A year ago Friday, Rebecca Roth experienced what she calls one of the "worst fears" she has known as a mother.

A large-scale chemical spill on the Elk River near her home in Charleston, West Virginia, had unleashed an unknown amount of a coal-washing agent, possibly poisoning the local water supply. Roth, who had a two-year-old daughter and was then pregnant, was afraid she "could not keep her children safe and healthy."

For weeks, nearly 300,000 people around Charleston, the state capital, were told not to drink or bathe with local tap water, since the spilled chemical-known as 4-methylcyclohexane methanol—can be harmful if ingested. (Learn more about the science behind the spill.)

The experience spurred Roth and others to start advocating