Diesel engine exhaust emissions (DEEEs) are a mixture of gases, vapours, liquid aerosols and particles created by burning diesel fuels. This means they are a chemical hazard and should be managed in the same way as any other chemical – for example, identification, assessment and control.
To identify DEEEs present in the workplace, some form of monitoring is usually required. Occupational hygiene monitoring involves taking air samples over a period of time, to highlight the presence of DEEEs and, if present, the levels of DEEEs measured.
Other ways of identifying DEEEs include reviewing process-generated emissions (from diesel generators, for example) and manufacturer’s information on emissions from their equipment.
Assessing exposure to a hazardous chemical involves looking at the type, intensity, concentration, length, frequency and occurrence of exposure to workers. This includes the amount of the chemical being produced and any indicative occupational exposure limit values (or equivalent) associated with it.
Assessment of a chemical is a subjective process and based on the assessor’s knowledge and experience of not only the chemical in question but also the activity and environment in which it is being used. Existing controls will influence how an assessor will decide on the level of risk. Methods for recording this decision-making process vary, but can be numerical, using a high, medium or low scale or a red/amber/green rating.
National or international legislation influences the permittable level of emissions. While this is sometimes not a true reflection of the actual emissions from a vehicle or other piece of equipment, it may give some idea of expected emissions.
Check legal requirements for the country where work is taking place. Diesel quality and emission standards vary depending on the local situation, so local standards should be checked.
In European Union (EU) countries, for example, high standards are set for vehicle emissions – since 1992/93 there has been a steady reduction in allowable emissions on new vehicles including cars, trucks, trains, tractors and barges. Reductions were made in 2008/09 with the Euro 5/V standard, and in 2013/14 with the Euro 6/VI standard. In other parts of the world, standards for diesel may be lower.
Different equipment will have different standards too. A diesel generator may not be covered by some vehicle exhaust emission standards, for example, and seagoing ships may also be excluded.
Higher standards mean that the risks may be reduced, but not necessarily eliminated.
In the EU, Directive 2004/37/EC was amended in 2019. This focused on the protection of workers from the risks related to exposure to carcinogens or mutagens at work. For the first time, it included exposure limits for DEEEs.
The exposure limit value for DEEEs has been set at 0.05 mg/m3, measured as elemental carbon (EC). This limit value becomes effective in general occupational health environments from 21 February 2023.
Once DEEEs are identified and the risks from them assessed, they need to be controlled. A methodology, called the hierarchy of control (HoC), can be used to prioritise controls from most to least effective.
Typical actions to control DEEE exposure include the following.
- Using alternative energy sources to diesel-powered engines such as electric.
Reducing or substituting DEEEs
- Reduce exposure to as low as possible by purchasing low-emission engines and more fuel-efficient engines.
- Using cleaner fuels such as low-sulphur diesel fuels.
- Using exhaust gas recirculation systems to reduce emissions.
- Using tailpipe exhaust extraction systems.
- Implementing local exhaust ventilation systems and other ventilation systems.
- Using diesel exhaust gas ‘after-treatment’ systems such as catalytic converters.
- Fitting emission control devices (air cleaners) such as scrubbers, collectors and particle traps.
- Ensuring engines are switched off when not required.
- Regular maintenance, tune-ups and exhaust leak checks.
- Reducing the number of workers or the time workers are exposed to areas where DEEEs are generated. Ensure that other workers not involved with DEEE-generating activities are not exposed to DEEE areas.
- Making sure cold engines are warmed up in spaces with good ventilation.
- Job/task rotation to limit potential exposure times.
- Filtering air in vehicle cabs.
- Providing information, instruction and training on DEEEs to workers.
Respiratory Protective Equipment (RPE)
Appropriate RPE should be provided to all required workers. Ensure that:
- wearers are face-fit tested and that the RPE fits correctly
- wearers should be clean shaven to ensure a proper skin to RPE seal
- wearers are trained for use of the RPE
- the RPE is cleaned and checked before and after use
- filters and disposable RPE are changed regularly
- RPE is stored correctly
- defects are reported immediately and the RPE is not used if defected or not clean.
RPE is designed to protect wearers from inhaling harmful dusts, fumes, vapours or gases, and should only be used as a last control measure. It is better to control DEEE exposure using other controls. However, for some activities or work tasks, RPE may be the only practicable solution.
Consideration of DEEE assessment in practice
It is important to consider the organisation’s activities and worker’s exposure in the context of real-world situations. IOSH published a study in 2020 on the exposure of 141 drivers in London to DEEEs. This not only demonstrated how DEEE measurement could be done in practice, but also presented some suggestions of control measures that could mitigate the identified exposures.