FAQs

Haloacetic acids (HAA) are a group of disinfection byproducts that form when chlorine compounds that are used to disinfect water react with other naturally-occurring chemicals in the water.  There are five significant HAA potentially found in disinfected drinking water and their combined concentration is referred to as total HAA5.

Levels of HAA5 can be affected by seasonal changes in source water quality or by changing amounts of disinfection added.  Water systems often can experience temporary increases in HAA5 due to short-term increases in chlorine disinfection.  Chlorine disinfection increases can occur when there is a water main break, when water systems are under repair, or when there is a potential microbial (example:  bacteria) problem or threat.

All water systems that use chlorine to disinfect the water are required by federal and state law to sample for HAA5 on a regular basis (quarterly, or once every three months).

Chlorine is used to disinfect drinking water.  Disinfection of water supplies is necessary to prevent illness and is a federal and state requirement.  The practice of disinfection has nearly eliminated most acute waterborne diseases in the United States. 

Disinfection of the water first kills any microorganisms that it may contain.  Then, a small amount of disinfectant is needed in the water as it travels through the pipes in the distribution system.  This prevents regrowth of microorganisms, or contamination from an outside source, such as during a water main break.

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 should the water not be adequately disinfected and the long-term risk of health effects, such as cancer, potentially associated with long term exposures to HAA5.  The USEPA and Montana DEQ have set an MCL for HAA5 of 60 parts per billion (ppb) or micrograms per liter (ug/L) as an annual average.  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.

The MCL for HAA5 is based on an average of the sample results for the last four quarters. Although the November 2022 sample result for the site showed an HAA5 level of 27 µg/L, the Helena system is in violation due in part to elevated HAA5 levels experienced in previous quarters that continue to affect the average.

The MCL for HAA5 is based on potential cancer risks following a lifetime of drinking the water.  HAA5 are considered to be possibly carcinogenic to humans by USEPA because of evidence of carcinogenicity in experimental laboratory animals and limited evidence in people.  Some of the individual chemicals that comprise HAA5 have also caused other effects in experimental laboratory animals following high levels of exposure, including toxicity to the liver, kidneys, neurological and reproductive systems.  Various adverse reproductive and developmental effects have been observed in experimental laboratory animals following exposure to disinfection byproducts (which include HAA5).  In some, but not all, studies in people, similar effects have also been reported.  In general, young children may be more susceptible to the effects from any chemical exposure, such as HAA5, because their ability to metabolize chemicals is not mature and because their exposures may be greater for their size than in adults.  More research is being conducted to better understand the potential risks from using water containing HAA5.

Based on the available information, long term consumption of HAA5 in drinking water above the MCL may increase the risk of certain types of cancer (e.g., bladder, colon, and rectal) and other adverse effects in some people.  The degree of risk for these effects will depend on the HAA5 level and the duration of exposure.  Consumption of water with HAA5 levels somewhat above the MCL for limited durations, for example, while corrective actions are being taken to lower the levels, is not likely to significantly increase risks of adverse health effects for most people.  

The degree of risk for any consumer depends on the contaminant level in the water at the time of use/consumption, and the duration or length of exposure. Anyone concerned with exposure can consider using bottled water that has been tested for HAA5.  Parents and caregivers may wish to limit the amount of water containing HAA5 and other disinfectant by-products exceeding the drinking water standard that they give their young children. Children are generally considered more sensitive to the effects of any chemical than others in the general population and may also consume more water for their size than adults. An effective way to reduce exposure is to also use bottled water for preparing formula, beverages, or food that retains water (e.g., hot cereals, rice, or pasta for young children).

The most significant measure that you can take to reduce your exposure to HAA5 is to use bottled water for drinking or preparing beverages and food that retain water such as oatmeal or pasta.  

Various types of home filters including Reverse Osmosis and Granular Activated Carbon treatment technologies have been shown to reduce exposure to HAA5. Consumers are encouraged to consult with an independent third-party organization that certify the effectiveness of home filter products prior to installation to make a well-informed and cost-effective decision. For consumers who choose to use a home treatment device, it is very important to follow the operation and maintenance specifications carefully to make sure that the device works as intended.  

If you have concerns about your exposure, particularly concerning a medical condition, you may wish to seek the advice of your health care provider. 

If you have a non-medical question regarding HAA5 or the notice you received, please submit it on the Be Heard Helena webpage so that others that may have the same question can get the answer as well. 

The City is required to continue to send public notices if test results remain above the MCL for that quarter. The notification process will copy what was done for the first violation. When tests return below the MCL, the City will share an update through its website, social media channels, as well as notifying local media. Staff will collect water samples for the fourth quarter of this year in mid December. Once test results are returned, the appropriate update will be shared.