Can the UK achieve the PM₂.₅ WHO 10 μg m-3 interim target by 2030?

Background: The UK Government is currently setting two PM₂.₅ targets for its Environment Bill. The first is a concentration target to be met by some future date and the second a population exposure reduction target, aimed at reducing exposure gradually over time. Aim: The aim of this research was to combine existing UK 2030 emissions forecasts, the UK’s Climate Change Committee (CCC) Net Zero vehicle forecasts, and the Greater London Authority’s policy forecasts, to establish whether the UK can meet the PM₂.₅ WHO 10 μg m-3 interim target by 2030, and to assess the likely exposure reduction. Method: We used a combination of European, UK National and London Atmospheric Emissions Inventory forecasts between 2018 and 2030. For road transport we calculated emissions for the Balanced Net Zero Pathway, published by the CCC, which includes widespread vehicle electrification, and two London specific policies aimed at reducing PM₂.₅. The emissions were combined with the WRF met. model and the CMAQ-urban coupled model, providing UK PM₂.₅ concentrations down to 2km spatially and then every 20m close to major roads. Results: UK PM₂.₅ concentrations in 2030 were below 10 μg m-³, for over 99% of the UK population. In London, the second scenario reduced PM₂.₅ locally, with <1% of the area of London predicted to be above 10 μg m-3. Accounting for model uncertainty resulted in ~4% of the UK remaining at risk of exceeding 10 μg m-3 albeit in cities such as Birmingham and Manchester. Conclusions: We have shown the combined benefits of UK air quality, Net Zero and local policies for PM₂.₂ control, in almost achieving the PM₂.₅ WHO interim target. We identified important but uncertain emissions sources, such as non-exhaust vehicle emissions, cooking aerosol and domestic and industrial wood burning. This work has been submitted to the UK Environment Bill consultation

Scorched earth:How will changes in the strength of the vegetation sink to ozone deposition affect human health and ecosystems?

This study investigates the effect of ozone (O3) deposition on ground level O3 concentrations and subsequent human health and ecosystem risk under hot summer "heat wave" type meteorological events. Under such conditions, extended drought can effectively "turn off" the O3 vegetation sink leading to a substantial increase in ground level O3 concentrations. Two models that have been used for human health (the CMAQ chemical transport model) and ecosystem (the DO3SE O3 deposition model) risk assessment are combined to provide a powerful policy tool capable of novel integrated assessments of O3 risk using methods endorsed by the UNECE Convention on Long-Range Transboundary Air Pollution. This study investigates 2006, a particularly hot and dry year during which a heat wave occurred over the summer across much of the UK and Europe. To understand the influence of variable O3 dry deposition three different simulations were investigated during June and July: (i) actual conditions in 2006, (ii) conditions that assume a perfect vegetation sink for O3 deposition and (iii) conditions that assume an extended drought period that reduces the vegetation sink to a minimum. The risks of O3 to human health, assessed by estimating the number of days during which running 8 h mean O3 concentrations exceeded 100 μg m−3, show that on average across the UK, there is a difference of 16 days exceedance of the threshold between the perfect sink and drought conditions. These average results hide local variation with exceedances between these two scenarios reaching as high as 20 days in the East Midlands and eastern UK. Estimates of acute exposure effects show that O3 removed from the atmosphere through dry deposition during the June and July period would have been responsible for approximately 460 premature deaths. Conversely, reduced O3 dry deposition will decrease the amount of O3 taken up by vegetation and, according to flux-based assessments of vegetation damage, will lead to a reduction in the impact of O3 on vegetation across the UK. The new CMAQ-DO3SE model was evaluated by comparing observation vs. modelled estimates of various health related metrics with data from both urban and rural sites across the UK; although these comparisons showed reasonable agreement there were some biases in the model predictions with attributable deaths at urban sites being over predicted by a small margin, the converse was true for rural sites. The study emphasises the importance of accurate estimates of O3 deposition both for human health and ecosystem risk assessments. Extended periods of drought and heat wave type conditions are likely to occur with more frequency in coming decades, therefore understanding the importance of these effects will be crucial to inform the development of appropriate national and international policy to mitigate against the worst consequences of this air pollutant

Scorched earth: how will changes in ozone deposition caused by drought affect human health and ecosystems?

Abstract. This unique study investigates the effect of ozone (O3) deposition on ground level O3 concentrations and subsequent human health and ecosystem risk under hot summer "heat wave" type meteorological events. Under such conditions, extended drought can effectively "turn off" the O3 vegetation sink leading to a substantial increase in ground level O3 concentrations. Two models that have been used for human health (the CMAQ chemical transport model) and ecosystem (the DO3SE O3 deposition model) risk assessment are combined to provide a powerful policy tool capable of novel integrated assessments of O3 risk using methods endorsed by the UNECE Convention on Long-Range Transboundary Air Pollution. This study investigates 2006, a particularly hot and dry year during which a heat wave occurred during the summer across much of the UK and Europe. To understand the influence of variable O3 dry deposition three different simulations were investigated during June and July: (i) actual conditions in 2006; (ii) conditions that assume a perfect vegetation sink for O3 deposition and (iii) conditions that assume an extended drought period that reduces the vegetation sink to a minimum. The risk of O3 to human health, assessed by estimating the number of days during which running 8-h mean O3 concentrations exceeded 100 μg m−3, show that on average across the UK, there is a difference of 16 days exceedance of the threshold between the perfect sink and drought conditions. These average results hide local variation with exceedances reaching as high as 20 days in the East Midlands and Eastern UK. Estimates of acute exposure effects show that O3 removed from the atmosphere through dry deposition during the June and July period would have been responsible for approximately 460 premature deaths. Conversely, reduced O3 dry deposition will decrease the amount of O3 taken up by vegetation and, according to flux-based assessments of vegetation damage, will lead to protection from O3 across the UK. The study therefore emphasises the importance of accurate estimates of O3 deposition both for human health and ecosystem risk assessments. Extended periods of drought and heat wave type conditions are likely to occur with more frequency in coming decades, therefore understanding the importance of these effects will be crucial to inform the development of appropriate national and international policy to mitigate against the worst consequences of this air pollutant. </jats:p

Pathway to WHO: Achieving clean air in the UK - Modelling air quality costs and benefits

Background/aim The Clean Air Fund commissioned us to investigate whether the WHO interim target of 10 µg/m3 PM2.5 could be met by 2030 with assessment of the health benefits of these air pollution reductions, to inform consultation on targets for the UK Environment Bill. Methods UK PM2.5 concentrations in 2030 were modelled from 2018 using CMAQ-Urban and emissions predictions from business as usual, electrification of vehicles Planned London specific policies (UK2030+LS1) or two further London scenarios (LS2/3) were added using the London, toolkit model. Life-table analysis at ward level assumed 2030 concentrations were maintained until 2134. Morbidity outcomes from changes in NO2, PM10 and PM2.5 were quantified using summary estimates from the UK Committee on the Medical Effects of Air Pollutants, WHO and published meta-analyses. Monetary values were then applied. Results For UK2030+LS1, concentrations in 2030 were below 10 µg/m3 across the UK except the centre of London, near major roads in cities, and industrial biomass burning locations. With LS2/3, the exceedances dropped to <1% of the area of London. Local authority population-weighted exposures above 10 µg/m3 reduced from 40% in 2018 to 1% in 2030 (UK2030+LS1) to 0% for LS2 and 3. 11.5 million life years were gained across the UK population from 2018–2134 for UK2030+LS1 compared with unchanged 2018 concentrations. 2 million life years were in London, increasing to 2.5 and 2.9 million life years for LS2/3. Substantial health benefits were generated e.g. avoiding 388,000 asthmatic symptom days in asthmatic children and 3,077 new cases of coronary heart disease per year for UK2030+LS1. The monetary benefits showed policies costing up to £383 billion between 2018-2134 would be justified. Conclusions The WHO interim target was met in most but not all locations by 2030 generating substantial health benefits. Keywords PM2.5, WHO Guidelines, air pollution, health impact assessment

Impact of climate change policies on environmental inequalities in Great Britain

The UK Climate Change Act of 2008 requires an 80% reduction in carbon dioxide-equivalent emissions by 2050 compared with 1990. Strategies implemented to achieve this target offer the opportunity to improve public health and reduce environmental inequalities across Great Britain.We investigated the effect of alternative pathways to achieve the carbon dioxide reduction target on particulate and gaseous air pollution levels across different subpopulations in Great Britain.We linked the sophisticated air quality model CMAQ-Urban with the energy systems model UK TIMES to predict air pollution concentrations in 2035 and 2050 for different scenarios (two scenarios meet the emissions reduction target, two do not). We aggregated model outputs (fine particulate matter [PM2.5], nitrogen dioxide [NO2] and ozone) to the small-area level (ward ~6000 people) and compared concentrations by ethnicity and socioeconomic status. We used data on ethnicity from the 2011 census to classify wards according to their ethnic composition as White or Non-White and a composite small-area socioeconomic indicator to rank wards from the most to least deprived 5th of wards.Both NO2 and PM2.5 concentrations were higher in Non-White compared to White wards (9.3 µg/m3 NO2 difference) in all scenarios, less so for ozone. In 2011, mean concentrations in the most deprived 5th of wards were 4.3 µg/m3 higher compared to the least deprived (ratio = 1.37). This difference decreased by 2050 in all scenarios, for example, to 2.8 µg/m3 in the baseline scenario, showing a narrowing in the air pollution inequality gap (ratio = 1.31). This general pattern varied by region. PM2.5 and O3 showed smaller differences. Despite significant reductions in NO2 and modest reductions in PM2.5 and ozone in 2050, air pollution inequalities still persist in all scenarios

Public health air pollution impacts of pathway options to meet the 2050 UK Climate Change Act target: a modelling study

BACKGROUND: The UK’s Climate Change Act 2008 (CCA; Great Britain. Climate Change Act 2008. Chapter 27. London: The Stationery Office; 2008) requires a reduction of 80% in carbon dioxide-equivalent emissions by 2050 on a 1990 base. This project quantified the impact of air pollution on health from four scenarios involving particulate matter of ≤ 2.5 µm (PM_{2.5}), nitrogen dioxide (NO_{2}) and ozone (O_{3}). Two scenarios met the CCA target: one with limited nuclear power build (nuclear replacement option; NRPO) and one with no policy constraint on nuclear (low greenhouse gas). Another scenario envisaged no further climate actions beyond those already agreed (‘baseline’) and the fourth kept 2011 concentrations constant to 2050 (‘2011’). METHODS: The UK Integrated MARKAL–EFOM System (UKTM) energy system model was used to develop the scenarios and produce projections of fuel use; these were used to produce air pollutant emission inventories for Great Britain (GB) for each scenario. The inventories were then used to run the Community Multiscale Air Quality model ‘air pollution model’ to generate air pollutant concentration maps across GB, which then, combined with relationships between concentrations and health outcomes, were used to calculate the impact on health from the air pollution emitted in each scenario. This is a significant improvement on previous health impact studies of climate policies, which have relied on emissions changes. Inequalities in exposure in different socioeconomic groups were also calculated, as was the economic impact of the pollution emissions. RESULTS: Concentrations of NO_{2} declined significantly because of a high degree of electrification of the GB road transport fleet, although the NRPO scenario shows large increases in oxides of nitrogen emissions from combined heat and power (CHP) sources. Concentrations of PM_{2.5} show a modest decrease by 2050, which would have been larger if it had not been for a significant increase in biomass (wood burning) use in the two CCA scenarios peaking in 2035. The metric quantifying long-term exposure to O_{3} is projected to decrease, while the important short-term O3 exposure metric increases. Large projected increases in future GB vehicle kilometres lead to increased non-exhaust PM_{2.5} and particulate matter of ≤ 10 µm emissions. The two scenarios which achieve the CCA target resulted in more life-years lost from long-term exposures to PM2.5 than in the baseline scenario. This is an opportunity lost and arises largely from the increase in biomass use, which is projected to peak in 2035. Reduced long-term exposures to NO2 lead to many more life-years saved in the ‘CCA-compliant’ scenarios, but the association used may overestimate the effects of NO_{2} itself. The more deprived populations are estimated currently to be exposed to higher concentrations than those less deprived, the contrast being largest for NO_{2}. Despite reductions in concentrations in 2050, the most socioeconomically deprived are still exposed to higher concentrations than the less deprived. LIMITATIONS: Modelling of the atmosphere is always uncertain; we have shown the model to be acceptable through comparison with observations. The necessary complexity of the modelling system has meant that only a small number of scenarios were run. CONCLUSIONS: We have established a system which can be used to explore a wider range of climate policy scenarios, including more European and global scenarios as well as local measures. Future work could explore wood burning in more detail, in terms of the sectors in which it might be burned and the spatial distribution of this across the UK. Further analyses of options for CHP could also be explored. Non-exhaust emissions from road transport are an important source of particles and emission factors are uncertain. Further research on this area coupled with our modelling would be a valuable area of research. FUNDING: The National Institute for Health Research Public Health Research programme

Comparing the performance of air pollution models for nitrogen dioxide and ozone in the context of a multilevel epidemiological analysis

Background: Using modeled air pollutant predictions as exposure variables in epidemiological analyses can produce bias in health effect estimation. We used statistical simulation to estimate these biases and compare different air pollution models for London. Methods: Our simulations were based on a sample of 1,000 small geographical areas within London, United Kingdom. &quot;True&quot; pollutant data (daily mean nitrogen dioxide [NO2] and ozone [O3]) were simulated to include spatio-temporal variation and spatial covariance. All-cause mortality and cardiovascular hospital admissions were simulated from &quot;true&quot; pollution data using prespecified effect parameters for short and long-term exposure within a multilevel Poisson model. We compared: land use regression (LUR) models, dispersion models, LUR models including dispersion output as a spline (hybrid1), and generalized additive models combining splines in LUR and dispersion outputs (hybrid2). Validation datasets (model versus fixed-site monitor) were used to define simulation scenarios. Results: For the LUR models, bias estimates ranged from -56% to +7% for short-term exposure and -98% to -68% for long-term exposure and for the dispersion models from -33% to -15% and -52% to +0.5%, respectively. Hybrid1 provided little if any additional benefit, but hybrid2 appeared optimal in terms of bias estimates for short-term (-17% to +11%) and long-term (-28% to +11%) exposure and in preserving coverage probability and statistical power. Conclusions: Although exposure error can produce substantial negative bias (i.e., towards the null), combining outputs from different air pollution modeling approaches may reduce bias in health effect estimation leading to improved impact evaluation of abatement policies. © 2020 Wolters Kluwer Health. All rights reserved