While at a national level air pollution continues to reduce, poor air quality is still the greatest global environmental risk to human health. On Clean Air Day, we spoke to air quality scientists from the National Centre for Atmospheric Science about the future of air pollution in the UK.

Professor Jacqui Hamilton, Professor Ally Lewis and Dr Sarah Moller outline the factors that will contribute to air quality in the future, both indoors and outdoors.

“The UK’s air pollution in the coming few decades will be different to the recent or distant past – and it will change as energy supplies and transport systems are decarbonised, lifestyles and working practices evolve, and as new materials, products and processes are adopted,” sets out Professor Jacqui Hamilton, Science Director at the National Centre for Atmospheric Science and atmospheric chemist at the University of York.

Over the coming decades, climate change will impact air quality in the UK and around the world.

“Hotter and drier summers in the UK will lead to a range of effects that could create poor air quality. These could range from increased emissions from wildfires, to calm and persistent weather events that cause stagnated air to accumulate in cities, and increased air conditioning use in buildings that might worsen indoor air quality,” explains Professor Hamilton.

Stormier, windier, and wetter winters are expected in future with climate change, which could lead to increased mixing of air and deposition of pollutants – improving air quality during those months.

Climate change has the potential to alter large-scale atmospheric circulation patterns, which might bring polluted air to the UK more frequently from other parts of the world.

Transboundary air pollution occurs when air pollutants emitted in one location are transported to another region or country, with impacts on the receiving environment, economy, and population’s health.

Air pollution is a transboundary challenge that requires both national and international solutions. To achieve the best possible air quality, the UK government will need to negotiate further international reductions in emissions – particularly from continental Europe.

Professor Ally Lewis, a senior air quality researcher at the National Centre for Atmospheric Science and University of York explains how air quality in northern Europe is closely related:

“When the UK reduces its air pollution emissions we derive health benefits here, and so do our neighbouring countries such as France, Belgium and the Netherlands. When those countries reduce their emissions, the UK is also a big beneficiary of cleaner air.”

The UK’s transition to net zero greenhouse gas emissions has the potential to reduce air pollution in nearly every sector, ranging from transport, and home heating to energy production, but the scale of benefits often depends on which replacement low-carbon technologies and processes are used and how they are managed.

Some actions to deliver net zero could counteract progress being made on air quality through introducing new sources, increasing emissions of air pollutants, or by changing behaviours.

Researchers from the National Centre for Atmospheric Science are working with government departments to advise, and provide evidence, on the likely positive and negative effects of the UK’s transition to net zero greenhouse gas emissions on air pollution.

Dr Sarah Moller, senior research fellow at the National Centre for Atmospheric Science and University of York, comments that:

“The UK’s transition to net zero greenhouse gas emissions presents a real opportunity to deliver multiple environmental benefits, including improvements in air quality. But the choices made about how we will meet this ambitious target will determine whether those co-benefits are realised. Reducing our reliance on combustion in transport, and energy and heat production would have large benefits for air pollution. While other proposed actions will be less clearly beneficial and may introduce new pollution sources;  the use of low carbon fuels and the processes that produce them would be an example of this.”

The UK’s pathway to net zero could bring immediate benefits for air quality. This is partly because air pollutants are being co-produced alongside greenhouse gases in a number of key sectors, including electricity production from fossil fuels, industrial manufacturing, and transportation.

However, not all types of pollution will fall straight away. Some pollutants, including fine particulate matter (referred to as PM2.5), may not fall significantly until later in the transition to net zero, which is planned to be complete by 2050.

Dr Moller states that:

Some low carbon technologies eliminate combustion emissions, but still retain pollutants derived from friction. For example, electric vehicles will still create particle pollution from road surface abrasion and brake wear. Because of that, walking, cycling and public transport remain the cleanest options for transitioning to net zero emissions.

Major low-carbon infrastructure projects could create localised air pollution during their construction phases, and plans for widespread forest planting should take account of the natural emissions released by certain tree species. Consideration of these wider impacts should mean that negative effects can be managed, minimised, or compensated for by action elsewhere.

Significant inequalities exist in where pollution emissions occur. Across the UK, people in the most deprived groups of society typically live in locations with the highest levels of locally emitted air pollution.

“The inequalities in the distribution of emissions are particularly significant for nitrogen oxides. People experiencing the highest levels of deprivation often live closest to major roads, and in areas of high housing density. Densely populated areas expose residents to pollutants created by combustion from heating,” explains Dr Moller. 

She adds: “These inequalities will persist in the future. Location plays such a large part in determining what emissions people are exposed to, and it is not yet clear how future policy will impact the level of inequality.”

Some changes should be beneficial, such as reducing nitrogen dioxide concentrations from road vehicles. The future impact of other measures is less certain, for example choices around decarbonisation of domestic heating.

Decarbonisation of domestic heating will impact inequalities in exposure – but whether this improves the situation or makes it worse will depend on which technology is chosen, and whether any emissions from alternative fuels are managed effectively.

Indoor air quality is a growing part of the problem for health. As a nation, we spend nearly 90% of our time indoors on average – yet our understanding of indoor air pollutants, and how to reduce exposure to them, is highly uncertain compared to our understanding of outdoor pollution.

“There is currently no national dataset that can be called on to analyse trends in indoor air pollution in the same way we can track outdoor air pollution over recent decades. And, every indoor space and its occupants represent a unique mix of factors that determine air quality,” explains Professor Lewis.

Additionally, indoor pollution is closely linked to outdoor pollution – as air moves between both environments. It is not yet fully understood how changes in air exchange may impact indoor air. For example, better home insulation might reduce air exchange allowing pollution to accumulate inside. And, improving outdoor air quality may mean less pollution enters our home than in previous decades.

The air pollution research teams at the National Centre for Atmospheric Science aim to understand where pollution comes from, the impacts it has on health and the environment, and how it can be reduced.

Moving forward in the research community, better account needs to be taken of indoor air quality – especially for vulnerable groups and young children.

Studies focusing on new pollutants will be required, to identify harmful gases and particles emitted as a result of novel materials, activities, and their interactions with the environment.

Environmental laws and technological innovation will continue to have a strong influence over air pollution.

Atmospheric scientists will need to track the air quality impacts of different behaviours and responses to future policies and technologies. The National Centre for Atmospheric Science will continue to play an important role in air pollution monitoring and modelling, in order to support the UK in improving air quality for all.