Swimming Pool Asthma

Swimming Pool Asthma

Swimming is generally the best form of exercise for asthmatics, as exercise induced asthma is mostly due to breathing in cold dry air. The air in swimming pools is moist and warm, and breathing control is obviously necessary while swimming.

Crowded Swimming Pool

A few asthmatics become allergic to the nitrogen trichloride (this is what the smell is in pools) in the air. Finding out whether this is a problem for you is a bit difficult. You should measure lung function, such as with a peak flow meter, hourly before swimming, then at the end of a swimming session, say every 15 minutes for the next hour and then hourly for the rest of the day. This should be compared with days not swimming. If the swimming day is worse than the non-swimming day, the swimming needs repeating in a different pool, particularly an outdoor pool where the air quality will not be a problem.

Disinfecting the pool

Water is usually disinfected upon entering a pool. Most pools continually pump water so the water is continually refreshed. However it takes some time for all the water in a pool to be refreshed and there has to be a disenfectant in the water to kill any new bugs that get into the water before it is refreshed. This is called residual disinfectant.

The faster the water is refreshed, the less residual disinfectant is needed in the water. Pools that have relatively slow water turnover usually have 1 - 2 % free chlorine in the water (if using chlorine releasing agents). Pools that have a rapid turnover usually only need 0.5%.

There are different systems used for disinfecting swimming pool water, chlorine releasing agents are the most common in the UK, although bromine releasing agents, and non-halogenated methods are also available. Free chlorine reacts with body proteins such as sweat and urine to form chloramines, the most prevalent and volatile of which is nitrogen trichloride. This is what pools smell of (rather than chlorine). There is very little if any free chlorine measurable in the air in indoor pools, but significant levels of nitrogen trichloride. There is conflict amongst physicians as to the dangers of nitrogen trichloride in the air. We believe that it can both cause asthma in pool staff as well as cause deterioration in pre-existing asthma; whether this is by allergic or other mechanisms is unclear. Nitrogen trichloride levels also correlate with the sore eyes and rhinitis which are prevalent in pool staff.

In my opinion bromamines are less volatile than chloramines, and are therefore less likely to be inhaled in swimming pool air. They may cause similar reactions to chloramines, but this has so far not been demonstrated.

Choosing a pool

Much of the problems come from swimmers who urinate in the pool and who fail to wash before getting in the pool. This seems to be particularly prevalent in the UK. In some countries, washing before going into the pool is mandatory and urinating in the pool leaves a blue stream (by adding a pH indicator to the water) behind the swimmer who can then be extracted.

Most indoor pools spend much more time worrying about the water quality than the air quality. Good ventilation with outdoor air is important to remove the nitrogen trichloride, although the air is often recirculated to preserve heat. Air levels of nitrogen trichloride increase with the number and dirtyness of the swimmers and often increase througout the day.

Having said that there are many public pools where residual disinfection is minimised and conditions excellent. These pools are well engineered, never over used, insist that bathers use pre swim hygiene procedures and they reduce the levels of residual disinfection in the pool to the minimum required to stop any cross-infection from one bather to another.

Pools that use supplementary treatments for disinfection such as Ozone, UV or Chlorine Dioxide are usually much better in terms of chloramine levels as the quantity of chlorine used for residual disinfection in the water is much less than a conventional pool.

In Salt Water pools salt is added rather than chlorine, but the salt is then converted to chlorine by electrolysis (called a chlorine generator).

If you have developed asthma due to chloramines, then you will need to use a pool with very good ventilation, one that uses another system for water treatment, such as bromine, or an outdoor pool.

Testing the air quality

For pools that use chlorine releasing agents sniffing the air is a quick and easy indicator of the air quality. A more accurate but extremely difficult method is mentioned below.

Nitrogen trichloride should be measured in the pool air after a period of use (when it has had time to build up). 

It is possible to measure nitrogen trichloride using a tube containing silica gel coated with sulphamic acid to trap hypochlorite and mono- and dichloramine along with a cassette containing a quartz filter treated with sodium carbonate and diarsenic trioxide to trap nitrogen trichloride.

The method is proposed in the reference below ("Exposure to chloramines in the atmosphere of indoor swimming pools"). We only have the abstract for this reference, the full text requires a fee. The sampling and recovery efficiency of the filters used has been reported to be >95%.

There is no commercially available kit to do this that we know of and the method requires a great deal of expertise.

References

Full Text Available for Ecological association between childhood asthma and availability of indoor chlorinated swimming pools in Europe Nickmilder M, Bernard A, Ecological association between childhood asthma and availability of indoor chlorinated swimming pools in Europe, Occup Environ Med, 2007;64:37-46,

Abstract Available for Exposure to trichloramine and respiratory symptoms in indoor swimming pool workers Jacobs JH, Paan S, van Rooy FGBGJ, Meliefste C, Zaat VAC, Rooyackers JM, Heederik D, Exposure to trichloramine and respiratory symptoms in indoor swimming pool workers, Eur Respir J, 2007;29:690-698,
Dick Heederik, Institute of Risk Assessment Sciences, Utrecht, an author of 'Exposure to trichloramine and respiratory symptoms in indoor swimming pool workers' Frits van Rooy, Utrecht University, an author of 'Exposure to trichloramine and respiratory symptoms in indoor swimming pool workers' JH Jacobs, Utrecht, an author of 'Exposure to trichloramine and respiratory symptoms in indoor swimming pool workers'

Full Text Available for Occupational asthma caused by chloramines in swimming-pool air Thickett KM, McCoach JS, Gerber JM, Sadra S, Burge PS, Occupational asthma caused by chloramines in swimming-pool air, Eur Respir J, 2002;19:827-832,
Sherwood Burge, Oasys, an author of 'Occupational asthma caused by chloramines in swimming-pool air' Jennifer McCoach (now Croft), Oasys, an author of 'Occupational asthma caused by chloramines in swimming-pool air' Steve Sadra, Institute of Occupational and Environmental Health, Birmingham, an author of 'Occupational asthma caused by chloramines in swimming-pool air'

Abstract Available for Exposure to chloramines in the atmosphere of indoor swimming pools Hery M, Hecht G, Gerber JM, Gendre JC, Hubert G, Rebuffaud J, Exposure to chloramines in the atmosphere of indoor swimming pools, Ann Occup Hyg, 1995;39:427-439,

No Abstract Available for "Coughing water", bronchial hyperreactivity induced by swimming in a chlorinated pool Pickering CAC, Mustchin CP, "Coughing water", bronchial hyperreactivity induced by swimming in a chlorinated pool, Thorax, 1979;34:682-683,
Tony Pickering, Wythenshawe Hospital, Manchester, UK, an author of '

Full Text Available for Specificity of Exercise in Exercise-induced Asthma FITCH KD, MORTON AR, Specificity of Exercise in Exercise-induced Asthma, Br Med J, 1971;4:577-581,

Links

Search for nearby swimming pools (UK only)
Sport England website to search for local pools and other sporting facilities. Lido (outdoor) pools can be searched for.

Non and Low-chlorine swimming pools
Worldwide list of non and low-chlorine pools treated with ozone, salt, UV, or other alternatives. Not searchable and not very extensive at present.

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