July 3, 2015
Health worries should be the last reason to stay indoors during the summer – exercise and vitamin D are established to prevent cancer!
Risks of solar radiation are not news. “Mad dogs and Englishmen go out in the midday sun,” penned by Noel Coward around 1930, noted that one must avoid UV radiation. The fair skinned are most at risk, so what should we do to minimize risks while having good, healthy fun, or working in the sun?
With thousands packing the world’s sunniest beaches, and skin cancers increasing, Australians famously advised “Slip, Slop, Slap,” that was later boosted with “Seek, Slide” – slip on a shirt, slap on a hat, slop on sunscreen, seek shade, and slide on sunglasses. Edgy, entertaining advertising included footage of a skin graft from the buttock after removal of cancer from the nose (“If you don’t want to wear your bum on your nose, then …”).
Springtime can be the worst for UV radiation, because the protective ozone layer thins during the winter, the sun is high, and reflective snow or water increases your exposure. As well, skin faded over the winter might be at greater risk.
The UV index was developed by Canadian scientists, then adapted and adopted internationally in the 1990s. It is linear, so at twice the UV index you’ll get a sunburn in half the time. A UV index of 10 was set to be the summer solstice mid-day irradiation in Toronto with a clear sky (perhaps a rare event, but you get the idea). Sun protection is recommended above a UV index of 3.
Hats and shirts obviously keep off the sun, but what about sunscreens? They are less reliable than opaque clothing, and research has yet to demonstrate that sunscreens reduce cancer rates or deaths. To be fair, this would be difficult to research. We do know, however, that melanoma risk increases with the number of sunburns early in life, raising the academic question of whether exposure intensity or duration is most important. They are both important, but clearly, don’t let the kids get a sunburn!
Sunscreens are certainly prudent. It is good to know that SPF numbers are not as important as frequent re-application. Sprays can be inhaled and harmful to lungs, so stick to creams. Ingredient names resembling alphabet-soup can spark uncertainties and concerns – some ingredients such as oxybenzone may unintentionally alter biochemistry, by interfering with actions of hormones, while vitamin A (sometimes called retinyl palmitate) might actually promote cancer. Mineral (zinc or titanium oxide) nano-particles can move through skin and might be harmful. The safest varieties are the products with zinc in particle sizes large enough to make you look pale, or the “war paint” type protection. Online resources such as the Environmental Working Group can help you sort out the better from the not-so-great sunscreens.
- SunSmart History. click here
- Environment Canada weather forecasts, including UV index available from here: click here
- Sun protection and the UV index, from Environment Canada here: click here
- Environmental Working Group’s Sunscreen Guide. click here
- Noel Coward – Mad dogs & Englishmen (with lyrics). click here
Prevent Cancer Now is a Canadian national civil society organization including scientists, health professionals and citizens working to stop cancer before it starts, through education and advocacy to eliminate preventable causes of cancer.
For further information please contact:
Meg Sears, PhD
Co-chair and science advisor, Prevent Cancer Now