Deborah Blum has a terrific story about the toxicity of MCHM, the chemical that Freedom Industries dumped into West Virginia’s water supply (a plume of poison which is now on its way to Cincinnati, and eventually Indiana). The answer on the degree of toxicity is…we don’t know. It’s had minimal testing.
She summarizes the toxicity tests that have been done on animals, which found it is “slightly toxic”, but that it caused suffering in the animals at all levels of exposure. There have been no long term studies done.
Complement that reading with this personal story of a West Virginian living without running water — which also mentions the powerlessness of being poor in Appalachia.