprised that the scientific literature had so little information about MCHM, because there is very little toxicological research about many chemicals. Priority for testing is given to chemicals used by consumers or in food preparation.
"There are 85,000 chemicals in commerce right now in the United States, and we cannot possibly test all the chemicals for all their different properties," says Rolf Halden, an engineering professor at Arizona State University who researches how chemicals move through the environment and people.
Halden used a computer model from the Environmental Protection Agency to calculate how this chemical would behave in the environment.
He says it likely would not persist long; half of it would be gone from water within two weeks, and half of it from soil within a month. That's because microbes in the soil will likely break it down.
"I would not be terribly concerned about long-term contamination of the environment with this chemical," Halden says.
Still, the spill shed light on how little is known about many chemicals. Members of Congress have been debating for years whether to update the 1976 law that governs these chemicals, The Toxic Substances Control Act.
Lynn Bergeson, a lawyer who specializes in the regulation of toxic chemicals, says she hopes the West Virginia accident will persuade lawmakers that it is urgent for them to act.
"These incidents are very painful for the local residents there in West Virginia," Bergeson says, and "are embarrassing to federal and state governments" that don't have the information residents want.