Fancy a chemical bath? How chlorinated swimming pools can trigger asthma, ruin teeth and turn hair green

Release time:2016-05-09

There’s nothing more appealing than a refreshing dip in a swimming pool on a summer’s day. But be warned. Some health experts are becoming concerned that swimming in chlorinated pools may be at the root of some serious health problems.

Chlorine has been widely used to disinfect our water supply in the UK and most other developed countries for more than 100 years.

Chemical analyst and forensic toxicologist Dr Nitin Seetohul, of Nottingham Trent University, says: ‘When added to water, chlorine is incredibly efficient at destroying a broad spectrum of dangerous water-borne bacteria and viruses, to the extent that it is widely credited with wiping out diseases such as typhoid and cholera in developed countries.’

Hidden dangers: An occasional swim is unlikely to do much harm, unless you are particularly sensitive to chlorine - But experts suggest anyone who swims once a week or more should be wary

Considered perfectly safe at the World Health Organisation’s recommended level of one part per million or less in our drinking water - it’s only when chlorine is added at higher levels around the two to five parts per million needed to keep swimming pools clean that problems seem to occur.

Dr Andrew Wright, professor of dermatology at the University of Bradford, says he wasn’t surprised to hear that 33 people were rushed to hospital last month after an accidental overdose of chlorine at the Wild Duck Holiday Park swimming pool near Great Yarmouth left swimmers with streaming eyes, struggling to breathe and vomiting.

‘I have been campaigning to change the way we keep our swimming pools clean for the past 25 years,’ says Dr Wright.

‘I regularly see people who suffer severe skin problems triggered by even the normal amounts of chlorine in swimming pools. Many of my patients can’t go swimming because the chlorinated pool water dries skin and irritates eczema so badly.’

‘There are other, gentler ways of disinfecting swimming pools - such as ozone filtration, which involves pumping oxygen, in the form of ozone gas, through the water and then filtering it.’
The problem, in fact, is not chlorine itself, but the chemical by-products - chloramines - that occur when chlorine combines with nitrogen in the dirt and detritus found in swimming pools, such as skin particles, sweat, urine, bacteria and body oils. 

Dr Wright adds: ‘It’s these toxic by-products that give off that tell-tale “bleach” smell we associate with swimming pools and cause problems.’

The stronger the smell, the more unhealthy the pool is likely to be. Have a shower before swimming to remove any make up, dry skin flakes, hair products and body lotion. These residues can also react with the chlorine to create chloramine irritants.

An occasional swim is unlikely to do much harm, unless you are particularly sensitive to chlorine. But experts suggest anyone who swims once a week or more should be wary.

Children are thought to be particularly at risk to chlorine-related ailments because they tend to spend longer in the pool than adults and are more likely to ingest water

In 2008, a Belgian study, published in the European Respiratory Journal, suggested that children who swam once a week in chlorinated pools were five times more likely to be asthmatic than those who’d never swum in a pool.

Another more recent study of 50 elite athletes, published in the British Journal of Sports Medicine, showed that almost all the swimmers they examined had inflamed lung tissue, with those who spent the most time in chlorinated pools showing most changes.

Children are thought to be particularly at risk because they tend to spend longer in the pool than adults and are more likely to ingest water.

‘Although more research is needed, it is thought that chlorine and it’s by-products, when inhaled or swallowed, can attack the cellular barriers in the lungs that protect them from allergens,’ says Dr Wright. This is why some experts believe persistent exposure to chemicals in cleaning products such as chlorine may also be responsible for the increase in allergies in the past 50 years. 

Colour wash: Dyed blonde hair can take on a grassy hue after a dip in a chlorinated pool

Poorly maintained chlorinated swimming pools, have also been found to be responsible for ‘rapid and excessive’ dental erosion in keen swimmers.

Dr Leila Jahangiri, a clinical associate professor at the New York College of Dentistry, recently issued a warning to people with swimming pools in their homes to keep a close eye on the chlorine and pH levels.

‘If the chlorine levels are not properly maintained, the pool water can become overly acidic,’ says Dr Jahangiri. ‘Regular contact with this acidic water as you swim can cause serious enamel erosion.’

‘Some people’s eyes are more sensitive to chlorine than others, but as a general rule, if the water in a swimming pool has a higher chlorine level, of five parts per million or more, it will act as an irritant,’ says Dr Seetohul.

Conversely, if levels of chlorine are too low, bacteria can linger. Then when the cornea is submerged, washing away its protective tear film, eyes are left vulnerable to the bugs. This can cause conjunctivitis.

Yes, dyed blonde hair can take on a grassy hue after a dip in a chlorinated pool, but the colour doesn’t come from the chlorine itself, says Dr Seetohul. 

‘It’s the copper in hair colourings, reacting with the chlorine, that turns hair green.’

If your hair starts to look a little green after a couple of swims - try neutralising the chlorine with a vitamin C spray, or rub a tablespoon of tomato paste through wet, freshly washed hair. Leave for five minutes, then rinse. 

The red pigment should help neutralise the green colour.

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