Healthy living

UVA rays linked to deadly skin cancer

UVA radiation and melanoma Damages skin cell DNA

UVA radiation can damage the genetic material in melanocyte skin cells, causing mutations which can lead to melanoma, scientists have discovered.

Malignant melanoma is the potentially life threatening type of skin cancer. Each year in the UK more than 10,000 men and women are diagnosed with the disease, and around 2,000 people die of it.

The biggest risk factor for melanoma is too much exposure to ulraviolet (UV) radiation in sunlight or from sunbeds.

It's generally thought that the more penetrating ultraviolet B (UVB) rays are behind the DNA damage which can lead to melanoma, but now scientists think that UVA rays also play a part.

In the study, researchers exposed lightly and darkly pigmented melanocyte skin cells to UVA radiation and assessed the damage the DNA. They also monitored how well the cells were able to repair the damaged DNA.

DNA damage was detected in all melanocyte skin cells exposed to UVA radiation. The cells were also unable to repair the DNA damage which occurred. However, when normal skin cells were exposed to the UVA radiation, no DNA damage was seen.

"For the first time, UVA rays have been shown to cause significant damage to the DNA of human melanocyte skin cells," said Dr Moon-shong Tang from the New York School of Medicine, who led the study.

He also explained why melanoma can develop on areas of the body which have never been exposed to the sun.

"..Melanocytes have a reduced capacity to repair DNA damage from UVA radiation, they mutate more frequently, potentially leading to the development of melanoma."

Sunscreens

The Sunscreen Protection Factor (SPF) on sunscreens indicates how long you can stay in the sun without burning compared to not wearing any sunscreen at all. But it only applies to UVB radiation.

The star rating on sunscreens indicates the level of protection it gives against UVA radiation *compared *with UVB. The higher the number of stars the greater the protection.

However, if you choose a sunscreen with a low SPF, it may still have a high star rating because it gives the same level of protection against UVA as UVB - both low!

So choose a sunscreen with a high SPF (15 or more), which also has a high star rating - five is the highest. Apply 15-10 minutes before going outside, reapply every two hours and after swimming or sweating.

The findings are published online and will appear in the Proceedings of the National Academy of Sciences on July 6, 2010.

This article was published on Fri 2 July 2010



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