Hard metal lung disorders: analysis of a group of exposed workers

The experience gained during the last 5 years in the study of 36 male workers exposed to hard metal dusts (10 engaged in mixing, 12 in presintering, three in sintering and 11 in grinding) is presented. The mean age was 33.2 years (S.D., 11.8) and the mean number of years of exposure was 9.4 (S.D., 7.6). All subjects received a physical examination, chest X-rays, pulmonary function test (VC, FEV₁, expiratory flows, RV, DLco, and metacholine bronchial provocation test), skin tests, brochoalveolar lavage (BAL) and determination of trace metals in BAL, blood, uring, pubic hair and toe nails. Two cases of bronchial asthma, six cases of interstitial lung disease and one case with both disorders were identified; eight of these cases presented at BAL signs of alveolitis with different cytologic features. Among the other 27 asymptomatic subjects, two showed an aspecific bronchial hyperreactivity, four showed a reduced DLco, 12 showed an inverted ratio of CD4/CD8 lymphocytes in BAL without signs of alveolitis while one subject presented both an aspecific bronchial reactivity and a reduced DLco. The presence of aspecific bronchial hyperreactivity in asymptomatic subjects might represent a preclinal indicator of a possible evolution towards bronchial asthma. An altered DLco, alone or associated with an inverted CD4/CD8 ratio of BAL lymphocytes, might constitute an early sign of a possible evolution towards interstitial lung disease. The association of aspecific bronchial reactivity and reduced DLco might indicate the possible evolution towards a mixed form. Only to follow up of these subjects might confirm or exclude these hypotheses. The nine symptomatic subjects have been followed up in time; three have continued their job in better hygienic conditions, six have completely discontinued the exposure; five were treated with corticosteroids. The clinical evolution of both asthma and interstitial diseasehas been variable and poorly influenced by changed working conditions and steroid treatment (two cases improved, two worsened, and five remained stationary). In consideration of the possible evolution of hard metal disorders towards a respiratory insufficiency and because of the unpredictable and questionable response to treatment, a thorough periodical surveillance of the exposed seems necessary in order to make early diagnoses in those still in an asymptomatic phase.