- BACKGROUND: Inhalation of fine particulate is hypothesized to increase risk of heart disease events. METHODS: Seven Ontario construction unions participated in a retrospective cohort mortality study. Proportional mortality ratios (PMRs) were computed and a mortality odds ratio (MOR) analysis was performed to compare the risk of ischemic heart disease (IHD) mortality among heavy equipment operators (HEO) to that of members of other unions. Deaths attributed to lung cancer, mesothelioma, and accidental causes were excluded from the comparison. RESULTS: Two hundred fifty nine of 1,009 deaths among the HEO were attributed to IHD. The PMR was 1.09 (0.96-1.2). None of the IHD PMRs among the other six unions exceeded 0.89. The MOR for IHD mortality, comparing the HEO to all other workers combined was 1.47 (1.17-1.84) for ages 25-64, was 1.20 (0.96-1.50) for ages 65 or more, and was 1.32 (1.13-1.55) for all ages combined. CONCLUSIONS: Increased risk of IHD mortality among HEO is consistent with the hypothesis that exposure to diesel fume has adverse effects upon the heart and circulatory system.