Next section Federal Legislation Nationwide concern over the safety of public water supplies culminated in the Safe Drinking Water Act passed by Congress in 1974. This act set in motion the first comprehensive national program to safeguard public drinking water and directed EPA to establish minimum drinking water standards for all public water systems. Under this directive, EPA is establishing maximum contaminant levels for any contaminant in water which might have adverse health effects. The limit on each substance allowed in drinking water is based on the amount a human can consume in a lifetime without adverse health effects.
Limits also take into account the amounts to which an individual is exposed from other sources.
Maximum contaminant levels have been established for ten chemicals, six pesticides, bacteria, radioactivity, and turbidity. Bacteria and nitrate are the only two substances which pose an immediate, or acute, threat to health whenever the standards are exceeded. Bacteria can cause waterborne diseases such as typhoid, cholera, infectious hepatitis, and dysentery. Other chemicals covered by the EPA drinking water standards are considered harmful if consumed over a long period of time in quantities exceeding the maximum levels. The chemicals with long-term, or chronic, effects are arsenic, barium, cadmium, chromium, fluoride, lead, mercury, selenium, and silver.