An epidemiological study of respiratory disease in workers exposed to polyvinylchloride dust. Report of survey carried out at the Hillhouse Works of Imperial Chemical Industries Ltd

Polyvinylchloride (PVC) is produced in industry in the form of a powder. A proportion of these particles of PVC is sufficiently small to be inhaled into the smaller airways of the lungs (respirable dust), and recent reports in the medical literature have suggested that this dust may cause lung disease.Astudy of a sample of the present and past workforce of the Hillhouse Works of Imperial Chemical Industries Limited, which manufactures PVC, has assessed the prevalence of respiratory symptoms, chest radiographic and lung function abnormalities, and has related them to estimates of exposure to respirable PVC dust based on measurement of current dust levels and detailed occupational histories.1. Environmental SurveyIn an environmental survey of the plants manufacturing or further processing PVC, personal sampling of respirable dust was carried out on 130 men engaged in occupations within the PVC plants. Selection of men to wear the dust samplers was based on subjective estimates of dustiness made during a preliminary visit to the Works and measurement of particle sizes of typical PVC dusts. The major sampling effort was directed towards the occupations thought to be dustiest.Results of the environmental survey indicated that respirable dust levels were highest for the drying and packing operations in an older plant making PVC by the emulsion method and the mixing process in a PVC processing plant. The highest mean average respirable dust exposure for any occupation over a shift was 2.88 mg/m3 (SD – 1.84). Dust levels in other plants were generally lower.2. Methods of Medical SurveyOn the basis of factory personnel records, a preliminary inspection of the factory and estimates of the particle sizes of typical PVC dusts, all current and many ex-employees were allocated to four broad categories corresponding to different probable exposures to PVC dust. The study sample was drawn in such a way that all those in the two higher exposure categories were included, and lower proportions of men in the other categories.Men were seen by appointment: a detailed occupational history was taken; a questionnaire of respiratory symptoms administered; chest radiograph and lung function measurements taken. The appearances of the chest radiographs were read by three medically qualified readers highly experienced in the interpretation of the radiographic appearances of occupational lung disease.3. Results of Medical SurveyResults for 818 men were analysed, 663 men currently employed at the factory, 98 pensioners and 57 men who had left for reasons other than retirement.(a) Respiratory SymptomsExposure to PVC dust was not associated with chronic cough or sputum production (chronic bronchitis), acute chest illnesses, acute bronchitis, pneumonia, pleurisy or asthma.There was a relationship between exposure to PVC dust and the complaint of breathlessness when hurrying on level ground or walking up a slight hill, but this relationship was found only in cigarette smokers and not in non- or ex-smokers.(b) Lung FunctionA measurement of the breathing capacity, the forced expired volume in one second (FEV1) was statistically significantly lower among men with higher PVC dust exposure. This effect was seen principally in current cigarette smokers, and not confirmed among non-smokers when considered separately. The pattern of results suggested that there were real differences in the response to PVC dust related to smoking habit. The magnitude of this reduction in all men in relation to the mean dust exposure was approximately one-seventh of that caused by ageing, and of a similar magnitude to the loss caused by smoking 20 cigarettes a day. (The FEV1 measures the rate at which air can be blown out of the lungs through the air passages, and reductions of the FEV1 are usually caused by narrowing of the air passages in the lung.)Another measure of breathing capacity is the forced vital capacity (FVC), the volume of air expired in a full breath, and this was also statistically significantly reduced at higher PVC dust exposure. The magnitude of this reduction was less than that of the(c) Chest RadiographsOne of the three expert readers who examined the chest radiographs detected small rounded opacities more commonly in the radiographs of men with higher exposures to PVC dust than in those with lower or no exposure. The other two readers did not detect an effect of PVC dust, though they saw small rounded opacities in a few cases. The opacities seen by these readers were not more common in those with higher exposures to dust than in those with lower or no exposure. Nevertheless, men with small rounded opacities also had reduced lung function, compared to those without(d) Autoclave WorkersThe observed effects could not be related to past exposure to vinylchloride monomer. Men working on the autoclaves may have been exposed to significant amounts of vinylchloride monomer in the past. However, the observed effects of PVC dust exposure could not be explained by an effect of working on the autoclaves, and thus were unlikely to be due to exposure to the monomer.(e) Factors other than PVC Dust EffectsThe associations with PVC dust exposure were detected against a background of other non-occupationally-induced effects. Cough, sputum and other respiratory symptoms were strongly related to smoking habits. So also were abnormalities of lung function; both deterioration in lung function and small opacities in the chest radiograph were strongly associated with age. The statistical analyses of the results have taken these factors into account.k. ConclusionExposure to respirable PVC dust is associated in a proportion of exposed workers with the presence of small rounded opacities on the chest radiograph and a decline in mean ventilatory capacity. This suggests that PVC dust causes a small but detectable effect on the respiratory health of the workforce.