Cleaner Air for Scotland 2 - Towards a Better Place for Everyone

A new air quality strategy to replace Cleaner Air for Scotland - The Road to a Healthier Future, setting out the Scottish Government's air quality policy framework for the next five years and a series of actions to deliver further air quality improvements.


1. In November 2015, the Scottish Government published 'Cleaner Air for Scotland – The Road to a Healthier Future'.[4] This was the first Scottish air quality strategy separate from the rest of the UK. CAFS sought to bring together the major policy areas relevant to air quality – climate change, transport, planning, health and energy – within one overarching framework. The strategy set out around 40 actions relating to these policy areas. Progress in delivering the CAFS actions is summarised in a series of annual reports, with a final report reviewing the overall achievements of CAFS published in February 2020.[5]

2. When CAFS was published, there was a commitment to review the strategy after five years. However, given the significant number of policy developments with implications for air quality over recent years, alongside an increasing body of evidence demonstrating the human and environmental health impacts of poor air quality, it was decided to bring this process forward. Therefore, in November 2018, the then Cabinet Secretary for Environment, Climate Change and Land Reform commissioned an independently-led review of CAFS. The purpose of the review was twofold, firstly to assess progress to date in implementing the actions contained in the strategy and secondly to identify priorities for additional actions to deliver further air quality improvements.

3. The review was overseen by a steering group chaired by Professor Campbell Gemmell and supported by four specialist working groups covering health and environment; placemaking; agricultural, domestic and industrial emissions; and transport. The steering group submitted its final report[6] to the Scottish Government in July 2019 setting out a series of conclusions and recommendations. Between October and December 2019, an online survey allowed individuals and organisations to submit their views on the recommendations.[7]

4. Both the review findings and those wider views were used to inform development of a draft version of CAFS 2 which was consulted on in late 2020 and early 2021.[8] This final version of CAFS 2 additionally takes into account the responses to that consultation.

The need for additional action on air quality

5. Over the last 50 years, air quality has improved beyond all recognition. The choking smogs of the 1950s are a thing of the past, driven by concerted action, especially on energy use, industry and transport. Air quality in Scotland's towns and cities is improving year on year, but there are still areas across the country where air quality standards for human and environmental health are not being met. Road transport in urban areas remains the significant contributor to poor air quality. Air pollution especially impacts on the more vulnerable members of society – the very young and the elderly or those with existing health conditions such as asthma, respiratory and heart disease. This makes air quality an important health inequalities issue.

6. As the CAFS review clearly demonstrated, additional work is necessary to ensure full compliance with legislative requirements, and to deliver further human health and environmental quality improvements. Also, the rate of decline in most regulated pollutant sources is now reducing. This suggests that the easier actions or at least those deemed priority, urgent and important have been taken and we are now dealing with the harder issues, where interventions may be more complex and more focused on behaviour change as well as technological improvement. An associated question is what our target levels for the key pollutants should be and how quickly we wish to reach these.

7. The majority of the 40 actions set out in CAFS, together with several additional actions not included at the time of publication have been completed; however some are still ongoing. Those actions will continue to be taken forward in parallel with the new actions set out in this strategy. The CAFS 2018-19 progress report[9] provides full details on completed actions and the status of those still being implemented.

8. Further reductions in air pollution will require concerted action across many sectors including national and local government, the private and public sectors, and by the public itself. Increased awareness and understanding of the key issues and the interlinkages between them is needed, built on the foundation of good place design.

9. At the outset, it is important to state that air pollution, climate change, quality of the urban environment and mobility are strongly interconnected. From this, it follows that effective policy coordination across these broad themes, at both central and local government levels, will deliver co-benefits greater than those possible by considering each in isolation. Although there has been some progress in this regard, it is clear that more needs to be done if these co-benefits are to be fully realised. Key to this will be embedding placemaking principles, with a strong focus on nature-based solutions, across policy areas to guide our way to a cleaner, healthier and more attractive environment. Reducing the need to travel, for example through the development of 20 minute neighbourhoods, along with making it easier for people to utilise sustainable travel options, are also relevant here.

Emissions trends – 1990 to 2018

10. Emissions of the eight main air pollutants are lower in 2018 than they were in 1990 (Figure 1), although the rate of decline for some of these has started to level off in recent years. This rate of decline is relatively similar for particulate matter (PM10 and 2.5), oxides of nitrogen (NOx), non-methane volatile organic compounds (NMVOC), sulphur dioxide (SO2) and carbon monoxide (CO). Lead (Pb) shows a much higher rate of reduction from 1990 to 2000, coinciding with the phase-out of leaded petrol from 2000. By contrast, ammonia (NH3) emissions have declined at a slower rate than other pollutants, and even increased slightly over recent years. More detailed information can be found in the 'Air Pollutant Inventories for England, Scotland, Wales and Northern Ireland: 1990-2018'[10]

Figure 1: Emissions trends for the main air pollutants in Scotland since 1990
This graph shows that all pollutant emission levels are lower in 2018 than they were in 1990, although the rate of decline for some of these has started to level off in recent years. Unlike emissions of the other main air pollutants, which have declined significantly over the last 30 years, ammonia levels have not declined at the same rate over this period. Agriculture accounts for around 90% of total ammonia emissions in Scotland.

(Source: National Atmospheric Emissions Inventory)

Coronavirus (COVID-19)

11. Since early 2020, the COVID-19 pandemic has changed the way we work, socialise and travel. The current state of knowledge and lessons learnt at the time of publication are reflected in this strategy. Any future developments relating to the pandemic which have implications for the policies set out in CAFS 2 over its five year lifespan will be addressed through updates to the delivery plan which was published alongside the strategy.

12. The unprecedented changes in living and working patterns associated with the COVID-19 lockdown had a significant effect on air pollution.[11], [12] In Scotland, during the initial lockdown period (March to June 2020), nitrogen dioxide (NO2) levels declined. Analysis of eight urban air quality monitoring stations showed peak decreases from 49% at Atholl Street, Perth to 72% at Hope Street, Glasgow.[13] Pollution levels gradually increased again once lockdown measures began to be relaxed and in many locations gradually returned to pre-lockdown levels. Subsequent reintroduction of certain lockdown measures also impacted on air quality. The significant decrease in pollution levels during lockdown was still not as much as expected, despite large reductions in traffic. This is because much of urban ambient NO2 is from heavy diesel vehicle emissions, and small numbers of trucks and buses contribute disproportionately to pollution levels. The impact of the lockdown on particulate matter (PM) is more complex. A significant component of PM is transboundary (transported in the atmosphere from elsewhere) and the relationship between traffic reductions and local air quality is therefore not as straightforward as for NO2. As restrictions are lifted, the key challenges will be to understand how the air pollution reductions seen during lockdown periods can be maintained long-term and sustainably, and how these changes can benefit the long-term health of the population.

Figure 2: Changes in NO2 concentrations at selected monitoring sites between January and June 2020
The dashed line represents the start of the lockdown on 23rd March 2020. Concentrations of NO2 decrease at most sites after this date. Highlighted lines represent monitoring sites which displayed the largest decrease. Glasgow Kerbside monitoring site shows the largest decrease in concentrations.

(Source: Ricardo Energy & Environment)

13. Many pieces of research looking at the relationship between air quality and COVID-19 have been undertaken around the world since the start of the pandemic. A number of these studies have identified an association between air pollution and both exacerbated symptoms and mortality levels attributed to COVID-19. However it is necessary to treat the results with caution at this stage. Long-term data covering the full period of the pandemic and beyond will be required in order to draw robust conclusions on the overall impacts of air pollution on total cases and numbers of deaths.

14. At the beginning of July 2020, the Air Quality Expert Group (AQEG), which advises the UK Government and devolved administrations on air quality, published a report of its call for evidence on changes in air pollution emissions, concentrations and exposure across the UK during the pandemic.[14] This provides a useful overview of the available evidence at that point in time. Post-lockdown, rising pollution levels in urban areas could potentially amplify the effects of COVID-19 if the virus is still in circulation at significant levels.

15. It is recognised that green recovery must form a central part of Scotland's emergence from the pandemic. The report of the Scottish Government's Advisory Group on Economic Recovery, published in June 2020, sets out a number of recommendations on how this might be achieved.[15] Such an approach will help Scotland meet its greenhouse gas emissions reduction targets and improve air quality, whilst supporting economic recovery.

Figure 3: Differences between actual and business as usual NO2 concentrations at Scottish monitoring network sites in 2020
For most of the sites the annual mean measured NO2 is lower than predicted by the business as usual model. Glasgow Kerbside, Dumfries, and Edinburgh St John's Road observe the greatest decrease in NO2, when compared to business as usual.

(Source: Ricardo Energy & Environment)

Air Quality Legislation National Emission Ceilings Directive (NECD)

16. The National Emission Ceilings Directive (NECD) (2016/2284/EU) sets national emission ceilings for certain atmospheric pollutants (nitrogen oxides, non-methane volatile organic compounds, sulphur dioxide, ammonia and (new in the 2016 Directive) fine particulate matter PM2.5). It implements at EU level obligations under the United Nations Economic Commission for Europe (UNECE) Convention on Long-Range Transboundary Air Pollution of 1979 (CLRTAP)[16] and, in particular, its 1999 Protocol to Abate Acidification, Eutrophication and Ground-level Ozone of 1999, which was revised in 2012[17] (the revised Gothenburg Protocol). The NECD transposes 2020 targets agreed under the revised Gothenburg Protocol, along with more ambitious targets for 2030. Following the UK's exit from the European Union (EU), the NECD is part of retained EU law.

17. The NECD has been transposed into domestic law through the National Emission Ceilings Regulations (NECR) 2018[18] and the requirements will be implemented at UK level through a National Air Pollution Control Programme (NAPCP).[19] Although the UK has met the 2020 targets for all pollutants (other than ammonia), new policies will be required to ensure 2030 compliance. Further information is set out in the joint UK NACP.[20] The actions set out in this strategy will make an important contribution to the NAPCP and Scotland's wider role in securing compliance with international commitments.

Table 1 – Source Emission Contributions Ranked by Sector, Scotland 2018
Sector NH3 CO NOx VOC PM10 PM2.5 SO2 Pb B[a]p Dioxins
Agriculture 92.0% IE 0.0% 9.3% 17.5% 4.5% IE IE IE IE
Energy Industries IE 4.1% 12.7% IE 1.6% 2.4% 34.5% 3.6% 0.0% 0.7%
Fugitive IE 0.7% IE 13.4% IE IE 1.1% IE IE IE
Industrial Combustion IE 26.5% 14.2% 1.1% 7.7% 13.5% 11.7% 14.9% 0.8% 11.4%
Industrial Processes 0.2% 0.2% 0.0% 53.1% 27.6% 9.2% 4.7% 19.9% 1.5% 6.8%
Residential, Commercial & Public Sector Combustion IE 43.3% 19.7% 3.2% 25.1% 44.2% 29.1% 9.1% 90.3% 42.9%
Solvent Processes IE IE IE 16.5% 0.6% 0.4% IE IE 0.1% 0.5%
Transport Sources 1.2% 23.4% 47.6% 2.7% 15.3% 20.1% 17.7% 51.9% 2.7% 5.1%
Waste 2.0% 0.7% 0.0% 0.0% 1.1% 1.8% IE 0.6% 4.5% 32.6%
Other 4.5% 1.2% 5.8% 0.6% 3.5% 4.0% 1.3% 0.1% 0.0% 0.0%

(Source: National Atmospheric Emissions Inventory)

*The sector: "other" includes all "other" categories in the inventory and also a number of categories that are insignificant for a specific pollutant. These have been marked in the table as "IE" (used in inventory reporting for "Included Elsewhere").

Local Air Quality Management

18. Under the Environment Act 1995 and associated regulations, all Scottish local authorities are required to regularly review and assess air quality in their areas against objectives for several air pollutants of concern for human health.[21] If this assessment indicates that any objective is not being met, the authority concerned must declare an Air Quality Management Area (AQMA) and produce an action plan setting out measures to address the issues identified. At the time of publication of this strategy, 36 AQMAs were in place in Scotland, all but two of which were declared for transport-related exceedences of nitrogen dioxide and/or PM10. The majority of issues in these AQMAs relate to localised pollution hotspots within urban centres. The remaining two AQMAs have been declared for industrial emissions of sulphur dioxide and PM10 respectively.[22]

19. Data from the Scottish air quality monitoring network, which consists of around 100 sites across the country,[23] show a clear downward trend in pollutant concentrations in recent years. In some cases, declared AQMAs are already compliant with the objectives; however the Scottish Government requires at least three consecutive years of compliance before revocation can proceed. The Scottish Government is working closely with relevant authorities to ensure revocation can take place as soon as possible. In remaining cases, further progress with action plan implementation is needed to secure compliance.

Figure 4: Changes in PM10 emissions in Scotland since 1990
Unlike most other pollutants, the emissions profile of PM10 is diverse: transport sources, residential and industrial processes each accounted for over 15% of total emissions in 2018. Emissions from energy industries and transport sources have had the most notable impact on the trend.

(Source: National Atmospheric Emissions Inventory)

Figure 5: Changes in PM2.5 emissions in Scotland since 1990
PM2.5 emissions have declined by 67% since 1990. The primary drivers for the decline in emissions since 1990 are the switch in the fuel mix used in electricity generation away from coal and towards natural gas, particularly in the early time series, and later reductions in emissions from the transport sector.  Since 2005, declines in emissions have been offset by increases in emissions from the residential sector, and in particular, the combustion of wood.

(Source: National Atmospheric Emissions Inventory)

Figure 6: Changes in NOx emissions in Scotland since 1990
NOx emissions have declined by 73% since 1990, mainly due to changes in transport sources, particularly in road transport. This decline is driven by the successive introduction of tighter emission standards for petrol cars and all types of new diesel vehicles over the last decade.

(Source: National Atmospheric Emissions Inventory)

Ambient Air Quality Directive

20. Following the UK's exit from the EU, under retained EU law, the UK is required to meet limit and target values for a range of air pollutants. In Scotland, full compliance has been secured with all of these limit and target values, with the exception of a small number of nitrogen dioxide exceedences.

National Nitrogen Balance Sheet

21. The Climate Change (Emissions Reduction Targets) (Scotland) Act 2019,[24] requires the creation of a Scottish Nitrogen Balance Sheet (SNBS) by March 2022. Once established, the SNBS will quantify nitrogen flows at the national scale across economic and environmental sectors, including agriculture, waste management, production and consumption, and between water, land and air. It will also cover all major forms of nitrogen, including air quality pollutants such as nitrogen dioxide and ammonia.

22. The SNBS will provide a baseline on Scotland's current nitrogen use efficiency, i.e. the proportion of nitrogen used for its intended purpose vs. losses to the environment, at a national scale. This baseline creates a new type of cross-sectoral evidence base that quantifies the uses and losses of nitrogen and enables identification of more and less nitrogen use-efficient processes, and will inform future decision-making across a range of policy areas, including air quality. The SNBS itself will also be regularly reviewed and updated.



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