The Centers for Disease Control and Prevention has warned pregnant West Virginians in the areas affected by last week’s chemical spill that they might want to drink bottled water until there’s no methylcyclohexane methanol detected in the region’s water system.Let’s put aside the facts that it’s a little bit ridiculous that the CDC came out with this recommendation nearly a full week after the spill, and that the fact sheet the agency distributed repeatedly contains the phrases “no information” and “no known risk” (emphasis mine—and see yesterday’s post about the reasons there’s little information about this chemical).But should pregnant women in Louisville sip freely on the city’s water when the chemical plume reaches the city Friday?Louisville Water Company spokeswoman Kelley Dearing Smith says the company is confident that there’s no public health concern posed by the chemical spill.The spill has been moving down the river for days, and is getting more and more diluted. The most recent data showed it will probably hit Louisville by early Friday morning, and will likely be at concentrations of anywhere from 5 to 20 parts per billion. That’s very low, and far below the benchmark of 1 part per million the CDC initially suggested would be protective of public health. And Dearing Smith says by the time the water exits the treatment plant, the chemical won’t be at detectable levels.“Drinking water is a manufactured product,” she said, pointing out that there are always materials—benign and undesirable alike—that the water company is filtering out of its system.The water company’s tools can detect the chemical as low as one or two parts per billion. And it’s worth noting that the city doesn’t have the reservoir capacity to close its water intakes, like Cincinnati did earlier this week.But still, questions remain.How did the CDC arrive at its conclusion that 1 part per million of MCHM is safe to ingest?In this case, it’s especially complicated because there’s a lot that’s not known about the chemical. But environmental and health officials begin by calculating maximum exposure.Bob Jacobs is the director of the University of Louisville’s Master of Public Health Program. He says in this case, the federal government assumes that the upper 95th percentile is people who drink 2 liters of water a day. This means 95 percent of people don’t drink that much water. So this number is calculated on what a safe exposure for that water-guzzling portion of the population would be.Now, the CDC says it suggests pregnant women avoid the water unless there is “no detectible level” of MCHM. What’s the non-detect limit?This is tricky, because different water systems use different tools to test the water, so it’s conceivable that two towns could have different levels of MCHM, but neither would be able to detect the chemical in the water. The Kentucky Energy and Environment Cabinet says that the detection limit range is 5 to 50 parts per billion, and the CDC says that even the upper end of that range is considered safe.In Louisville, Water Company spokeswoman Kelley Dearing Smith says the company can detect levels as low as one or two parts per billion, and the chemical should be non-detectible by the time it leaves the treatment plant and goes to your tap.I’m still concerned. Should I stock up on bottled water?It’s probably not necessary. But it’s a personal decision; Bob Jacobs at the U of L says everyone should decide for him or herself what the appropriate course of action is. “The prudent public health official would say ‘if you’re concerned about this, take the appropriate precautions. But we cannot provide evidence that’s going to say you’re at risk,’” he said.If the thought of trace amounts of MCHM in your water is disturbing, or if you’re pregnant and want to err on the side of caution, he says go ahead and drink bottled water through the weekend. The plume is expected to take about 24 hours to pass by Louisville.
