Do you recall fond Summer memories when you get a whiff of Chlorine around a pool? Ever get off an elevator at a hotel and knew straight away that the pool was on that level? We all know that Chlorine is added to pool water as a disinfectant to protect our health but most of us don’t understand that the ‘Chlorine pool smell’ is not due to Chlorine, but to;
Chloramines (Combined Chlorine)
Chloramines are chemical by-products formed when Chlorine reacts with organic substances such as sweat or inorganic substances such as makeup and deodorant and can build up in pool water when improperly treated. These Chloramines come in various chemical forms called Monochloramine, Dichloramine and Trichloramine. Trichloramine, in particular, is considered quite toxic and exists 100mm under the water surface, releasing into the atmosphere as a gas when the surface tension of the water is broken, directly where swimmers are breathing.
Not only are Chloramines poor disinfectants, they irritate mucous membranes and cause exposed swimmers to suffer with stinging red eyes and itchy skin. Respiratory and Asthma problems related to Chloramine exposure are also common amongst regular swimmers.
Cyanogen Chloride (Tear Gas)
Cyanogen Chloride is a chemical by-product formed when urine reacts with Chlorine to form Cyanogen Chloride (CNCL – an unstable chemical structure). Cyanogen Chloride decomposes slowly with heat (heated water) to form Hydrogen Cyanide, Hydrogen Chloride and Nitrogen Oxide fumes. These fumes are highly toxic and corrosive and can be harmful to our lungs, heart, central nervous system and other organs if inhaled. These nitrogen based by-products have a greater tendency to cause cellular damage and Cancer. The Cyanide component is that found in CS gas (tear gas), used for riot control.
To limit the formation of Chloramines/Cyanogen Chloride, swimmers should always use the toilet and shower before entering the water to decrease the amount of contaminants entering the pool. This is particularly an issue for swim schools who have large numbers of infant swimmers that are not toilet trained.
Legally, to protect the health and safety of swimmers, combined Chlorine levels (Chloramines) must not exceed 1ppm in any public swimming pool or spa. If levels rise higher than this, Chloramines must be removed by adding very high amounts (up to 10x normal operating level) of Chlorine or by using Ozone, UV or a combination of the two technologies (Advanced Oxidation Process). When combining Ozone and UV the end result is Hydroxyl Free Radicals, one of the most reactive agents known to chemistry. These reactive species can oxidise virtually any compound found in water, maximising disinfection whilst killing all types of bacteria, fungi, virus and Chlorine resistant parasites such as Cryptosporidium. More importantly, these AOP systems will dramatically lower combined Chlorine levels to keep water well below health regulation limits.
Use your senses/common sense
Facility managers are responsible for maintaining adequate pool chemistry however you can also use your senses/common sense to decide for yourself if the pool is safe to swim in:
Is there a strong Chlorine odour? Does it irritate your sinuses or cause you to cough?
Does the water look clear or cloudy?
Do the pool surfaces feel slimy?
Always avoid getting water in your mouth and don’t swallow if you do!
Always shower before entering the pool to reduce the amount of contaminants that may enter with you.
Encourage kids to take regular bathroom breaks and do not go swimming if you have been ill or have Diarrhoea.
Written by John Morrison BSc