Low emission zones have been introduced to help cities to reduce the amount of air pollution being emitted in densely populated areas, with a primary focus on tackling emissions from road transport.

Cities have been granted the authority to create their own regulations in areas designated as low-emission zones. The idea is to reduce the number of polluting vehicles on our roads and encourage cleaner forms of transport in the city.

London is the best-known example of a low-emission zone. Most vehicles driving in London’s low emission zone must meet strict emissions standards, or pay a daily charge to travel within the area.

The strictest demands are placed on diesel vehicles, and that includes passenger cars, lorries and buses. The rules are slightly more relaxed for petrol vehicles because they have turned out over the last decade to be somewhat cleaner from an air quality perspective than was expected. 

Elsewhere in the UK, cities are introducing their own variation of the low-emission zone, such as Bath, Leeds and Birmingham.

But they will not all follow the London template. Professor Alastair Lewis from the National Centre for Atmospheric Science and the University of York explains:

Professor Lewis anticipates that the most significant impact of low emissions zones will be a reduction in nitrogen dioxide concentrations. And, the biggest reductions will be seen at the roadside because nitrogen dioxide in cities is produced predominantly from road traffic.

This would be good news for city dwellers, as nitrogen dioxide is associated with respiratory issues, asthma prevalence and reduced life expectancy.

There will be other benefits to pollutants like particulate matter, but they may be less pronounced because particles come from a far larger range of sources. Therefore restricting vehicle emissions is only going to have a moderate effect.

It’s also important to remember that with traffic, a lot of the focus today in low emissions zones is around emissions from the exhaust, but most modern vehicles still create particle pollution from the wear of tyres on the ground and the use of brakes. This won’t be covered by the new low-emission zones.

And beyond vehicles, there are many other different sources of pollution that aren’t being included in low emissions zone rules just yet. We use boilers for heating, burn fuel for cooking, and a huge range of other volatile chemical substances are also emitted from industrial processes and domestic products. 

The complex nature of air pollution and the large number of contributing sources mean that no single action will cure the problem for us.

Cities are working towards the air quality standards set out at a national level, but it’s not just about passing the test. Most of the evidence we have on air pollution suggests that we would all continue to see health benefits by reducing pollution, even when cities are below the legislative limits.

Professor Lewis points out that measuring the impact of low emission zones will be tricky because air pollution is also influenced by other changing factors, such as new vehicle standards and weather patterns.

However, that shouldn’t detract from the positive steps being taken.

You can hear more from Professor Lewis on BBC Sounds, where he shared his take on low-emission zones with Radio 4’s Inside Science.