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Sunday, July 4, 2010

Does Sunscreen Really Work?

This weekend I’m spending the Fourth at the beach with my family in South Carolina. Today, after spending 20 minutes slathering sunscreen on my somewhat disgruntled children and myself, I gathered up my straw hat, sunglasses, book, two kites, a couple of chairs, and several more tubes of sunscreen, making our daily exodus to the beach. Things have changed a lot since I was a teenager, back in the eighties--the Hawaiian Tropic Coconut Oil is nowhere to be found, despite my Brazilian heritage and cultural proclivity toward small bathing suits and a good tan.

But just how much protection do these bottles of SPF 30+ sunscreen actually provide us?

Skin cancer is the most common form of cancer diagnosed in the United States. There are three major types: basal cell, squamous cell and melanoma. Of those, basal cell and squamous cell are most common, accounting for about 3.5 million cases in the United States per year. Although, these types typically do not metastasize, they can be quite disfiguring, particularly after resection when they occur on the face. On a population level, melanoma is the most dangerous type of skin cancer, accounting for approximately eight thousand of the ten thousand deaths per year attributed to skin cancer.

This year the Environmental Working Group and Senator Charles Schumer brought to light concerns that have arisen about a form of vitamin A, retinyl palmitate, found in 41 percent of sunscreens. This compound has been found to accelerate the development of skin cancer in laboratory animals. Schumer and EWA were critical of the FDA for its slowness to address the existing studies and for its failure to regulate the safety and efficacy of sunscreens. Although there is significant evidence that sun exposure is a strong risk factor for skin cancer, there is relatively scant evidence that sunscreen use mitigates this risk. Randomized controlled trials have demonstrated a decreased incidence of actinic keratosis (a skin cancer precursor) and squamous cell cancer in sunscreen users. In these same trials, basal cell skin cancer was not similarly impacted. Moreover, no studies have confirmed a protective relationship with respect to melanoma incidence, and in fact several studies have shown increased risk in sunscreen users, perhaps because high SPF sunscreen users spend more time in the sun than those who user lower SPF’s.

Other factors reduce the effectiveness of sunscreen, including the failure of people to apply it appropriately, in adequate quantity, and to reapply after sweating, swimming or toweling off. A whole host of high SPF sunscreens are available, but labels touting high SPF content may be inaccurate. In addition, beyond SPF 15 the difference amongst sunscreens is minimal--SPF 15 filters 93% of UVB light, compared with SPF 30, which filters 98%. The SPF refers to the UVB blocking property. Sunscreen components that block UVA include zinc oxide, titanium dioxide and avobenzone and Mexoryl SX.

What can you do to avoid skin cancer risk?

• Avoid the sun between the hours of 10 AM and 4 PM.
• Use protective clothing when outdoors, including wide brimmed hats and shirts. Tighter weaves and darker colors do a better job, and UV protective fabric is also effective.
• Use sunscreen of SPF 30 or greater that blocks both UVA and UVB light, applied in adequate quantity, and reapplied frequently
• Avoid sunlamps and tanning equipment.
• Practice skin self-examination.

1 comment:

  1. I recently heard or read about a potential danger in the use of some sunscreens. Limiting high exposure to the sun seems the best way to avoid its dangers.

    That said, do we have evidence of a higher number of skin cancers in people whose job force them to stay under the sun (farmers, outdoor workers...)

    thanks for your article, Juliet and say hello to the whole gang.