A letter about water could be in the mailbox of some Westport residents.

The Herald News says water testing showed trihalomethane levels of 52 parts per billion in the Fall River water supply for Westport users.

Jim Ferson, a spokesman for the state Department of Environmental Protection, says that is below the state limit of 80 parts per billion, but still high enough to require a letter be sent to 158 customers informing them of the high levels.

Trihalomethanes are considered possible carcinogens. The EPA says they form when chlorine used to treat the water interact with organic materials such as decaying vegetation.