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9.1 Introduction to managing airborne contaminant risks

This section offers guidance for persons conducting a business or undertaking (PCBUs) on managing the risks to road and roadside workers of being exposed to harmful airborne contaminants.

Airborne contaminants, such as dust, diesel exhaust, chemical vapours, and fumes can cause damage and disease (like lung cancer) when inhaled.

If workers could be exposed to harmful airborne contaminants while working, consider getting an exposure assessment done to better understand the risk.

If the assessment indicates excessive or unacceptable risk from exposure to airborne contaminants, you should take action to eliminate or minimise worker exposure to those airborne contaminants.

9.2 Dust

Airborne dust is a common occurrence at road and roadside worksites.

You must manage the risks to worker health caused by exposure to different types of dust, including:

  • respirable crystalline silica dust (see respirable crystalline silica below)
  • metal dust
  • asbestos dust (see asbestos below)
  • other hazardous inhalable or respirable dusts
  • airborne soil contaminants. 

Respirable dust is dust that penetrates deep into the lungs when inhaled. Dust particles can permanently damage a worker’s lungs.

Road and roadside workers can be exposed to many difference sources of dust, including:

  • dust kicked up from unsealed roads or worksites
  • dust produced during concrete cutting
  • dust from using powdered products such as cement
  • dust or dirt produced during excavation or gardening
  • wind-blown dust or dust stirred up while sweeping.

Respirable crystalline silica (RCS)

Silica is a natural substance found in concrete, bricks, rocks, stone, sand, and clay.

RCS dust is created when materials containing silica are cut, ground, drilled, or otherwise disturbed.

RCS particles are extremely small, and they cannot always be seen with the naked eye.

Workers who inhale RCS are at risk of permanent lung damage including silicosis and lung cancer.

PCBUs must manage the risk of RCS.

For more information, see Silica dust in the workplace


Asbestos is a naturally occurring mineral made up of many small fibres.

Asbestos can cause lung cancer and illnesses such as asbestosis and mesothelioma.

The main way people are exposed to asbestos is by breathing in air that contains asbestos fibres.

Road and roadside workers could be exposed to asbestos through things like windblown soil from excavation of old uncontrolled landfill sites or while exposing old underground asbestos pipes.

PCBUs must manage the risk of asbestos exposure.

For more information, see Asbestos

Control measures for dust exposure

If you are unable to eliminate dust from the worksite, look at what you can do to minimise the risk. This might mean doing a job differently or making sure you have the right equipment for the job.

  • Before work starts, check that any land that may be disturbed does not contain dangerous soil contaminants. If there is a risk that contaminated soil is present, you may need to hire a suitably qualified environmental practitioner to make an assessment. For more information, see The Ministry for the Environment: National Environmental Standard for assessing and managing contaminants in soil to protect human health(external link)
  • Control dust by wetting work materials and work areas with clean water.
  • Where relevant, choose equipment and machinery with good dust control and dust collection systems.
  • Schedule potential high-exposure work for times where there are fewer workers and others around (for example, during breaks or after normal working hours).
  • Encourage workers to leave dust-covered clothes at work to be cleaned, rather than taking them home. Workers should not be using compressed air to dust themselves down, as this spreads dust particles.
  • Encourage workers to wash hands before eating and drinking so that dust particles are not ingested.
  • Provide workers with appropriate respiratory protective equipment (RPE). RPE should only be considered when all other reasonably practicable means of control have been applied and a risk still remains. For more information, see Respiratory Protective Equipment (RPE)
[image] examples of using water to dampen dust at unsealed worksites
Figure 9: Examples of using water to dampen dust at unsealed worksites

9.3 Fumes, gases, vapours, and smoke

Airborne contaminants such as fumes, gases, vapours, and smoke can cause harm to road and roadside workers. Examples include:

  • paint application operations
  • solvent spray cleaning (some solvents are known or suspected to cause cancer)
  • kerbside weed control chemicals
  • welding metal fumes (metal oxides produced from welding)
  • bitumen or asphalt fumes (bitumen and asphalt contain class 1 carcinogens that can be inhaled and absorbed through intact skin)
  • de-icing agent preparation and mixing
  • hydrogen sulphide (commonly present in geothermal areas, sewers, cesspools, and areas of stagnant water, particularly in enclosed spaces)
  • toxic fumes, gases, or vapours from historically contaminated soil (such as old landfill sites).

The risk is more significant when working in confined spaces such as trenches, tunnels, or any other environment where there is poor air circulation.

The health effects of these contaminants depend on their composition, airborne concentration, the duration of exposure, and frequency of exposure. Effects can include:

  • metal fume fever (a short-term painful ailment with symptoms of fever and chills). For more information, see Welding
  • chronic obstructive lung disease
  • pneumoconiosis (lung disease due to accumulation of mineral or metallic particles)
  • occupational asthma
  • irritation of the eyes and respiratory tract
  • lung and other cancers
  • respiratory failure and death.

Control measures for exposure to fumes, gases, vapours, or smoke exposure

If exposure to fumes, gases, vapours, or smoke cannot be eliminated, look at how you can minimise the risk of exposure. For example, by:

Providing RPE should only be considered when all other reasonably practicable control measures have been applied and a risk still remains. For more information, see Respiratory Protective Equipment (RPE)

9.4 Diesel exhaust

Diesel engine exhaust is a complex mixture of gases and particles including carbon monoxide, nitrogen dioxide, sulphur dioxide, and diesel particulate matter (DPM). Diesel engine exhaust can cause cancer.

Road and roadside workers may be exposed to diesel exhaust from things like diesel-powered mobile plant and diesel-powered generators, and from diesel exhaust from passing vehicles.

Most outdoor work environments will have low concentrations of diesel exhaust because it can disperse easily, so the risk to workers will be low. However, some environmental factors can limit the dispersal of diesel exhaust and make its concentration higher. Examples of such factors include:

  • tunnels and trenches (including cut and cover roads)
  • city streets (where tall buildings can create a canyon effect which stops diesel exhaust from dispersing)
  • highways with acoustic barriers in place (while blocking noise, these barriers can also block airborne pollution from dispersing)
  • worksite sight screens (these can also block airborne pollution from dispersing).

Short-term acute symptoms of diesel exhaust exposure include:

  • irritation of the eyes, nose, and throat
  • headaches
  • dizziness or light-headedness
  • nausea
  • coughing
  • laboured breathing, or having difficulty breathing
  • tightness of chest.

Exposure to excessive levels of carbon monoxide can lead to loss of consciousness and death.

Some workers may be more sensitive to diesel exhaust or air pollution, for example those with certain pre-existing conditions.

Long-term exposures can lead to more serious, chronic health problems such as cardiovascular disease, cardiopulmonary disease, and cancer.

Control measures for diesel exhaust exposure

PCBUs should take steps to manage the risk of harm from diesel exhaust exposure, so far as is reasonably practicable. Examples of ways to manage the risks include:

  • choosing plant that does not run on diesel (check that alternative options do not introduce other risks that outweigh the risks of using diesel)
  • using equipment with enclosed cabs with good ventilation to maintain air quality. For more information, see Maintaining air quality in enclosed cabins
  • making sure engines in vehicles and plant are well maintained
  • making sure site vehicles and plant are not left idling unnecessarily
  • keeping workers that do not need to be there away from machinery and plant while it is operating
  • providing indoor break facilities away from areas subject to air pollution
  • directing generator exhausts away from where people are working or congregating
  • keeping cab doors and windows closed.

In high-risk locations, such as tunnels and trenches, consider:

  • seeking advice from a specialist such as a ventilation engineer since you may need to provide mechanical ventilation
  • putting in place a diesel emissions management plan
  • limiting work undertaken in areas where exhaust is contained and cannot be ventilated
  • rotating workers frequently.

Note: Work within tunnels may be subject to requirements under the mining regulations. For more information, see Ventilation in underground mines and tunnels

Providing RPE should only be considered when all other reasonably practicable control measures have been applied and a risk still remains. For more information, see Respiratory Protective Equipment (RPE)

Tunnels and trenches can develop dangerously high concentrations of diesel exhaust and other air contaminants that can be difficult to monitor without specialised equipment. Consider bringing in an occupational hygienist to monitor and advise on how to manage this risk.

For more information, see Section 16.0: Exposure monitoring 

9.5 Monitoring exposure to airborne contaminants

Once you have taken all reasonably practicable steps to eliminate or minimise the risks from airborne contaminants, you should consider if ongoing monitoring of air quality is needed.

Ongoing monitoring can help inform whether control measures are or remain effective at minimising the risks from airborne contaminants. For more information, see Section 16.0: Exposure monitoring

You may need to add appropriate tests to the health monitoring program. A suitably qualified person should provide advice on what tests or health monitoring may be appropriate. For more information, see Section 17.0: Health monitoring

9.6 More information on airborne contaminants