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Sun exposure and sunscreens

 

Over exposure to the sun with UVA, (ultraviolet light, wavelength group A) causes skin aging and skin cancer and UVB causes burning and more skin cancer. Whilst the sun has its benefits (i.e. vitamin D discussed later), it is important to control exposure, especially with rising skin cancer rates in NZ. Experts say it is prudent to seek shade and go to the beach in the morning or late afternoon. Just how much exposure we need is not clear or well studied. Definitive guidelines are difficult due to variation in skin colour, seasonal UV ratings and location on earth, which affects the angle of the sun and the intensity of exposure and not all sunglasses protect eyes from ultraviolet light. 

The focus is to avoid sunburn, as this increases the risk of skin cancer. Consider broad brimmed hats instead of caps that give little protection, but remember that air scatters UV light, so you can still burn under shade. SPF (acronym for sun protection factor) gives an indication of protection from UVB, but not UVA, which is important, because it reduces the body’s ability to kill skin cancers. An SPF of 30 means it gives an individual protection for 30 times what it normally takes for reddening of the skin (burn time). On a day with a burn time of 10 minutes, a SPF30 product allows for a sun exposure time of 5 hours (30 times 10 minutes) assuming it is used according to manufacturer’s instructions and not sweated or washed off. Reapplying does not extend the exposure time, but replaces any washed or sweated off.

Aim for products with a SPF of 30 or more, but remember going from an SPF 30 to 50 means minimal extra protection. To my knowledge, there are currently no international standards for UVA protection, however look for broad-spectrum protection (UVA and UVB) products and follow storage conditions and expiry dates to ensure efficacy. Zinc and titanium oxide provide a physical broad-spectrum block, but beware of products made with tiny nano-particles that may be absorbed, the significance of which is not yet apparent, as more research is needed. An adult needs about 10ml (2 teaspoonfuls) for the face and arms and 35ml for full body coverage i.e. seven teaspoonfuls! A study of beach volleyball players, found the majority used less than a quarter of the recommended amount.[i] As it is not easy to see areas missed, apply two coats, as you would to paint a house, ideally with a spray or a lotion that spreads easily. Apply sunscreen 15 minutes before going into the sun and reapply every two hours, or according to the manufacturer’s instructions.

Researchers have noted a rise in melanoma incidence, even though more people are using sunscreens, suggesting that chemical ones may not give as good protection as first thought and some patients get melanomas in places not normally exposed to sunlight. Absorbed sunscreens may increase free radicals. Take extra care if you have already had skin cancer. NZ dermatologist, Dr Marius Rademaker, stresses the hazards of UVA tanning lamps, with a recent UK study finding they increase skin cancer by up to 75%.[ii]



[i] ‘What’s really in our….’ www.TV3.co.nz (2011)

[ii] ‘What’s really in our….’ www.TV3.co.nz (2011)