The Board of Supervisors will vote next week to support the San Francisco Department of Public Health’s request for a formal position on the additive by the California Conference of Local Health Officers. The local resolution carries little legal weight, but it may bolster the health department’s demands.

Chlorine and ammonia

Chloramine is the combination of chlorine and ammonia and is used as a disinfectant in the public water supply. The San Francisco Public Utilities Commission — which oversees the Hetch Hetchy water system along the Peninsula — switched from chlorine to chloramine Feb. 1 to comply with stricter environmental standards. Chlorine kills germs but isn’t considered as effective or long-lasting as chloramine. Opponents, though, have publicly questioned if the change left the system of 2.4 million customers more at risk.

Chloramine can harm kidney dialysis patients, fish in aquariums and businesses or industries that use treated water. The ongoing questions about chloramine’s safety led the county to dive into the controversy.

“We believe an impartial, medical evaluation of chloramine is warranted,” said Mark Church, president of the Board of Supervisors. “Although chloramine has been around for decades, the extent to which it is potentially harmful to certain people is still unknown.

Kidney patients can drink, cook and bathe with the water but it is not safe for them to have the water be part of their dialysis treatment. The human body neutralizes chloramine by the digestive process but cannot when the water goes straight into the blood stream. The water similarly affects fish, amphibians and some reptiles. The chloramine binds to the iron in red blood cells, reducing the ability to carry oxygen. Chloramine is toxic to both fresh and salt water fish.

Resolution

Church and board Vice President Rich Gordon will ask the other supervisors Tuesday to support their resolution. The two sit on the board’s water subcommittee. Gordon cautioned the request for a formal investigation shouldn’t imply the additive is necessarily dangerous to the masses.

“We are not saying that chloramine is unsafe. We don’t know and therein lies the problem,” Gordon said. Some cities receiving water from Hetch Hetchy held public meetings on chloramine in the past year. In May, Millbrae residents grilled a science consultant hired by the city. She said chloramine is safe although often confused with Chloramine-T, a different compound, by worried residents.