Disinfection Byproducts: HAA5
Haloacetic acids (HAA5) in MN Community Water Systems:
Disinfecting water helps prevent disease
Many community water systems (CWS's) use disinfectants in drinking water, to kill microbes like giardia and cryptosporidium that can cause illness. When the disinfectants react with organic material (like decomposing plants), they form disinfection byproducts (DBPs). People may be exposed to DBPs when using tap water for drinking, cooking, bathing, or swimming. DBPs are not normally found in private well water.
High levels of DBPs may be harmful to health
Some studies suggest that they might increase the risk of cancer and adverse pregnancy outcomes. However, the risk of not disinfecting drinking water (and exposing people to microbes that can cause gastrointestinal illnesses) far outweighs the risk of DBPs - particularly at the low levels typically found in US water supplies.
All water systems that disinfect their water (generally all surface water systems and some groundwater systems) are required to monitor for disinfection byproducts. The DBPs that are tracked are trihalomethanes (TTHMs) and haloacetic acids (HAA5). The Maximum Contaminant Limit (MCL) for HAA5 is 60 µg/L
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.
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 CWS's, 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.
How do you find out about DBPs in your water?
Customers of community water systems can find out about the DBP levels in their drinking water by reading the Consumer Confidence Report issued each year by their water utility. For those wishing to take extra precautions, granulated activated carbon (GAC) filters are effective in lowering DBP levels in drinking water, and several types of GAC filters are available for home use.
For more information on DBP regulations and health effects, see Disinfection Byproducts.
- Drinking Water Quality - Trihalomethanes (another disinfection byproduct)