As authorities race to understand the toxic impact of the leak of the coal-cleaning chemical, 4-methylcyclohexane methanol (or MCHM), on the water supply of 300,000 West Virginia residents, experts caution that this chemical is only one of “tens of thousands of industrial compounds” not tested for their risk to human health.

“West Virginia is getting a hard lesson in how little we know about these chemicals,” Marshall University environmental engineer Scott Simonton told the Wall Street Journal Friday. “This chemical is not even listed as something the water company has to look for.”

Unlike pesticides or pharmaceuticals, a “detergent” such as MCHM wouldn’t be regulated under the primary drinking water standards that regulate chemicals.

Richard Denison, a senior scientist at the Environmental Defense Fund, said that unlike pesticides or pharmaceuticals, such industrial chemicals are rarely tested for toxicity to humans.

The Wall Street Journal reports:

As a “foaming agent” used to clean coal, Paul Ziemkiewicz, Director of the West Virginia Water Research Institute, explained that MCHM “would fall in the secondary drinking water standards which are regulated at about half a milligram/liter,” West Virginia Public Broadcasting reports.

Secondary standards, he added, “are more to regulate aesthetic issues such as color, taste, and texture.”