CARRBORO — The Orange Water and Sewer Authority found a possible carcinogen in water samples taken the week of Aug. 11.
OWASA sampled water from 19 locations for trihalomethanes and haloacetic acids, byproducts of disinfecting water with chlorine. OWASA uses a combination of chlorine and ammonia to disinfect drinking water.
THMs and HAAs form when chlorine reacts chemically with natural organic matter in water. People who drink water with elevated levels of THMs or HAAs for many years may have an increased cancer risk.
On Sept. 3, OWASA received the test results: THMs in 13 of the 19 samples exceeded 80 parts per billion, and HAAs in five samples exceeded 60 ppb. One part per billion is like one penny in $10 million.
Under the Federal Safe Drinking Water Act and related state regulations, THM levels may average up to 80 ppb for the past 12 months, and the HAA level may average up to 60 ppb. THM levels in OWASA's sampling program have averaged 53 ppb in the past year. The average for HAAs was 48 ppb.
OWASA's drinking water is safe to drink, OWASA officials said in a release. According to the U.S. Environmental Protection Agency and the N.C. Department of Environment and Natural Resources' Public Water Supply Section, a person would have to drink 2 liters of water with elevated levels every day for a lifetime to have a one-in-a-million chance of getting cancer from the water.
OWASA is investigating the problem. Staff members will have additional water samples tested to evaluate the recent information and will report the results.