Serum Angiotensin-converting Enzyme Is Elevated in Association with Underground Coal Mining

Serum angiotensin-converting enzyme activity (SACE) and lysozyme activity were measured in a group of 40 underground coal miners and two control groups, 20 subjects with sarcoidosis and 15 normal non-dust-exposed volunteers. The miners were grouped first according to whether they had recent exposure (still actively mining or retired three years or less prior to measurement) or temporally more distant exposure (retired more than three years prior to measurement). Secondly, they were grouped as to whether or not they had coal workers' pneumoconiosis (CWP). The subjects with sarcoidosis were grouped according to disease activity. As expected, the subjects with active sarcoidosis had elevated SACE activity compared with normal subjects. The coal miners as a group did not have elevation of their SACE activity. However, the coal miners with recent exposure had elevated SACE activity (57.1±3.9 U/ml) compared with normal controls (43.8±1.5 U/ml, p=0.007). The SACE activity in miners without recent exposure was not elevated (39.8±1.3 U/ml) compared with the normal controls. No increase in SACE activity was found when the miners were grouped according to the presence or absence of CWP. In contrast, the miners' serum lysozyme activity was not elevated. Since alveolar macrophages are a potential source of SACE, elevation of SACE activity in underground coal miners may reflect alveolar macrophage activation caused by increased pulmonary mixed coal mine dust burden. Furthermore, since both SACE and serum lysozyme are elevated in association with silicosis, these findings may confirm that the macrophage responses to inhaled silica and coal dust differ.