Mortality among pyrite miners with low-level exposure to radon daughters. Scand J Work Environ Health 14 (1988) 280-285. A cohort mortality study was conducted with regard to a pyrite mine located in central Italy. Exposure to radon ranged from 0.12 to 0.36 working levels (WL) in the work areas; most measurements were around 0.2 WL. The concentration of free silica in the dust was less than 2%. The cohort was determined from company files and included 1,899 subjects. Mortality was studied for the years 1965-1983. The loss to follow-up was less than 2%. The standardized mortality ratio for all causes and all neoplasms was 97 and 107, respectively. That for lung cancer and for nonmalignant respiratory diseases was 131 (95% confidence interval 97-175) and 173 (95% confidence interval 135-231), respectively. It was estimated that the extra cases of lung cancer attributable to radon daughters numbered 13 per 10(6) person-years and working level month in the whole cohort and 21.3 per 10(6) person-years in the subcohort with 10-25 years of exposure.