Chloramination

Chloramination is the treatment of drinking water with a chloramine[1] disinfectant. Both chlorine and small amounts of ammonia are added to the water one at a time which react together to form chloramine (also called combined chlorine), a long lasting disinfectant. Chloramine disinfection is sometimes used in large distribution systems.

Use

The maintenance of what is called a “residual” of disinfectant that stays in the water distribution system while it is delivered to people's homes is required by the Environmental Protection Agency (EPA).

The EPA regulations give two choices for disinfectant residual — chlorine or chloramine. Many major water agencies are changing to chloramine to better meet current and anticipated federal drinking water regulations and to protect the public health.

Chlorine v. Chloramine

There are many similarities between chlorine and chloramine. Both provide effective residual disinfection with minimal risk to public health. Both are toxic to fish and reptiles. Both chlorine and chloramine react with other compounds in the water to form what are called “disinfection byproducts”.

The difference is that chlorine forms many byproducts, including trihalomethanes (THM) and haloacetic acids (HAA), whereas chloramine forms a significantly lower amount of THMs and HAAs but also forms N-nitrosodimethylamine (NDMA). One of the principal benefits of chloramine is that its use reduces the overall levels of these regulated contaminants compared to chlorine.

Adverse Effects

Chloramine is toxic to fish and reptiles (chloramine, like chlorine, comes in direct contact with their bloodstream through their gills) and must be removed from water added to aquariums and fish ponds. It must also be removed from water prior to use in dialysis machines, since water comes into direct contact with the bloodstream during treatment. When drinking water, people have no trouble digesting chlorine or chloramine at the levels found in our drinking water; this water is not introduced directly into the bloodstream.

Much of the discussion about chloramine has focused on NDMA, and it is critical to distinguish between chloramine and NDMA. NDMA can be a byproduct of chloramination or chlorination, but drinking water is not a major source of exposure to NDMA. The biggest sources of human exposure to NDMA are tobacco smoke, chewing tobacco, bacon and other cured meats, beer, fish, cheese, toiletries, shampoos, cleansers, interior air of cars, and household pesticides. In addition, NDMA can form in the stomach during digestion of foods or drugs that contain alkylamines, which are naturally occurring compounds.

At very high levels--100,000 times greater than even the highest levels seen in a recent survey of chlorinated and chloraminated drinking waters--NDMA may cause serious human health problems, such as liver disease. Such effects are seen at concentrations ranging from 5 to 50 parts per million in water; for comparison a study conducted by the California Department of Health Services in 1999 and 2000 found the highest level of NDMA in drinking water that had been treated with chloramine was 0.00006 parts per million. In that study, most of the concentrations of NDMA were far lower than that, and many water samples in the California Department of Health Services study, including those from the San Francisco Public Utilities Commission water system taken in 2000, did not have any detectable concentrations of NDMA.