The U.S. Environmental Protection Agency estimates that more than 30 percent of the United States’ large water systems currently use monochloramine at some point in their systems. That number is likely to rise as more communities seek to reduce exposure to potentially harmful byproducts that can form during the disinfection process. In 1998 over 68 million U.S. customers safely used water that was treated by monochloramine as a scondary disinfectant. At present, it's estimated that monochloarmine serves 100 million U.S. customers.

Monochloramine is a disinfectant used to kill bacteria and other microbes as a part of drinking water treatment. While chlorine is the most commonly used primary disinfectant, an increasing number of water providers are using monochloramine to help them comply with new regulations. The new regulations are designed to limit certain disinfection byproducts in finished water. These disinfection byproducts – which are potentially harmful to humans -- are formed when organic and inorganic matter in the water react with chlorine or other disinfectants.

Many water systems also favor the use of monochloramine because they experience fewer taste and odor complaints from customers than when they use chlorine.

It is likely that monochloramine formed in wastewater and in waters containing natural ammonia for some time before the term “chloramine” existed.

• In the early 1900s, the chlorine-ammonia combination received attention when it was found that the cost of chlorination might be reduced if ammonia was added.
• The practice of monochloramine treatment was adopted in 1916 at the treatment plant in Ottawa, Ontario.
• The first installation in the United States was in 1917 in Denver, Colo. Both locations used ammonia and hypochlorite and noted improvements in taste.
• More than 400 utilities were using monochloramine disinfection by 1938. During World War II, when ammonia supplies were low, the use of monochloramine was reduced.
• Monochloramine was used sparingly until the 1970s when the potentially harmful disinfection byproducts trihalomethanes (THMs) were discovered. Depending on local circumstances, monochloramine produces fewer THMs than free chlorine does, so the use of monochloramine increased. Haloacetic acids (HAAs), another set of disinfection byproducts, were regulated in 1998, further supporting the use of monochloramine.

Monochloramine has been widely and successfully used as a drinking water disinfectant since the 1930s. However, there are specific considerations that need to be taken into account by those who are kidney dialysis patients.

• Like chlorine, monochloramine can harm kidney dialysis patients during the dialysis process if it is not removed from water. This is a result of water coming into contact with patients' bloodstream during the dialysis process. It is safe for dialysis patients to drink, cook with and bathe in monochloraminated water because the digestive process neutralizes monochloramine before it enters the bloodstream.
• Two methods are typically used to remove monochloramine from water before dialysis: ascorbic acid, or a granular-activated carbon filtration system specifically designed to remove monochloramine.
• Home dialysis patients should work with their home dialysis facility and physician to ensure that any necessary adjustments to their equipment are made. It is important to know that monochloramine cannot be removed by boiling water or adding salt.
• Additional information about current dialysis standards can be found on the website of the Association for the Advancement of Medical Instrumentation.
• Monochloramine is formed by a reaction between chlorine and ammonia. It is commonly used because it results in reduced levels of certain disinfection byproducts (DBPs) while still maintaining adequate disinfection. This is important because some studies have indicated that high levels of DBPs may cause health problems.
• Monochloramine also is favored because it is less reactive and remains in solution longer, providing added protection from contamination.

If there is scientifically compelling evidence that shows a large number of U.S. drinking water systems have detected monochloramine at levels that exceed the HALs set forth by the EPA, it’s possible the agency may decide to regulate monochloramine in the future. Before regulating a contaminant, EPA considers projected adverse health effects from the contaminant, the extent of occurrence of the contaminant in drinking water, and whether regulation of the contaminant would present a meaningful opportunity for reducing risks to health.

Though safe for drinking by humans, monochloramine, like chlorine, is toxic to fish and other aquatic organisms at levels used for drinking water. Fish hobbyists or home aquarium owners must neutralize or remove monochloramine from water used in aquariums or ponds.

As with chlorine, fish (including fresh and salt water fish), amphibians, and reptiles are harmed by monochloramine as it passes through the gills, directly entering their bloodstream.

Products are available at fish and pet supply stores to remove monochloramine from aquarium water including: treatment products (drops or tablets) that remove both ammonia and chlorine, or iological filters (for ammonia) and chemical agents (for chlorine).

Aquarium owners should routinely test their water for ammonia and chlorine concentrations. Test kits are available at pet shops and aquarium products suppliers.

Monochloramine, a combination of chlorine and ammonia, has been widely and successfully used as a drinking water disinfectant since 1917. By the mid-1950s, major U.S. cities, including Denver, Boston, Indianapolis, St. Louis, Portland and Minneapolis were using chloramines in their water treatment processes.

• “Monochloramine” is a disinfectant used to kill bacteria and other microbes as a part of drinking water treatment. While monochloramine can sometimes be used as a water system’s primary disinfectant, it is far more often added into the distribution system to ensure that the water remains safe as it is delivered to your home.
• While chlorine is the most commonly used primary disinfectant, an increasing number of water providers are using monochloramine to help them comply with new regulations. The new regulations are designed to limit certain “disinfectant byproducts” in finished water. These disinfection byproducts – which are potentially harmful to humans -- are formed when organic and inorganic matter in the water react with chlorine or other disinfectants.
• Many water systems also favor the use of monochloramine because they experience fewer taste and odor complaints from customers than when they use chlorine.
• Like chlorine, monochloramines must be removed from the water used in the kidney dialysis process. Kidney dialysis patients can safely drink, cook, and bathe in monochloraminated water, but dialysis systems require some modifications to remove the monochloramine. Patients should check with their physicians to be certain the necessary changes are made.
• Though safe for drinking by humans, monochloramine, like chlorine, is toxic to fish and other aquatic organisms at levels used for drinking water. Fish hobbyists or home aquarium owners must neutralize or remove monochloramine from water used in aquariums or ponds. Treatment products for this purpose are readily available at aquarium supply stores.
• To avoid effects on aquatic life from chlorine and monochloramine, de-chlorinating chemicals must be used if large volumes of monochloraminated water are being discharged to rivers or lakes.