Cancer, chronic obstructive pulmonary disease and ischaemic heart disease in Ontario, Canada workers exposed to diesel engine exhaust.

OBJECTIVE

This study assesses potential exposure-response relationships between diesel engine exhaust (DEE) and lung and bladder cancers, chronic obstructive pulmonary disease (COPD) and ischaemic heart disease (IHD) in Ontario workers in the Occupational Disease Surveillance System.

METHODS

Approximately 2.3 million workers were identified through workers' compensation claims (1983-2019) and followed for cancer through linkage with the Ontario Cancer Registry (1964-2019). COPD and IHD cases were identified using hospital discharges (2006-2020), emergency department visits (2006-2020) and physician billing records (1999-2020). Exposure was assessed using the Diesel Exhaust in Canada Job-Exposure Matrix, a semiquantitative job-exposure matrix based on expert assessment and published measurement data. Cox-proportional hazards models were used to estimate HRs and 95% CIs, adjusted for age, birth year and sex by exposure status (exposed/unexposed) and for increasing exposure level (unexposed, low, moderate, high and very high). Trend tests were run using exposure category midpoints (µg/m3 elemental carbon).

RESULTS

Overall, 39 743 incident lung cancer, 12 528 bladder cancer, 77 124 COPD and 302 876 IHD cases were identified. Among exposed cases (all outcomes), the majority (90%) were assigned low exposure. Significant increased risks of lung cancer (HR=1.33, 95% CI 1.29 to 1.37), bladder cancer (HR=1.19, 95% CI 1.13 to 1.26), COPD (HR=1.34, 95% CI 1.31 to 1.37) and IHD (HR=1.15, 95% CI 1.13 to 1.16) were observed among exposed workers compared with unexposed workers. Exposure-response relationships were observed (all outcomes) although increases in risk were non-monotonic. Trend tests suggested increased risk (p trend <0.001).

CONCLUSIONS

This study improves understanding of DEE-related diseases. These results could be used to improve prevention efforts and workers compensation practices for DEE-related occupational diseases.