Epidemiological study of respiratory disease in workers exposed to polyvinylchloride dust.

The respiratory health of workers exposed to polyvinylchloride (PVC) dust has been investigated in 818 men sampled from the work force of a factory manufacturing PVC. In a cross-sectional survey, the lung function and prevalences of respiratory symptoms and chest radiographic abnormalities were compared with estimates of individual PVC dust exposures based on detailed occupational histories and current measurements of respirable PVC dust. Complaints of slight exertional dyspnoea were associated with PVC dust exposure, though age and smoking effects were much stronger. The forced expired volume in one second (FEV1) and forced vital capacity (FVC) were inversely related to dust exposure after age, height, and smoking effects had been taken into account. This effect was seen principally in cigarette smokers, and there was suggestive evidence that PVC dust exposure and cigarette smoking interacted in the reduction of FEV1 and FVC. Gas transfer factor was not related to dust exposure. The chest radiographs were read according to the ILO U/C classification by three experienced readers. One reader recorded a low prevalence of small rounded opacities, and these were not related to age or dust exposure. Another reader recorded a higher prevalence of small rounded opacities category 0/1 or more, and these were related to age but not to dust exposure. The third reader recorded the highest prevalence of small rounded opacities (though none greater than category 1/1), and these were independently related both to age and to PVC dust exposure, indicating an effect of PVC dust on the appearance of the chest radiography. These appearances were so slight that only the higher sensitivity of this reader in the interpretation of profusion of small rounded opacities on the ILO U/C scale enabled detection of this effect of PVC dust. In conclusion, exposure to PVC dust is associated with some deterioration of lung function, slight abnormalities of the chest radiograph, and complaints of slight dyspnoea. The mean decline in FEV1 associated with the average dust exposure experienced in the study was small, though some of the men with higher dust exposures may have suffered clinically important loss of lung function as a result of their occupation.

Fibre concentrations and size distributions of airborne fibres in several European man-made mineral fibre plants.

Although the nominal diameters of fibres produced in the glass and rock wool industries are usually 6-15 micrometers, these products contain a small proportion of respirable fibres (less than 3 micrometers diameter). Particular significance has been attached to the biological risk arising from the long (greater than 10 micrometers), fine (less than 1 micrometers) fibres. Therefore, the medical research sponsored by the Joint European Medical Research Board into the effects of man-made fibres on health has included detailed environmental studies on both the exposure levels to respirable fibres and the fibre size distributions at the European plants selected for epidemiological work. This paper summarizes the results obtained so far. The size distributions (length and diameter) of the airborne man-made mineral fibres are compared with similar data previously reported for airborne asbestos fibres.

An investigation into the cytotoxicity of respirable dusts from British collieries.

A series of respirable dusts from British collieries was collected and analysed for mineral content and physical characteristics. Where possible 2 samples of dust were collected from the same site at 8-month intervals. All dusts were tested for their cytotoxic potential using a permanent line of macrophage-like cells (P388D1). In addition, for some dusts, a haemolytic technique was used. With both techniques a positive overall correlation was found between cytotoxicity and the total ash content of the dusts. When the results from collieries producing high- and low-rank coals were considered separately, however, it was found that the ash content of high-rank dusts (r=0.75) showed a much closer correlation with cytotoxicity than low-rank dusts (r=0.40). With the cell test system the ash components, kaolin and mica (r=0.58) and to a lesser extent quartz (r=0.48) showed significant positive correlations with cytotoxicity for high-rank coal dusts but not for low. Using the haemolytic system, however, only the quartz content of the high-rank dusts showed a significant relationship (r=0.69) to levels of haemoglobin release. Both the results of mineralogical analysis of dust samples and cytotoxicity tests showed that the mineral content and cytotoxic potential of dusts collected from the same colliery, and even from the same underground site, at different times, varied considerably. A poor correlation was found between cytotoxicity and various measurements of pneumoconiosis risk but this may well be partly due to this great variation of dust composition with time. In general, the overall results of this study were in good agreement with those of previous work on coal dust toxicity in that both the rank and composition of colliery dusts were found to be of importance, whereas the role of quartz remained enigmatic.

The effect of quartz and other non-coal dusts in coalworkers' pneumoconiosis. Part II. Lung autopsy study.

Preliminary pathological and mineralogical studies are reported on seventy-four sets of lungs from British coal miners who have been employed at the collieries included in the National Coal Boards's Pneumoconiosis Field Research. The degree of lung damage was considered in relation to the lung dust content and to the known dust exposures of the men concerned. Lungs were classified as having soft macules, fibrotic nodules or PMF. Those with soft macules had the lowest dust content but there was no significant difference between the dust contents of the lungs with fibrotic lesions and those with PMF. The percentage of non-coal minerals in the lung dust appeared to increase with the pathological classification from soft macules to PMF, and comparisons with the exposure data indicated a preferential retention of non-coal minerals, and especially of quartz, in the cases with the more severe lesions. Histological examination of the lesions showed the packing of dust was less close and the cellular response more vigorous with the lungs with the highest quartz content.