Skin Cancer in a Subtropical Australian Population: Incidence and Lack of Association with Occupation

Abstract

Because it is not possible to monitor skin cancer accurately using routine methods, special surveys have been undertaken in Nambour, a typical subtropical community in Queensland, Australia. Estimates of incidence reported here are based on skin cancers medically treated between 1985 and 1992 and new cases diagnosed by dermatologists in two examination clinics in 1986 and 1992. Among men and women aged 18-69 years in 1986, age-adjusted incidence rates of basal cell carcinoma were 2,074 and 1,579 per 100,000 per year, respectively-the highest incidence rates of a specific cancer ever reported. Squamous cell carcinoma occurred at half the rate of basal cell carcinoma among men and at about one third the rate among women. Although as expected, fair skin, a history of repeated sunburns, and nonmalignant solar skin damage diagnosed by dermatologists were strongly associated with both types of skin cancer, outdoor occupation was not. Significant self-selection was observed among outdoor workers, whereby people with fair or medium complexions and a tendency to sunburn were systematically underrepresented among those in long-term outdoor occupations although they accounted for more than 80 percent of the community study sample. The mitigating effect of this selection bias may partly explain the paradox of the lack of quantitative evidence of a causal link between sun exposure and skin cancer in humans.