Lucy Siegle: Slip and slap - but think twice about slopping

I used to think worrying about sunscreens was the beach equivalent of angsting about using a microwave: the latter's energy-saving credentials and a lack of evidence of harm overrides doubt for me. And with sunscreen I reasoned the protection it affords outweighs any niggling doubts about its ingredients.

But then a little light holiday reading began to erode my confidence.

It turns out that a 2008 study by Italian scientists found that UV filters in sunscreens cause coral bleaching. According to researchers, 10,000 tonnes of UV filters are produced every year, about 10 per cent of which are used by the 78 million tourists visiting sensitive coral areas.

As a 20-minute slathered-up dip in the sea is enough to wash off 25 per cent of the ingredients into the water, 4000 to 6000 tonnes of UV sunscreen are released annually into the sea, affecting 10 per cent of the world's coral reefs. Some resorts now specify "no sunscreen".

Sunscreens increasingly contain nanoparticles, smaller than one one-thousandth the diameter of a human hair. Often this simply enables a sunscreen with a sun protection factor (SPF) to dry clear and disappear into the skin rather than forming a white paste that takes all day to rub in. But for something so tiny, these nanoparticles cause massive debate, the main charge being that their application has outrun regulation.

Alongside unease about parabens and other chemicals common in personal care products, 2001 research by Swiss toxicologist Margaret Schlumpf tested six UV-screening chemicals, including 4-MBC.

When it was mixed with olive oil and applied to rat skin, it doubled the rate of uterine growth well before puberty, which led to claims that "gender-bending chemicals that mimic the effect of oestrogen are common in sunscreens".

Enough, you might think, to drive sunseekers into the arms of "natural" sunscreens. Except that a couple of the originals have disappeared from sale, apparently unable to provide sufficient SPF without help from man-made chemicals. But there are still some strong alternative sunscreens that are biodegradable and possibly old-fashioned, in the sense that they rely on a physical barrier, like zinc oxide.

The current issue of Ethical Consumer (www.ethicalconsumer.org) contains an in-depth review. And yes, they do work - although some represent a compromise. You might consider a parasol, or large-brimmed hat.

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