Prevalence of radiographic appearance of pneumoconiosis in an unexposed blue collar population.

Blue collar employees currently working in environments free from exposure to respiratory hazards were examined with chest radiography and a standard occupational history questionnaire. Workers who had worked for a total of 5 yr or more in previous jobs with possible hazardous respiratory exposures were excluded. Each radiograph was read independently by 3 NIOSH-certified "B" readers. For small opacities, the median profusion was accepted as a summary reading. The 1,422 readable films represented a population of 50.6% males, 49.4% females, 52.5% whites, 44.2% blacks, 47.0% current smokers, and 38.5% nonsmokers. The mean age was 33.8 yr, with a range from 16 to 70 yr. Small opacities of profusion greater than or equal to 1/0 were identified in only 3 (0.21%) of the radiographs--2 with small rounded opacities and 1 with small irregular opacities. Small irregular opacities of profusion category greater than or equal to 0/1 were statistically associated with age, gender, and pack-years of smoking. The results suggest that using the median of 3 independent readings should rarely result in interpretation of chest radiographs as "positive" for pneumoconiosis in active workers who have not had significant dust exposure.