A good whiff of a cup of household bleach will irritate eyes and nasal passages. Imagine the effects of the gas contained in a four-foot-tall, 100-pound cylinder. The chlorine gas stored these cylinders flows out through tubes into the water of thousands of swimming pools around the world. Its byproducts may be as troubling as the chemical itself but its use will continue because of its effectiveness as a disinfectant.
Chlorine in the Pool
Sodium hyperchlorite, commonly called chlorine, is highly efficient in killing organic contaminants in pools. According to the Chlorine Institute (CI), chlorine is highly reactive and dissipates quickly when released into the atmosphere, making a sudden release of gas from a storage tank or faulty chlorinator the primary danger for swimmers. Undiluted chlorine or over-chlorinated water will also harm aquatic and plant life if released suddenly. Although chlorine exposure can cause general irritation to eyes, nose and throat, it is the caustic hyperchlorite solution that can cause the most serious damage to the esophagus, stomach and digestive tract, according to the U.S. Agency for Toxic Substances and Disease Registry (ATSDR).
People with chronic respiratory conditions may be more sensitive to chlorine and some may develop reactive airways dysfunction syndrome (RADS). Most effects of swimming in a properly chlorinated pool are short-lived, though. Chlorine evaporates quickly and breaks down when subjected to sunlight.
Chlorine in the Atmosphere
Because chlorine evaporates quickly, a pool that is over-chlorinated may release some chlorine or chlorine compounds into the atmosphere. The CI admits that highly reactive chlorine can contribute to hydrochloric acid in rainfall and that it may be an agent in forming and destroying troposphere ozone, which is a fundamental component of urban smog. In both cases, however, swimming pools contribute less elemental chlorine than industrial usage or internal combustion engines. It is also not as important to acid rain and depletion of the ozone layer as chloroflourocarbons, sulfur dioxide and nitrogen oxides.
Chloramines
Sodium hyperchlorite kills germs and bacteria carried on the surface of the skin, in perspiration, body oils, urine, cosmetics and other personal products of the bathers. It does so by forming new compounds called chloramines. A 2002 article in the "European Respiratory Journal" cited the interaction of hypochlorite with ammonia and amino-compounds that forms chloramines as the basis for the "chlorine smell" in indoor pools. A 2008 summary of research in the National Institute of Environmental Health Sciences journal Environmental Health Perspectives focuses on the suggested relation between asthma in children and atmospheric trichloramine in indoor pools, suggesting chloramines may be as toxic as chlorine itself.
Other studies focused on cancer, reproductive processes, skin, gastric and digestive problems have been inconclusive. The American Chemistry Council points out that study of chloramines is incomplete and that the way to minimize the environmental impact of pool chlorine at this point is to use it carefully and encourage good swimmer hygiene.
References
- The Chlorine Institute: Chlorine Effects on Health and the Environment
- U.S. Agency for Toxic Substances and Disease Registry:Toxic Facts; Chlorine
- National Institute of Environmental Health Sciences: Childhood Asthma and Environmental Exposures at Swimming Pools
- European Respiratory Journal: Indoor Swimming Pools, Water Chlorination and Respiratory Health
- American Chemistry Council:ACC Cautions Against Study Linking Asthma With Swimming
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