Fibre type and burden in parenchymal tissues of workers occupationally exposed to asbestos in the United States.

Lung tissues obtained from 53 asbestos-exposed workers, and one person exposed in a domestic setting, were studied. Amosite is the most prevalent fibre, occurring in 74% of the specimens. Amosite is always found in the lungs of insulation workers whereas chrysotile is found in only 50% of this population. Crocidolite has been detected in 24% of the lungs examined, but this increases to 40% in workers with shipyard histories. Exposure to chrysotile is widespread; the fibre has been observed in 61% of the tissues studied. Chrysotile occurs as the lone fibre in about 22% of the tissues examined, but tremolite is present in one-third of these. Fibre consumption data cannot be used as indices of exposure in the workplace; amphibole exposure appears to be product- and job-category-related. The assessment of risk to asbestos disease in the general population of the United States, exposed to chrysotile, should be based on appropriate chrysotile-exposed cohorts.