Diesel - declared carcinogen

IARC concludes diesel exhaust fumes are carcinogenic

A panel of scientific experts convened by the World Health Organization's (WHO) International Agency for Research on Cancer (IARC) concluded in June 2012 that diesel engine exhaust is a Group 1 carcinogen – that is, carcinogenic to humans.   Previously, the IARC classification for diesel exhaust was "probably carcinogenic to humans," but with the publication of additional epidemiological and toxicological studies over the last 20 years, the expert panel determined there was sufficient evidence to change the compound's cancer designation.   The IARC panel wrote:

"The scientific evidence was reviewed thoroughly by the Working Group and overall it was concluded that there was sufficient evidence in humans for the carcinogenicity of diesel exhaust. The Working Group found that diesel exhaust is a cause of lung cancer (sufficient evidence) and also noted a positive association (limited evidence) with an increased risk of bladder cancer."    IARC Press Release, [pdf] June 2012

However, in a tactic not unlike those of tobacco or asbestos companies, just prior to IARC's announcement, the U.S. based Diesel Technology Forum (DTF) issued a statement about clean-diesel technology.  The trade group suggests in its statement that the U.S. EPA and the California Air Resources Board say that diesel exhaust has few biological effects. IARC officials were unable to comment on the statement given its vague nature, but responded by saying that the expert panel had reviewed hundreds of studies, and suggested that if such a study claiming "few biologic effects" was in the literature, they would have reviewed it.   Source: The Pump Handle Science Blog

Hazard information

The exhaust gases which are discharged from the engine contain several constituents that are harmful to human health and to the environment.

The exhaust from diesel engines is made up of two main parts: gases and soot. Each of these, in turn, is made up of many different substances.

  • The gas portion of diesel exhaust is mostly carbon dioxide, carbon monoxide, nitric oxide, nitrogen dioxide, sulphur oxides, and hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs).
  • The soot (particulate) portion of diesel exhaust is made up of particles such as carbon, organic materials (including PAHs), and traces of metallic compounds. Both the gases and the soot of diesel exhaust contain PAHs.

Many workers in workplaces where diesel-powered equipment is used, such as railroad workers, truck drivers, farmers, miners, mechanics, and toll booth workers, are exposed to hazardous diesel exhaust emissions on the job. The exhaust from diesel fuel can cause health effects - as noted above: cancer, but also conditions ranging from cough and eye irritation to wheezing and difficulty breathing. 

Health Effects

Acute Effects
The acute (immediate) health effects associated with exposure to diesel exhaust exposure include irritation of the nose and eyes, lung function changes, respiratory changes, headache, fatigue and nausea.

Chronic Health Effects
Chronic (long term) exposures are associated with cough, sputum production and lung function decrements. In addition to symptoms, exposure studies in healthy humans have documented a number of profound inflammatory changes in the airways, notably, before changes in pulmonary function can be detected. It is likely that such effects may be even more detrimental in asthmatics and other subjects with compromised pulmonary function.

In addition, there are observations supporting the hypothesis that diesel exhaust is one important factor contributing to the allergy pandemic. For example, in many experimental systems, diesel exhaust particles can be shown to act as adjuvants to allergen and hence increase the sensitisation response. 

Carcinogenicity

Based on studies of worker exposure, there has been growing concern that diesel exhaust could potentially cause cancer - as noted, IARC classified diesel engine exhaust as carcinogenic to humans (Group 1), determining that exposure to diesel exhaust emissions increases the risk for lung cancer and possibly bladder cancer. In March 2012, the findings of a large study of diesel emissions exposures in underground miners showed an increased risk of death from lung cancer in exposed workers. This study was conducted by the US National Cancer Institute (NCI) and National Institute for Occupational Safety and Health (NIOSH). 

(much of the above information on the hazard and the health effects comes from a Chemwatch Hazard Alert)

At risk for exposure

People everywhere are exposed to some diesel exhaust, as there are increasing numbers of vehicles fueled by diesel. However, people working where diesel engines are running indoors or in enclosed spaces, such as bridges and tunnels, engine maintenance garages, carparks, underground mines, and fire stations have some of the highest exposures to the exhaust, and are at increased risk for illness.

Other workers who are at high risk for diesel exhaust exposure include:

  • operators of diesel powered engines (such as in trains, trucks, buses, tractors, and forklifts)
  • mechanics
  • roadside inspection workers
  • loading/shipping dock workers
  • truck drivers
  • farm workers
  • railroad workers
  • ship crew members
  • carpark attendants

Legal Standards

The employer has a duty under the Victorian Occupational Health and Safety Act (2004) to provide and maintain for employees, as far as practicable, a working environment that is safe and without risks to health. This includes ensuring 'so far as reasonably practicable' ensuring safety and the absence of risk to health in connection with the use, handling, storage or transport of plant or substances, a safe system of work, information, training, supervision, and where appropriate personal protective equipment. The employer also has the duty to monitor conditions at the workplace and to monitor the health and safety of employees. 


Thus, to comply, employers should assess the risks to the health of workers exposed to diesel exhaust and take the necessary precautions to prevent or reduce the amount that workers breathe.  Any decisions must be made in consultation with HSRs and workers.  Further, employers should educate employees on the risks of exposure to diesel exhaust, implement controls to eliminate/minimise exposure, provide instruction and training on control measures, and any personal protective equipment that they must use.


If exposure cannot be eliminated by using safer alternative fuels (e.g. natural gas or electricity), the employer must use a combination of control measures to reduce risk:

  • Changing to reformulated diesel, or biodiesel fuel to reduce emissions, or switching to low-emission diesel engines that burn fuel more efficiently.
  • Installing vehicle accessories such as exhaust extenders that re-direct the exhaust away from the operator and attach filters to tailpipes and oxidation catalytic converters to reduce exhaust.
  • Attaching exhaust extractor hoses on the tailpipes of vehicles that idle for long periods (such as in vehicle maintenance shops).
  • Running diesel engines outdoors rather than indoors when possible.
  • Maintaining engines regularly, and inspect the bodies of vehicles and seal cracks or holes to prevent exhaust from getting into the cabin.
  • Turning engines off whenever possible to reduce engine idling.
  • Putting fixed diesel engines (eg generators) in separate, ventilated areas under negative air pressure.
  • Ventilating indoor work areas well with vents in the walls and ceiling, and with air extraction fans to pull diesel exhaust-contaminated air away from workers, and exhaust it outdoors.
  • Monitoring worker exposure to diesel exhaust emissions.
  • Supplying a respirator if ventilation and other control methods are not effective and suitable.
  • Using job rotation to reduce worker exposure to diesel exhaust.

More Information

Last updated, August 2017

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