hygiene study in a factory . metal workers : an occupational Respiratory diseases in hard


A hygiene study of a hard metal factory was conducted from 1981 to 1984. All workers exposed to hard metal were medically examined and their exposure to cobalt measured. Eighteen employees had occupational asthma related to exposure to hard metal, a prevalence rate of 5-6%. Nine had a positive bronchial provocation test to cobalt and reactions of the immediate, late, or dual type were elicited. Exposure measurements suggest that asthma may be caused by cobalt at a mean time weighted average concentration below 0.05 mg/m3. Only two of the nine individuals with cobalt asthma had a positive patch test to cobalt. Chest radiographs of three workers showed diffuse shadows of category 1 or over. X ray microanalysis of lung biopsy specimens from two of these three workers showed the presence of tungsten, titanium, cobalt, nickel, and some minerals. One of the two was diagnosed as having pneumoconiosis due to exposure to silica in a steel industry and the other was suspected of having pulmonary fibrosis caused by dust generated from the carborundum wheels used to grind hard metal. There were no cases with interstitial pneumonitis in the factory. Hard metal is 90-95% as hard as diamond. It is used when strength, rigidity, and resistance to heat and wear are needed, such as for the cutting edges of tools, rock drills, and dies, etc. In Japan research into producing hard metal began in 1928 and hard metal was first on sale in 1931. In 1956 Japan produced only 100 tons of hard metal but in 1978, 1100 tons were produced. Today, Japan is the fourth largest producer of hard metal in the world. There are said to be more than 30 corporations manufacturing hard metal and more than several thousand people are engaged in producing it. To date few cases of respiratory disorders related to hard metal have been reported in Japan and only one cross sectional field study has been conducted in a hard metal factory. These may be briefly summarised: Ohi found 11 of 38 shapers to have micronodulations in chest x ray examinations in a cross sectional study.' Shirasaki2 and Tanizima (personal communication) reported two cases of pulmonary fibrosis in a large hard metal company, one of whom died of respiratory failure. Tanizima also observed 27 workers developing asthma related to exposure to hard metal between 1960 and 1976. Three cases with non-specific interstitial pneumonitis3-5 and one case …


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