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Global impact of landscape fire emissions on surface level PM2.5 concentrations, air quality exposure and population mortality

Research output: Contribution to journalArticlepeer-review

G. Roberts, M. J. Wooster

Original languageEnglish
Article number118210
JournalATMOSPHERIC ENVIRONMENT
Volume252
DOIs
Published1 May 2021

Bibliographical note

Funding Information: The CAMS is supported by the Copernicus Programme of the European Union (EU), and has six focus areas providing near continuous monitoring of Earth's atmosphere at regional and global scales using a combination of satellite data, in situ observations and atmospheric modelling, the latter primarily conducted using the Integrated Forecasting System (IFS) of the European Centre for Medium Range Weather Forecasting (ECMWF). The IFS is a state-of-the-art global data assimilation, modelling and forecasting system providing atmospheric composition data (aerosols, greenhouse gases, reactive gases) at 6 hourly intervals and forecasts at 3 hourly intervals for a maximum forward look of 5 days. The current IFS cycle operates with 137 vertical levels from the surface up to 0.01 hPa at a nominal horizontal resolution of ~40 km. Modelled data outputs can be resampled up to 0.125? resolution using the Meteorological Interpolation and Regridding scheme (MIR, Malardel et al., 2016). We are here primarily concerned with the surface-level PM2.5 abundances, which include contributions from fine and coarse nitrate and ammonium aerosols, sea salt covering three size distributions (0.03?0.5 ?m, 0.5?5 ?m, 5?20 ?m), dust (0.03?0.55 ?m, 0.55?0.9 ?m, 0.9?20 ?m), and sulphate, organic matter (OM) and black carbon (BC) aerosols emitted from both anthropogenic and natural sources. Biomass burning emissions are confined to the BC and OM components, and in no part of this study do we include the fine and coarse nitrate and ammonium aerosols since they were only recently introduced into the IFS (July 2019).The PM2.5 and GFAS data were provided by the Copernicus Atmosphere Monitoring Service (CAMS, https://atmosphere.copernicus.eu/). The MACCITY and CAMS-ANTH emissions inventories were provided by the Emissions of atmospheric Compounds and Compilation of Ancillary Data (ECCAD, https://eccad.aeris-data.fr/). The population datasets were provided by WorldPop (https://www.worldpop.org/). The MODIS active fire (MCD14) and burned area (MCD64) data were obtained through the NASA Reverb service (http://reverb.echo.nasa.gov/reverb/). The surface station air quality data were obtained from the AirNOW (https://www.airnow.gov/), Purple Air (https://www2.purpleair.com/) and CPCB (https://cpcb.nic.in/) air quality networks. We would like to thank the reviewers for their constructive comments which helped improve the manuscript. Funding for certain aspects of this research was provided by NERC National Capability funding to the National Centre for Earth Observation (NE/Ro16518/1) and by the Leverhulme Centre for Wildfires, Environment and Society through the Leverhulme Trust, grant number RC-2018-023. Publisher Copyright: © 2021 Elsevier Ltd Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

King's Authors

Abstract

Airborne fine particulate matter (PM2.5) represents the greatest ambient air pollution risk to health. Wildfires and managed burns, together referred to hereafter as ‘landscape’ fires, are a significant PM2.5 source in many regions worldwide, able to affect air quality in areas far away from the fires themselves. We use 0.125°, 3 hourly outputs (2016–2019) from the Copernicus Atmospheric Monitoring System (CAMS) to investigate patterns of global population exposure to ambient surface level PM2.5, and specifically to the contribution coming from landscape fires. We calculate both the air quality impacts and annual average mortality at the level of the nation state, and our analysis highlights both the burden of poor air quality and the significance of landscape fire sources in developing nations in particular. We find 143 countries to have an average population weighted (PW) total PM2.5 surface level concentration exceeding the 10 μg m−3 guideline recommended by WHO, with 67.2 million people annually exposed to PM2.5 levels classed as ‘hazardous’ (>250.5 μg m−3) according to the US Environmental Protection Agency (EPA) air quality index (AQI). Landscape fires alone result in 44 million people annually being exposed to air quality considered unhealthy (PM2.5 > 55 μg m−3), and 4 million to that considered ‘hazardous’ to health (>250.5 μg m−3). Populations in central and west Africa and south and south east Asia are most affected by the landscape fire smoke, and eight countries exceed the WHO annual mean 10 μg m−3 guideline from this source only - with the contribution from fires highest in Laos (61% of the total PM2.5), Democratic Republic of Congo (45%) and Sierra Leone (44%). Combining published dose-response functions with these landscape-fire PM2.5 contributions, we estimate that 677,745 premature deaths annually result from exposure to landscape fire smoke, with almost 39% of these in children under five. This mortality represents between 8 and 21% of the estimated 3.2 to 8.9 million people dying annually from outdoor air pollution exposure, highlighting landscape fires as a significant contributor. Our results indicate that environmental programmes aimed at lessening the use of fire in land clearance and agricultural residue management in developing nations would very likely result in significant co-benefits for health.

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