To investigate the prevalence of pneumoconiosis in Portland cement wor
kers, a controlled cross-sectional survey wets conducted. Chest radiog
raphs of approximately 2640 Portland cement workers showed prevalence
rates of about 1% for rounded and for irregular small opacities and ab
out 2% for pleural abnormalities. After age and smoking adjustment, th
e overall prevalences were still significantly elevated over controls,
but when examined separately by smoking status, the significant incre
ases were confined to smokers. Although statistically significant, the
prevalences were only elevated about 1% in cement workers, compared W
ith controls. A statistically significant relationship with exposure w
as found for pleural abnormalities but not for rounded or irregular sm
all opacities. Thus a weak association. exists between pulmonary radio
graphic abnormalities and employment in US Portland cement plants, and
there appears to be a dose-response relationship, between exposure an
d pleural abnormalities.