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Chloramination is the treatment of drinking water with a chloramine 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.
In the United States, 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 amphibians. 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.
Chloramine is toxic to fish and amphibians. Chloramine, like chlorine, comes in direct contact with their bloodstream through fish 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. Since the 1980s, most dialysis machines are built with filters to remove chloramines.
Chloramine is generally considered a problem in brewing beer, (like chlorine it can react with and change some of the natural plant flavors that make up the beer, and it may slow or alter the yeast). Because chloramine dissipates much more slowly than chlorine from water, beer-makers prefer carbon filtration and / or Campden tablets to neutralize it in the water.
People have no trouble digesting chlorine or chloramine at the levels found in public drinking water; this water is not introduced directly into the human bloodstream. In the United States, the United States Environmental Protection Agency set minimum and maximum health-based safe levels for chloramine in drinking water. Elsewhere, similar oversight agencies may set drinking water quality standards for chloramine.
Two home builders filed lawsuits against Moulton Niguel Water District in 2012, (in Orange County CA), arguing that pinhole leaks in copper water piping in their homes was due to faulty water treatment with chloramine. Pinhole leaks cause expensive damage to people's homes, and the builders claim that they must repipe houses at great expense to deal with the problem. Officials observed that only the two builders have filed suit, but as of late 2013 the number of lawsuits had expanded. 
Much of the recent discussion about chloramine has focused on N-Nitrosodimethylamine (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.
- Chloramines, Water Quality Association
- http://www.ncbi.nlm.nih.gov/pubmed/8914698 Ward, Chloramine removal from water used in hemodialysis, October 1996, Advances in Renal Replacement Therapy
- http://water.epa.gov/drink/contaminants/basicinformation/disinfectants.cfm EPA basic information about chloramines
- http://www.ocregister.com/articles/water-340682-leaks-copper.html, http://www.newmeyeranddillion.com/pdf/Claims_Against_Water_Districts_Over_Copper_Pipe_Leaks_Form.pdf
- http://www.cdph.ca.gov/certlic/drinkingwater/pages/NDMA.aspx California Department of Health