EFFECTS OF THE INTENSITY AND TIMING OF ASBESTOS EXPOSURE ON LUNG-CANCER RISK AT 2 MINING AREAS IN QUEBEC

Mortality data from 9609 workers at two asbestos mining areas in Quebe c were analyzed to assess the effects of the intensity and timing of e xposure on lung cancer risk. Summary exposure measures based on differ ing assumption were computed for lung cancer cases and matched control s and were fitted to the data using conditional logistic regression, A non-linens relationship between intensity and risk fit both mining ar eas, but risk was greater at one area than the other, At the mine with lower risk, exposure occurring more than 30 years prior to death had little effect, while at the other mine risk did not vary with time sin ce exposure and men starting employment before 1924 were at elevated r isk, The results point to differences in dust composition at the two a reas and illustrate the difficulties in estimating risk.