Counting alveolar macrophages (AM) from expectorate samples of exposed workers as a test for lung irritation from occupational exposure

Alveolar macrophages (AM) have a natural function in the human body in keeping the lung tissue sterile and in dealing with any foreign material contaminating the airways. AM increase in number when the lungs are exposed to inhaled particles or gases. These investigations have shown that the number of AM changes in relation to the quantity and the type of compounds inhaled, and that this change can be measured by differential counting of the total number of free lung cells, or of AM alone in samples recovered by lung lavage. A method had been developed by which AM are counted in expectorate samples from exposed workers. A primary aluminum reduction plant was chosen, because the kind and degree of chemical pollution of the working atmosphere had already been relatively well investigated.