"Labrador lung": an unusual mixed dust pneumoconiosis.

Forty-eight workers involved for various periods from 1962 in mining and milling iron-containing rock in the Carol Lake area of western Labrador were found in late 1974 and early 1975 to have pneumoconiosis. Their annual chest roentgenograms demonstrated irregular nodular densities, and several revealed mild hilar lymphadenopathy or pleural thickening. All 48 workers were asymptomatic and had normal pulmonary function; their average age was 38 years. At work they had been exposed to high levels of dust containing iron, silica and anthophyllite, a type of asbestos. Lung biopsy specimens from 13 of them showed widespread focal fibrosis, large amounts of hemosiderin and silica and many ferruginous bodies; one ferruginous body was identified as having a core of anthophyllite. A granulomatous reaction was seen in two biopsy specimens and typical silicotic nodules were found in two others. The relatively brief exposure, especially in ones case (11 months), and the short latent interval before the development of the pneumoconiosis are reasons for concern for the health of iron ore workers.