In recent years, an increasing number of researchers have warned that depltion of the Earth's ozone layer by chlorofluorocarbons allows extra ultraviolet radiation from space to strike our planet, causing a rise in the incidence of skin cancers and precancerous dermatoses worldwide. This motivated us to perform a series of screening for skin cancers on the inhabitants at age 40 and above of the Saku District, Nagano Prefecture, where the intensity of the sun's harmful ultraviolet radiation is thought to be relatively high.
The first screening was carried out from 1993 through 1995. The number of subjects totaled 7, 528-2, 658 men and 4, 870 women-which represents 7.4% of the populace. Of the total, 67 people had a histopathological examination. The result revealed that there were four cases of malignancy and 45 cases of precancerous dermatosis. The malignant cases were made up of one case of malignant melanoma and three cases of basal-cell carcinoma, while the precancerous cases were one case of Bowen's disease and 44 cases of solar keratosis.
The follow-up examination was conducted in 1996 on 93 subjects (40.6%) of the 229 examiness who had been found to need to be watched in the first screening. Biopsy was indicated in five subjects. Treatment was suggested to 11 subjects. A visit to the department of dermatology at Sake Central Hospital was recommended to 10 people. Further observation was needed in 24 cases.
The screening project for skin cancers under a long-range plan would raise awareness of the diseases among the people and contribute to the early detection, treatment and prevention of various forms of skin cancer. It could also serve the purpose of protecting the environment from deterioration on n global srnle.