When coal is burned, it makes coal ash that contains arsenic, mercury, lead, and other toxic substances. In December 2008, more than a billion gallons of coal ash sludge spilled from a containment pond into homes and rivers in Tennessee. The spill caused an estimated $1.2 billion in costs, plus expenses associated with more than 50 lawsuits.

In a letter to the Environmental Protection Agency, Domini has joined institutional investors representing more than $240 billion in calling on the EPA to enforce strict regulations on coal ash. The investors called for a "consistent national requirement that will help reduce potential value loss and allow investors to better assess this sector’s risk profile."