CDC dropped plans for MCHM air ‘screening level’
Citing a lack of data on potential health effects, federal officials dropped plans immediately after the January Elk River chemical leak to devise a “screening level” for what amount of MCHM in the air would be dangerous if inhaled, the U.S. Centers for Disease Control and Prevention has confirmed.
CDC officials backed off the idea on Jan. 10 — the day after the leak — after a search of scientific literature and government publications found “little supporting information” to guide the development of an inhalation screening level, agency spokeswoman Bernadette Burden said Friday.
The CDC’s disclosure comes after a team of experts hired by Gov. Earl Ray Tomblin found that inhalation of MCHM fumes could have been an important route of exposure for the 300,000 West Virginians whose water was contaminated by the Freedom Industries leak.
Members of the West Virginia Testing Assessment Project, or WVTAP, said in an April 1 report that inhalation risks should have been included when the CDC came up with its 1-part-per-million screening level for MCHM in the region’s water. The CDC considered only the impact of drinking contaminated water, not inhalation of fumes or skin contact with the water, WVTAP said.
WVTAP tried to account for potential inhalation risks and, in doing so, came up with a screening level of 120 parts per billion, about eight times more stringent than the CDC figure.
In releasing WVTAP’s preliminary report, Michael Dourson, president of a consulting firm called TERA, said an expert panel he’d chaired for WVTAP was able to improve on the CDC’s work because members had access to new information about MCHM that the CDC did not have. For example, Dourson said, reports of residents experiencing adverse health effects from MCHM fumes in the air led the panel to include inhalation risks in its calculations.
“We had more information than the Centers for Disease Control, so we were able to use that information, Dourson said.
However, a chemical data sheet from Eastman Chemical, the makers of MCHM, clearly warned that “At elevated temperatures, vapor may cause irritation of eyes and respiratory tract.” That data sheet was available the night of the Jan. 9 leak and was used by the CDC when it first developed its screening level. While the data sheet — and studies later provided by Eastman — did not provide specifics about the levels of MCHM inhalation that could cause such effects, they made clear the vapors were something to be concerned about.
At a Feb. 5 news conference organized by Tomblin, then-CDC official Tanja Popovic argued that her agency had considered inhalation exposures when it added an “uncertainty factor” to its screening-level calculation to take into account “the lack of information on specific questions.”
However, WVTAP officials and other experts have explained that particular part of the risk-assessment formula used by the CDC actually was meant to take into account the fact that there’s little published data examining the potential toxic effects of MCHM, and not to take into account routes of exposure other than drinking water.
Earlier this month, the CDC disclosed its initial consideration of a separate screening level for inhalation exposures in a three-page briefing paper written to answer questions posed to the agency by Sen. Jay Rockefeller, D-W.Va.
“We evaluated the potential for developing an air-screening level but learned this may be difficult due to the lack of supporting toxicological information,” said the briefing paper, provided to Rockefeller on April 1. “We will continue to work with other federal partner agencies to explore whether an air-screening level is feasible.”
In response to questions from the Sunday Gazette-Mail, Burden, the CDC spokeswoman, confirmed that the agency had considered putting together an air screening level for MCHM. She said the CDC and its sister agency, the Agency for Toxic Substances and Disease Register, or ATSDR, discussed the issue “early on” in meetings with the U.S. Environmental Protection Agency.
“On January 10, CDC/ATSDR searched the scientific literature and government publications for existing air screening values for MCHM and similar compounds in the material safety data sheet [MSDS],” Burden said in an email to the newspaper. “We found very little supporting information for development of an inhalation screening value.”
Burden said the agencies “revisited the need for an inhalation screening level for MCHM” in early February, but again determined there was not enough data available to establish such a screening level.
In its briefing paper to Rockefeller, the CDC said that because current levels of water from West Virginia American Water’s Elk River treatment plant turned up “non-detect” results for MCHM, “any detected levels in air would be extremely small and of no health concern.”
In her response to the Gazette-Mail, Burden put that slightly differently, saying, “both air and oral levels were considered too low to be of any health concern,” because water from the treatment plant tested as “non-detect” for MCHM “by a little over two weeks after the spill.”
However, on March 25, as a result of the WVTAP investigation, West Virginia American revealed that more sensitive detection methods had actually turned up small levels of MCHM — between 0.42 parts per billion and 0.60 parts per billion — in water that had completed various stages of filtering and treatment at the plant. On April 1, West Virginia American began replacing the filters at the plant, a move company President Jeff McIntyre has said was being done only because of a public “perception” that the filters had become contaminated and were leaching MCHM into the water supply.
MCHM levels found in a 10-home pilot testing project by WVTAP found levels far below the 120-ppb screening level development by WVTAP’s expert panel.
WVTAP leader Andrew Whelton, though, has noted that the 10-home study, involving tests taken in February, does not accurately characterize contamination levels many weeks before, just after the leak or even after the “do not use” order was lifted by the state and the water company. Additionally, some experts continue to say there simply wasn’t enough data on MCHM’s potential toxicity to be support any sort of screening level for the chemical.
“This remains an example of a regulation or a standard being made in the absence of good data,” said Laura Vandenberg, an assistant professor of environmental health at the University of Massachusetts School of Public Health.
Reach staff writer Ken Ward Jr. at firstname.lastname@example.org or (304) 347-1702.