Additional diesel engine emissions resources, related campaigns and FAQs

It’s true that the standards for diesel emissions have been improving steadily over the past 20, and many people are now of the view that modern diesel engines are ‘safe’, at least in Europe and North America. The Euro 6 standard for light passenger and commercial vehicles has come into force, and a new standard for emissions from trucks and buses came into force in 2013. Permitted particulate emissions are now almost 40 times lower than they were in the 1990s. However, 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. So, it will take time for exposures to decrease to levels that don’t pose a risk to worker health.

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:

1. there is a diesel particulate filter present in the vehicle, assuming it was fitted when the vehicle was new
2. 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.

Natural ventilation outside may provide adequate control, but you need to consider how likely it is that workers will be exposed to diesel engine exhaust fumes, how many of them, to what extent, for how long and whether the exposures can be avoided. If exposure to diesel fumes is likely, then other actions may be needed. Check out our guidance in this section on how to manage exposure.

Diesel engine exhaust fumes 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 and will take enforcement action where risks of exposure are not effectively managed.