The job of the Environmental Protection Agency is to protect ground water and surface water to provide safe drinking water for the people in the United States. The Safe Drinking Water Act ensures this will be carried out. There are legal limits on the amount of certain contaminants that are allowed in drinking water.For exmple, the level for arsenic is .010 ppm which is the standard to protect people from arsenic exposure. There is a chemical phase rule, a lead and copper rule, a radionuclides in drinking water rule, rules about microbials and disinfection byproducts, contaminants such as radon, sulphates, perchlorates and MTBE's. Most of these rules and standards find the maximum contaminant level allowed, before these adversely affect human health. Many of these substances are carcinogenic and sometimes, some of these can act as teratogens.