NEWPORT —The city’s drinking water system exceeded a federal standard for a hazardous chemical during the past year, but the violation does not indicate that the water is unhealthy to drink, according to a notice sent out by the Public Works Department.

The city went above the limit set by the Environmental Protection Agency for total trihalomethanes, a disinfectant byproduct. Newport’s annual average for 2006 was 81.96 parts per billion, while the federal standard is 80 parts per billion.

“This is not an emergency or immediate risk,” the notice reads. “There are no actions that you need to take at this time. You do not need to use an alternate (i.e., bottled) water supply. You do not need to boil your water or take other corrective action. However, if you have specific health concerns, consult your doctor.”

The notice, not the first of its kind to be issued by the Water Division, explains the chlorination process and the byproducts that the EPA expects to be controlled.

``Many water systems treat water with a chemical disinfectant, such as chlorine, in order to inactivate pathogens that cause disease. While disinfectants are effective in controlling many harmful microorganisms, they react with organic and inorganic matter in the water to form DBPs, some of which pose health risks at certain levels. Some people who drink water containing trihalomethanes in excess of the limit over many years may experience problems with their liver, kidneys, or central nervous system, and may have an increased risk of getting cancer.

``The public health benefits of chlorine disinfection practices are significant and well recognized. Consequently, one of the most complex questions facing water supply professionals is how to reduce risks from disinfectants and DBPs while providing increased protection against microbial contaminants.

The notice states that the city’s consulting engineer, working closely with the state Department of Health, is attempting to modify the treatment processes to reduce the level of disinfectant byproducts.

“In order to not compromise compliance with other drinking water regulations, this treatment change will take time to implement,” the notice reads.

Testing of the water after the modifications is expected to take place in January.