Drinking Water Health Advisories (HAs)

On this page:

• Health Advisories (HAs) Explained
• Published HAs for Chemicals
• Per- and Polyfluoroalkyl Substances (PFAS)
• Published HAs for Microbial Toxins
• HAs Currently Under Development

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Health Advisories (HAs) Explained

The Safe Drinking Water Act (SDWA) authorizes the U.S. Environmental Protection Agency to issue HAs for contaminants that are not subject to a National Primary Drinking Water Regulation (NPDWR) (42 U.S.C. §300g-1(b)(1)(F)). HA documents provide technical information on chemical and microbial contaminants that can cause human health effects and are known or anticipated to occur in drinking water. HA values/levels identify the concentration of a contaminant in drinking water at which adverse health effects and/or aesthetic effects are not anticipated to occur over specific exposure durations (e.g., 1 day, 10 days, a lifetime). HAs primarily serve as information to drinking water systems and officials responsible for protecting public health when emergency spills or other contamination situations occur. They help states, Tribes, and local governments inform the public and determine whether local actions are needed to address public health impacts in affected communities. The EPA’s HA documents describe information about health effects, analytical methodologies and treatment technologies. HAs are not to be construed as legally enforceable federal standards and are subject to change as new information becomes available.

The EPA can develop interim or provisional HA levels to provide information in response to an urgent or rapidly developing situation. Interim or provisional HAs are also based on health-based hazard concentrations above which action should be taken to reduce exposure to unregulated contaminants in drinking water. They can be updated or removed as additional information becomes available. For example, the EPA published provisional HAs for PFOA and PFOS in 2009 and interim updated HAs for PFOA and PFOS in 2022.

The EPA’s Drinking Water Standards and Health Advisories tables contain HA levels for approximately 200 contaminants based on non-cancer health effects for different durations of exposure (e.g., one-day, ten-day, and lifetime) as well as the underlying reference dose (RfD) supporting the lifetime HAs or, if applicable, the cancer risk values for drinking water contaminants. The tables also include the contaminants currently regulated under SDWA for which the EPA has established Maximum Contaminant Level Goals (MCLGs) as well as Maximum Contaminant Levels (MCLs; also known as drinking water standards). An MCLG is the level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals. An MCL is the highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.

• EPA Drinking Water Standards and Health Advisories tables (March 2018)
  NOTE: Tables were published in 2018 and do not include 2022 PFAS Health Advisories.
• More information on the EPA’s National Primary Drinking Water Regulations

Published HAs for Chemicals

• EPA Drinking Water Standards and Health Advisories tables
• Per- and Polyfluoroalkyl Substances (PFAS)
  • 2022 Interim HA for Perfluorooctanoic Acid (PFOA)
  • 2022 Interim HA for Perfluorooctane Sulfonate (PFOS)
  • Hexafluoropropylene Oxide (HFPO) Dimer Acid and its Ammonium Salt [“GenX chemicals”]
  • Perfluorobutane Sulfonic Acid and its Potassium Salt (PFBS)

Published HAs for Microbial Toxins

• Two Cyanotoxins - Cylindrospermopsin and Microcystins
  • Fact Sheet: Drinking Water Health Advisories for Two Cyanobacterial Toxins (June 2015, EPA 820-F-15-003)
  • Cylindrospermopsin Health Advisory Document (June 2015, EPA 820-R-15-101)
  • Cylindrospermopsin Health Effects Support Document (June 2015, EPA 820-R-15-103)
  • Microcystins Health Advisory Document (June 2015, EPA 820-R-15-100)
  • Microcystins Health Effects Support Document (June 2015, EPA 820-R-15-102)
• Cryptosporidium Health Advisory (March 2001, EPA 822-R-01-009)
• Giardia
  • Fact Sheet (September 2000)
  • Giardia Health Advisory (November 1999, EPA 822-R-99-008)
• Legionella
  • Fact Sheet (September 2000)
  • Legionella Health Advisory (March 2001, EPA 822-B-01-005)
• Mycobacteria
  • Fact Sheet (March 2002)
  • Mycobacteria Health Advisory (August 1999, EPA 822-B-01-007)

HAs Currently Under Development

Per- and Polyfluoroalkyl Substances (PFAS)

As stated in the EPA's PFAS Strategic Roadmap, PFAS contamination has impacted drinking water quality across the country. Going forward, the EPA anticipates developing HAs for additional PFAS or categories of PFAS as the agency publishes toxicity assessments.