Hidden dangers in busy pools…How chemicals used to keep water clean carry health risks

  • US scientists find harmful compounds can be produced in the pool
  • Sweat, urine and sun-tan lotion can react with chlorine used to clean water
  • Studies show the by-products can cause damage to human cells
  • Swimmers advised to take showers before entering the water

Swimming 30 lengths regularly or relaxing in the gym hot tub might seem like healthy choices. But a new study warns that these apparently harmless activities may have a hidden risk.

US scientists have discovered the existence of harmful compounds in hot tubs and swimming pools which occur when sun-tan lotion, sweat – and urine – react with chlorine and other chemicals used to keep pool water clean.

Previous studies have shown that disinfection by-products can cause genetic damage to cells in laboratory settings.

Other studies have looked at associations between pool water and bladder cancer and respiratory conditions such as asthma.

In the new report from the American Chemical Society, scientists tested water from public and private hot tubs and pools, from tap to basin, after both normal and intense use.

They identified more than 100 disinfection by-products in the water and tested extracts of the samples for their potential to cause genetic damage to cells in the lab.

On average, pool and hot-tub samples were respectively 2.4 and 4.1 times more mutagenic (genetically altered) than the original tap water used to fill them. The more frequently the pools were used by bathers, the more mutagenic the water samples became.

The scientists advised that gym and spa managers could reduce the number of disinfection by-products by cleaning and changing the water more frequently.

Swimmers and hot-tub users taking a shower beforehand, and refraining from anti-social habits, would also help reduce the risk, they said.

Dr Jana Witt, Cancer Research UK’s health information officer, said: ‘While this study is interesting, it only looked at how the chemicals that form in water treated with disinfectants affect bacteria.

‘It doesn’t tell us if they affect human health, or how long people would have to be exposed to them to experience any effects.

‘We wouldn’t suggest people avoid swimming pools or spas – in fact, swimming is a great way to keep active, which can reduce the risk of three types of cancer.’