[Hard-metal pneumoconioses in Switzerland]

On the question of the pathogenetic importance of cobalt for hard metal fibrosis of the lung

Pulmonary fibrosis in hard metal grinders has been observed to an increasing degree in recent years. Most authors attribute the cause of this disease to the influence of the cobalt contained in hard metals. The present case dealt with a 36-year-old man who had been exposed to the grinding dust from sintered hard metal parts for more than 10 years. Biopsy of the lung revealed an advanced, active pulmonary fibrosis. In the biopsy specimens cobalt was determined by flameless atomic absorption. The cobalt content in the biological specimens of the patient (urine: 7.5 micrograms/l; lung: 1010 micrograms/kg wet weight) was significantly increased compared with the values measured in normal controls.

Pulmonary deposition following inhalation of chromium-cobalt grinding dust in rats and distribution in other tissues

Twenty rats were exposed to dust particles of chromium-cobalt alloy abrasives produced in dental material handling. The exposure was carried out in chambers for periods up to 107 days at concentrations of particulate matter of about 10-50 mg/m3. The content of chromium and cobalt in autopsy specimens of lung, liver, kidney and trachea was measured with nuclear techniques. The alloy particles were found to be markedly accumulated in lung tissue. Increased levels of chromium and cobalt were also observed in the trachea. In addition, a moderate increase of cobalt in liver and kidney was demonstrated. The lungs of six exposed rats were examined microscopically. The main part of the dust particles was observed within macrophages. Only a minor fraction of particles were seen in the bronchial lumen close to the epithelial surface. The majority of dust-filled macrophages were located in groups within the bronchial wall or in the interstitium close to the terminal broncheoli. No fibrosis, dysplasia or tumor formation occurred. No acute adverse effects in the lungs were observed.

Hard metal lung disease: importance of cobalt in coolants

Four patients were found to react to occupational exposure to grinding of hard metal (tungsten carbide). Three of the patients had symptoms and signs compatible with an allergic alveolitis, the symptoms disappearing and the chest radiograph clearing when they were absent from work for a few months. Re-exposure to the offending agent led to new signs and symptoms. The first patient was re-exposed twice and each time reacted a little more seriously. After the last episode her chest radiograph has not cleared completely, in contrast to the first two times. The fourth patient had more typical occupational asthma. All the cases occurred in the part of the factory where air concentrations of cobalt were the lowest. The cobalt there is dissolved in the coolant necessary for grinding the hard metal. It occurs mainly in the ionised form, which is known to react with proteins and therefore presumably acts as a hapten. Protective measures, including choosing a coolant with minimal ability to dissolve cobalt and an effective exhaust system, should minimise the risk of this occupational disease in the future.

Effects of cemented tungsten carbide dust on rat lungs following intratracheal injection of saline suspension

In order to examine the effect of cemented tungsten carbide dust on the animal lung, saline suspensions were intratracheally administered into the lungs of rats in a single dosage. About one-fifth of the animals died during the first three days. The acute response of the lungs was hemorrhagic edema with intense alveolar congestion. The animals killed at six months all presented pulmonary lesions of patchy fibrosis in the vicinity of the deposited dusts, occasionally associated with focal traction emphysema and bronchobronchiolar ectasia. At twelve months, two-third of the animals had neither fibrosis nor dust deposition, although the remaining animals showed pulmonary lesions similar to those seen in the six-months responders. Fibrosis of the lungs seemed to consist of collapsed alveoli with condensation of the preexistent reticulin fibers, but without noticeable collagenization. It is supposed that both the early toxic and the late fibrogenic effects of the carbide dust are attributable to the cytotoxic action of cobalt present in the dust particles. It is possible that recovery of the pulmonary lesions results from removal of the dusts from the lesions.

Cemented tungsten carbide pneumoconiosis

An autopsy case of cemented tungsten carbide pneumoconiosis, the first lethal case in our country, is presented. A 28-year-old woman, who had been engaged in grinding presintered metallic matrix for four years, developed respiratory symptoms. X-ray examinations were indicative of interstitial pulmonary fibrosis. Corticosteroid therapy revealed only little effect. She expired five years after the onset of the symptoms. Postmortem examination showed nonspecific interstitial pneumonitis resulting in marked lung fibrosis. Ultrastructurally, crystals were observed in cytoplasm of presumable macrophages in the fibrotic lung tissue. Electron probe microanalysis of the lung tissue showed the presence of tungsten and other constituents of tungsten carbide except for cobalt. Metal analysis demonstrated a large amount of tungsten in the lung. Cobalt was detected tenfold of the normal value in the bone. In pathogenesis of the pneumoconiosis in the cemented tungsten carbide workers, toxicity of cobalt is most suspectable, and in addition, individual susceptibility may be also important.

[Air pollution in an industrial environment and occupational diseases]

Most of the occupational diseases are related to air pollution at the work place. The distribution of gases and vapours and their human absorption are briefly described. The deposition of particles is a function of their physical properties, of the pattern of the respiratory airways and of pulmonary ventilation parameters. Several defence mechanisms also play a role. Illustrative examples are given of occupational diseases caused by solvents, carbon monoxide, metals, dusts (silicosis, asbestosis, pneumoconiosis due to dust of hard metals), allergens and carcinogens. The importance of prevention is emphasized.