The health burden of air pollution in the UK: a modelling study using updated exposure-risk associations.

BACKGROUND: Long-term exposure to ambient air pollution, in particular fine particles or PM2·5, is a leading global disease burden. PM2·5 in the UK, dominated by agricultural emissions of ammonia (NH3), has been estimated to be responsible for 29 000-34 000 adult early deaths a year. These estimates use models that relate exposure to health risk that predate cohort studies that have identified a supralinear relationship between exposure and risk at relatively low PM2·5 concentrations typical of the UK (5-12 mg m-3). Here we used this new knowledge to estimate adult premature mortality in the UK in 2019. METHODS: For this modelling study, we used the GEOS-Chem model nested over the UK to simulate ambient PM2·5 concentrations, UK Office for National Statistics (ONS) health data provided by the Global Burden of Disease (GBD), and a hybrid health-risk assessment model. The hybrid model fuses a well established linear relationship between PM2·5 and risk for PM2·5 exceeding 10 mg m-3 with a supralinear curve at lower concentrations that is constrained with cohort studies conducted in Canada and confirmed with similar relationships from cohort studies in the USA and Europe. FINDINGS: We estimated that adult premature mortality attributable to exposure to ambient PM2·5 in the UK totalled 48 625 deaths in 2019 (95% CI 45 118-52 595); 15 000-20 000 more deaths than those estimated using outdated health-risk assessment models. Older people (aged 65 years or older) account for most UK deaths (86%). All adult premature mortality (in people aged 25 years and older) in Greater London (4861, 95% CI 4549-5247) exceeded that in Scotland (3673, 3214-4073), Wales (2462, 2270-2660), and Northern Ireland (1052, 934-1156). INTERPRETATION: According to our findings, PM2·5 is more hazardous to UK adults than previously reported, but a supralinear exposure-response curve also suggests that there are substantial public health gains in targeting dominant source contributors to PM2·5, in particular the unregulated agricultural sector. FUNDING: Department for the Environment, Food and Rural Affairs (DEFRA).

Global mortality from outdoor fine particle pollution generated by fossil fuel combustion: Results from GEOS-Chem.

The burning of fossil fuels - especially coal, petrol, and diesel - is a major source of airborne fine particulate matter (PM2.5), and a key contributor to the global burden of mortality and disease. Previous risk assessments have examined the health response to total PM2.5, not just PM2.5 from fossil fuel combustion, and have used a concentration-response function with limited support from the literature and data at both high and low concentrations. This assessment examines mortality associated with PM2.5 from only fossil fuel combustion, making use of a recent meta-analysis of newer studies with a wider range of exposure. We also estimated mortality due to lower respiratory infections (LRI) among children under the age of five in the Americas and Europe, regions for which we have reliable data on the relative risk of this health outcome from PM2.5 exposure. We used the chemical transport model GEOS-Chem to estimate global exposure levels to fossil-fuel related PM2.5 in 2012. Relative risks of mortality were modeled using functions that link long-term exposure to PM2.5 and mortality, incorporating nonlinearity in the concentration response. We estimate a global total of 10.2 (95% CI: -47.1 to 17.0) million premature deaths annually attributable to the fossil-fuel component of PM2.5. The greatest mortality impact is estimated over regions with substantial fossil fuel related PM2.5, notably China (3.9 million), India (2.5 million) and parts of eastern US, Europe and Southeast Asia. The estimate for China predates substantial decline in fossil fuel emissions and decreases to 2.4 million premature deaths due to 43.7% reduction in fossil fuel PM2.5 from 2012 to 2018 bringing the global total to 8.7 (95% CI: -1.8 to 14.0) million premature deaths. We also estimated excess annual deaths due to LRI in children (0-4 years old) of 876 in North America, 747 in South America, and 605 in Europe. This study demonstrates that the fossil fuel component of PM2.5 contributes a large mortality burden. The steeper concentration-response function slope at lower concentrations leads to larger estimates than previously found in Europe and North America, and the slower drop-off in slope at higher concentrations results in larger estimates in Asia. Fossil fuel combustion can be more readily controlled than other sources and precursors of PM2.5 such as dust or wildfire smoke, so this is a clear message to policymakers and stakeholders to further incentivize a shift to clean sources of energy.

Impact of Legislated and Best Available Emission Control Measures on UK Particulate Matter Pollution, Premature Mortality, and Nitrogen-Sensitive Habitats.

Past emission controls in the UK have substantially reduced precursor emissions of health-hazardous fine particles (PM2.5) and nitrogen pollution detrimental to ecosystems. Still, 79% of the UK exceeds the World Health Organization (WHO) guideline for annual mean PM2.5 of 5 µg m-3 and there is no enforcement of controls on agricultural sources of ammonia (NH3). NH3 is a phytotoxin and an increasingly large contributor to PM2.5 and nitrogen deposited to sensitive habitats. Here we use emissions projections, the GEOS-Chem model, high-resolution data sets, and contemporary exposure-risk relationships to assess potential human and ecosystem health co-benefits in 2030 relative to the present day of adopting legislated or best available emission control measures. We estimate that present-day annual adult premature mortality attributable to exposure to PM2.5 is 48,625 (95% confidence interval: 45,188-52,595), that harmful amounts of reactive nitrogen deposit to almost all (95%) sensitive habitat areas, and that 75% of ambient NH3 exceeds levels safe for bryophytes and lichens. Legal measures decrease the extent of the UK above the WHO guideline to 58% and avoid 6,800 premature deaths by 2030. This improves with best available measures to 36% of the UK and 13,300 avoided deaths. Both legal and best available measures are insufficient at reducing the extent of damage of nitrogen pollution to sensitive habitats. Far more ambitious reductions in nitrogen emissions (>80%) than is achievable with best available measures (34%) are required to halve the amount of excess nitrogen deposited to sensitive habitats.

Rapid rise in premature mortality due to anthropogenic air pollution in fast-growing tropical cities from 2005 to 2018.

Tropical cities are experiencing rapid growth but lack routine air pollution monitoring to develop prescient air quality policies. Here, we conduct targeted sampling of recent (2000s to 2010s) observations of air pollutants from space-based instruments over 46 fast-growing tropical cities. We quantify significant annual increases in nitrogen dioxide (NO2) (1 to 14%), ammonia (2 to 12%), and reactive volatile organic compounds (1 to 11%) in most cities, driven almost exclusively by emerging anthropogenic sources rather than traditional biomass burning. We estimate annual increases in urban population exposure to air pollutants of 1 to 18% for fine particles (PM2.5) and 2 to 23% for NO2 from 2005 to 2018 and attribute 180,000 (95% confidence interval: -230,000 to 590,000) additional premature deaths in 2018 (62% increase relative to 2005) to this increase in exposure. These cities are predicted to reach populations of up to 80 million people by 2100, so regulatory action targeting emerging anthropogenic sources is urgently needed.