Pool Chlorine

Chlorine was first recognized as a valuable chemical in treating water when John Snow used it to purify the cholera-causing water of the Broad Street Pump. Noting the disinfecting nature of chlorine and its ability to curb cholera deaths, government officials in Great Britain began to chlorinate the public drinking water. This application of chlorine resulted in a sharp decline in deaths from typhoid.

After the tremendous success of drinking water chlorination in England, chlorination began in New Jersey and soon spread through the entire United States. Chlorination of drinking water, combined with the use of sand water filters resulted in the virtual elimination of waterborne diseases. Chlorine was so effective at eliminating the outbreak and spread of waterborne diseases that Life magazine named water chlorination as “probably the most significant public health advance of the millennium”.

Chlorine is the chemical most often used to keep swimming pools and Jacuzzis free of bacteria that can be hazardous to humans.  Chlorine kills bacteria though a fairly simple chemical reaction. The chlorine solution you pour into the water breaks down into many different chemicals, including hypochlorous acid (HOCl) and hypochlorite ions (OCl-). Both kill microorganisms and bacteria by attacking the lipids in the cell walls and destroying the enzymes and structures inside the cell,  rendering them oxidized and harmless. The difference between HOCl and OCl- is the speed at which they oxidize. Hypochlorous acid is able to oxidize the organisms in several seconds, while the hypochlorite ion may take up to 30 minutes.

Scientists are now beginning to more closely examine the effects of using chlorine in drinking water. Recent publicity about the possible adverse health effects of chlorine have led many people to install shower filters or whole house water filter systems into their homes. There is little evidence to raise concerns, however, about the use of chlorine in outdoor pools.