The New York City Department of Environmental Protection (DEP) regularly tests the drinking water that is distributed within the five boroughs to ensure that it is of the highest quality.

DEP is notifying customers that they have found a higher annual average amount of haloacetic acids (HAA5) in drinking water than usual in the following zip codes: 10301, 10302, 11235.

The higher average is not an immediate health risk and customers may continue consuming and using their water as normal.

Find HAA5 Notice.

What are HAA5?

Haloacetic acids (HAA5) are byproducts formed when drinking water is disinfected with chlorine, the most commonly used disinfectant in New York State. The amount of haloacetic acids in drinking water can change from day to day, depending on the temperature, the amount of natural organic material in reservoirs, the amount of rainfall, the amount of chlorine added, and a variety of other factors.
Are there health risks associated with drinking/using water containing HAA5?

There are no immediate health risks.

Health risks over time are minimal, and less than the risk for illness from drinking inadequately disinfected water.

Why is chlorine added to drinking water?

Water utilities have been using chlorine to disinfect drinking water for more than a century because it effectively kills bacteria and viruses that could cause serious illnesses. Using chlorine to disinfect drinking water is also a federal and state requirement.

Does New York City test its drinking water for HAA5?


All water systems that use chlorine to disinfect drinking water are required by federal and state law to sample for HAA5 on a regular basis (quarterly, or once every three months). If test levels exceed the drinking water standard, water utilities are required to notify their customers and consumers.

What is the drinking water standard for HAA5 and how is compliance determined?

Drinking water standards are called Maximum Contaminant Levels (MCLs). MCLs are set to limit risks to people from chemicals in drinking water. Some MCLs limit the daily amount consumed (for chemicals that pose an immediate risk), and some limit the amount averaged over a long period of time (for chemicals that pose a long-term risk).

The HAA5 MCL is set at a level that balances the immediate risk of bacterial contamination and the long-term risk of health effects potentially associated with long term exposure to HAA5. The United States Environmental Protection Agency (EPA) has set a MCL for HAA5 of 0.060 milligrams/liter (mg/L). 

Federal and state compliance with the MCL requires that the running annual average of four samples (i.e., quarterly, or once every three months over a year) not exceed the MCL at each sampling location. 

How can consumers be exposed to HAA5 in drinking water?

The major route of exposure is through ingestion of chlorinated drinking water. Skin contact with chlorinated water is not a major route of exposure because HAA5 are not easily absorbed through the skin.

The following health information characterizes the available studies on human populations exposed to haloacetic acids, and provides a general summary of the effects of haloacetic acids in animals, which occur at exposure levels much higher than exposure that could result through normal use of the water:

  • Some studies suggest that people who drank water containing haloacetic acids for long periods of time (e.g., several decades) have a minimally increased risk for cancer. However, how long and how frequently people actually drank the water, and how much haloacetic acids the water contained, is not known for certain. Therefore, the evidence from these studies is not strong enough to conclude that the observed increased risk for cancer is due to haloacetic acids, other disinfection by-products, or some other factor. Studies of laboratory animals show that the two specific types of haloacetic acids, dichloroacetic acid and trichloroacetic acid, can cause cancer and other effects in laboratory animals after very high levels of exposure, primarily on the liver, kidney, and nervous system and on their ability to bear healthy offspring.

Where can I get additional information?

If you have concerns about your exposure, please contact your health care provider.

You can report an illness caused by drinking water.

Where can I get additional information?

  • If you have concerns about your exposure, please contact your health care provider.
  • If you have health related questions about water but do not want to report an illness you can speak to the Department of Health and Mental Hygiene.

Call 311 or 212-NEW-YORK (212-639-9675) for assistance.

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