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 used in both small and large water treatment plants. Use 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 versus 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. Adverse effects 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