If West Virginia’s Water Isn’t Safe for Pregnant Women, Is It Safe for Anyone?

Absence of evidence of a spilled chemical doesn't mean evidence of its absence in the water supply

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Many West Virginians remain suspicious of their tap water a week after a major chemical spill

Tap water has been declared safe to use for more than 74,000 West Virginia homes and businesses nearly a week after chemicals used to clean coal leaked into the water supply around Charleston, the capitol city. As the contaminated water is flushed out of the system, officials expect to life the “do not use” order for the rest of the nearly 300,000 residents who have been unable to safely use their tap water for anything other than flushing toilets since Jan. 9, when authorities first warned of the danger.

But that brings us back to the question of safety. I wrote earlier this week about how little was known about the possible health impacts of the coal solvent 4-methylcyclohexane (MCHM), and about doubts over the “safe” level established for the chemical—1 part per million in drinking water. Given the lack of data about MCHM, health experts at the Centers for Disease Control (CDC) were forced to rely on a single study of the chemicals effects on rats to jury rig a red line that would allow officials in West Virginia to reestablish water service.

But in a letter to West Virginia health officials on Jan. 15, which was first reported by the West Virginia GazetteCDC director Thomas Frieden said that more caution might be needed—at least for pregnant women:

Due to limited availability of data, and out of an abundance of caution, you may wish to consider an alternative drinking water source for pregnant women until the chemical is at non-detectable levels in the water distribution system.

(MORE: Officials Don’t Really Know How Dangerous the Chemical Spilled in West Virginia Is)

Which of course raises a question. If pregnant women are being advised to avoid drinking tap water until MCHM levels were undetectable, is the water safe for anyone in the Charleston area to drink?

It’s important to remember that it’s not uncommon for officials to advise pregnant women to take precautions with their health that would be considered unnecessary for everyone else. Pregnant women, for example, are advised to avoid types of fish that may be high in mercury because the metal can impact fetal neurological development, but other adults generally have little to worry about. Pregnant women are considered more vulnerable to illnesses than the general population. And the CDC does appear to be acting with some caution, as an FAQ from the agency notes:

There are no known studies showing harm to the fetus as a result of consuming water with MCHM levels below 1 ppm. Although there is no information that suggests harm to the fetus, out of abundance of precaution, pregnant women may wish to consume bottled water until levels of MCHM are undetectable in the water system.

By that logic, it would seem to make sense to advise pregnant women to be even more cautious with water in the wake of a contamination event like this one. But there’s a difference—contaminants like mercury have been studied deeply by scientists, which allows them to make accurate judgements about health risks, for pregnant women and for everyone else. But that’s simply not the case for a virtually unknown chemical like MCHM, where scientists are working in real time to assess hazy risks. When it comes to risk, this is not a case where absence of evidence means evidence of absence.

Hopefully, as scientists have more time to study the little data that’s out there about MCHM, they’ll be able to have more confidence in their warnings—and so will the public. Friedman’s letter noted that scientists had found additional animal studies involving MCHM that were being reviewed—though these studies aren’t public—which could help them better understand the risks MCHM does and does not pose. But it’s hard to blame West Virginians who remain suspicious about the water coming out of their taps—and the warnings coming from their public officials.

(MORE: Report: 2013 Wet, Warm Year for Much of U.S.)