It is no secret that pollution is a serious problem. Visit any major city for a day, and as well as soaking up the culture, you are sure to be will be inhaling a myriad of toxic chemicals. Now, the governments of Paris, Madrid, Mexico City, and Athens are taking a stand against air pollution by pledging to remove all diesel vehicles from their roads by 2025. The UK is following suit, with talks underway for taxes and bans on diesel vehicles. But what effect can we expect this to have?

Smog in China. Source:

Although many people associate just serious air pollution problems just with visible pollution, such as the smogs seen in China, this is definitely an extreme case. Far lower levels of toxic gasses can still be incredibly damaging; in Europe alone, overexposure to dangerous gasses causes 467,000 premature deaths every year!

Emissions from diesel vehicles are a huge contributor to air pollution – especially in big cities! When diesel is used in car engines, it releases huge amounts of both nitrogen oxide gasses, and tiny pieces of carbon called particulates into the atmosphere. Nitrogen oxide gasses are incredibly toxic, and inhaling high concentrations them can cause reduced lung capacity, headaches, and breathing problems. These gasses cause 23,500 premature deaths in the UK every year, and in London, 40% of them are emitted solely by diesel vehicles.

“Emissions from Diesel vehicles are a huge contributor to air pollution”

Particulates are also hugely damaging if inhaled; they can sit in the lungs, or be absorbed into the blood stream, causing heart and breathing problems, and even leading to cancer! The smaller the particulates are, the more easily they can be absorbed into the body, and the more damage they can cause. Unfortunately, diesel vehicles emit the tiny particulates (measuring just 2.5 microns in diameter) in huge quantities. Ontop of this, they also produce black carbon, which can be nine times more harmful than other types of particulate emissions, and are notorious contributors to global warming!

Vehicle emissions. Source: wikimedia

So what is that alternative? If the ban on diesel goes ahead, we can expect people to switch out their diesel cars for the less polluting petrol alternatives. With Diesel vehicles emitting 4X more NO2 than petrol cars, and 22X more particulates, and so it is hoped that switching out diesel for petrol will drastically reduce pollution levels in major cities!

However, as it turns out, petrol vehicles may come with their own problems, as they emit far more greenhouse gasses than their diesel alternatives. In fact, as recently as the early 1990s, back when diesel cars were made up only 10% of vehicles on the road, the government was encouraging the use of diesel cars over petrol! This is because not only do diesel cars emit 15% less CO2 than petrol cars, but they have a higher energy content, and use up between 20-25% less fuel (by volume) than equivalent petrol cars for the same drive.

“Whilst diesel cars Produce fewer greenhouse gasses, petrol is less polluting”

The toss-up between petrol and diesel cars boils down to a choice between decreased pollutants or decreased greenhouse gasses. Whilst diesel cars produce fewer greenhouse gasses, petrol is less polluting in terms of particulates and nitrogen oxide gasses. This puts government policy makers in a difficult position, as by choosing to ban diesel, they could be speeding up the rate of climate change.

Never fear though – it’s not all bad news for the environment. Electric and solar powered vehicles gaining popularity, and are becoming increasingly common choices for people looking to buy a new car! Scientists and policy makers alike hope that people will choose these green alternatives.


For more on London’s air pollution problem, check out ‘London breaks annual pollution limit’

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