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Side effects of chlorine in pools
As mentioned, there are many immediate actions that occur when chlorine is added to water. After chlorine has effectively done its work, it will react with excess contaminants that are present in pool water. This could be nitrogen ammonia or organic nitrogen contamination. The dispersal of these contaminants comes from swimmers or the surrounding environment and animals. As an example, one dog in an average size pool is the contamination equivalent of 50 people. The reaction of chlorine to these contaminants forms combined chlorine or chloramines. There are three formations of chloramines in pool water.
- Nitrogen ammonia appears as NH3;
- Chlorine replaces one hydrogen and forms mono-chloramine NH2Cl; and
- When chlorine replaces two hydrogens, di-chloramine is formed NHCl2.
The replacement of all the hydrogen by chlorine creates tri-chloramines NCl3. Tri-chloramines are very volatile, causing an extreme chemical odour that can be quite apparent in indoor facilities. This odour is carcinogenic and causes eye and lung irritation. Airborne chloramines cause severe lung and asthma type symptoms. In the water, chloramines are absorbed through the skin and can cause many health issues.
Chlorine will immediately combine any time ammonia enters pool water. Ammonia can enter via the environment, from perspiration and urine, or chemically introduced. Ammonia ceases to be in the presence of free chlorine and converts quickly to mono-chloramines. Mono-chloramines formed from ammonia convert to di-chloramines as free chlorine concentrations are increased. The increased free chlorine concentration causes di-chloramines to dissipate and leave the water rapidly. Tri-chloramines will form when too much chlorine is added. Chloramines formed by ammonia are referred to as inorganic.
Organic waste from swimmers also combines with chlorine in the same manner as ammonia. The organic waste comes primarily from sweat, spit, urine, and other bodily contaminants. These types of chloramines are known as organic. Inorganic chloramines are readily destroyed by increasing the free chlorine enough to overcome the demand and create an effective residual. That said, the organic form of chloramine is more difficult to destroy. In many cases, adding heavy amounts of chlorine to deal with organic chloramines can make matters worse. One reason for this is the presence of urea from urine that reacts very slowly with chlorine. Adults produce up to 29.5 mL (1 oz) of urea daily that is dispersed in one’s urine. Chlorine demand is much higher when organic contaminants such as urea are present. Therefore, it takes longer to remove demand and create an effective free-chlorine residual.