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Frequently Asked Questions (FAQ)

co-ordinated by

Janet F. Bornman and Jan C. van der Leun

Health Effects

1) How do we balance the good and bad effects of sunlight on human health?

In general, moderate exposure to sunlight in the course of everyday life is not detrimental. This basic exposure evidently allows us to function normally, and it proves to be sufficient to maintain an adequate level of vitamin D (in combination with our dietary intake). While sunlight is important for physical health it also causes various adverse health effects such as skin cancer, ageing of the skin, eye disorders and suppression of the immune system. It is clear that excessive UV exposure should be avoided to minimise the risk of development of such disorders.

2) How strong is the evidence that UV-B radiation causes skin cancer in humans?

The evidence is strong. The earliest experimental evidence that UV-B radiation causes skin cancer was acquired with animals; in humans there was a clear association between sun exposure and skin cancer, but that did not point specifically to UV-B. In recent years the advancement of molecular biology has provided us with analyses that produce direct evidence that genetic alterations found in human skin carcinomas are indeed caused by UV-B radiation.

3) Should one have all moles removed to decrease the risk of skin cancer?

No, there is no evidence to suggest that removing all of the moles would reduce the risk of skin cancer. However, it is important to be alert to atypical moles, especially those exhibiting changes in appearance (in colour or at the edges), and to screen those individuals that are known to run a high risk, either from a family history of melanoma mortality or of atypical moles.

4) Do sunglasses protect against cataracts?

Sunglasses that markedly reduce the UV-exposure of the eyes will reduce UV damage, such as cataracts. The best protection is achieved by a combination of UV-absorbing glasses and a shielding against light coming into the eyes from the sides. However, some sunglasses may not effectively block UV radiation and eye damage may occur.

Duration of Exposure to UV-B Radiation

5) Is the UV amount one receives as a child important even in later years?

Yes. Children should not be overexposed to UV radiation: sunbathing should be strongly discouraged. UV exposure, and especially sunburns, in early life can substantially increase the skin cancer risk later in life (especially the risk of basal cell carcinoma and melanoma).

Even if the risk is related to total accumulated exposure, as appears to be the case for a part of the non-melanocytic skin cancers (SCC), exposures early in life still may carry a greater risk. There is a long lag time, typically of several decades, between exposure and the development of a tumour. Therefore, early exposures have a greater probability in resulting in a tumour.

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