Global warming cancer warning

Global warming could lead to higher rates of skin cancer by amplifying the harmful effects of the sun's rays, scientists said.

New evidence suggests that the same amount of sunshine becomes more likely to trigger cancer as temperature rises.

The findings imply that a 2-4% increase in average summer temperatures could produce "substantial increases" in numbers of new skin cancers, say the researchers.

Scientists from the Netherlands and Argentina analysed data from two surveys of non-malignant skin cancer in the US.

The incidence of cancer in the 10 regions studied correlated strongly not only with local levels of sunlight, but also with average daily maximum temperature in summer.

For cases of one type of skin cancer called squamous cell carcinoma, incidence increased by 5.5% per degree centigrade rise in temperature. The incidence of another type, basal cell carcinoma, rose by 2.9% per degree centigrade increase.

The findings tied in with previous research on mice which showed that increasing room temperature enhanced the induction of cancer by a given level of ultraviolet (UV) radiation. Effective UV dose in the mouse experiments increased by 3-7% for every degree centigrade of extra warmth.

The new research led by Dr Jan van der Leun, from the energy consultants Ecofys Netherlands in Utrecht, appears in the Royal Society of Chemistry journal Photochemical & Photobiological Sciences.

Ambient UV radiation only explained about 80% of the variation in skin cancer incidence, the scientists said. Other factors included genetic background and sun-seeking behaviour - and now, it appeared, temperature.

The researchers wrote: "Mainly owing to the substantial summer temperature differences between the West coast and other parts of the USA with comparable ambient UV loads, we found evidence that some of the remaining variance in incidence may be attributed to temperature.. These figures would imply, for instance, that with a long term increase of summer temperatures by 2-4% we could end up with substantial increases in incidence of skin carcinomas, which have already risen to very high numbers over the last century in white Caucasians."