Controlling the risk of exposure to diesel exhaust

This guidance helps employers to eliminate or reduce the health risks associated with diesel exhaust.

What is diesel exhaust

Diesel exhaust is a complex mix of airborne gases, vapours, liquid aerosols and fine particles that occurs when diesel fuels are burnt in engines. Diesel exhaust, like diesel fuel, is a hazardous substance.

Diesel exhaust is a known carcinogen.

The International Agency for Research on Cancer, which is part of the World Health Organization, classifies diesel exhaust as carcinogenic to humans (Group 1).

The gases, vapours and particles found in diesel exhaust can include:

  • those commonly found in the air (eg nitrogen, oxygen, water vapour and carbon dioxide)
  • fine particles known as diesel particulate matter (DPM) including fine carbon particles – hazardous chemicals known as poly aromatic hydrocarbons (PAH) – adhere to the surface of carbon particles.

DPM can act like a gas and stay airborne for long periods of time. DPM can penetrate deep into the lungs because of its small size.

Note: PAH is a Schedule 9 Hazardous substance under the Occupational Health and Safety Regulations 2017 (OHS Regulations). Specific health monitoring duties apply for Schedule 9 Hazardous substances, see the ‘Health Monitoring’ section for further details.

Workplaces likely to have diesel exhaust

Employees in industries like transport, agriculture, automotive, aviation, construction, docks, emergency services, freight, logistics, and the extractives industries (mining and quarrying) are most likely to be exposed to diesel exhaust.

The major source of exposure to diesel exhaust is working on, in, near or with heavy vehicles, plant and equipment that use diesel fuel (eg trucks, forklifts, generators, buses, trains, excavators, cranes, tractors and ships).

Where diesel engines or generators are used in enclosed, poorly ventilated workplaces, exposure may be higher.

Incidental exposure to diesel exhaust is also a risk for employees in workplaces where diesel exhaust is present, even if they don’t directly work with diesel engines.

Health risks

Diesel exhaust can be harmful when it is inhaled. It can cause short-term and long-term health effects and ongoing exposure can lead to deadly diseases.

  • Short term exposure to high concentrations of diesel exhaust can irritate the eyes, nose, throat and lungs and cause light-headedness, coughing, phlegm and nausea. Very high levels of diesel exhaust exposure can lead to asphyxiation from carbon monoxide poisoning.
  • Long term exposure can worsen asthma and allergies and increase the risk of heart and lung disease, and lung and bladder cancers.

Diesel exhaust is the second most common carcinogen workers are exposed to.

Identifying hazards and assessing risks

Under the Occupational Health and Safety Act 2004, employers must provide and maintain, so far as is reasonably practicable, a working environment that is safe and without risks to health. This includes identifying hazards and assessing risks with regards to exposure to diesel exhaust fumes.

Employers also have a duty to ensure other persons are not exposed to risks to their health or safety arising from the conduct of the employer.

Employers need to consider the following factors when identifying and assessing the hazards and risks of diesel exposure and any controls that are currently in place to reduce the risk.

Control the risks

Employers must control the risks associated with exposure to diesel exhaust by applying the hierarchy of control in Part 4.1 of the OHS Regulations.

Employers must, so far as is reasonably practicable, eliminate the risks associated with exposure to diesel exhaust in their workplace.

If it is not reasonably practicable to eliminate a risk associated with diesel exhaust, the employer must reduce the risk so far as is reasonably practicable by:

  • substitution
  • isolation
  • engineering controls (see below) or
  • a combination of any of the above risk control measures

If the risk of exposure still remains, these controls must be added:

  • administrative controls (for example, housekeeping, work practices)
  • personal protective equipment (for example, respiratory protective equipment).

More than one control may need to be implemented to control the risk sufficiently.

For further information, please see Compliance code: Communicating occupational health and safety across languages.

Review and revise risk controls

Employers must review and, if necessary, revise risk controls:

  • before making a change to systems of work that is likely to change the risk associated with exposure to diesel exhaust
  • if advice is received by a registered medical practitioner that identifies adverse health effects
  • after an incident has occurred
  • if the risks are not adequately controlled
  • after receiving a request from a HSR.

Consultation

Employers must consult with their employees and any HSRs, if there are any, when identifying hazards and risks associated with diesel exhaust exposure, and when deciding on how to control risks. This requirement includes the obligation to consult with independent contractors, and employees of independent contractors.

Workplace exposure standards

Employers must ensure their employees are not exposed to an atmospheric concentration of a hazardous substance (eg PAH and DPM) above the exposure standard (if any) for a hazardous substance or any of its ingredients.

Exposure standards represent airborne concentrations of substances in a person’s breathing zone, which should not impair an employee’s health nor cause them undue discomfort.

Diesel exhaust does not have a workplace exposure standard in Australia, however the Australian Institute of Occupational Hygienists guidelines recommend that exposure to DPM is kept below 0.1 mg/m3 time-weighted average over 8 hours - measured as sub-micron elemental carbon.

Air monitoring

Atmospheric monitoring must be conducted where there is uncertainty whether an exposure standard for a hazardous substance may be exceeded, or it is necessary to determine if there is a risk to health.

Atmospheric monitoring needs to be completed by a competent person (eg an occupational hygienist). It requires specialised equipment and recognised and/or approved methods must be followed.

Employers must provide results of atmospheric monitoring to employees who have been, or who may be, exposed to the hazardous substance. All monitoring results should be communicated to the employees and HSRs, regardless of whether the results indicate excessive or minimal employee exposure to the substance(s).

Health monitoring

Health monitoring is the process of checking the health of employees exposed to certain hazardous substances in the workplace. The main purpose of health monitoring is to detect adverse changes to health due to exposure to substances in the workplace.

Some diesel exhaust contains PAH, a Schedule 9 Hazardous substance under the OHS Regulations.

Where PAH is present in the workplace atmosphere, employers must provide health monitoring for their employees (at the employer's expense) when:

  • employees are exposed and
  • there is a reasonable likelihood of an adverse health effect occurring