Diesel engine exhaust is a complex mixture of gases and particulates formed when diesel fuel is burned. The composition of the mixture can vary depending on the type of engine, the fuel and oil used, the type of operation, engine maintenance, and emission control systems. Diesel engines can be used in vehicles such as trucks, buses, trains, and ships, as well as industrial equipment.
Diesel engine exhaust causes lung cancer, and there is some evidence that it may cause bladder cancer [1]. Exposure can also cause eye and throat irritation, nausea, cough and phlegm, and allergic reactions.
CAREX Canada estimates that approximately 897,000 Canadians are currently exposed to diesel engine exhaust at work [2].
Approximately 560 lung cancers and possibly 200 suspected bladder cancers diagnosed annually are due to occupational diesel engine exhaust exposure, based on 2011 cancer statistics [3]. This amounts to 2.4% of all lung cancers and possibly 2.7% of all bladder cancers diagnosed each year. The cost of these cancers is approximately $684 million. Most diesel exhaust-related cancers occur among workers in the mining and transportation sectors (see pie charts).
While occupational exposure limits exist for various components of diesel engine exhaust across the provinces, outside of the mining industry there are currently no limits anywhere in Canada for diesel engine exhaust measured as elemental carbon. Measuring elemental carbon is considered the best way to understand the potential carcinogenic effects of diesel exhaust [3].
Where limits for the mining industry exist, they are out of date and do not reflect our current understanding of the risk of cancer due to diesel exhaust exposure. The OCRC recommends adopting limits of 20 µg/m3 elemental carbon for the mining industry and 5 µg/m3 elemental carbon for other workplaces, based on evidence of health effects at low levels and feasibility considerations [5,6], while continuing to work towards limits that reflect the current science. Canada could strengthen interim limits over a transition period to achieve a truly health-based exposure limit.
Upgrading or replacing old trucks and diesel engines with newer, cleaner models could also significantly reduce exposure. Though this may be costly, regulations could be rolled out incrementally and accompanied with financial supports to reduce the economic burden on companies. Mandatory emissions testing for older vehicles could help identify vehicles most in need of replacement. Preventing occupational exposure by reducing emissions will also help reduce exposure to the general population.
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