Don’t go swimming while wearing sunscreen – unless you want cancer. 

A compound used in the protective lotions turns toxic when it reacts with chlorine and ultraviolet rays, researchers found. 

Avobenzone is considered the most popular sun-blocker in the world due to its ability to absorb sunlight at different wave lengths – preventing skin damage. 

But Russian scientists suggest the UV-filtering compound forms cancer-causing toxins when exposed to a mixture of sun and chlorinated water.

Aldehydes, phenols and chlorinated acetyl benzenes were created in experiments simulating swimmers wearing sunscreen. 

The latter two are considered extremely toxic and are strongly linked to deadly tumours and infertility, Lomonosov Moscow State University experts say.

While a study earlier this year hinted that aldehydes can raise the risk of cancer as they interfere with the body’s natural repair mechanism. 

The researchers used a scanning technique called chromatomass spectrometry to make their findings, published in Chemosphere. 

This technique, on laboratory cells, allows precise analysis of the most complex mixtures of chemical compounds. 

For the study, they simulated the real situation when a sunscreen, applied on the skin of a swimmer, comes into contact with pool water. 

The breakdown of avobenzone may take place right on the wet human skin, on which a sunscreen is spread. 

Sunscreen containing avobenzone are known to be applied by millions of people all over the world. 

Chemical UV filters like avobenzone absorb ultraviolet light due to the peculiarities of their structures. The substance in itself is safe. 

As well as being common in sunscreen, they are also used in some personal care products, such as makeup, moisturisers and lip balms. 

The researchers are now studying how avobenzone breaks down under conditions of chlorination and bromination of fresh and sea water. 

During chlorination or bromination of sea water the number of the breakdown products of avobenzone will be even wider. 

And if water contains copper salts – which are added into many swimming pools for getting nice light-blue colour – then bromoform is formed in large quantities. 

This substance could provoke dysfunctions of liver and kidneys – along with nervous system disorder, the experts implied. 



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