More than 55,000 California residents get public water that’s tainted with unsafe levels of arsenic, according to the nonprofit advocacy organization Environmental Integrity Project. The chemical is a carcinogen that’s been linked to cancer, developmental difficulties, cardiovascular disease and diabetes. “The longer you are exposed, the more likely you are to suffer serious health effects,” said Eric Schaeffer, executive director of the Environmental Integrity Project. “As is done now with private well users, really you ought to take steps to protect your family and try to avoid the water until its clean again.”