Workers Health & Safety Centre

Diesel engine emission study offers solutions to protect drivers

New research suggests training is critical in efforts to reduce exposure to deadly diesel engine exhaust for taxi drivers, couriers and others who make a living behind the wheel.  
According to Dr. Ian Mudway, Senior Lecturer at the MRC Centre for Environment and Health, Imperial College London (United Kingdom) and lead researcher of the Driver Diesel Exposure Mitigation Study (DEMiSt), “This is a widespread and under-appreciated issue. Indeed, it was very noticeable to us just how surprised drivers taking part in the study were at the levels of their exposure to diesel.”

Critical health impacts

Diesel is often used to power on-road (and off-road) vehicles including transport and courier trucks, buses, taxis and emergency service vehicles. Diesel engine exhaust (DEE) is a complex mixture of hundreds of different compounds found as particulates or gases readily inhaled by exposed workers and the public. Exposure can lead to a range of acute and chronic illnesses including lung and bladder cancer. In fact, the International Agency for Research on Cancer (IARC) classifies DEE as a definite human carcinogen (Group 1).

   Hazardous exposure common

This recent study found, on average, drivers were exposed to 4.1 micrograms of black carbon (BC) per cubic metre of air (µg/m3) while driving [BC is a component of diesel engine exhaust (DEE) and used as a proxy for measuring exposure]. These findings were almost four times higher than their exposure at home and almost two times higher then when they are at work but not driving.
The highest levels of exposure were experienced by taxi drivers (6.6 µg/m3), couriers (5.5 µg/m3) and waste removal drivers (4.3 µg/m3). The researchers speculated this was possibly reflective of the fact their work is largely undertaken within congested areas and where conditions impede the dispersion of emissions including tunnels and traffic corridors surrounded by high buildings. The highest exposure for any individual worker over a shift measured at 39.8 µg/m3. The data also found drivers experienced high exposure spikes, often exceeding 100 µg/m3 and lasting up to an hour before returning to pre-spike levels.
“Because these levels are higher than those we find at the roadside, this suggests that being inside a vehicle doesn’t necessarily offer any protection – in fact, the opposite may be true, that air pollution can get trapped inside the vehicle for extended periods of time,” explains Shanon Lim, air quality scientist, Imperial College London School of Public Health and study team member. “Imagine an office worker operating from a desk placed on the busiest street corner in London; well, they would be less exposed to black carbon than a passing taxi driver, who I expect would be feeling more protected in their cab,” he stressed.

   Prevention solutions

The researchers suggest employers, when purchasing new (or used) vehicles, consider those with zero tailpipe emissions (i.e., electric cars) and airtight cabins. They also call for more effective and wider reaching policies and regulation to reduce congestion and vehicle emissions. Here in Ontario, some communities for instance have sought relief from harmful DEE through idling control by-laws and purchasing policies for public transit and other fleet vehicles. 
This study also noted the importance of worker consultation, citing conversations with participants who suggested having air conditioned vehicles is likely to lead to more drivers keeping windows closed during summer months—an important measure to limit DEE exposure.  
The following solutions are additional examples of recommendations offered to reduce drivers’ exposure to DEE:
• train drivers before they start work and ongoing refresher training  
• plan the route to avoid high pollution areas (i.e., dense urban areas and tunnels)
• when entering high pollution areas and tunnels ensure windows are closed and ventilation set to recirculate (The recirculate setting should only be used for short periods as extended use can lead to hazardous accumulation of CO2. After exiting the polluted area windows should be opened to ensure the vehicle cabin is well ventilated.)
• reduce frequency of driving during the evening peak period (between 4pm and 7pm)
• move shifts from weekdays to weekends when traffic is lighter, where possible, and
• use in-cabin filters (though researchers did suggest additional research needed).

   Towards an Ontario prevention plan

Diesel engine exhaust is considered a priority carcinogen according to the 2017 Burden of Occupational Cancer in Ontario report. More than 300,000 Ontario workers, including many drivers of diesel engine vehicles, are exposed every year. These exposures account for 170 new cases of lung cancer and 45 bladder cancers annually, among other acute and chronic health impacts.
Still, Ontario and all other Canadian jurisdictions, have no legal occupational exposure limits (OEL) for whole diesel exhaust or diesel particulate matter. Many, including CAREX Canada and the authors of the report mentioned above, call for this lack of regulatory protection to be remedied by introducing an OEL based on elemental carbon (another proxy for DEE) of 20 µg/m3 for the mining industry and 5 µg/m3 for other workplaces to protect worker health. CAREX Canada explains in a 2019 report, the higher OEL recommended for the mining industry takes into account the feasibility of implementation in this industry. According to the report, mining has particular challenges but the higher recommended OEL is only meant as an interim target in a staged approach to eventually have one harmonized OEL for all workers.
Even still, these are well above levels research suggests would be adequate to protect exposed workers and the general public for that matter.

   WHSC…here to help

Workers Health and Safety Centre (WHSC) offers hazard awareness training on vehicle emissions and many programs to help employers meet training and competency requirements for supervisorsjoint health and safety committees and worker health and safety representatives, all of whom play essential roles in the pursuit of healthier, safer workplaces, including recommending measures to eliminate or reduce DEE. Many of these training essentials are currently scheduled in our COVID-safe virtual classroom.

Beyond scheduled classes, and where participant numbers warrant, we can work with you to coordinate almost any of our training courses in a virtual classroom for all workers, workplace representatives and supervisors.

Need more information still?
Contact a WHSC training services representative near you.
Call: 1-800-869-7950
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Want to read more about diesel engine exhaust from WHSC?
WHSC diesel engine exhaust hazard bulletin
Groundbreaking report focuses on occupational cancer prevention in Ontario
Cancer burden of diesel exhaust steep for exposed workers