Optical determination of coated and uncoated mineral fibers in lungs of subjects without professional exposure.

Coated and uncoated mineral fibers, more than 10 micron long, were counted by light microscopy in digested lung samples from 82 adult subjects without professional exposure. Up to about 150 coated and 12,500 uncoated fibers/g dry weight were found, without any correlation to sex, occupation and smoking habit. An association between counts of more than 1,000 fibers and ages over 50 was observed. The ratio of uncoated to coated fibers was very inconstant. Only the counts of both coated and uncoated fibers seem advisable for an optical evaluation of the possibly pathological mineral fiber burden in the lungs of unexposed persons.