Virginia Tech experts pinpoint MCHM odors
CHARLESTON, W.Va. -- Researchers at Virginia Tech believe they have pinpointed a form of the chemical MCHM that could be causing licorice-like odors to linger in the region's drinking water long after the January chemical leak that contaminated drinking-water supplies for 300,000 residents in a nine-county region of West Virginia.
Using specialized equipment, experts at Virginia Tech's College of Engineering traced the odors to one of MCHM's two chemical structures, or isomers, and analyzed at what levels that form of MCHM could be smelled in the air and estimated what concentrations could be smelled in water.
A team led by Virginia Tech environmental engineer Andrea Dietrich estimated the odor threshold for that form of MCHM at 7 parts per billion. That's 100 times less than the levels the U.S. Centers for Disease Control and Prevention advised were acceptable for people to drink. However, the CDC's 1-part-per-million number remains controversial, and Dietrich said the continuing odor problems have their own important impacts on residents.
"The toxicity aside, annoying odors have a psychological burden," Dietrich said. "Let's hope this chemical doesn't have any toxicity and the CDC is right, but if people are living with it for two or three months, it imparts a fear and a reminder, and it's a psychological burden. If you can smell it, it's still around."
Dietrich is an expert on water quality and treatment, as well as on taste and odor assessments of water. After the Freedom Industries chemical leak, she received an emergency grant from the National Science Foundation to study MCHM and its potential impacts, and one focus of the Virginia Tech team is the coal-cleaning chemical's odor.
On Tuesday morning, Virginia Tech issued a news release to outline some of its team's preliminary findings.
"Based on our increased understanding of the chemicals involved in the water crisis, the complexities and implications of the spill keep growing," Dietrich said in the release. "People are still afraid to drink the water; odors persist in schools, residences, and businesses; data are still lacking for the properties of the mixture of chemicals in the crude MCHM that spilled."
The Virginia Tech findings come just one day after West Virginia American Water revealed new test results that show low levels of MCHM appear to be leaching from the filters at their Elk River treatment plant into drinking water the company pumps into the region's homes and businesses.
Water company President Jeff McIntyre had said last week that the company didn't think the filters needed changed, but would start doing so on April 1, to address public "perception" that the filters were contaminated. When the new test results were announced, though, McIntyre said it was "not unexpected that MCHM effectively captured in the filter material may show up in trace amounts in water leaving the plant."
In a news release, the water company downplayed the test results - showing MCHM concentrations ranging from 0.42 parts per billion to 0.60 parts - by noting that "one part per billion is equivalent to one drop in a large tanker truck or one second in 32 years."
However, in an interview Tuesday morning, Dietrich said a more complete knowledge of long-standing scientific understanding about chemical odors and about various routes that residents could have been exposed to MCHM from the contaminated water supply might have been helpful in responding to the chemical leak.
Well-established science, Dietrich said, supports the observations of residents who smelled licorice more readily in their showers than from their kitchen taps, and the reactions of public school cooks who complained of odors when they were operating industrial dishwashers. Better flushing guidance that warned residents to open windows or conducting air-quality tests when school employees complained of odors would have been helpful, Dietrich said.
"One of the points of our research is you have to look at MCHM in its entirety - not just ingestion, but inhalation," Dietrich said. "Our goal is to connect the dots."
Virginia Tech researchers used equipment called "olfactory gas chromatography" to independently measure the concentrations and odors of two isomers found in 4-methylcyclohexane methanol, the main component of the Crude MCHM mixture that leaked from Freedom Industries into the Elk River on Jan. 9.
The 4-MCHM consists of two isomers, called cis- and trans-isomers. These isomers are forms of MCHM that have the same chemical formula but a very slight difference in shape that can have enormous effects on the physical, chemical and biological properties of the substance. Virginia Tech experts said only the "trans" isomer has the stronger licorice-like odor.
In a procedure approved by the university's research review board, Dietrich and her team used a panel of non-experts to smell for MCHM in the air, and determined that the odor threshold for the chemicals trans-isomer is "exceedingly low," at a level of 350 parts per trillion by volume in the air. Using standard chemical formulas, the team then estimated the odor threshold in water to be about 7 parts per billion.
Using a different methodology, the West Virginia Testing Assessment Project, or WVTAP, the independent team hired by Gov. Earl Ray Tomblin, previously said it had determined the odor threshold for MCHM was 0.15 parts per billion, or about 47 times lower than the Virginia Tech number.
The WVTAP number, though, was for the Crude MCHM mixture -- not for pure 4-MCHM or for the pure chemical's trans-isomer. Also, the WVTAP research, by environmental consultant Michael McGuire, used odor experts who actually smelled water that contained MCHM. The Virginia Tech researchers used lay people to come up with an airborne-odor threshold, and then converted that to a number for odors in water.
On Monday night, WVTAP issued a news release commenting on the Virginia Tech release that had not yet been publicly issued. Dietrich said Virginia Tech had provided a courtesy copy of its release in advance to Tomblin's office.
In its release, WVTAP noted that McGuire's report offered a differing explanation for the licorice odors than the one outlined by Virginia Tech researchers.
"It is important to realize that the odor threshold reported by Virginia Tech was conducted on pure MCHM," McGuire stated in the WVTAP release. "However, pure MCHM has not been causing the licorice odor problem in the Charleston, WV, area."
"We knew that 'Crude' MCHM which consists of a mix of odorous compounds had a sharper licorice odor characteristic than pure MCHM," McGuire said. "We chose to do our testing on the compound that the public experienced and which caused all of the odor problems."
In his report, McGuire wrote that, "Minor components of the chemical compound mix called Crude MCHM could have an impact on the threshold concentrations experienced by panelists and consumers. We are still not certain that only the pure MCHM is responsible for the licorice odor in Charleston drinking water. More research is needed to determine the contribution of the minor components of Crude MCHM to the aesthetic responses experienced by Charleston residents."
Virginia Tech researchers, though, say an important implication of their work is to independently measure the concentrations of the two MCHM isomers. "The licorice odor will be proportional to the amount of the trans-isomer, not the total amount of methylcylohexane methanol," Dietrich said. "While there may be a tendency to measure 'total methylcyclohexane methanol,' this could lead to misleading interpretations."
Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.