Assessment of lung particle accumulation in factory workers by magnetic field measurement.
OBJECTIVE
In industrial settings, minute particles of industrial substances lodge in the lungs and accumulate over decades, often leading to pneumoconiosis. Although these particles have been almost impossible to detect with x-rays, especially initially, we still rely upon them for detection of such deposits. As a result, particle accumulation is not detected early enough, and eventually diagnosed pneumoconiosis is typically irreversible. Accordingly, we investigated an alternative detection method that utilizes the magnetic characteristics of the particles after they are excited by an external magnetic field. Using accumulation of magnetic particles as a surrogate marker for total particle accumulation, our goal was to develop a method that can determine particle quantity and distribution in the lungs of individuals in different types of industrial situations. This method would allow us to identify factors that affect particle accumulation and to detect early such accumulations, before the pneumoconiosis stage. The pilot study reported herein represents proof of principle that such a method is feasible.


METHODS
After a magnetic field generated by a strong direct current is applied to particles, they continue to generate a weak magnetic field even after the external field is removed (relaxation). We measured relaxation using an external detector (scanning a flux-gate magnetometer, Helmholtz coil). To field test this method. we studied 150 subjects in various industrial settings. We studied a variety of factory workers, including those involved in welding and cutting for different employment durations. A static magnetic field of 50mT to the chest, and the residual magnetic field distribution were measured by scanning a flux-gate magnetometer in a 2-dimensional region covering the whole chest.


RESULTS
The strength of the magnetic field from the lungs of our subjects generally increased with the length of employment, particularly after 11-20 years. Welders showed higher particle accumulation than the others. Across all types of jobs, and work durations, smokers had lung particle accumulations substantially higher than non-smokers.


CONCLUSIONS
1. In the study reported herein, we describe application of a novel, portable device for measuring the accumulation of magnetizable particles in the lungs of factory workers. These particles are viewed as a surrogate for determining the extent and distribution of total particles in the lung. This is based on the detection of signal emanating from para- and ferromagnetic particles when they relax after an external magnetic field is switched off. 2. Particle accumulation increases proportionally to employment duration in welders, but may be less severe in other types of workers within the same company. 3. Smoking greatly increases the extent of particle accumulation. 4. Additional studies are now necessary to correlate signal with: (a) particle density at various sites, (b) total particle accumulation in the lungs, (c) lung function, and (d) the severity of lung fibrosis and pneumoconiosis. If correlated, the method may be useful in the early detection of particle accumulation and may allow for the assessment of outcomes following interventions for the treatment and prevention of pneumoconiosis.
Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Kanagawa, Tokyo, Japan. muwete@gray.plala.or.jp
Muwete
M
Muluaka
D003952:Diagnostic Imaging / Q000379:methods*; D006801:Humans; D008168:Lung / Q000473:pathology*; D008280:Magnetics; D016273:Occupational Exposure; D010316:Particle Size; D010865:Pilot Projects; D012044:Regression Analysis; D012907:Smoking / Q000009:adverse effects