Many people use sunscreens to protect themselves and their children against the most lethal effects of UVR. Unsettlingly, data so far have failed to show that the use of sunscreen protects against melanoma, the deadliest form of skin cancer (see page 851). This and associated controversies have produced responses tanging from deep epidemioiogical curiosity to a recently filed class-action lawsuit against the sunscreen industry83.
Sunscreens are widely used as protection against developing skin cancers. The evidence for protection against melanoma is as yet to be proven. With keratinocyte-derived skin cancers such as squamous-cell carcinoma are , the association between Ultra Violet Radiation and carcinogenesis has been clearly established Correspondingly, sunscreens, when applied correctly, are effective at reducing the incidence of squamous-cell carcinoma and its precursor.
Sunscreens are defined according to ‘sun protection factor’ (SPF), which is measured by calculating the minimal dose of UVR necessary to cause confluent redness at 24 h after exposure on protected skin compared with unprotected skin. At present, the SPF measurement is based mainly on protection against UVB radiation (wavelengths 290-320 nm), although newer sunscreens may also shield UVA radiation (wavelengths 320-400 nm). UVB can cause DNA damage, and there is growing evidence that UVA might also have carcinogenic effects8”. Another question raised is whether sunscreen inhibits vitamin D production. However, there is little evidence to suggest that sunscreen prevents adequate vitamin D production, or that low vitamin D levels are associated with increased melanoma risk.
Nature, vol 445 22nd Feb 2007 p846.
- Martin Eastwood