The West Virginia Poison Control Center has received nearly 800 calls from concerned residents.
So what exactly IS 4-methylcyclohexanemethanol? (beside impossible to spell) Few actually know.
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.