The New York Times has an incredible, comprehensive report on the toxicity levels of water throughout the United States:
Examine whether contaminants in your water supply met two standards: the legal limits established by the Safe Drinking Water Act, and the typically stricter health guidelines. The data was collected by an advocacy organization, the Environmental Working Group, who shared it with The Times.
They have an entire section on United Water of New Rochelle:
Environmental Working Group*: United Water of New Rochelle
*SOURCE: New York Department of Health- Bureau of Public Water Supply Protection
New York Times: United Water of New Rochelle
U.S. Environmental Protection Agency: Safe Drinking Water Information System (SDWIS)