Haloacetic Acids in Water

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If your drinking water is supplied by your local municipality, it’s likely to contain a group of disinfection byproducts known as haloacetic acids (HAAs). These invisible chemical compounds have known human health issues when consumed in excess.

This glossary discusses everything you need to know about haloacetic acids in drinking water, including how they’re formed, how they may affect your health, and how to remove them from your tap water.

❔ What are Haloacetic Acids?

Haloacetic acids (HAAs) are a relatively new group of disinfection byproducts, including:

  • Dibromoacetic acid
  • Dichloroacetic acid
  • Monobromoacetic acid
  • Monochloroacetic acid
  • Trichloroacetic acids

Collectively, these five most common haloacetic acids are known as the HAA5.

These chemicals are formed when disinfection chemicals react with naturally occurring organic matter in the water distribution system.

There are no uses of haloacetic acids in any industry – they’re simply byproducts found in drinking water supplies.

In Water AsHAA5
SourcesChlorine, ozone, or chloramine disinfection of public water supplies
Contaminant Levels (MCLs)
US EPA: 0.060 mg/L
For individual HAAs:
Dichloroacetic acid - 0 mg/L
Trichloroacetic acid: - 0.02 mg/L
Monochloroacetic acid - 0.07 mg/L
Canadian Drinking Water Guidelines: 0.08 mg/L (annual)
Potential Health RisksIncreased risk of developing bladder cancer
Rectal and colon cancer risk
Adverse reproductive and developmental effects in pregnant women
TreatmentsActivated Carbon Filters
Reverse Osmosis
Water Distillers

🩺 What are the Potential Health Effects of Haloacetic Acids?

According to the EPA, one of the most well-known adverse health effects of HAAs is their cancer risk.

Some of the potential public health effects of haloacetic acids are:

  • Increased risk of developing bladder cancer
  • Rectal and colon cancer risk
  • Adverse reproductive and developmental effects in pregnant women

The health effects of HAAs are thought to only occur if haloacetic acids are consumed in high levels over a long period. Exposure to levels of HAAs below the national drinking water standard shouldn’t adversely affect the general population.

Woman not feeling well after drinking water with haloacetic acids

🚰 How Do Haloacetic Acids Get Into Drinking Water?

Haloacetic acids get into drinking water that has been disinfected by chlorine, ozone, or chloramine.

When a chemical used to disinfect drinking water reacts with organic matter and small amounts of bromide, which are naturally found in most water supplies, numerous HAAs are formed.

The concentration of haloacetic acids in a water distribution system is determined by:

  • The water’s acidity – slightly acidic water promotes HAAs formation
  • The level of organic matter present in the water – high organic matter content increases the formation of HAAs (surface water sources are most likely to have a high concentration of organic matter)
  • The water temperature – Elevated temperature promotes HAAs formation
  • The chlorine dose – The more chlorine the water contains, the more haloacetic acids it’s likely to produce

Haloacetic acids aren’t naturally present in the atmosphere or the environment. This means that surface water and groundwater supplies are unlikely to contain HAAs, unless they have been polluted by chlorinated wastewater. If you own a private well, your raw water should be HAAs-free.

municipal drinking water chlorination

📉 Do Water Treatment Facilities Monitor Levels of Haloacetic Acids in Drinking Water?

Yes, water distribution systems must legally monitor the levels of haloacetic acids in disinfected drinking water.

The Environmental Protection Agency (EPA) has produced two Disinfection Byproducts Rules that protect public water users from the chemicals produced during drinking water disinfection. These Rules are in place to protect public health and are applicable to all community and non-community water systems, including those with a customer base of less than 10,000.

The two EPA Disinfection Byproducts Rules are:

  • Stage 1 Disinfectants and Disinfection Byproducts Rule (DBPR): reduces public exposure to disinfection by-products, including HAAs, in drinking water systems.
  • Stage 2 DBPR: Stringent monitoring requirements for haloacetic acids and trihalomethanes.

📌 Under these Rules, the Maximum Contaminant Level (MCL) for haloacetic acids (HAAs) in drinking water is 0.060 mg/L. This MCL is the maximum amount of HAAs that public water suppliers can retain in drinking water systems.

The EPA also has separate Maximum Contaminant Level Goals (the maximum amount of a contaminant that is thought to pose no health risk) for individual HAAs:

  • Dichloroacetic acid: 0 mg/L
  • Trichloroacetic acid: 0.02 mg/L
  • Monochloroacetic acid: 0.07 mg/L

Bromoacetic acid and dibromoacetic acid are also regulated in the HAAs group but the EPA currently has no MCLGs for these contaminants.

In Canada, the Canadian Drinking Water Guidelines dictate that a running annual average of 0.08 mg/L is the maximum acceptable concentration for HAAs in public water systems.

You might be wondering why your local public water treatment plant doesn’t simply stop using chlorine to disinfect your water supply. Chemical disinfection is the simplest and most affordable means of water treatment, and is needed to kill bacteria and other pathogens that are known to cause waterborne diseases. Other, more natural methods of water disinfection are considered too costly for large-scale use.

Municipal city water treatment plant

🔎 How Can I Tell if Haloacetic Acids are in My Drinking Water?

Haloacetic acids don’t change water quality in any way, so you won’t be able to detect these contaminants by tasting, smelling, or looking at your water.

The only way to know for certain whether your water contains haloacetic acids is to test a water sample from your faucet.

A laboratory test will give you the most accurate testing data for HAAs levels in your water. Some tests give an overview of the presence of haloacetic acids, while others may test individually for trichloroacetic acid, monobromoacetic acid, dibromoacetic acid, and the other common HAAs. Most laboratory tests provide results within one to two weeks.

water testing with tap score

Your water supplier should also publish their HAAs monitoring results in your annual Consumer Confidence Report or Water Quality Report.

This should give you an idea of the presence of HAAs in your water. Keep in mind that your Consumer Confidence Report is only applicable to a single day of the year, and doesn’t account for fluctuations in disinfectants and naturally occurring organic materials in your water.

Tap score water testing kit

👩🏜‍⚕ How Can I Protect My Family from Haloacetic Acids in Drinking Water?

The best way to protect your family from haloacetic acids is to install a home treatment device.

Some of the most effective water filters for removing HAAs are:

  • Granular activated carbon filters: These filters use adsorption to remove chlorine, disinfection by-products (including haloacetic acids), tastes, and odors from water. GAC filters may be used as part of a multi-stage filter for whole home or under-sink use, or may be standalone filters (such as in a pitcher filter or a faucet filter).
  • Reverse osmosis systems: The reverse osmosis filtration process separates water particles from contaminants larger than 0.0001 microns with a semipermeable membrane. RO is one of the most effective HAAs removal technologies, but it’s also wasteful – around 1-4 gallons of water are washed down a drain for every 1 gallon of water purified. Common applications for RO units are countertop, under-sink, and whole house systems.
  • Nanofiltration: Nanofilters use a similar process to reverse osmosis, blocking contaminants with a membrane that allows only water particles to pass through. Nanofiltration removes all contaminants larger than 0.2–2 nanometers (depending on the filter pore size). These filters are most commonly found as under-sink units.
  • Water distillers: A water distiller purifies water by boiling it until it evaporates, then condensing it into a separate container. Most contaminants are unable to vaporize with water and are left behind in the boiling chamber. An activated carbon filter removes any lingering impurities as water drips out of the distiller’s spout. Distillation takes up to 6 hours to purify a 1-gallon batch of water, so it’s not the best option for large families.

If you test your water and discover unusually high levels of HAAs, switch to bottled water while you consider methods of removing the contaminant from your water. Make sure the bottled water isn’t chlorinated.

Private well supplies are only at risk of HAAs contamination if the water is treated with a chlorination system. If you currently chlorinate your well water system, consider switching to UV purification, a chemical-free disinfection method with a high success rate.

Types of carbon filter cartridges

⚠ How Else Can I Be Exposed to Haloacetic Acids?

Drinking tap water containing haloacetic acids is the primary source of exposure to these chemicals. However, you may also be exposed to HAAs by:

  • Eating foods or drinking beverages that have been cooked with, stored in, or prepared with chlorinated water, such as pre-prepared salads, milk, and some soft drinks.
  • Skin contact with water containing HAAs, such as while showering in your public water system or swimming in a chlorinated pool.
  • Eye contact by touching your eyes with wet hands or water containing haloacetic acids.
  • Inhaling HAAs while bathing, showering, washing dishes, or swimming in water containing HAAs.

By installing a water filtration system in your home, you can reduce not only your risk of consuming HAAs, but also touching and inhaling these chemicals in your home.

📝 Where Can I Get More Information?

You can get more information about haloacetic acids in drinking water, including their potential health effects and the national regulations for these contaminants, in the links below.

  • Jennifer Byrd
    Water Treatment Specialist

    For 20+ years, Jennifer has championed clean water. From navigating operations to leading sales, she's tackled diverse industry challenges. Now, at Redbird Water, she crafts personalized solutions for homes, businesses, and factories. A past Chamber President and industry advocate, Jennifer leverages her expertise in cutting-edge filtration and custom design to transform water concerns into crystal-clear solutions.

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