"Sunscreen is the snake oil of the 21st-century,” said Samuel Rudman, a lawyer at Lerach Coughlin, announcing that the firm was filing a class-action lawsuit in the Los Angeles Superior Court against five leading sunscreen manufacturers. Rudman’s allegation – that the companies behind household names such as Hawaiian Tropic and Neutrogena were misleading consumers about the cancer-protective powers of their products – was based on the evidence of consumers who had worn sunscreen, but still contracted skin cancer. It sent tremors across the sun-kissed beaches of the Californian coastline.

The outcome of this case is still pending, but it’s not just our sun-spoilt friends on Santa Monica beach who should be sweating. With Britons set to bask in another scorching summer, even the more sun-savvy tanners, who slather on a high SPF, may not be as protected as they think. Why? Because the SPF rating on the average sunscreen relates only to UVB rays that cause sunburn and are associated with the development of skin cancer, not the wrinkle-causing UVA rays, which, until recently, were thought to be relatively harmless.

However, it is now believed that UVA rays penetrate the skin, distorting the structure of cells, elastin and collagen. The cumulative damage is irreversible and can go undetected for years. A growing number of scientists think that prolonged exposure to UVA rays greatly contributes to melanoma, the deadliest skin cancer. Brian Diffey, professor of photobiology at Newcastle University, warns: “By 2035, there could be 21,000 new cases of melanoma a year in the UK, as those who sunburnt badly in the 1980s and 1990s suffer the long-term effects.” Yet millions of people are oblivious to this time bomb and will still spend hours in the sun, striving for a perfect bronze glow.

Dr Des Fernandes, a plastic surgeon and founder of Environ skincare, claims that 60% of UVA rays penetrate even the best sunblock. If this is the case, why are we no clearer on what UVA protection sunscreens offer? The problem is that the men in white coats and beauty corporations have failed to establish a universal, SPF-type rating system for UVA, because they have yet to agree on a method of measuring the effectiveness of UVA-blocking products. So, while protection against UVB rays is indicated with a number, such as SPF 15, UVA protection is denoted in many different ways, including broad-spectrum, broad-band protection, numbers and stars.

Boots has been commended for attempting to bring clarity to the issue by introducing the star-rating system for UVA protection as early as 1991. However, Cancer Research UK describes it as “vague” and “confusing” in the way it measures UVA protection only in relation to UVB: for example, a high-SPF sunscreen with two stars may give better overall protection than a low SPF with three stars. And other critics point out that the star system does not account for photostability (the ability of the product to remain on the skin during sun exposure).

Faced with the challenge of creating a standardised guide to UVA protection, beauty companies argue that as long as there is no universal method to objectively measure the long-term effects of UVA on the skin, such a system seems a long way off. Animal testing has proved inconclusive: tests on mice suggest that UVB rays cause melanoma; tests on fish found UVA rays incubated the disease. As Chris Flower of the Cosmetic, Toiletry and Perfumery Association (CTPA), a group that promotes the interests of companies such as Estée Lauder, Johnson & Johnson and Procter & Gamble, says: “It takes time to prove a scientific theory. If UVA takes years to lead to premature ageing, how are you going to test the product’s benefit if it won’t show for years?”

Various companies claim to have discovered their own “ground-breaking” products to protect against UVA rays. L’Oréal says its patented filters, Mexoryl SX and Mexoryl XL, contained in brands such as Ambre Solaire, form the most effective UVA filtering system available. Other companies suggest that mineral filters – the zinc oxide and titanium dioxide contained in Z01 Body Protection Lotion, for example – provide the best broad-band UVA and UVB protection. Fernandes believes his Environ range of antioxidant-rich products will fight the free radicals caused by sun exposure, and that this is crucial to preventing skin cancer. The New York dermatologist Dr Dennis Gross, the man behind MD Skincare, says the answer lies in chelators, a group of metal-binding molecules. He believes chelator-rich products counteract iron, an aggressive free radical found on the skin that generates other free radicals, which, in turn, are a trigger for skin cancer.

However, many scientists say that nobody can lay claim to the ultimate UVA protection. “Skincare companies are not the founts of all knowledge. Their primary objective is to sell products,” says Diffey. “There are active ingredients that can provide equal, if not broader, UVA screening than Mexoryl. The protection provided by antioxidants is small; as for chelators, reducing free-radical damage can help, but shade and clothing can provide you with 10 times the protection of these ingredients.” His only advice to people wanting to protect themselves from harmful rays is: “Stay indoors with the curtains closed.” But, as we head into the holiday season, that is not going to happen.

However, there is hope on the horizon. The European Cosmetic Toiletry and Perfumery Association (Colipa) has developed a test-tube (in vitro) method of assessing UVA protection that meets European commission recommendations. This could form the basis for a universal system, but initially it would apply only to Europe. The CTPA has indicated that it plans to adopt Colipa’s standardised system, but due to product cycles, sunscreens featuring the Colipa logo will not appear until next year.

Seemingly, sun-worshippers will have to remain in the shade for at least one more summer.

CREAMS WITH UVA PROTECTION

Environ RAD Antioxidant Sunscreen, £15.95; 020 8450 2020

Garnier Ambre Solaire Moisturising Protection Milk SPF20, £10.49

MD Skincare All-in-one Tinted Moisturizer Sunscreen SPF15, £32, from Space NK; 020 8740 2085

ZO1 Body Protection Lotion, £14.50; 01753 759746

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