Public Health England published a very important report on the evidence, feasibility and effectiveness of measures to improve outdoor air quality. This helps government bodies focus their resources on measures that are actually beneficial and value for money. I’m still absorbing the report but in a first reading, I found many key quotes that I think are worth sharing. I skipped the sections on industrial and agricultural measures since they are less relevant to Portsmouth. The report confirms much of what we have been saying in #LetPompeyBreathe for some time.

P.S. A motion to declare a climate emergency in Portsmouth is going to be debated 19th March. Includes pledge to achieve net zero carbon emissions in the Portsmouth by 2030 – this could have a drastic impact on air quality. Demonstration in support by XRPortsmouth at 11am. See item 16a in the agenda.

General principles, background

“Neighbouring authorities therefore need to work together, especially on interventions that apply to defined spatial areas, such as clean air zones.”

“It is better to reduce air pollution at source that to mitigate the consequences.” “Prioritising interventions that prevent or reduce emissions over those that address pollution once it has occurred.”

“Improving air quality can go hand in hand with economic growth. A common misconception is that air pollution is a necessary consequence of economic prosperity, whereas a clean environment is increasingly understood to support, rather than hinder, economic growth.”

“those whose livelihoods depend on driving but who do not have access to or the resources for cleaner vehicles may need particular support because some of the most effective interventions target road vehicle emissions. Without such support, action on air quality may have the perverse impact of increasing inequalities.”

“Systematically evaluating all interventions. Evaluation should be embedded in the design and costing of all future interventions, from their outset, to systematically gather evidence to inform best practice in the future.”

“A joined-up spatial planning and transport strategy is one of the most effective ways of increasing public transport use and active travel and reducing emissions from existing vehicles over time – some local authorities have successfully used workplace or other levies to fund improvement and use of public transport. Spatial planning can be used to reduce the need for vehicle use by design, and has a wider role in reducing emissions from buildings through energy-efficiency measures and use of renewable energy technologies. Promising local interventions that can help reduce demand for more polluting forms of transport are associated with use of public transport and active travel and include: subsidising public transport, designating new and priority bus measures, new tram and taxi schemes, providing school buses, providing infrastructure to enable walking and cycling, and promoting walking and cycling, which provide significant health benefits associated with physical exercise.”

‘This report proposes the adoption of a “net health gain” principle in any new policy or work programme which affects air pollution. If this is adopted, then any new development or proposal for change to existing developments will intend to deliver an overall benefit to people’s public health.’

“Children are particulary vulnerable to the effects of air pollution. […] We therefore recommend taking a particularly focused approach on reducing the impact of air pollution on children.”

“Those with lower socioeconomic status and those from ethnic minorities can be disproportionately exposed to environmental hazards, including proximity to industrial facilities, hazardous waste sites, air pollution, noise and occupational exposures (13). […] As it requires actions across social classes to reduce the gap between them, this includes measures to promote changes among those who are wealthier to reduce their impacts, especially if they affect the poorest or most vulnerable groups or areas.”

“During the course of 2 recorded episodes of poor air quality in March-April 2014, and for 2 days afterwards, there were statistically significant increases in the proportion of daily telephone calls to NHS 111 for difficulty breathing, daily consultation rates for GP in-hours for severe asthma and wheeze or breathlessness, and in the proportion of GP out-of-hours consultations for difficulty breathing or wheeze or asthma and attendances at sentinel emergency departments (16).”

Fraction of mortality attributable to particulate air pollution 2017, South east – 5.6%

Vehicle/fuel interventions

“Use of taxation is one of the most cost-effective measures and typically straightforward as it is implemented within an existing system. The literature is clear that any pricing mechanism scheme, whether it is a national tax duty or local road toll, should be designed with care as the unintended social inequality impacts of increased cost of transport affects the most deprived in society (51).”

“Very effective interventions for enhancing public health were road pricing measures, particularly in the case of low and integrated fares (for more than one public transport mode) which facilitate greater public transport use and help reduce social exclusion, and congestion and parking charges, which can help reduce car use (68).

“For road transport, interventions that aim to reduce the use of polluting forms of transport, such as national road pricing, increased fuel duty and LEZs, can be effective at reducing traffic emissions. This is mainly at local level, but they can also have national benefits if implemented at many areas across the country. However, such measures can be unpopular because of their restrictive nature, if not handled sensitively with considerable prior consultation and engagement. […] The promotion of walking and cycling, as well as subsidising public transport, have the greatest overall health benefits, providing flexibility to select routes away from heavily trafficked main roads whilst active travelling. Furthermore, these transport modes increase physical activity that leads to multiple health co-benefits. They also have potential to improve health inequalities, as they can be made equally accessible to all population categories.”

Measures found to be effective for improving air quality locally (Table 16 & 17):

  • Promote walking and cycling (mainly for potential for public health co- benefits rather than air quality)
  • National road pricing
  • Increase fuel duty/target at diesels
  • Promote abatement retrofit


“the interventions with the highest potential to be effective both at national but mainly at local level are related to traffic. Driving restrictions produced the largest scale and most consistent reductions in air pollution levels for all the interventions, the effectiveness strength was low, and the uncertainty range was high, with only 1 exception: driving restrictions. However, the paucity of evidence of effectiveness should not be confused with or assumed to be evidence of ineffectiveness […] measures, such as Low Emission Zone (LEZ) and road pricing, produced reductions in traffic, but not necessarily great improvements in air quality, perhaps due to localisation of emissions, for example by displacement. LEZ are potentially effective at reducing air pollutant levels (more effective for particulate matter, PM 10 than for nitrogen dioxide, NO 2 ) in cities. […] green infrastructure is potentially effective not only to improve air quality related public health outcomes, but also to improve health inequalities in urban areas and promote our health and well-being

“From the interventions identified for spatial/transport planning, driving restrictions produced the largest scale and most consistent reductions in air pollution levels at a city level, and seem to be an effective way to both reduce air pollution and improve public health. However, these restrictions may require changes in the political thinking and practice in the UK, and their longer-term effectiveness is not well evidenced.”

“There is evidence that appropriately designed urban green infrastructure can improve air quality and reduce exposure to noise on a local scale but should not be used in isolation to address air pollution (121).”

“Although the implementation of LEZs seems to be effective at reducing PM 10 levels, there is less evidence that LEZs are effective at reducing NOx. […] Although road pricing (congestion charge) is an effective mean of controlling traffic and reducing emissions (eg, in Stockholm), the impact on air quality is not always clear. […] They are expected to work best if combined with interventions that incentivise the use of both heavy and light duty vehicles with the most recent Euro 6 standards, which have a greater impact than earlier emission standards. The practical feasibility of this intervention should not be an issue, as it is mainly a matter of political will.”

“Health benefits from speed limits that slow down traffic mainly derive from the need to prevent fatalities and serious injuries to motorists, cyclists and pedestrians, and promote active travel. However, this measure does not necessarily result in significant decreases in ambient air pollution levels, even within the intervention zone.”

“Based on the results from ex-ante health impact assessments, the implementation of multiple traffic-related and infrastructure interventions is more likely to produce benefits for air quality and population than single interventions. The most effective combinations of these interventions depend on the issues and contexts of each local area.”

“The evidence from this rapid evidence assessment suggested that planning interventions are crucial for improving air quality and reducing population exposure to air pollution. The interventions with the highest potential to be effective both at national but mainly at local scale are related to traffic.”

“For some interventions, public health ‘co-benefits’ outweigh benefits of reduction of exposure to air pollution. […] there is a wealth of high-quality evidence showing that investing in infrastructure to support walking and cycling can increase physical activity, leading to multiple public health benefits, such as improved cardiovascular outcomes and improved weight status among children, adults and older adults (137). These are convincing reasons to promote these interventions.”

Measures found to be effective for improving air quality locally (Table 18):

  • Encouraging walking and cycling (for its health benefits rather than just for air quality)
  • Driving restriction (plus it has stronger evidence than most measures)
  • Co-implementation of various measures

Behaviour changes

“Little evidence was identified of behavioural interventions that promote alternative methods of transport as having a direct impact on air pollution or health outcomes. However, they should not be discounted, as there is a wealth of evidence showing that removing vehicles from the road can reduce emissions. There is also strong evidence for the health benefits of physical activity associated with active travel, such as walking and cycling. Raising awareness in itself is not enough to effect change: it must be done in conjunction with other behavioural and non-behavioural interventions.”

“The rapid evidence assessment found no substantive evidence of economic costs and benefits associated with behavioural interventions in any of the papers identified.” “The rapid evidence assessment of behavioural interventions found little direct evidence of public health benefits from any individual intervention or group of interventions. To achieve significant changes in behaviour (and associated reductions in emissions), a wide range of soft and hard measures need to be combined to maximise the effectiveness of the overall package of interventions.”

Measures found to be effective for improving air quality locally (Table 22):

  • No highly effective measures found, although several potentially effective measures identified


“Strategies that deliver the highest public health benefit relative to transport are actions or interventions aimed at reducing the use of polluting forms of transport, such as low emission zones and road pricing.”

Selected transport interventions’ evaluated public health impact (Figure 23):

  • Subsidising public transport (higher impact)
  • Promote abatement retrofit
  • National road pricing
  • Provision of school buses
  • Promote walking and cycling
  • Promotion of low emission zones
  • Increase fuel duty/target at diesels (lower impact)

“Planning policy focuses on ensuring air quality standards are achieved, rather than reducing emissions to as low as possible.”

Figure 24: Selected planning interventions’ evaluated public health impact:

  • Co-implementation of various measures (Planning) (higher impact)
  • Green infrastructure – urban vegetation
  • Driving restriction
  • Road pricing/Congestion charge
  • Encouraging walking and cycling (lower impact)

Figure 28: Selected behavioural interventions’ evaluated public health impact

  • Exposure reduction programmes (higher impact)
  • Public engagement
  • Eco-driver training
  • Investment in public transport (Encouraging)
  • Air quality messages/alerts/indices
  • No idling campaigns (lower impact)