There is the opportunity to design future Clean Air Zones to maximise health benefits – rather than simply achieve concentration limits.
On the global stage, COP26 in Glasgow saw a series of commitments that kept the “Paris Goal” – of limiting global warming to 1.5° C – just about alive. There are Clean Air gains from many climate policies – from aspects of the transition to electric vehicles (have we witnessed a milestone on the journey to the end of the internal combustion engine?), and from reducing fossil fuel combustion for power and heat. In many cases, these air quality gains will be local and near-term – improved local air quality benefitting local health – lending a local immediacy to the global carbon challenge. A notable trend from COP was for city regions, private sector and business groups to increasingly take the lead in climate commitments.
International progress towards cleaner air was mixed – with COP26 commitments to reduce coal use from many nations, but the final Glasgow Climate Pact committed to “phase down unabated coal power and inefficient fossil fuel subsidies”. Abated coal power – with carbon capture on the exhaust stream – remains at the demonstrator stage, while “inefficient” will be very much in the eye of the beholder – implying likely continuing coal use in many regions, with associated carbon and air pollutant emissions.
In September, the World Health Organisation (WHO) published a long-awaited update to their global Air Quality Guidelines (the first such since 2005). These are levels below which no risk to human health has been found (irrespective of the cost or feasibility of achieving these levels).
For fine particles (PM2.5), the annual guideline was reduced from 10 to 5 mg m-3 – a level which will be very challenging to achieve, given background (natural and imported) concentrations of a similar magnitude. In November, the Government defeated a Lords amendment to adopt the previous WHO guideline for PM, of 10 mg m-3, as a legally binding target in the Environment Bill for England – now the new Environment Act, with targets due to be set following further consultation in 2022.
For nitrogen dioxide gas (NO2), the WHO guideline was reduced from 40 to 10 mg m-3. In UK cities NO2 comes overwhelmingly from diesel emissions – and achieving compliance with the UK legal limit of 40 mg m-3 has been a key driver for Clean Air Zone (CAZ) policies which target the most polluting vehicles. The Birmingham CAZ was introduced in June 2021 – only the second such charging zone outside London, where the existing Ultra Low Emission Zone was extended. While pollutant reductions arising from the Birmingham CAZ are complex to separate from effects of weather and other changes in travel patterns, our own analyses show a clear reduction in NO2 levels in the city centre, after correcting for these influences, in the first three months of the scheme. However, direct health benefits from the current CAZ scheme are likely to be marginal, and NO2 levels will still exceed the WHO guideline level in all wards across the West Midlands.
The CAZ will have a limited effect on PM2.5 – which also drive significant health impacts. For 2022, we expect a far greater local and national government focus on PM, tackling air pollution sources beyond road transport - such as agriculture and domestic heating. We also expect an increasing focus on poor air quality as a healthcare sector issue, intensified by emerging evidence that poor air quality is linked to worse outcomes from COVID-19 disease (although impacts of the Omicron variant are unknown at the time of writing).
Key challenges remain coherently linking Carbon / Net Zero and Air Quality policy – for example around the use of biomass/wood combustion for local heat and power – which can be (nominally) carbon neutral, but which may challenge deforestation/biodiversity aspirations, and can represent a major local air pollution source. There is the opportunity to design future Clean Air Zones to maximise health benefits – rather than simply achieve concentration limits. Shaping holistic policies which avoid trade-offs and optimise societal benefits will be essential to maximise clean air gains.