Does a sunscreen with a sun protection factor of 30 protect offer twice as much protection as a product with an SPF of 15? According to the American Cancer Society, about 5.4 million basal and squamous cell skin cancers are diagnosed each year. Melanoma, the deadliest variety of skin cancer, will account for about 76,380 cases of cancer in 2016. [...] another study, from the Johns Hopkins University School of Medicine, gives further evidence many people aren’t using sunscreen correctly, including some who are otherwise vigilant about sun protection. In the study, published in the Journal of the American Academy of Dermatology, researchers looked at the sun habits of 758 people with a history of nonmelanoma skin cancer, and 34,161 control subjects. Ibrahim said people should wear protective clothing, such as a hat or clothes with sun protection built in, when going out in sunny weather.