Gloucester's drinking water this year failed tests for substances other than the coliform bacteria that prompted a boil-water order this summer, according to the state Department of Environmental Protection.

The newly identified substances, total trihalomethanes, are not necessarily harmful and are not triggering a new water emergency, the city said tonight in a series of statements issued by Mayor Carolyn Kirk.

"You do not need to use an alternative water supply such as bottled water," reads a letter being sent to residents by the city. "This is not an emergency, nor is there an imminent risk."

Trihalomethanes are a byproduct of the drinking water disinfectant process. They are substances created when excess chlorine intended to kill bacteria combine with suspended solids — like the ones that shut down the Babson Plant in August.

While they do not cause an imminent health threat "some people who drink water containing trihalomethanes in excess of the maximum contaminant level over many years may experience problems with their liver, kidneys, or central nervous system and may have an increased risk of getting cancer," the city notification says.

The notification does not come with any dates for when the trihalomethanes turned up in the water, only that city water exceeded the yearly limit. However, the chain of events began when Babson failed due to murky water, which was followed by coliform bacteria and then supplemental chlorine being pumped into the system, is suspected by the city.

For more on this story, look to tomorrow's print and online editions of The Gloucester Daily Times and gloucestertimes.com

Patrick Anderson can be reached at panderson@gloucestertimes.com