Health effects of swimming pool disinfection
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Disinfectants that are used for swimming pool disinfection water can affect human health.
Too much chlorine can cause eczema and rashes. Water that has a high pH value increases susceptivity to these kind of ailments.
When water is mobile, it comes in contact with a sufficient amount of of air. Carbon dioxide is released into the water, causing the pH value to decrease. When one applies chlorine, chlorine gas will evaporate.
Free active chlorine
Hypochlorous acid (HOCl) and hypochlorite (OCl-) are the main components of free active chlorine.
Swimming pool water has a high pH value and the amount of dissolved chlorine gas as free active chlorine is negligible.
Free active chlorine hardly ever causes eye irritations. These only occur above concentrations of 20 mg/L.
Dissolved chlorine and chlorine substances dehydrate hair and skin.
The air above the pool contains chlorine gas concentrations
between 0,01 and 0,1 mg/m3. These concentrations are far below the level that irritates respirational tracts.
Through the formation of combined active chlorine, free active chlorine can cause irritation.
Combined active chlorine
Combined active chlorine is the generic term for reaction products produced by free active chlorine with organic and inorganic nitrogen pollutions.
These pollutions are made of swimmers excretion products. Combined active chlorine is a complex mixture of partly unknown substances, such as chlorine ureum combinations, chloramines and chlorine kreatines.
The irritating effects of combined active chlorine are often ascribed to chloramines (NH2Cl, NHCl2, NCl3).
Chloramines are volatile substances that partly escape from water as gas. Like chloroform, chloramines cause the well known 'chlorine smell' in swimming pools.
The formation of di- and trichloramines increases when the free active chlorine concentration is increased and the pH value is lowered.
The typical 'chlorine smell' in swimming pools arises at ureum levels of 0,5 mg/L and free active chlorine concentrations of 1,0 mg/L.
There is no relation between chloramine formation and ureum concentration.
Monochloramines cause eye irritations. At normal pH levels in swimming pools, monochloramine is produced predominantly.
Both di- and trichloramines irritate eyes. These substances reach the eyes through water and through the air above the pool.
Trichloramine also irritates air tracts. Other chlorinated organic subtances are suspected to irritate as well, particularly chlorinated ammonia, kreatinine and urine acid.
The combined active chlorine concentration in swimming pools should be below 1 mg/l.
Disinfection byproducts: chloroform
Some disinfection byproducts, such as trihalomethane chloroform, are suspected carcinogenic.
Trihalomethane concentration depends upon total organic carbon,
the number of swimmers and the water temperature.
Chloroform is the most important reaction product.
Additionally, other trihalomethanes, dichloromethane, tetrachloromethane, trichloroethene, bromodichloromethane and other chlorobromo hydrogen carbons can be found.
Chloroform and similar substances are volatile. Some part escapes from water and swimmers are exposed through inhalation.
Chloroform concentrations in swimming pools vary a lot. Chloroform concentrations are highest just above the water. The suggested health standard for chloroform 100 mg/m3, this concentration is found in indoor swimming pools.
Swimming is one of the main sources of non-professional exposure to chloroform (over 70% percent after one hour of swimming).
In outdoor swimming pools exposure is lower, because the wind ventilates the air above the water.
Exposure to chloroform can be measured in blood plasma of swimmers.
Swimmers that swim for a long time with great physical effort (competitive swimmers) take up most chloroform.
Chloroform concentrations in air is the main factor that determines the amount of chloroform that is absorbed. The time interval, the number of swimmers and the chloroform concentration in water are less important factors.
Effects of chloroform
Exposure to low concentrations of chloroform causes renal and liver defects. These can be demonstrated by enzymes in the blood which are indicators for renal- and liver functions.
Epidemiological research shows there might be a relation between skin exposure to chlorinated organic substances and hypochlorite, and skin cancer.
This relation has not been proved by laboratory animal tests.
Long-term oral exposure of laboratory animals to chloroform through food caused liver cancer.
Health complaints of swimming pool attendants
Especially swimming pool attendants are exposed to swimming pool disinfection byproducts for a long period of time.
Dutch research, carried out in 2001 by Abvakabo Nederland, concerned working conditions in swimming pools.
Swimming pool attendants were interviewed. The research shows that a lot of employees suffer from forgetfulness, fatigue, chronic colds, voice problems, eye irritations, headache, sore throat, eczema and frontal sinus inflammation.
Fertility problems are also mentioned. All problems are probably caused by working conditions. People work long hours in a warm, humid environment and are exposed to chemical substances.
Swimming pool ventilation is often insufficient and volatile disinfection byproducts remain.
If swimming pool attendants do not work, health problems vanish and a sense of health returns.
Alternative disinfectants that produce less disinfection byproducts and improved ventilation can prevent or at least minimize problems.
Epidemiologich research
Effects of exposure to swimming pool disinfectants and byproducts have been researched a couple of times.
Competitive swimmers weekly spent many hours in swimming pools. During exercise their physical effort is large. Their inhalation is more deeply and more powerful than that of recreational swimmers. They inhale more air and absorb more chlorine products.
Lung functions of swimmers decrease when they are swimming in pools that are disinfected by chlorine. Many competitive swimmers suffer from asthma.
Complaints disappear when they swim in outdoor pools, because the wind removes gases from the air above the pool.
Children inhale more air per unit body than adults do. They relatively absorb more gaseous substances and the health risk for children is bigger.
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| At low pH values in swimming pools, the teeth can be damaged |
Swimming pools that are disinfected by chlorine gas can produce hydrochloric acid with sunlight. This causes the pH value to drop.
When pH values drop below 3,6, swimmers can suffer from dental abrasion. Tooth enamel dissolves and the teeth become brittle and sensitive.
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