Temperature-related mortality and associated vulnerabilities: evidence from Scotland using extended time-series datasets

BACKGROUND: Adverse health impacts have been found under extreme temperatures in many parts of the world. The majority of such research to date for the UK has been conducted on populations in England, whilst the impacts of ambient temperature on health outcomes in Scottish populations remain largely unknown. METHODS: This study uses time-series regression analysis with distributed lag non-linear models to characterise acute relationships between daily mean ambient temperature and mortality in Scotland including the four largest cities (Aberdeen, Dundee, Edinburgh and Glasgow) and three regions during 1974–2018. Increases in mortality risk under extreme cold and heat in individual cities and regions were aggregated using multivariate meta-analysis. Cold results are summarised by comparing the relative risk (RR) of death at the 1(st) percentile of localised temperature distributions compared to the 10(th) percentile, and heat effects as the RR at the 99(th) compared to the 90(th) percentile. RESULTS: Adverse cold effects were observed in all cities and regions, and heat effects were apparent in all cities and regions except northern Scotland. Aggregate all-cause mortality risk in Scotland was estimated to increase by 10% (95% confidence interval, CI: 7%, 13%) under extreme cold and 4% (CI: 2%, 5%) under extreme heat. People in urban areas experienced higher mortality risk under extreme cold and heat than those in rural regions. The elderly had the highest RR under both extreme cold and heat. Males experienced greater cold effects than females, whereas the reverse was true with heat effects, particularly among the elderly. Those who were unmarried had higher RR than those married under extreme heat, and the effect remained after controlling for age. The younger population living in the most deprived areas experienced higher cold and heat effects than in less deprived areas. Deaths from respiratory diseases were most sensitive to both cold and heat exposures, although mortality risk for cardiovascular diseases was also heightened, particularly in the elderly. Cold effects were lower in the most recent 15 years, which may be linked to policies and actions in preventing the vulnerable population from cold impacts. No temporal trend was found with the heat effect. CONCLUSIONS: This study assesses mortality risk associated with extreme temperatures in Scotland and identifies those groups who would benefit most from targeted actions to reduce cold- and heat-related mortalities. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12940-022-00912-5

Science-policy interplay on air pollution governance in China

Air quality in China is a major public health, social and economic concern. Air pollution governance and research in China have been increasingly active in the past decade, especially since 2013 when strict emission controls were implemented. Such emission control policies have been informed through dialogue between scientists and policy-makers on the sources and transport of air pollution in order to identify potential control measures. However, the process of making regulatory decisions about air pollution controls at this science-policy interface in China has rarely been analysed or discussed. We outline four classical science-policy models for making regulatory decisions proposed by scholars: (i) the decisionist model – whereby policy dictates what science and regulatory decisions are required; (ii) the technocratic model – where science dictates policy directly; (iii) the inverted decisionist model (where scientists advise policy-makers on what policy is required); and (iv) the co-evolutionary model (where policy-makers and scientists jointly create regulatory decisions). Boundary-actors play a key role in this co-evolutionary model. They operate as ‘gate-keepers’ between scientists and policy-makers. Most contemporary studies of the science-policy interface argue that the co-evolutionary model best captures the reality of how science and policy interact effectively to make regulatory decisions. To assess which of these models most closely resemble decision-making at the air pollution science-policy interface, we conducted a case study on “air quality climate services” and held workshops with Chinese scientists, decision-makers and stakeholders. A typology of existing scientific approaches to explore air quality climate science is presented. The workshop results show that the current air quality climate science-policy interplay occurs most strongly in accordance with the co-evolutionary model whereby the Beijing Climate Centre and the National Environmental Monitoring Centre operate as the key boundary actors between science and policy, specifically for a seasonal air pollution haze outlook service. We illustrate that current seasonal haze outlooks carefully avoiding quantification. We then present a conceptual framework of the air pollution science-policy interface in China, which captures the main participants and the interactive flow of information between them

Modulation of daily PM2.5 concentrations over China in winter by large-scale circulation and climate change

We use the United Kingdom Earth System Model, UKESM1, to investigate the influence of the winter large-scale circulation on daily concentrations of PM2.5 (particulate matter with an aerodynamic diameter of 2.5 &mu;m or less) and their sensitivity to emissions over major populated regions of China over the period 1999&ndash;2019. We focus on the Yangtze River Delta (YRD), where weak flow of cold, dry air from the north and weak inflow of maritime air are particularly conducive to air pollution. These provide favourable conditions for the accumulation of local pollution but limit the transport of air pollutants into the region from the north. Based on the dominant large-scale circulation, we construct a new index using the north-south pressure gradient and apply it to characterize PM2.5 concentrations over the region. We show that this index can effectively distinguish different levels of pollution over YRD and explain changes in PM2.5 sensitivity to emissions from local and surrounding regions. We then project future changes in PM2.5 concentrations using this index and find an increase in PM2.5 concentrations over the region due to climate change that is likely to partially offset the effect of emission control measures in the near-term future. To benefit from future emission reductions, more stringent emission controls are required to offset the effects of climate change.</p

Process-based modelling of NH3 exchange with grazed grasslands

In this study the GAG model, a process-based ammonia (NH3) emission model for urine patches, was extended and applied for the field scale. The new model (GAG_field) was tested over two modelling periods, for which micrometeorological NH3 flux data were available. Acknowledging uncertainties in the measurements, the model was able to simulate the main features of the observed fluxes. The temporal evolution of the simulated NH3 exchange flux was found to be dominated by NH3 emission from the urine patches, offset by simultaneous NH3 deposition to areas of the field not affected by urine. The simulations show how NH3 fluxes over a grazed field in a given day can be affected by urine patches deposited several days earlier, linked to the interaction of volatilization processes with soil pH dynamics. Sensitivity analysis showed that GAG_field was more sensitive to soil buffering capacity (β), field capacity (θfc) and permanent wilting point (θpwp) than the patch-scale model. The reason for these different sensitivities is dual. Firstly, the difference originates from the different scales. Secondly, the difference can be explained by the different initial soil pH and physical properties, which determine the maximum volume of urine that can be stored in the NH3 source layer. It was found that in the case of urine patches with a higher initial soil pH and higher initial soil water content, the sensitivity of NH3 exchange to β was stronger. Also, in the case of a higher initial soil water content, NH3 exchange was more sensitive to the changes in θfc and θpwp. The sensitivity analysis showed that the nitrogen content of urine (cN) is associated with high uncertainty in the simulated fluxes. However, model experiments based on cN values randomized from an estimated statistical distribution indicated that this uncertainty is considerably smaller in practice

Integrating Shared Socioeconomic Pathway-informed adaptation into temperature-related mortality projections under climate change

The extent to which populations will successfully adapt to continued warming temperatures will be a crucial factor in determining future health burdens. Previous health impact assessments of future temperature-related mortality burdens mostly disregard adaptation or make simplistic assumptions. We apply a novel evidence-based approach to model adaptation that takes into account the fact that adaptation potential is likely to vary at different temperatures. Temporal changes in age-specific mortality risk associated with low and high temperatures were characterised for Scotland between 1974 and 2018 using temperature-specific RR ratios to reflect past changes in adaptive capacity. Three scenarios of future adaption were constructed consistent with the SSPs. These adaptation projections were combined with climate and population projections to estimate the mortality burdens attributable to high (above the 90th percentile of the historical temperature distribution) and low (below the 10th percentile) temperatures up to 2080 under five RCP-SSP scenarios. A decomposition analysis was conducted to attribute the change in the mortality burden into adaptation, climate and population. In 1980-2000, the heat burden (21 deaths/year) was smaller than the colder burden (312 deaths/year). In the 2060-2080 period, the heat burden was projected to be the highest under RCP8.5-SSP5 (1285 deaths/year), and the cold burden was the highest under RCP4.5-SSP4 (320 deaths/year). The net burden was lowest under RCP2.6-SSP1 and highest under RCP8.5-SSP5. Improvements in adaptation was the largest factor reducing the cold burden under RCP2.6-SSP1 whilst temperature increase was the biggest factor contributing to the high heat burdens under RCP8.5-SSP5. Ambient heat will become a more important health determinant than cold in Scotland under all climate change and socio-economic scenarios. Adaptive capacity will not fully counter projected increases in heat deaths, underscoring the need for more ambitious climate mitigation measures for Scotland and elsewhere

Meteorological drivers and mortality associated with O3 and PM2.5 air pollution episodes in the UK in 2006

In this study we examine the meteorological drivers resulting in concurrent high levels of ozone (O3) and particulate matter smaller than 2.5 andmu;m in diameter (PM2.5) during two five-day air pollution episodes in 2006 (1st - 5th July and 18th andndash; 22nd July) using an air quality model (AQUM) at 12 km horizontal resolution to simulate air pollutant concentrations. The resultant UK health burden associated with short-term exposure to simulated maximum daily 8-h O3andnbsp;(MDA8 O3) and daily mean PM2.5andnbsp;is estimated at the national and regional level. Both episodes were found to be driven by anticyclonic conditions with light easterly and south easterly winds and high temperatures that aided pollution build up in the UK. The estimated total mortality burden associated with short-term exposure to MDA8 O3andnbsp;is similar during the chosen episodes with about 70 daily deaths brought forward (summed across the UK) during the first and second episode, respectively. The estimated health burden associated with short-term exposure to daily mean PM2.5andnbsp;concentrations differs between the first and second episode resulting in about 43 and 36 daily deaths brought forward, respectively. The corresponding percentage of all-cause mortality due to short-term exposure to MDA8 O3andnbsp;and daily mean PM2.5during these two episodes and across the UK regions, ranges from 3.4% to 5.2% and from 1.6% to 3.9%, respectively. The attributable percentage of all-cause mortality differs between the regions depending on the pollution levels in each episode, but the overall estimated health burdens are highest in regions with higher population totals. We estimate that during these episodes the short-term exposure to MDA8 O3and daily mean PM2.5andnbsp;is between 36-38% and 39andndash;56% higher, respectively, than if the pollution levels represented typical seasonal-mean concentrations. This highlights the potential of air pollution episodes to have substantial short-term impacts on public health.</p

Future air pollution related health burdens associated with RCP emission changes in the UK

Intergovernmental Panel on Climate Change (IPCC) Representative Concentration Pathways (RCPs) are used to simulate future ozone (O3), nitrogen dioxide (NO2), and fine particulate matter (PM2.5) in the United Kingdom (UK) for the 2050s relative to the 2000s with an air quality model (AQUM) at a 12 km horizontal resolution. The present-day and future attributable fractions (AF) of mortality associated with long-term exposure to annual mean O3, NO2 and PM2.5 have accordingly been estimated for the first time for regions across England, Scotland and Wales. Across the three RCPs (RCP2.6, RCP6.0 and RCP8.5), simulated annual mean of the daily maximum 8-hr mean (MDA8) O3 concentrations increase compared to present-day, likely due to decreases in NOx (nitrogen oxides) emissions, leading to less titration of O3 by NO. Annual mean NO2 and PM2.5 concentrations decrease under all RCPs for the 2050s, mostly driven by decreases in NOx and sulphur dioxide (SO2) emissions, respectively. The AF of mortality associated with long-term exposure to annual mean MDA8 O3 is estimated to increase in the future across all the regions and for all RCPs. Reductions in NO2 and PM2.5 concentrations lead to reductions in the AF estimated for future periods under all RCPs, for both pollutants. Total mortality burdens are also highly sensitive to future population projections. Accounting for population projections exacerbates differences in total UK-wide MDA8 O3-health burdens between present-day and future by up to a factor of ~3 but diminishes differences in NO2-health burdens. For PM2.5, accounting for future population projections results in additional UK-wide deaths brought forward compared to present-day under RCP2.6 and RCP6.0, even though the simulated PM2.5 concentrations for the 2050s are estimated to decrease. Thus, these results highlight the sensitivity of future health burdens in the UK to future trends in atmospheric emissions over the UK as well as future population projections