CHARLESTON, W.Va. -- A key corporate study used by federal health officials to set a screening level for "Crude MCHM" in the West Virginia American Water system actually tested a pure form of the material's main ingredient and might not account for potential toxicity of other components, documents and interviews with public health officials showed Friday.
"That is a huge problem," said Dr. Lynn Goldman, dean of the School of Public Health and Health Services at George Washington University.
U.S. Centers for Disease Control and Prevention officials did not disclose the issue when they discussed their 1-part-per-million screening level for safe drinking water and did not respond Friday to repeated requests for comment.
The issue, revealed when Eastman Chemical Co. made public its previously secret studies of the chemical it made and sold to Freedom Industries, raises more questions after last week's toxic leak that fouled drinking water for more than 300,000 West Virginians.
Gov. Earl Ray Tomblin and other state officials, along with West Virginia American Water have been assuring residents -- except for expectant mothers -- that it's safe to use Elk River water, once the water company clears their particular neighborhood and home plumbing systems.
Tomblin and his top public health officials have cited the screening number developed on an emergency basis by scientists at the CDC, who were working without any existing regulatory standards or published health guidance and dealing with very little data about the chemical.
State and federal officials also pointed to water test results they say show a continuing decline in contaminant levels in the system. They also say the CDC safety figure was conservative and that the advisory for pregnant women was issued out of an "abundance of caution."
The CDC's number was based largely on an April 1990 Eastman study in which rats were exposed to varying levels of 4-methylcyclohexanemethanol. The study concluded that a concentration of 100 milligrams per kilogram of the chemical was the "No Observable Adverse Effects Level," or NOAEL, for the material.
CDC scientists used relatively standard risk-assessment procedures to translate that figure into a level of 1 part per million of the chemical they said likely would cause no adverse health effects in humans.
However, emergency response and public health officials, as well as company documents, have said the chemical that actually leaked into the Elk River was Crude MCHM.