Safe Drinking Water Act (SDWA)

• THE LAW: US federal law concerning standards for safe public drinking water
• DATE: Enacted on December 16, 1974

The Safe Drinking Water Act was the first law passed in the United States to set standards for acceptable levels of certain pollutants in the nation’s more than 170,000 public drinking-water supplies.

Under the Safe Drinking Water Act of 1974, the US Environmental Protection Agency (EPA) is required to set standards regarding the maximum amounts of certain materials allowed in public drinking water; these include harmful inorganic and organic substances, radioactive substances, microorganisms, and suspended materials. The act requires the individual US states to enforce the EPA’s standards, and it requires each public drinking-water supplier to monitor the quality of its water sent to home users. Initially, the EPA included twenty-five materials on its list of contaminants, but over time, it has added many others.

Drinking-Water Contaminants

The EPA sets maximum allowable levels for a wide range of contaminants in public drinking water. These include microorganisms, such as viruses, coliform bacteria, Giardia, and Cryptosporidium; disinfection by-products like bromate and chlorite; disinfectants such as chloramines and chlorine; inorganic chemicals including arsenic, asbestos, chromium, cyanide, fluoride, lead, mercury, and nitrate; organic chemicals such as atrazine, benzene, dichlorobenzene, and dioxin; and naturally occurring radionuclides.

In addition to setting the maximum allowable amount of each contaminant—known as the maximum contaminant level (MCL)—in drinking water, usually measured in milligrams per liter, the EPA also identifies the ideal goal level for each contaminant. It provides information on the typical sources of these contaminants and their potentially harmful effects on human health.

Nitrate, for example, is a common pollutant in natural waters that may come from sewage, animal waste, fertilizer runoff, or the erosion of natural deposits. Nitrate levels thus can become high in groundwater near feedlots for cattle or in areas where large amounts of fertilizers are used, such as agricultural areas. Nitrogen compounds formed from nitrate may bond with hemoglobin in the blood of humans, so that less oxygen can be transported through the body by hemoglobin. Humans, especially babies, can become seriously ill from drinking nitrate-polluted water. The EPA sets the MCL for nitrate (measured as nitrogen) in public drinking water at 10 milligrams per liter (0.00134 ounces per gallon).

Harmful microorganisms in water often come from human and animal fecal material. They can produce diarrhea, vomiting, and cramps. Harmful organic materials found in water supplies often come from chemical plants, herbicides, sewage, or insecticides. These can have a variety of negative health impacts, including increased risk of cancer, liver and kidney damage, anemia, reproductive problems, and nervous system problems. Harmful radioactive materials, such as uranium or radium, may enter water supplies from natural materials or as a result of improper disposal of radioactive wastes. Humans and animals exposed to such materials may have an increased risk of cancer.

Municipal Water System Problems

Individual US states have often failed in their enforcement of the EPA drinking-water standards. In 1985, for example, more than eighteen hundred cases were reported in which water in public supplies contained contaminants at levels higher than the maximum allowed. The most common problems involved levels of microorganisms, nitrate, and fluoride that exceeded EPA-required levels.

Because of such problems, amendments to the Safe Drinking Water Act were passed by Congress in 1986. This legislation gave the EPA deadlines by which it was to set and enforce reasonable standards for more than eighty potentially dangerous contaminants in public water systems. In setting the MCLs, the EPA was required to take into consideration not only the danger of the contaminants, but also the costs of meeting these standards in public waters. Also included in this law was a ban on the use of lead solder and pipes in public water systems. In addition, the 1986 amendments required the EPA to monitor materials injected under the ground, such as oil field brines, to ensure that the injected materials do not contaminate groundwater supplies. The Energy Policy Act of 2005 contained a provision that amended the Safe Drinking Water Act by providing an exemption for "the underground injection of fluids or propping agents (other than diesel fuels) pursuant to hydraulic fracturing operations"; this alteration of the Safe Drinking Water Act has drawn significant criticism for exempting contaminants introduced by hydraulic fracturing ("fracking") operations from federal regulations under the Safe Drinking Water Act.

In 2024, the EPA finalized its first enforceable national drinking water standards for six per- and polyfluoroalkyl substances (PFAS) under the Safe Drinking Water Act, setting Maximum Contaminant Levels (MCLs) that public water systems must monitor and comply with over the coming years. In 2025, the agency announced an extension of the compliance deadline to 2031 to give communities—particularly small and rural systems—additional time to upgrade treatment infrastructure. This marks one of the most significant updates to SDWA enforcement in recent decades, addressing emerging contaminants that pose risks to public health.

Bibliography

Cech, Thomas V. “Water Quality.” Principles of Water Resources: History, Development, Management, and Policy. 3rd ed., Wiley, 2010.

Dorsheimer, Wesley T. “Removing Nitrate from Groundwater.” Water Engineering and Management, vol. 144, no. 12, 1997, pp. 20–24.

"EPA Announces Changes to PFAS Drinking Water Standard ." American Waterworks Association, 15 May 2025, www.awwa.org/AWWA-Articles/epa-announces-changes-to-pfas-drinking-water-standard. Accessed 18 Sept. 2025.

Gray, N. F. Drinking Water Quality: Problems and Solutions. 2nd ed., Cambridge UP, 2008.

Ketcham-Colwill, J. “Safe Drinking Water Law Toughened.” Environment, vol. 28, no. 7, 1986, pp. 42–43.

"Regulations." Center for Disease Control, 10 Aug. 2022, www.cdc.gov/healthywater/drinking/public/regulations.html. Accessed 23 July 2024.

Royte, Elizabeth. Bottlemania: Big Business, Local Springs, and the Battle over America’s Drinking Water. Bloomsbury, 2009.

"Summary of the Safe Drinking Water Act." United States Environmental Protection Agency, 2024, www.epa.gov/laws-regulations/summary-safe-drinking-water-act. Accessed 23 July 2024.