Workers Health & Safety Centre

New diesel exhaust study supports growing call for action

Miners working inside a mine
Workplace exposure to diesel exhaust (DE) is associated with high rates of fatal lung cancer in miners, according to a recent Australian study.
As is the case here in Ontario, there is no legal occupational exposure limits for DE or diesel particulate matter in Australia.

Study results

The Australian Institute for Occupational Hygienists recommends an average exposure limit of 100 µg/m3 over eight hours measured as elemental carbon (EC)—a common marker for measuring DE.
Authors of the study, entitled Estimation of quantitative levels of diesel exhaust exposure and the health impact in the contemporary Australian mining industry, estimated exposure levels faced by miners (underground) to be well below the recommended limit averaging 44 µg/m3 EC over 12 hours. The concern, however, even at this exposure level over a 45-year working career, the miners would suffer 38 extra lung cancer deaths per 1,000 males when compared to the general population. Even those exposed for as little as five, 10 and 20 years faced elevated risk of lung cancer death.
Above-ground mine workers were found to face a lower but still excess risk, with an average exposure of 14 µg/m3 EC. Over a 45 year working career they would face 5.5 additional lung cancer deaths per 1,000 workers.
"You don't want anyone to get lung cancer but generally what we can accept as a risk is one in 1,000 workers, so you can image that 38 workers in 1,000 is way too high," says lead investigator Dr. Susan Peters, senior research fellow, University of Western Australia. "So that's why I refer to the fact that the exposure limit should be much, much lower than 100 µg/m3.”
The study concluded “exposure levels in the contemporary Australian mining industry are still substantial, particularly for underground workers. The estimated excess numbers of lung cancer deaths associated with these exposures support the need for implementation of stringent occupational exposure limits for diesel exhaust.”
Also cited in the study were a range of prevention solutions to reduce DE exposure and the importance of worker training.

Ontario’s experience

Here in Ontario, efforts have been ongoing to convince government regulators to implement an occupational exposure limit (OEL) for diesel exhaust and other important measures to protect all exposed workers. The Occupational Health Clinics for Ontario Workers (OHCOW), for instance, just this past summer called on the Ministry of Labour to establish an OEL for diesel exhaust below 10 µg/m3 EC.
According to CAREX Canada, 800,000 Canadians are exposed to diesel exhaust as a result of work. Here in Ontario, more than 275,000 workers are exposed to diesel exhaust including miners, truckers, bus drivers, heavy equipment and farm tractor operators, landscaping labourers and maintenance workers.
Diesel exhaust is also a significant threat to public health. With vehicles being a major source of diesel exhaust, anyone living, playing, working and going to school near busy highways and roads is at risk.
The International Agency for Research on Cancer (IARC) classifies diesel engine exhaust as a definite human carcinogen (Group 1)—a classification that also includes asbestos, silica and tobacco smoke.
With battery-operated, electric and cleaner diesel engines and retrofit emission control systems for older engines now available, some workplaces have already taken steps to reduce harmful exposures. Some Ontario and Canadian communities have also sought relief from harmful DE through various initiatives such as idling control by-laws and purchasing policies for hybrid, electric and biodiesel public transit and other fleet vehicles. 
Given the availability of these prevention solutions, some worker, community and health activists are calling on the government to extend Ontario’s Climate Change Action Plan to include green bank incentives for workplaces to purchase low-carbon and zero-emission off-road vehicles. Others say the government should require workplaces to establish and implement benchmarks for mandatory phase-out of diesel-powered equipment.
For our part, the Workers Health & Safety Centre offers a diesel exhaust fact sheet highlighting these and other precautions designed to protect workers and the public. The fact sheet also outlines numerous additional risks to health posed by DE. This information and more including employer obligations to address the risk to health are also explored in the WHSC Vehicle Emissions training program.   
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