Magnetic lung measurements in relation to occupational exposure in asbestos miners and millers of Quebec

Fe₃O₄ particles (ferrimagnetic) are usually attached to asbestos fibers (nonferrimagnetic) in the chrysotile asbestos mining and milling industries; therefore, a magnetic measurement of Fe₃O₄ in the lungs of workers in these industries could help determine the amount of asbestos which has been inhaled and retained in their lungs. As a first assessment of this method, magnetic measurements were made of Fe₃O₄ in the lungs of 115 miners and millers in Quebec. These measurements at an industrial site were found to be feasible and practical; however, the amount of Fe₃O₄ seen in the lungs of those with welding exposure was large enough to mask the Fe₃O₄ contributed by asbestos, and this subgroup was considered separately. For the remainder (nonwelders), the amount of Fe₃O₄ was plotted against a total dust exposure index (asbestos and other dust) estimated for each worker. Although the correlation between these quantities was not high, it was statistically significant at the 1% level. Because retained asbestos is likely to increase with increasing exposure to total dust, this correlation suggests that a magnetic lung measurement of a chrysotile miner or a miller does reflect, to some extent, the amount of asbestos in his lung. There was considerable scatter in the data, partly due to individual variations in deposition and clearance, to which this method is sensitive. When the data of only the nonsmokers were plotted, the amount of Fe₃O₄ was greater than for the total group of nonwelders. This is consistent with previous findings that less dust is deeply deposited in the lungs of smokers, due to constriction of small airways.