Chloramines are formed by reaction of chlorine used to disinfect swimming pools with ammonia and urea introduced into the pools by human perspiration, saliva, mucus, urine, and other biologic substances, and by insects and other pests.
The presence of chloramines in swimming pools is often a result of the reaction between chlorine disinfectants and various substances that enter the water from human sources, such as sweat, saliva, and urine, as well as contaminants like insect waste.