Chlorine in the bathwater is linked to cancer
jan 2007
Low levels of chlorine in tap water used for bathing can almost double the risk
of bladder cancer, a study claims.
Scientists found chemical by-products from mains water containing the
disinfectant can be absorbed through the skin in the bath or shower and
accumulate in the bladder.
Swimming in public pools can also present a risk because chlorine levels are
much higher.
The risk is caused by chemical by-products called THMs which are produced when
chlorine is added to water.
Researchers found that those living in areas with high-chlorine content water,
who bathed in it regularly, were 83 per cent more likely to get a tumour than
those in low-chlorine areas.
Those who drank high-chlorine tap water were 35 per cent more likely to get
bladder cancer.
Regular swimming in pools increased the risk by 57 per cent.
Absorbing chlorine through the skin is thought to be more dangerous because it
bypasses the liver, which filters out many harmful chemicals when water is
swallowed.
Chlorine has been used to disinfect Britain's household water supplies for 100
years.
Regulations say THMs must not exceed 100 micrograms per litre. The Spanish
study, reported in the American Journal of Epidemiology, suggests only 50
micrograms - present in some areas of the UK - is required to increase the
tumour risk.
Researchers at the Municipal Institute of Medical Research in Barcelona compared
1,200 men and women with bladder cancer to a healthy group, questioning each
about their exposure to chlorine.
Lead researcher Dr Cristina Villenueva said: "Inhaling or absorbing THMs may
lead to a higher concentration in target organs, such as the kidney, bladder or
colon.
"Experimental studies have shown a significant uptake of THMs when showering,
bathing or swimming in pools. If confirmed, this has significant public health
implications."
Bladder cancer, of which the single biggest cause is smoking, kills nearly 5,000
in the UK every year.
A spokesman for the National Pure Water Association said: "There is now a lot of
research on chlorine in drinking water that shows we should be concerned.
"Water firms use the cheapest products possible to disinfect water, such as
chlorine. Yet there are safer methods used by other countries, such as ozone gas
or ultraviolet light."
In 1999, a government committee decided against removing chlorine from water,
despite evidence of a slight increase in the risk of bladder cancer.
A spokesman for the Drinking Water Inspectorate said the amount of THMs in water
ranged across the country from one microgram per litre up to 50 - but no higher.
"This report hasn't changed the World Health Organisation"s view that the
evidence is not sufficient to support chlorine being the cause of bladder
cancer," she added.
Ed Yong, campaigns officer at Cancer Research UK, said: "This is one of a number
of studies suggesting this link, but larger studies are needed before we can say
for sure if high exposure to chlorinated water can cause bladder cancer.
"In the meantime, people shouldn't be worried every time they step into the
bath, shower or swimming pool. Any potential cancer risks must be weighed
against the risk of the many infectious diseases caused by improperly
disinfected water."
Three years ago chlorine in water was linked to a risk of birth defects or
miscarriages.
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