CHARLESTON, W.Va. -- As hundreds of thousands of residents in and around the Kanawha Valley struggle with the "do not use" order from West Virginia American Water Co., one stubborn fact continues to frustrate residents and some local health officials alike: No one seems to be able to say for sure what the coal-cleaning chemical that's been dumped into our water supply might do to us.Water company officials have identified the chemical -- which leaked from a Freedom Industries tank just upstream from the regional drinking-water intake on the Elk River -- as something called "Crude MCHM." That material is made up almost entirely of another chemical, 4-methylcyclohexanemethanol.Material-safety sheets from several manufacturers list little in the way of health information. Toxicological databases provide few answers."No specific information is available in our database regarding the toxic effects of this material for humans," one chemical fact sheet explains. "However, exposure to any chemical should be kept to a minimum. Skin and eye contact may result in irritation. May be harmful if inhaled or ingested."Carcinogenic effects? No information available.Mutagenic effects? No information available.Developmental toxicity? No information available.Such a dearth of data can leave even the local experts scratching their heads."There's not much known about this chemical," said Dr. Elizabeth Scharman, longtime director of the West Virginia Poison Center, which has been fielding calls from concerned residents since the emergency began.What Scharman and toxicologists she's consulted with are comfortable saying is that the material is likely an "irritant" that could cause itching or burning of eyes, skin and the respiratory tract. It could, in some cases, prompt vomiting or diarrhea.Beyond that, it's not entirely clear, but health officials are certainly not saying exposure to small amounts diluted in the water are going to cause residents to start dropping dead anytime soon. Still, they advise everyone to follow the water company's order and avoid drinking or otherwise using water from their taps."We're not, from a toxicological aspect, overly concerned at this point," Scharman said. "But because we don't know, it's prudent from a public-health perspective to tell people not to use it."Still, some emergency response and environmental protection officials have been quick to assure the public that 4-methylcyclohexanemethanol isn't "hazardous." They've made that statement based on one limited piece of evidence: the fact that it's not listed as a material whose shipment is regulated by the federal Department of Transportation.However, the material-safety data sheet, or MSDS, being cited by some of those same officials indicates that the substance is considered hazardous under other regulatory standards, such as those set by the U.S. Occupational Safety and Health Administration.Some officials also pointed to something called the median lethal dose, or LD50, for the material. It's listed as 825 milligrams per kilogram and means that, when tested on rats, an 825-milligram dose per kilogram of body weight was enough to kill half the rats. Basically, if you do the math, the LD50 shows you someone would have to ingest a lot of this stuff for it to kill them, officials have said.What officials citing that figure weren't saying is that, depending on which scale you use, 4-methylcyclohexanemethanol would still be classified as either "moderately" or "slightly" toxic.And while used widely by emergency responders and on MSDS sheets for a quickly accessible rule of thumb based on an easy to do test, the LD50 is considered by toxicologists to be a rather crude measure. Among other things, it doesn't tell you anything about what levels would make people sick -- only what levels would immediately kill a rat."In day-to-day toxicology," Scharman said, "that's not very helpful."Based on her research so far, Scharman said that even though residents could have consumed the water for hours before the "do not use" order was issued, the short-term, acute impacts are of greater concern than any long-term effects -- assuming residents don't go back to their taps before they're told it's safe to do so.Along with the vacuum of health-effect information, Scharman noted, there's been some confusion about exactly what substance was involved.For one thing, 4-methylcyclohexanemethanol has quite a few synonyms. For another, because there's so little known about it, searches of online databases can easily pull up a different substance, leading to misunderstandings about the potential health impacts.Some residents -- and some news outlets -- have cited health information about chemicals other than those that were actually involved in the Freedom Industries leak.Also, during a news conference Friday morning, West Virginia American Water President Jeff McIntyre revealed that his company initially was given incorrect information -- he didn't know by whom -- about what material was involved in the spill.McIntyre said his company thought the treatment systems at its Elk River facility would be adequate for the chemical that it was initially told had leaked. Crews later figured out that wasn't the case, especially after treated supplies at the plant had a "licorice" smell -- the same that nearby residents complained of earlier in the day.Now, West Virginia American says it's left with no treatment options. The company says it only can try to clear the contaminant by physically flushing its many miles of service lines."Unfortunately, this is in the distribution system," McIntyre told reporters. "Once it's in the system, there is no treatment for it."While residents depend on regulators and the water company to ensure their drinking water is safe, federal and state laws set limits and mandate sampling for only certain chemicals, and 4-methylcyclohexanemethanol is certainly not among them.McIntyre said his company began trying to test for the substance only after it learned about the leak. He said the substance was detected, but that West Virginia American was not able to quantify the concentrations. Even if it had, he said, the company had no regulatory or public-health guidelines to judge if the detected levels were safe.Later, during a Friday afternoon news conference, National Guard Gen. James Hoyer said the federal Centers for Disease Control had advised that 1.0 parts per million would be an acceptable level for drinking water. Hoyer said the CDC told state officials the chemical concentration would have to get below 0.1 parts per million for residents to not notice the smell or color changes.It was not clear Friday how those figures were developed by the CDC, but the tests had shown the chemical levels dropped from 2.0 parts per million to 1.7 parts per million, Hoyer said.The lack of health guidelines or regulatory limits isn't that unusual, either. Few chemicals are actually regulated by safe-drinking-water or other water-quality rules, and the U.S. Environmental Protection Agency has tested only about 200 of the 84,000 chemicals in the agency's inventory."Most chemicals in commerce we know very little about," said Celeste Monforton, a George Washington University public-health researcher. "This stuff is in the water now, and people have ingested it, and we just don't know. It's very concerning."Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.