steel arc welders . determination of lung dust loads in magnetopneumographic Non-invasive

Magnetopneumography was used to measure non-invasively the concentration of the ferrimagnetic fraction of retained welding fume in the thoraces of steel arc welders. This was done by measuring the remanent magnetic fields due to ferrimagnetic particles. The 11 welders studied had concentrations of thoracic ferrimagnetic mineral several orders of magnitude greater than three machinists, 16 former asbestos insulators, and 24 control subjects. These concentrations correlated well with total years welding (p < 0-01) and radiographic evidence of small rounded densities (p < 0 05), but not with smoking history. There was a higher concentration of ferrimagnetic mineral over the hilar regions. Magnetopneumography offers a non-invasive indicator of the accumulation of welding fume in the thorax. Magnetopneumography is a non-invasive technique for detecting the presence and location of magnetic dust particles retained in the thorax.' The randomly orientated magnetic moments of these particles are first aligned by an external magnet and then measured with a sensitive magnetometer adjacent to the chest. Welding fume may contain 25-70% magnetite (FeO Fe2O3), a strongly ferrimagnetic compound.2 By contrast, endogenous organic compounds, including those containing iron, have not been found to have significant ferrimagnetic properties and therefore do not contribute to the remanent magnetic field over the thorax (D E Farrell, personal communication). The detection of ferrimagnetic minerals (FM) in the thorax by their permanent magnetic properties was first reported by Cohen3 4 and subsequently studied by Kalliomaki' and by Kalliomaki et a15-7 and by our group8'10 in welders, foundry workers, asbestos miners, and coal workers. Although the major FM in welding fume, magnetite, is considered non-toxic,11 it serves as a magnetic tracer for the other constituents of the fume. Presented in part at the Annual Scientific Assembly of the American College of Chest Physicians, Houston, November 1979. Partially supported by Contract NCI CA 12376 with the National Cancer Institute. Received 20 October 1980 Accepted 13 November 1980 We performed this study of FM concentrations in steel arc welders to evaluate the potential role of magnetopneumography in monitoring pulmonary accumulation of welding fume.