The Environmental Protection Agency (EPA) regulates the allowable levels of over 90 drinking water contaminants in accordance with the Safe Drinking Water Act. In addition, states are allowed to set their own standards as long as they meet the EPA’s minimum requirements.
Public water systems are required by the EPA to notify customers if they violate EPA or state drinking water regulations, or if they provide drinking water that may pose a risk to consumers’ health. However, in the case of lead, an alert is only issued when more than 10% of a system’s tap water samples show lead concentrations above EPA limits of 15 ppb (parts per billion).