In Japan the extrinsic asthmatic bronchitis and the interstitial lung disease were legally recognized as occupational bronchopulmonary diseases due to the hard metal dust for the first time in February, 1981. But their pathogeneses are still unknown. In 1981, we examined clinically 247 workers employed in a hard metal factory (14 powder workers, 20 press operators, 40 shapers, 29 sintering workers, 119 grinders, and 25 others). The clinical evaluation was based on respiratory questionnaires, physical examinations, chest X-ray films and pulmonary function tests (VC, FEV, DLCO). These thorough investigations for all workers exposed to hard metal dust was thought to be the first trial conducted in this country. As a result, 27 workers with chronic bronchitis were found, but the relation between the chronic bronchitis and the exposure to the hard metal dust could not be confirmed. Three workers complained of asthmatic attacks without any relation to such dusty work. Pulmonary function tests revealed seven workers with restrictive ventilatory impairment, two with obstructive impairment and one with mixed impairment. Out of the seven, one with restrictive disorder revealed micronodulations on the chest X-ray film, and four of them had old tuberculous scars and/or pleural adhesions. Two of them had neither respiratory symptoms nor abnormal chest X-ray findings. Two with obstructive impairment and one with mixed ventilatory impairment complained of persistent coughs and sputa and/or asthmatic attacks. Chest roentgenograms taken from three workers engaged in shaping, press operation and powder handing, respectively, showed diffuse micronodulations mainly in bilateral middle lung fields. The findings were nearly the same as those in chest X-ray films taken three years ago. Two of them had been exposed exclusively to the hard metal dust and had had the longest exposure history among the workers in this factory. These radiological changes may represent nuisance particle shadows which were due to accumulations of hard metal dust predominantly of tungsten carbide. Serial chest roentgenograms of one worker, who had been employed as a press operator for 5 years and then as a shaper for 4 years, revealed progressive reticulonodular opacities with confluent tendency in upper and middle zones bilaterally. Previously he had been exposed to iron and sand dusts for only one year. Lung specimens obtained by means of transbronchial lung biopsy showed peribronchiolar and perivascular fibrosis with black deposited particles and peribronchiolar cellular aggregation. Particles in speciments examined by X-ray microanalysis were identified as tungsten. This case is highly suspected to be related to hard metal dust inhalation and to his individual susceptibility. Japan Association of industrial Health has not yet proposed recommendations to the industry as to the threshold limit values for cobalt, tungsten etc. Therefore, all the hard metal industries have to undergo thorough medical and environmental evaluations by themselves to take preventive and precautionary actions without delay.
