Durability of various mineral fibres in rat lungs

The durability of crocidolite, glass fibres, and wollastonite in rat lungs was examined after intratracheal instillation. Experiments were based on the assumption that thin (< 2µm), long (> 5µm) and durable fibres are of special importance for the carcinogenic potency of these materials. After serial sacrifices up to two years after administration of the test materials, the retained fibres in lungs were analysed by scanning or transmission electron microscopy. Retention half times of between 10 and more than 500 days were calculated for the various fibre types investigated. The results show that the chemical composition of mineral fibres is an essential determant of the durability of these materials in lungs. A correlation between the durability of fibres in lungs and results for carcinogenic potency in the intraperitoneal test (i. p.) shows the plausability of an interrelationship.