What respiratory hazards do road workers face?
The materials, processes and equipment used in road construction generate harmful airborne contaminants, causing irritation and discomfort in the short term and increasing workers’ risk of developing occupational lung disease.
Understanding the dangers and learning how to implement effective control measures is crucial to protect road workers against respiratory hazards.
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Silica dust
Silica is a mineral found in many construction materials including stone and concrete. When these materials are broken up, a fine dust is released – known as respirable crystalline silica (RCS) – which is extremely harmful if inhaled. RCS inhalation can lead to life-threatening lung diseases including silicosis, chronic obstructive pulmonary disease (COPD) and lung cancer.
Activities such as cutting, drilling and breaking paving slabs, kerbs, flags, concrete and rock can release high concentrations of RCS dust. The workplace exposure limit (WEL) for RCS dust is extremely low – just 0.1mg/m3 over 8 hours. This amount of dust is illustrated in the image below.
The WEL is set as a practical guide, and it is important to keep in mind that inhaling any amount of RCS can be harmful. Exposure should be reduced as much as possible using the relevant control measures.
When implementing measures to combat respiratory hazards in the workplace, it is important to follow the hierarchy of controls. For some tasks, exposure to RCS dust can be eliminated by purchasing pre-cut materials. Planning work to minimise the number of cuts and breaks can also reduce the amount of dust created. Water suppression and on-tool extraction can further reduce RCS dust exposure.
If silica exposure cannot be controlled effectively through these measures alone, respiratory protective equipment (RPE) should be worn. The general requirement for silica dust is a particulate respirator offering a UK assigned protection factor of APF 20 as a minimum? / or above preferably. An APF of 20 can be achieved by using a reusable half mask with P3 filters, FFP3 disposable respirator, or TH2P/TM2P powered air device. ?
All wearers of tight-fitting RPE must be fit tested. Concentration levels and other hazards present may require a different class or type of respirator. A full risk assessment is required to identify appropriate RPE.
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Asphalt fume
Asphalt is made up of aggregates and bitumen. Bitumen does not present a hazard under ambient conditions; however, because asphalt mix is produced at temperatures of 170-190°C and laid whilst hot, high concentrations of inorganic particulates and organic compounds can be released as a fume, posing a danger to road workers.
Bitumen fume contains variable mixtures of particulates and organic compounds, including polycyclic aromatic hydrocarbons (PAHs), and heterocyclic aromatic compounds containing sulphur, nitrogen and oxygen.
Exposure to bitumen fume can cause dizziness, nausea, respiratory discomfort, burns, and irritation of the eyes and skin. Some research suggests inhalation of asphalt fumes can contribute to the development of lung cancer.
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The 8-hour WEL for asphalt fume is 5mg/m3. To prevent excessive fume, do not exceed the recommended temperature whilst laying asphalt mix. Use workplace planning to keep those not directly involved in the task away from the source of asphalt fume.
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Diesel engine exhaust emissions
Diesel engine exhaust emissions, or diesel fumes, contain a mix of harmful gases, vapours, liquid aerosols and particulates. Working near generators and site vehicles like excavators, planers and lorries increase exposure to diesel fume.
When inhaled, prolonged, frequent exposure to diesel fumes can cause coughing, a congested nose, breathlessness and wheezing. Inhalation of diesel fumes has also been linked to a long-term increased risk of lung cancer.
There is currently no WEL for diesel engine exhaust fumes. Gaseous components each have separate 8-hour WELs:
-??????? Carbon monoxide: 20ppm
-??????? Nitrogen monoxide: 2ppm
-??????? Nitrogen dioxide: 0.5ppm
Use alternative fuels for equipment where possible to eliminate diesel engine exhaust emissions at source. Plan jobs to keep workers as far away from diesel engines as possible and locate generators in open areas. Exhaust systems and mechanical ventilation can help to reduce accumulation of diesel fumes in more enclosed areas. When operating vehicles, avoid engine idling and revving as much as possible.
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Reducing exposure to silica dust, asphalt fume and diesel emissions is key to protect road workers against respiratory illness and lung disease. Depending on the type of work being carried out and materials in use, there may be other respiratory hazards to consider.
The use of detection, identification and monitoring equipment (workplace air surveillance) is prudent to capture the true health concerns to those located in the hot zone along with those situated in the cooler zones of the application. Air surveillance can be used to understand the values of hazard concentration in workplace areas. Air sampling assessments / air quality assessments will offer advice to reduce levels as low as reasonably practicable. Any observations from the surveillance will assist continued compliance where a level of reassurance in the workplace is needed. The report raised by air surveillance / air sampling assessments can be used by the customer to incorporate findings within their workplace risk assessment for the specific task they have in mind.