A new report by the advocacy group Clean Water Action found trace amounts of contaminants in the water of nearly 100 of the 300 Bay State communities tested.
The Boston Globereports the three chemicals found had gone undetected because they are not on the federal list of monitored substances.
Massachusetts test results from 2001 to 2004 showed 86 communities had minute amounts of MtBE, a gasoline additive designated as cancer-causing in California.
Low levels of the herbicide DCPA, used to spray crops, was found in 17 communities. Perchlorate, a chemical (used in explosives) that can cause thyroid problems, was found in nine communities, according to the Globe.