Cryptic pulmonary lesions in workers occupationally exposed to dust containing silica

Fibrotic lesions associated with deposits of crystalline silica were found postmortem in the lungs of 15 granite workers who lacked radiological evidence of pneumoconiosis. All members of this occupational group had been employed in the granite quarrying and monument industry of Vermont since ambient air-dust standards were introduced in 1937. Although particulate silica was not revealed in the lesions by traditional polarization light microscopy, it was identified by scanning electron microscopy in conjunction with backscatter imaging and x-ray spectrometry. The etiologic basis of the fibrotic pulmonary disease would not have been diagnosed without the aid of these modern analytical tools. Exposure to silica-containing dust can result in cryptic pulmonary disease that is not detectable radiologically. In these retrospective postmortem studies, it was not possible to define the distribution of the lesions in the lungs.