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.