Melanoma is believed to have a lag time of 20 years, but even factoring that in, the epidemic should have shown itself a decade earlier. Some believe that the rise in melanoma incidence correlates with the widespread use of sunscreen. Sunscreens prevent sunburn, which is Nature's warning to get out of the sun. With sunscreen, people can stay out in the sun longer, and they receive an excessive dose of UV-A, which is not blocked by sunscreen. It is UV-A that is thought to cause melanoma.
Some sunlight is beneficial.