IOSH
Diesel fumes
What they are, why they’re harmful and how to reduce exposure
Anyone who works with or around diesel-powered equipment or vehicles may be concerned about fumes. These are called diesel engine exhaust emissions (DEEE).
Facts about diesel fumes
- 14,728 people who died between 2000 and 2016 due to occupational exposure to DEEE, according to the World Health Organization (WHO).
- DEEE exposure limit value has been set at 0.05 mg/m3, measured as elemental carbon (EC). It came into effect in general occupational health environments in February 2023.
What are diesel engine exhaust emissions?
They are a mixture of gases, vapours, liquid aerosols and particles created by burning diesel fuels. They can contain:
- alcohols
- aldehydes
- ammonia
- aromatic compounds (benzene, polycyclic aromatic hydrocarbons and toluene)
- carbon dioxide
- carbon monoxide
- carbon (soot particles)
- fine diesel particulate matter (ash, carbon, soot, metallic abrasion particles, polycyclic aromatic hydrocarbons, silicates and sulphates). This can stay in the air for long periods of time, which allows the particulates to enter and penetrate deep into the lungs
- hydrocarbons
- ketones
- nitrogen
- nitrogen dioxide
- nitrogen oxide
- oxygen
- sulphur dioxide
- water vapour.
DEEE may contain more than 10 times the amount of soot particles than petrol exhaust fumes, and the mixture includes several carcinogenic substances. The International Agency for Research on Cancer, part of the WHO, has upgraded them to a group one carcinogen. They are treated as a cause of cancer in humans.
What's the issue?
Breathing in high quantities of DEEE can cause irritation in the respiratory tract within a few minutes of exposure, but prolonged exposure over many years may be more harmful.
The health effects will depend on:
- the type and quality of diesel fuel being used (for example, whether it’s low sulphur)
- the type and age of engine being used
- where and how it’s used and maintained – blue or black smoke can indicate a problem with the engine, which could mean that more toxic fumes are being produced
- the speed and workload demand on the engine
- the state of engine tuning
- the fuel pump setting
- the temperature of the engine
- the type of oil used
- whether a combination of different diesel-powered engines is contributing to overall exposure
- any emission control systems.
At the very least, short-term, high-level exposures to DEEE can irritate the:
- eyes
- throat
- nose
- respiratory tract
- lungs.
It can also cause:
- lung irritation
- allergic reactions (causing asthma)
- worsening of asthma
- dizziness, headaches and nausea.
Continuous exposure to DEEE can cause chronic respiratory ill health, with symptoms including coughing and feeling breathless. If people are exposed to DEEE regularly and over a long period, there is an increased risk of lung cancer.
How to manage diesel fumes
DEEE are a chemical hazard and should be managed in the same way as any other chemical – identification, assessment and control.
Once DEEE are identified and the risks from them assessed, they need to be controlled. A methodology, called the hierarchy of control, can be used to prioritise controls from most to least effective.
Controls
These are the typical actions to control DEEE exposure.
Managers and business owners
The plan, do, check, act (PDCA) health and safety management system provides eight simple steps to reduce DEEE exposure for workers.
Occupational safety and health professionals (OSH)
OSH professionals may need to help implement a DEEE exposure plan, liaise with an external provider who is implementing a plan or support with the maintenance of a DEEE exposure system that is already in place.
They will need to work with both managers and workers to help risk assess, implement controls, and eliminate or reduce DEEE exposures.
Tasks may include:
- regularly consult with workers
- provide support with the organisational DEEE risk assessment
- support with identifying and implementing suitable controls by following the hierarchy of controls
- support with the implementation or maintenance of the DEEE exposure plan
- routinely inspect known working tasks and activity areas that may be exposed to DEEE
- check that workers are following and understand procedures and safe systems of work
- source and provide suitable DEEE information and training
- investigate incidents and exposures
- support with health monitoring and surveillance requirements
- support with evaluations and instate any learning lessons to prevent future DEEE exposure incidents.
Workers
Workers should ensure they have been informed about the risks of DEEE exposure and how to avoid them. Here are some examples of what workers can do to protect themselves.
- Follow safe systems of work that are in place.
- Know how to use associated equipment correctly or control equipment and components.
- Be able to detect faults with equipment and know how to report them.
- Be able to use ventilation methods.
- Turn off engines when they are not in use and do not leave them idle, if possible.
- Do not eat or drink in areas known for DEEE exposures and wash hands and face before eating, drinking and leaving the workplace.
- Avoid skin contact with diesel fuel or oil.
- Know how to use RPE correctly.
- Report any symptoms associated with DEEE exposure and visit a medical professional.
More about diesel engine exhaust emissions
Why fumes still pose a risk
Standards for diesel emissions have been improving steadily over the past 20 years. Many people are now of the view that modern diesel engines are ‘safe’, at least in Europe and North America. We need to remember there are a lot more diesel vehicles on the roads in our towns and cities and this has offset some of the benefits from cleaner technologies. Also, there is a mixed fleet – both on the road and off – with many older vehicles and plants still in service. It will take time for exposures to decrease to levels that don’t pose a risk to worker health.
Why MOTs cannot pick up on potentially dangerous DEEE
All diesel engines emit particles into the air. These are very fine particles that in moderate concentrations are invisible to the eye. The MOT test provides a way of checking that these emissions are not excessive, but it does not mean there are no emissions. The test checks two things:
- there is a diesel particulate filter present in the vehicle, assuming it was fitted when the vehicle was new
- there is not excessive smoke – essentially, visible blue smoke.
It is really a fairly crude screening assessment to weed out the worst polluters.
Of course, MOTs in the UK only apply to on-road vehicles. Emissions from new off-road vehicles and other diesel engines used in construction, mining, quarrying, railways, agriculture, etc have been regulated in the EU since 1997. However, these standards are less demanding than for on-road vehicles and there is no real ongoing assessment of the acceptability of engine emissions such as with the MOT test.
Why DEEE are still an issue outside
Natural ventilation outside may provide adequate control, but you need to consider:
- how likely it is that workers will be exposed to DEEE
- how many of them
- to what extent
- for how long
- whether the exposures can be avoided.
If exposure to diesel fumes is likely, then other actions may be needed. Check out our guidance in the section on how to manage exposure.
UK enforcement activity
DEEE are covered by the Control of Substances Hazardous to Health Regulations 2002. Health and Safety Executive inspectors look for prevention or control of exposure to hazardous substances in the workplace. They will take enforcement action where risks of exposure are not effectively managed.