Changing patterns in incidence of non-melanoma skin cancer.

Surveillance of skin cancer is important to evaluate prevention programmes and to monitor the effect of stratospheric ozone depletion. Evidence available from a limited number of studies suggests that incidence rates of basal cell carcinoma and squamous cell carcinoma have been increasing for at least two decades. In white populations in the United States, Canada and Australia, average annual increases of 3%-7% for basal cell carcinoma and 2%-8% for squamous cell carcinoma have been observed, though variation in ascertainment levels or changes in treatment practices during the study periods may have contributed to these apparent changes in incidence patterns.