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Maximum contaminant levels (MCLs) are standards that are set by the
“Drinking Water: A Half Century of Progress.”
EPA Alumni Association. March 1, 2016. An MCL is the legal threshold limit on the amount of a substance that is allowed in public water systems under the Safe Drinking Water Act (SDWA). The limit is usually expressed as a
To set a maximum contaminant level for a contaminant, EPA first determines how much of the contaminant may be present with no adverse health effects. This level is called the ''maximum contaminant level goal'' (MCLG). MCLGs are non-enforceable public health goals. The legally enforced MCL is then set as close as possible to the MCLG. The MCL for a contaminant may be higher than the MCLG because of difficulties in measuring small quantities of a contaminant, a lack of available treatment technologies, or if EPA determines that the costs of treatment would outweigh the public health benefits of a lower MCL. In the last case, EPA is permitted to choose an MCL that balances the cost of treatment with the public health benefits. MCLs require monitoring, remediation, and public notice when standards are exceeded. As of 2019 EPA has issued 88 standards (78 MCLs and 10 Treatment Techniques) for microorganisms, chemicals and radionuclides.
For some contaminants, EPA establishes a Treatment Technique (TT) instead of an MCL. TTs are enforceable procedures that drinking water systems must follow in treating their water for a contaminant.
MCLs and TTs are known jointly as " National Primary Drinking Water Regulations" (NPDWRs), or primary standards.
Some contaminants may cause aesthetic problems with drinking water, such as the presence of unpleasant tastes or odors, or cosmetic problems, such as tooth discoloration. Since these contaminants do not cause health problems, there are no legally enforceable limits on their presence in drinking water. However, EPA recommends maximum levels of these contaminants in drinking water. These recommendations are called " National Secondary Drinking Water Regulations" (NSDWRs), or secondary standards.
EPA - National Drinking Water Program
{{United States environmental law Environmental law in the United States Water supply and sanitation in the United States United States Environmental Protection Agency Drinking water regulation
United States Environmental Protection Agency
The Environmental Protection Agency (EPA) is an independent agency of the United States government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it began operation on De ...
(EPA) for drinking water
Drinking water or potable water is water that is safe for ingestion, either when drunk directly in liquid form or consumed indirectly through food preparation. It is often (but not always) supplied through taps, in which case it is also calle ...
quality.Joseph Cotruvo, Victor Kimm, Arden Calvert“Drinking Water: A Half Century of Progress.”
EPA Alumni Association. March 1, 2016. An MCL is the legal threshold limit on the amount of a substance that is allowed in public water systems under the Safe Drinking Water Act (SDWA). The limit is usually expressed as a
concentration
In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', '' molar concentration'', '' number concentration'', ...
in milligrams or micrograms per liter of water.
Federal MCL development
To set a maximum contaminant level for a contaminant, EPA first determines how much of the contaminant may be present with no adverse health effects. This level is called the ''maximum contaminant level goal'' (MCLG). MCLGs are non-enforceable public health goals. The legally enforced MCL is then set as close as possible to the MCLG. The MCL for a contaminant may be higher than the MCLG because of difficulties in measuring small quantities of a contaminant, a lack of available treatment technologies, or if EPA determines that the costs of treatment would outweigh the public health benefits of a lower MCL. In the last case, EPA is permitted to choose an MCL that balances the cost of treatment with the public health benefits. MCLs require monitoring, remediation, and public notice when standards are exceeded. As of 2019 EPA has issued 88 standards (78 MCLs and 10 Treatment Techniques) for microorganisms, chemicals and radionuclides.
For some contaminants, EPA establishes a Treatment Technique (TT) instead of an MCL. TTs are enforceable procedures that drinking water systems must follow in treating their water for a contaminant.
MCLs and TTs are known jointly as " National Primary Drinking Water Regulations" (NPDWRs), or primary standards.
Some contaminants may cause aesthetic problems with drinking water, such as the presence of unpleasant tastes or odors, or cosmetic problems, such as tooth discoloration. Since these contaminants do not cause health problems, there are no legally enforceable limits on their presence in drinking water. However, EPA recommends maximum levels of these contaminants in drinking water. These recommendations are called " National Secondary Drinking Water Regulations" (NSDWRs), or secondary standards.
MCLs issued by states
Some state laws and regulations use the term "maximum contaminant level" to refer to MCLs promulgated within a state pursuant either to the federal SDWA or state law; for example, the ''New Jersey Safe Drinking Water Act.'' In some cases, a state may issue an MCL for a contaminant that has not been regulated by EPA under federal law. For example, in 2018 New Jersey promulgated an MCL for perfluorononanoic acid (PFNA).See also
* Drinking water quality in the United States * Maximum residue limit (standard for pesticides in food) * Maximum concentration (pharmacology)References
External links
EPA - National Drinking Water Program
{{United States environmental law Environmental law in the United States Water supply and sanitation in the United States United States Environmental Protection Agency Drinking water regulation