Safe Drinking Water Act
The Safe Drinking Water Act is the primary federal law in the United States intended to ensure safe drinking water for the public. Pursuant to the act, the Environmental Protection Agency is required to set standards for drinking water quality and oversee all states, localities, and water suppliers that implement the standards.
The SDWA applies to every public water system in the United States. There are currently over 148,000 public water systems providing water to almost all Americans at some time in their lives. The Act does not cover private wells.
The SDWA does not apply to bottled water. Bottled water is regulated by the Food and Drug Administration, under the Federal Food, Drug, and Cosmetic Act.
National Primary Drinking Water Regulations
The SDWA requires EPA to establish National Primary Drinking Water Regulations for contaminants that may cause adverse public health effects.The regulations include both mandatory requirements and nonenforceable health goals for each included contaminant. As of 2019 EPA has issued 88 standards for microorganisms, chemicals and radionuclides.
MCLs have additional significance because they can be used under the Superfund law as "Applicable or Relevant and Appropriate Requirements" in cleanups of contaminated sites on the National Priorities List.
For some contaminants, EPA establishes a Treatment Technique instead of an MCL. TTs are enforceable procedures that drinking water systems must follow in treating their water for a contaminant.
Federal drinking water standards are organized into six groups:
- Microorganisms
- Disinfectants
- Disinfection byproducts
- Inorganic chemicals
- Organic chemicals
- Radionuclides.
Microorganisms
Disinfectants
EPA has issued standards for chlorine, monochloramine and chlorine dioxide.Disinfection by-products
EPA has issued standards for bromate, chlorite, haloacetic acids and trihalomethanes.Inorganic chemicals
EPA has issued standards for antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, copper, cyanide, fluoride, lead, mercury, nitrate, nitrite, selenium and thallium."Lead Free" plumbing requirements
The 1986 amendments require EPA to set standards limiting the concentration of lead in public water systems, and defines "lead free" pipes as:EPA issued an initial lead and copper regulation in 1991. The regulation specifies a Treatment Technique rather than an MCL.
Congress tightened the definition of "lead free" plumbing in a 2011 amendment to the Act. EPA published a final rule implementing the amendment on September 1, 2020.
In response to the Flint, Michigan water crisis, EPA published revisions to the Lead and Copper Rule on January 15, 2021 addressing testing, pipe replacement and related issues. The rule mandates additional requirements for sampling tap water, corrosion control, public outreach and testing water in schools. Several citizen and environmental groups immediately filed lawsuits challenging the rule. Following the lawsuit, EPA issued its final "Lead and Copper Rule Improvements" regulation on October 8, 2024, which requires the removal of all lead pipes within ten years. Additionally, the regulation lowers the action level of lead contamination to 10ppb from the current limit of 15ppb.
Organic chemicals
EPA has issued standards for over 53 organic compounds, including benzene, dioxin, PCBs, styrene, toluene, vinyl chloride and several pesticides.Perfluorinated alkylated substances
In March 2021 EPA announced that it would develop regulations for perfluorooctanoic acid and perfluorooctanesulfonic acid. In April 2024 EPA published final standards for PFOA, PFOS, perfluorohexanesulfonic acid, perfluorononanoic acid, hexafluoropropylene oxide dimer acid and perfluorobutanesulfonic acid. The agency is providing grant funds to assist small and disadvantaged communities in testing for and treating PFAS contamination in their water systems.Radionuclides
EPA has issued standards for alpha particles, beta particles and photon emitters, radium and uranium. EPA proposed regulations for radon in 1991 and 1999.Secondary standards
Secondary drinking water standards are non-regulatory guidelines for aesthetic characteristics, including taste, color, and odor.Health advisories
EPA issues "health advisories" for some contaminants; some of which have not been regulated with MCLs. Health advisories provide technical information to public health officials about health effects, methods for chemical analysis, and treatment methods. The advisories are not enforceable. EPA was given explicit authority to issue advisories in the [|1996 SDWA amendments]. As of 2022, health advisories have been issued for the following contaminants.| Chemical Contaminants | Microbial Contaminants |
| Boron | Cyanotoxins |
| Dacthal and Dacthal degradates | Cryptosporidium |
| 2,4- and 2,6- Dinitrotoluene | Legionella |
| Fluoride | Giardia |
| GenX | Mycobacteria |
| Manganese | |
| Methyl tert-butyl ether | |
| Oxamyl | |
| Perchlorate | |
| Perfluorooctanoic acid and Perfluorooctane sulfonate * | |
| Perfluorobutanesulfonic acid | |
| Sodium | |
| Sulfate | |
| 1,1,2,2-Tetrachloroethane | |
| * Note: In 2024 EPA stated that its 2022 advisories for PFOA and PFOS were outdated. Updated toxicity assessments were published concurrently with the final 2024 regulation. |
State standards
The SDWA allows states to set standards which are more stringent than the federal standards, and to issue standards for contaminants that EPA has not regulated. Several states have issued their own standards for a few contaminants, including fluoride, perchlorate and perfluorinated alkylated substances.Future standards
Unregulated contaminants
The SDWA requires EPA to identify and list unregulated contaminants which may require regulation. The Agency must publish this list, called the Contaminant Candidate List every five years. EPA is required to decide whether to regulate at least five or more listed contaminants. EPA uses this list to prioritize research and data collection efforts, which support the regulatory determination process.As of 2024, EPA has developed five CCLs:
- CCL1: 50 chemical and 10 microbiological contaminants/contaminant groups were listed in 1998. In 2003 EPA made a determination that no regulatory action was needed on nine of these contaminants.
- CCL2: EPA carried forward the remaining 51 contaminants from CCL1 for consideration in 2005. In 2008 EPA determined that no regulatory action was needed on 11 of these contaminants.
- CCL3: EPA revised its listing process, based on recommendations from the National Research Council and the National Drinking Water Advisory Council. It expanded its initial review to 7,500 potential chemical and microbial contaminants, and subsequently narrowed this universe to a list of 600 for further evaluation. 104 chemicals or chemical groups and 12 microbiological contaminants were listed in 2009. In 2011 EPA announced it would develop regulations for perchlorate, which had been listed beginning with CCL1. In 2016 EPA determined that no regulatory action was needed on four other listed contaminants, and delayed determination on a fifth contaminant, in order to review additional data.
- CCL4: EPA carried forward the CCL3 contaminants for which determinations had not been made, and requested public comment on additional contaminants. 97 chemicals or chemical groups and 12 microbial contaminants were listed in 2016. In March 2021 EPA announced that it would develop regulations for two of the CCL4 contaminants: PFOA and PFOS.
- In November 2022 EPA published CCL5. The list includes 66 chemicals, three chemical groups and 12 microbes.
On December 27, 2021 EPA published a regulation requiring drinking water utilities to conduct monitoring for 29 PFAS compounds and lithium. The data are to be collected during 2023 to 2025. EPA will pay for the monitoring costs for small drinking water systems. The agency may use the monitoring data to develop additional regulations.
Perchlorate
The Natural Resources Defense Council filed a lawsuit in 2016 to accelerate EPA's regulatory process on perchlorate. Following a consent decree issued by a federal district court in New York, EPA published a proposed rule on June 26, 2019, with a proposed MCL of 0.056 mg/L.In 2020 EPA announced that it was withdrawing its 2019 proposal and its 2011 regulatory determination, stating that it had taken "proactive steps" with state and local governments to address perchlorate contamination. In September 2020 NRDC filed suit against EPA for its failure to regulate perchlorate, and stated that 26 million people may be affected by perchlorate in their drinking water. Following a court order, EPA stated that it will publish a proposed standard for perchlorate in 2025, and issue a final rule in 2027.