Maximum Contaminant Levels
The Safe Drinking Water Act of 1974, as amended, includes requirements for the Environmental
Protection Agency (EPA) to set standards for 83 specific contaminants. The selection is based
on the potential for causing adverse health effects and for known or potential occurrence in
drinking water. The standards set for each include the Maximum Contaminant Level (MCL) and
the Maximum Contaminant Level Goal (MCLG). The MCLG, while not legally enforceable, is a
health based standard on the amount of the contaminant in drinking water that the EPA has
decided will not endanger human health over a lifetime of exposure. The MCL is established
as close to the MCLG as possible and is enforceable for public water supplies but not for
private well water supplies. It is the maximum permissible level of a contaminant in water
to protect human health.
The list of parameters include specific contaminants along with other physical, and biological
risk factors to drinking water resources. A description of the factor, along with information
on where it comes from, and its potential human and environmental health impacts is given in
the table. If additional information is available from other sources, a link is provided.
