Asphalt and Bitument Fumes

Asphalt and Bitumen, What's the Difference? 

Asphalt and bitumen are often used interchangeably, but there are differences between the two:

1. Bitumen:

   • Bitumen is a naturally occurring, highly viscous, and sticky black or dark brown substance. It is a byproduct of crude oil refining and can also be found naturally.
   • Bitumen is the binder or adhesive component in asphalt pavement. It provides the cohesiveness that holds the materials together.

2. Asphalt:

   • Asphalt is a mixture of bitumen and aggregate materials (such as sand, gravel, or crushed stone). This mixture is used for various construction purposes, primarily in road construction.
   • The term "asphalt" is often used to describe the finished product, which is the surface on roads, highways, and parking lots.

In essence bitumen is the raw, sticky substance derived from crude oil or found naturally, while asphalt is the composite material created by mixing bitumen with aggregate materials for use in construction. 

Fumes from Asphalt and Bitumen, what are the risks?

Studies show that exposure to unsafe levels of asphalt and bitument fumes is a significant health hazard. Effects include the development of some cancers such as skin, lung, bladder or stomach cancers as well as leukemia. Additionally, exposure to asphalt and bitumen fumes can cause headaches, skin rashes, fatigue, reduced appetite, throat and eye irritation and coughs. Safe Work Australia currently sets the maximum safe rate of exposure to asphalt & bitument fumes at 5mg/m³ in an 8-hour time-weighted average. Temperature is the dominant factor in emission release. Bitumen begins to oxidize at 170°c, which increases the risk of hazardous emission being released. Warm mix asphalt should be used to control this risk. 

Asphalt made with recycled waste materials, polymers or recycled plastic

Some research states that the health and safety risks associated with the use of asphalt made with polymers or recycled plastic and/or waste materials are generally similar to those associated with traditional asphalt. However this research is insufficient research and further research is needed to properly understand the risks associated with the inhalation of fumes from recycled materials used as aggregate materials in bitumen. 

The additional plastic or other materials that are used can be varied. They can include car tyres, plastic bags, hard plastic waste amongst others.

Cleaning products that have handled asphalt or bitumen

Diesel is commonly used to clean products that have handled asphalt or bitumen. However, the handling of diesel to clean these products comes with health and safety risks. Breathing in diesel exhaust can cause lung irritation and/or an allergic reaction causing asthma (wheezing and difficult breathing), or making pre-existing asthma worse. Other symptoms may include feeling lightheaded, headache, or nausea. Long term exposure may lead to serious health effects. Additionally diesel has serious consequences for the local environment. There are several alternatives available that employer's must consider to control the risks associated with cleaning with diesel. 

A list of commercially available slip agents and/or bitumen remover/cleaners is provided below in alphabetical order: 

• Avalanche A 
• True Blue - Canola Oil  
• DUOGUARD B.A.R 
• Duoguard HD 550 
• Enviroslip 
• Enviro slip plus 
• Nyflex 804 
• Pavertrend 
• SLIPWAY Heavy Duty 

An overview of the intended application of the products listed above is presented below: 

Alternatives must be considered in consultation with worker's and HSR's to ensure that they both effective in performing the task and safe.

How can the risk from the inhalation of fumes be controlled?

Under Section 21 of the OHS Act 2004, employers have a duty to eliminate risks to health and safety so far as is reasonably practicable. This means that they have a duty to address the risks associated with the inhalation of asphalt fumes. There are a number of control measures that can be used such as: 

Substituting Hot Mix Asphalt with Warm Mix Asphalt (WMA):

• WMA is typically produced and placed at temperatures significantly lower than HMA, often ranging from 50°C to 100°C  lower than hot asphalt which is typically mixed at between 150-175 degrees Celsius. Reduced production temperatures can result in fewer emissions of harmful volatile organic compounds (VOCs) and particulate matter as well as reduced emission of hazardous gasses. 

Implementing engineering controls such as good ventilation:

• Local exhaust ventilation systems, such as hoods and fans, can be installed near asphalt operations to capture and remove fumes at the source. Employers should also ensure adequate general ventilation in work areas to dilute fume concentrations. This may include natural ventilation or mechanical ventilation systems.

Implementing administrative controls such as minimizing the time workers spend near asphalt fumes by scheduling tasks efficiently and reducing unnecessary exposure.

Administrative controls could also include restricting access to areas of asphalt operations to reduce exposure and training workers on safe exposure limits and proper use of PPE. 

Monitoring and Testing:

Employer should conduct regular air monitoring to assess the levels of asphalt fumes in the workplace. Controls should be adjusted as needed based on monitoring results Periodically test the effectiveness of respirators and other PPE to ensure they provide adequate protection. There is currently no standardised testing regime for measuring bitumen fume monitoring. The Australian Workers Union is pushing for industry wide headspace testing to accurately support onsite monitoring by identifying all potential hazardous compounds emitted by fuming bitumen. This will also support accurate Safety Data Sheets which currently are generic and do not identify the hazardous additives in bitumen products.

Regular asphalt temperature recording must be conducted to substantiate whether the products are safe to use onsite and whether the temperature recorded at the production plant is accurate and below spec.

Hygiene and Decontamination:

• Employers should provide facilities for workers to change into clean clothing to prevent contamination of personal clothing.

Personal Protective Equipment (PPE):

• Respirators: Workers should wear appropriate respiratory protection, such as N95 or higher-rated respirators, to filter out asphalt fumes. The selection of the respirator should be based on a proper hazard assessment.
• Eye Protection: Safety goggles or a face shield should be worn to protect the eyes from splashes and irritants.
• Gloves: Gloves made of nitrile or other chemical-resistant materials should be worn to prevent skin contact with asphalt.

Under Section 35 of the OHS Act your employer must consult HSR's and workers on matters of health and safety and any changes being implemented in the workplace related to health and safety. Make sure that HSR's and workers are consulted on any controls being implemented to address the hazard of asphalt/bitumen fume inhalation. 

Further Reading

The Institute for Safety, Compensation and Recovery Research has published two studies into asphalt and bitumen fume exposure here and here. 

The US Department of Labor's Occupational Safety and Health Administration's guidance on Asphalt Fumes

Updated September 2023