The Guardian reports:
1. Don't rub in suncream
It turns out we have got it wrong all these years. If you rub suncream into your skin until it vanishes, regardless of what factor it is, you will have reduced its efficacy to zero, and your risk of skin cancer will be undiminished. The correct way to apply it, it transpires, is to slide on a thick buttery layer that remains clearly visible, and leave it there to dry on the surface of your skin. Attractive, eh? Maybe best to cover up or stay out of the sun altogether...
This is an example where journalistic pressures have distorted the actual scientific findings. This bit of reporting comes from a recent report from the The Restoration of Appearance and Function Trust which was also reported by the BBC (who did a better job, but still managed to distort the issue). The scientific paper upon which these findings are reported is,
Haywood R, Warden P, Sanders R, Linge C. Sunscreens inadequately protect against ultraviolet A-induced free radicals in skin: implications for aging and melanoma? J Invest Dermatol 2003;121:862–68. It's three years old so I'm puzzled why only now is this issue being trotted out to the public. Anyway, a closer reading of the paper spells a slightly different picture to the popular accounts.
The findings were that rubbed in sunscreen had minimal protection against UVA induced production of free-radicals. Free radicals are a possible mechanism by which certain types of skin cancers (melanomas) may be induced, though the link is far from clear in humans. The protection against UVB was practically unaffected by rubbing in the sunscreen, it is usually how SPF is determined . UVB has been strongly linked to basal and squamous cell carcinomas, the mechanism is direct DNA damage.
The Guardian report totally misrepresents the reduction in effectiveness of rubbed-in sunscreen, not reducing it to zero as claimed. The BBC report fails to mention that UVB, aside from causing reddening of the skin, is also responsible for skin cancer as well.
Why is this important? I'm not advocating we become blasé about the dangers of sun exposure (I grew up in a country where we're paranoid about skin cancer, not without cause mind you with the highest skin cancer rate in the world, 6 times that of the UK) and it's a risk which can be easily avoided. The issue of science reporting is much greater and extends to the role of the media in presenting science to the public. The public perception of science is greatly skewed by the "spin" journalists and editors place upon science stories. The real issues are not so simple as the media makes them out to be, inviting simplistic responses. The research upon which this latest scare-mongering is based upon seems like perfectly good science, the methods and results are uncontroversial. However, the interpretation and conclusions as translated in the media are unwarranted.
With scientific issues such as anthropogenic climate change, radiological safety, pollution, biodiversity and asteroidal impact threats of great importance, media driven agenda are not beneficial, especially when the scientific bases upon which we need to decide what actions to take are being misreported to the public, who ultimately have the power to shape governmental and corporate action.
It also undermines public trust as well. With the media cherrypicking and presenting contrary views, science is portrayed as unreliable, arbitrary and ineffective, when in fact the picture, though uncertain in parts (the bits the media tend to concentrate on), is in the whole consistent and reliable.
Addendum: I found the latest paper on this result, Rachel Haywood. 2006: Relevance of Sunscreen Application Method, Visible Light and Sunlight Intensity to Free-Radical Protection: A Study of ex vivo Human Skin. Photochemistry and Photobiology: Vol. preprint. It's a pre-print so it hasn't been published yet. This paper basically repeats the results of the aforementioned paper, perhaps over a wider range of exposures and target preparations. The link between UVA/free-radicals and melanoma is still to be firmly established however.