According to MassDEP’s Disinfection By-Product Rule (DBPR) coordinator, TTHM exposure is not an acute issue but a chronic exposure issue, stating “chronic exposure” is defined as a lifetime of high-level exposure. Specifically, consumption of 2 liters of water per day for 70 years of water that is consistently over the Maximum Contaminant Level (MCL).
The Maximum Contaminant Level (MCL) is 80ppb*, calculated using Locational Running Annual Average (LRAA). Georgetown’s 3rd Quarter LRAA at the Patriot Lane Booster Station was 83ppb. LRAA is used for MCL because it is a chronic exposure issue; not acute. The logic being that rather than penalizing a system for a single high test, compliance is evaluated using the average of four consecutive quarterly sample results taken at each specific monitoring location in the distribution system. This site-specific sampling exceedance (Patriot Lane Booster Station) does not represent the entire town’s water system on a daily basis.
By rule, we must inform residents that prolonged exposure to these compounds over extended periods may cause health effects. Water with by-products at this level can still be consumed while the Department works to improve the issues that may have attributed to the problem.
By regulation, the Department adds chlorine to the water supply as a disinfectant. It creates safer water by reducing the possibility of pathogenic bacteria contaminating the water supply. Chlorine has been used for over 100 years and is the most common disinfection chemical in water treatment. However, chlorine also reacts with natural organic matter found in our wells to form by-products, in this case, THHM’s.
Reverse osmosis and carbon filters can reduce THHM contaminants. Indoor refrigerator filters have carbon filters, which have been proven to reduce the amount of disinfection byproducts.
If you have questions about drinking water regulations or THHM mentioned above, you can email the MassDEP Drinking Water Program at program.director-dwp@mass.gov. Some residents have mentioned the phone number to the MassDEP Drinking Water Program is incorrect. The initial letter you received is a template from MassDEP and have brought this to their attention.
For more information, regarding attributes and cause that can increase levels, or any other questions you may have, please contact us at 978-352-5750.
*parts per billion (ug/L)