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Tuesday, 30 April, 2002, 17:05 GMT 18:05 UK
Pool staff in asthma link
Changing the water and air in swimming pools more regularly could help
Changing the water and air in swimming pools more regularly could help
People working in indoor swimming pools could be at risk of developing asthma, researchers suggest.

A study by Birmingham doctors suggests chemicals called chloramines could cause occupational asthma.

The paper, published in the European Respiratory Journal (ERJ), suggests regular swimmers could also be at risk.

It concentrates on just three cases, but the researchers, from Birmingham's Heartlands Hospital, said it opened the door for other studies in the area.

There's nothing in this report to show that asthma has been caused by swimming pools

Ralph Riley, National Pool Water Treatment Advisory Group
Chloramines are produced when chlorine reacts with polluting proteins from swimmers that enter the water from swimmers' bodies from sweat and urine - they cause the characteristic smell of pools.

Chlorine-based chemicals are used to ensure the water is disinfected so infections cannot be passed between swimmers.

The researchers say the amount of chloramines present in the air depends on factors such as swimmers' personal hygiene and the how often the water is changed.

Although there are various kinds of the chemical, nitrogen trichloride is the most common, and the kind the researchers believe causes asthma in indoor swimming pools.

Asthma and work link

The team monitored two lifeguards and a swimming teacher who worked at different pools.

All three had worked in swimming pools for some years before developing asthmatic symptoms.

However, all had begun to suffer cough and wheezing symptoms at work which improved when they were on holiday.

The three were asked to measure their peak expiratory flow (PEF), the maximum volume of air that they were able to force out of their lungs in a second, every two hours for two weeks.

Tests were also carried out using nitrogen trichloride.

In two of the three cases, the researchers found a significant relation between the subjects' asthma and their work.

In the third case, the person was not able to carry out the PEF checks in full because they suffered from wheezing within half an hour of arriving at the pool and had to use an inhaler.

In all three, the nitrogen trichloride tests produced an immediate asthmatic reaction.

None had a reaction to chlorine itself.

Chlorine an 'irritant'

Dr Sherwood Burge, who led the researchers told BBC News Online: "If you have asthma, which is worse when you go swimming, it could be linked to the water in the pool."

He added: "This shows that air in swimming pools is a possible cause of asthma."

Dr Burge said further studies needed to be done, looking at people who worked in swimming pools.

The researchers say their findings should not result in "extreme measures" such as preventing children swimming.

But they suggest disinfectants used in pools should be more carefully chosen and that air and water should be replaced as often as possible.

Professor Benoit Nemery, of the Department of Occupational Medicine of Leuven Hospital, writing in the ERJ, said the Birmingham study was significant, despite its size: "It serves as evidence that asthma caused by indoor swimming pools could be an occupational disease and there is reason to believe that cases are more common than they might seem."

Ralph Riley, head of the National Pool Water Treatment Advisory Group said: "We have known for a long time that chloramines can trigger, rather than cause asthma. There's nothing in this report to show that asthma has been caused by swimming pools."

He said water was constantly being cleaned, and that air was also changed four to six times per hour.

Mr Riley added the industry was constantly looking at ways of reducing the levels of chloramines whilst retaining the protection against infection in the water.

A spokeswoman for the National Asthma Campaign said: "We know that chlorine is an irritant and can trigger asthma but there is not enough evidence to state conclusively that it can cause asthma.

"This is an interesting study but more research is needed to prove there is a possible causal relationship."

See also:

26 Jul 00 | Health
Material filters out pool bugs
21 Aug 00 | Health
Dirty swimmers urged to shower
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