Disinfection byproducts: HAA5

Haloacetic acids (HAA) are a type of disinfection byproduct. HAA5 is a group of five haloacetic acids: dibromoacetic acid, dichloroacetic acid, monobromoacetic acid, monochloroacetic acid, and trichloroacetic acid.

Disinfecting water helps prevent disease

Public water systems play an essential role in protecting public health through treatment and disinfection processes. The most common method of disinfection is through the addition of chlorine to drinking water supplies. Chlorine effectively kills waterborne bacteria and viruses and continues to keep the water safe as it travels from the treatment plant to the consumer's tap.

Disinfection makes our water safer to drink, and we do not have to worry about the waterborne diseases of the past. Both the World Health Organization and the Centers for Disease Control regard disinfection of drinking water as one of the most important advances in public health.

What are disinfection byproducts (DBPs)?

Although chlorine has been a literal lifesaver with regard to drinking water, it also has the potential to form byproducts that can cause harmful health effects. Chlorine can react with organic materials in water to form disinfection byproducts (DBPs).
The formation of DBPs is usually a greater concern for water systems that use surface water, such as rivers, lakes, and streams, as their source. Surface water sources are more likely to contain the organic materials that combine with chlorine to form DBPs.

Health effects of HAA5

Some people who drink water containing haloacetic acids in excess of the MCL over many years may have an increased risk of getting cancer.

The risk of not disinfecting drinking water—and exposing people to microorganisms that can cause illnesses—outweighs the long-term, low level risk of DBPs, particularly at the low levels typically found in U.S. water supplies. Water systems review their operations to minimize HAA formation without compromising public health protection from disinfection.

Standard for HAA5 in community water systems

All community water systems that disinfect test for TTHMs and ensure levels meet the Environmental Protection Agency drinking water standard, or Maximum Contaminant Level (MCL). The MCL for HAA5 is 60 µg/L (one µg/L equals one part per billion). This MCL is for five HAAs added together.

Most community water systems provide drinking water with HAA5 below the standard

Mean HAA5 levels of Minnesota community water systems

The MCL is 60 µg/L. Concentrations are the mean annual levels for community water systems in Minnesota.
The MCL is 60 µg/L. Concentrations are the mean annual levels for community water systems in Minnesota.

The Maximum Contaminant Level (MCL) for HAA5 is 60 µg/L.

This chart shows the percent of systems by HAA5 annual mean concentration. The percent of systems in violation of the MCL is not equivalent to the percent of systems listed in the chart with concentrations above the MCL, because the MCL is currently based on a "locational" running annual average (i.e., monthly averages of each sample collected at the specified location collected in the previous 12 months), rather than a system-wide calendar year average.

Maximum HAA5 levels of Minnesota community water systems

The MCL is 60 µg/L. Concentrations are the maximum annual levels for community water systems in Minnesota.
The MCL is 60 µg/L. Concentrations are the maximum annual levels for community water systems in Minnesota.

This chart shows the percent of systems by annual maximum HAA5 concentration. A system may have a number of different locations in the distribution system with differing levels of HAA5. In this chart, the maximum value reflects the sample with the highest concentration at a single sampling location. The level of HAA5 in water that ultimately reaches the consumer's tap may be different.

Most drink water with HAA5 below levels of concern

The table below shows the number of people served by CWSs, by HAA5 mean concentration. Note that the estimates of number of people served by each system are rough calculations periodically updated by water system manager.

Population served by community water system mean HAA5 concentration, 2019

HAA5 Systems Population served Percent
0-15 643 2,897,586 66.4%
15-30 70 906,050 20.8%
30-45 32 541,806 12.4%
45-60 9 19,292 0.4%
60+ 0 0 0.00%
75+ 0 0 0.00%

What can be done about HAA5 in drinking water?

All public water systems that disinfect must regularly test their treated water to determine if regulated DBPs are present and at what levels. If they are above the limits set by EPA, the water system must take action to reduce the DBPs. Actions could include adjustments to organics removal processes, disinfection dose and location, and distribution system management. The water system must also notify all of their customers of the DBP levels.

You can find the level of HAA5 in your community water system detected by reading their Water Quality Report (also known as a Consumer Confidence Report [CCR]). Call your community water system to get a copy of your CCR, or find it online at Search for Your Consumer Confidence Report (CCR).

If you want to take additional steps to reduce your exposure to DBPs in drinking water, you can use a home water treatment system. For more information on home water treatment, visit Home Water Treatment.
For more information on DBPs, see Disinfection and Disinfection Byproducts.

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