January 16, 2014 5:29 PM EST

Of all the questions surrounding a Jan. 9 chemical spill in West Virginia, this might be the most disturbing: How dangerous was the chemical? About 7,500 gal. (28,390 L) of 4-methylcyclohexane methanol (MCHM) seeped into the Elk River when a tank holding the coal-cleaning solvent ruptured. Three hundred thousand people were left without access to running water and were unable to use their faucets to drink, cook or bathe for five days.

No human health data exists on MCHM, just a single study on rats. That’s because MCHM is one of almost 62,000 chemicals that were grandfathered in when the Toxic Substances Control Act was passed in 1976. But even new industrial chemicals–and hundreds are introduced in the U.S. each year–generally receive little review from the Environmental Protection Agency. At this point even the chemical industry agrees that the outdated law needs to be updated, but reform efforts have been stuck in gridlock. The West Virginia accident might change that–the Senate is scheduled to hold hearings on the spill in February.

–BRYAN WALSH

This appears in the January 27, 2014 issue of TIME.

Contact us at letters@time.com.

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