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PubMed1979

Risk of asbestosis in crocidolite and amosite mines in South Africa.

X-rays of all while and mixed-race men employed in crocidolite and amosite mines and mills were read independently by three experienced readers according to the ILO U/C classification. Abnormality was regarded as present if reported by two or more readers. Parenchymal abnormality, defined as the presence of small irregular opacities of profusion 1/0 or greater, was found in 7.3% of the workers. Pleural thickening was found in 4.5% of the workers, costophrenic angle obliteration in 3.2%, and pleural calcification in 1.7%. The prevalences of both pleural and parenchymal abnormality were strongly related to the duration of exposure to asbestos at work. The overall prevalence of abnormality increase from 4.0% in men with exposure for 1 year or less to 47.9% in men with more than 15 years of exposure. After taking into account the effects of age and duration of asbestos exposure, the prevalence of pleural abnormality was not predicted by fiber concentration. However, white men working with amosite tended to develop a higher prevalence of pleural abnormality than did those working with crocidolite. Compared to whites, men of mixed race, who only work with crocidolite, had a high prevalence of pleural abnormality in each exposure duration category. In contrast to pleural abnormality, the prevalence of parenchymal abnormality, after taking into account the effects of age and duration of exposure, was significantly predicted by fiber concentration but not by race or asbestos type. Our results suggest that parenchymal abnormality in workers in South African asbestos mines could be largely prevented by reducing exposure to fibers visible under the light microscope. However, this may not be the case for pleural abnormality.

Adult↗
PubMed1991

Variability in interpretation of radiographs for asbestosis abnormalities: problems and solutions.

Interobserver variation continues to be a substantial problem for interpretation of asbestos-workers' X-rays, despite incremental improvements in the International Labour Office (ILO) classification system. The apparent degree of agreement/variability is affected by the population disease prevalence. For most populations, experts will be able to agree routinely about normal films. Yet designed trials show that selected experts exhibit a two-fold or greater range for perceived prevalence of abnormal profusions. This degree of variability would be adequate for many population studies were it achieved under real-life conditions of interpretation. Unfortunately, the realistic degree of interobserver variability is probably much higher under actual population surveillance conditions. Asbestos population surveillance programs have provided little or no quality assurance for ILO interpretations, so the very high variability suggested by available data are not surprising and are not the fault of the classification. Recommendations include required participation in quality-assurance panels for those who wish to be certified as interpreters, with consistent feedback and the dropping of outliers. If quality-assurance programs are implemented, the classification will achieve its intended epidemiologic purposes.

Asbestosis↗
PubMed1978

Experimental asbestosis: an investigation of functional and pathological disturbances. I. Methods, control animals and exposure conditions.

The measurement of respiratory function and quantitative assessment of changes in lung morphology are described in a long-term study of asbestos-exposed guinea pigs. Resistance and dynamic compliance of the guinea pig respiratory system were measured non-destructively, and the tidal volume and rate of spontaneous breathing were also determined. A point counting technique was used with histological preparations to quantify morphological changes. In one group of control animals, investigated between 3 and 28 months of age, dynamic compliance and tidal volume tended to increase, but resistance and breathing rate tended to decrease, as the animals matured. In contrast the percentage by volume of various lung components remained constant throughout this period. The animals were exposed to chrysotile and amosite aerosols, both aerosols containing high concentrations of short fibres (less than 5 micrometer) and at least 1000 fibres/ml longer than 5 micrometer. The total fibre concentration during chrysotile exposure was probably at least double that during amosite exposure. A gradient of fibre concentration (less than 5 micrometer) was detected along the exposure chamber, but this gradient was not reflected in the respiratory function of animals exposed at different positions along the chamber. These findings are discussed in relation to possible dose-dependence of the response.

Animals↗