Disinfection Byproducts Information for Total Trihalomethane (TTHM) and Haloacetic Acid 5 (HAA5)
What are Disinfection Byproducts and how do they form?
Total trihalomethanes (TTHM) and 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. All water systems that use chlorine to disinfect the water are required by federal and state law to sample for TTHM and HAA5 on a regular basis (quarterly, or once every three months). Levels of TTHM and HAA5 can be affected by seasonal changes in source water quality or by changing amounts of disinfection added. Water systems often can experience increases in TTHM and HAA due to increases in chlorine disinfection.
TTHM are a group of disinfection byproducts that are colorless and will evaporate out of the water into the air. There are four significant TTHM potentially found in disinfected drinking water and their combined concentration is referred to as total TTHM. There are five significant HAA potentially found in disinfected drinking water and their combined concentration is referred to as total HAA5.
What is the drinking water standard for TTHM and 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 TTHM and HAA5 MCL’s are 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 potentially associated with long term exposures to HAA5. Federal and state compliance requires that the 12 months Locational Running Annual Average (LRAA) (average of four samples taken three months apart) not exceed the MCL. MassDEP set an MCL at 80 parts per billion (ppb) for TTHM and 60 ppb for HAA5 as an LRAA at each sample location.
What are the health risks associated with using water containing TTHM and HAA5?
The MCL’s for TTHM and HAA5 are based on potential cancer risks following a lifetime of drinking the water. TTHM and 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 TTHM and 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 TTHM and 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 TTHM and 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 TTHM and HAA5.
Based on the available information, long term consumption of TTHM and 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 TTHM and HAA5 level and the duration of exposure. Consumption of water with TTHM and 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. Because some data indicate that disinfection byproducts may increase the risk of developmental effects, women who are pregnant or may become pregnant may wish to avoid consuming water containing HAA5 and other disinfection byproducts exceeding the drinking water standard.
What are the TTHM and HAA5 sample results for Southwick’s water system?
The Southwick Water Department (SWD) tests for TTHM and HAA5 quarterly at the Jarry Drive Pump Station. SWD draws water from Springfield Water & Sewer Commission’s (SWSC) system in addition to maintaining our own wells. This water sample for TTHM and HAA5 is taken directly at the entry to the Town’s distribution system and before it is blended with water from the Town’s source. These samples are taken once a quarter (every 3 months). In addition, once per year SWD tests for TTHM and HAA5 at the Town Hall at 454 College Highway where water from SWSC has already blended with water from the Town’s system. A summary of all TTHM and HAA5 sample results since 2014 are summarized in the tables below. It is important to note that once water is blended between the Town’s water source and SWSC’s, the level of TTHM and HAA5 drops significantly as shown by comparing the Third Quarter sample results from the Jarry Drive Pump Station (before blending) to Town Hall (after blending) taken on the same days.
TTHM & HAA5 Results Chart 2013-Present
Has Southwick violated the MCL for TTHM and HAA5?
The Southwick Water Department is not currently under any MCL violations for TTHM or HAA5. However, a total of 6 consecutive routine quarterly samples taken from February 8, 2022 through May 11, 2023 at the Jarry Drive Pump Station all violated the MCL for HAA5. Per MassDEP, these were considered Tier 2 violations which required a public notification mailed or hand-delivered to each customer within 30 days of receiving the results. Additionally, the public notice must be posted. Copies of these Public Notices are included in the links below.
Public Notice for HAA5 MCL Violation - March 14, 2022
Public Notice for HAA5 MCL Violation - June 6, 2022
Public Notice for HAA5 MCL Violation - August 30, 2022
Public Notice for HAA5 MCL Violation - December 7, 2022
Public Notice for HAA5 MCL Violation - March 6, 2023
Public Notive for HAA5 MCL Violation - June 1, 2023
What is being done to address this issue?
SWSC continues to advance efforts on a long-term solution which includes constructing a new treatment plant. A pilot study was completed in 2019 and 2020 to determine the most effective treatment process to remove more dissolved NOM and reduce HAA5. Results from the pilot study are being used to complete a Facilities Plan and to design permanent treatment plant upgrades necessary to reduce disinfection by-products, including HAA5. The procurement for the selection of a design firm for the permanent treatment plant upgrades is underway. Construction is anticipated to begin in FY24. SWSC is accelerating this work as quickly as possible while committing significant resources to the process. Land management tools are also being implemented per a Source Water Protection Plan to optimize raw water quality.
Representatives from SWSC met with the Southwick Board of Water Commissioners at the March 24, 2022 meeting. At this meeting SWSC gave a presentation explaining about how disinfection byproducts are formed and why the levels are exceeding the MCL. A portion of this presentation also demonstrates the current filter and treatment process and an overview of the new treatment plan expected to go online in 2027. SWSC's presentation can be viewed here or at the bottom of this page. The slideshow can also be viewed here.
Will there be future violations?
SWSC’s new treatment facility is not expected to be placed on-line until 2027. Until that work is complete, it is possible there will be additional violations that require future public notices. In the meantime, SWSC has taken several short-term measures to address this issue, but they may not be adequate to address it completely until the new plant is operational.
Where can I find more information?
Feel free to contact the Southwick DPW at 413-569-6772 or email Randy Brown, DPW Director, at rbrown@southwickma.gov.
Additional Information can be found the following links:
Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rules | US EPA
TTHM in Drinking Water: Information for Consumers | Mass.gov
HAA5 in Drinking Water: Information for Consumers | Mass.gov