Negligence – Causation. The Queen's Bench Division dismissed the claimant's action against his former employer on the basis that he had suffered from interstitial lung fibrosis due to an exposure of asbestos dust over a period in the late 1950s. The claimant failed to show that the activities complained off, had resulted in him being exposed to 25 fibres/ml-years, or greater, of mixed asbestos fibres.