Vegetation and peatland fires cause poor air quality and thousands of premature deaths across densely populated regions in Equatorial Asia. Strong El-Niño and positive Indian Ocean Dipole conditions are associated with an increase in the frequency and intensity of wildfires in Indonesia and Borneo, enhancing population exposure to hazardous concentrations of smoke and air pollutants. Here we investigate the impact on air quality and population exposure of wildfires in Equatorial Asia during Fall 2015, which were the largest over the past two decades. We performed high-resolution simulations using the Weather Research and Forecasting model with Chemistry based on a new fire emission product. The model captures the spatio-temporal variability of extreme pollution episodes relative to space- and ground-based observations and allows for identification of pollution sources and transport over Equatorial Asia. We calculate that high particulate matter concentrations from fires during Fall 2015 were responsible for persistent exposure of 69 million people to unhealthy air quality conditions. Short-term exposure to this pollution may have caused 11,880 (6,153–17,270) excess mortalities. Results from this research provide decision-relevant information to policy makers regarding the impact of land use changes and human driven deforestation on fire frequency and population exposure to degraded air quality.
Exposure to ambient fine particulate matter (PM2.5) is a leading contributor to diseases in India. Previous studies analysing emission source attributions were restricted by coarse model resolution and limited PM2.5 observations. We use a regional model informed by new observations to make the first high-resolution study of the sector-specific disease burden from ambient PM2.5 exposure in India. Observed annual mean PM2.5 concentrations exceed 100 μg m−3 and are well simulated by the model. We calculate that the emissions from residential energy use dominate (52%) population-weighted annual mean PM2.5 concentrations, and are attributed to 511,000 (95UI: 340,000–697,000) premature mortalities annually. However, removing residential energy use emissions would avert only 256,000 (95UI: 162,000–340,000), due to the non-linear exposure–response relationship causing health effects to saturate at high PM2.5 concentrations. Consequently, large reductions in emissions will be required to reduce the health burden from ambient PM2.5 exposure in India.
Humans make extensive use of fire to clear forests and vegetation and to prepare and maintain land for agriculture 8,9 . Emissions of particulate matter (PM) from fires can dominate atmospheric concentrations particularly during the dry season 6,10 . Inhalation of PM from fires has adverse impacts on human health, including increased hospital admissions and premature mortality 3,4,11,12 .Rapid deforestation is occurring across the tropics 5 . Between 1976 and 2010, more than 750 000 km 2 of the Brazilian Amazon was deforested, equivalent to ~15% of the original forested area 1 . Recently, Brazil has achieved well documented reductions in deforestation rates 1,5,6 .Over Figure S1). Reduction in deforestation rates have numerous social and environmental benefits 1 . We were interested in whether the reduction in deforestation rates has also improved air quality across Brazil.Satellite-derived datasets of fire occurrence show the total number of active fire counts across Amazonia is positively related to both deforestation rates and occurrence of drought 1,7,13,14 .During 2001 to 2010, years with high deforestation rates had a factor 2 greater incidence of fire compared to years with low deforestation rates 1 . Significant declines in fire frequency across Brazil have occurred over this period, with the largest reductions in regions of high cumulative deforestation 7 .We used three different datasets of satellite-derived fire emissions 2,15,16 available over 20022,15,16 available over to 2011 to further explore the relationship between deforestation and PM emissions from fire. Substantial fire emissions occur across Brazil (Fig. 2), accounting for 12-16% of global particulate emissions from fire (Supplementary Table S1). In South America, particulate emissions from fire are greatest across southeast Amazonia where there is rapid deforestation (Fig. 2). Tropical forests of central Amazonia have little fire emission because high moisture, dense forest canopies and little deforestation mean fires are a rare occurrence 17,18 . Regions with frequent agricultural fires also have lower total fire emission compared to regions of active deforestation, because agricultural fires result in a factor 3-5 lower emission per unit area burned due to lower fuel loads 19 .One satellite fire dataset classifies emissions according to fire type 2 , allowing the specific contribution of deforestation fires to be estimated (see Methods). Deforestation fires only account for 20% of global total particulate fire emissions but 64% of Brazil's total, meaning deforestation fires dominate regional air quality impacts. Classification of fire types is an uncertainty -deforestation fires may spread out of the deforested area into surrounding forest, where they are classified as a different fire type not associated with deforestation. Throughout our analysis, we therefore analyse both total particulate fire emissions and emissions specifically classified as from deforestation fires.Over 2001 to 2011, Amazonia experienced drought conditions du...
Abstract. Combustion of fuels in the residential sector for cooking and heating results in the emission of aerosol and aerosol precursors impacting air quality, human health, and climate. Residential emissions are dominated by the combustion of solid fuels. We use a global aerosol microphysics model to simulate the impact of residential fuel combustion on atmospheric aerosol for the year 2000. The model underestimates black carbon (BC) and organic carbon (OC) mass concentrations observed over Asia, Eastern Europe, and Africa, with better prediction when carbonaceous emissions from the residential sector are doubled. Observed seasonal variability of BC and OC concentrations are better simulated when residential emissions include a seasonal cycle. The largest contributions of residential emissions to annual surface mean particulate matter (PM 2.5 ) concentrations are simulated for East Asia, South Asia, and Eastern Europe. We use a concentration response function to estimate the human health impact due to long-term exposure to ambient PM 2.5 from residential emissions. We estimate global annual excess adult (> 30 years of age) premature mortality (due to both cardiopulmonary disease and lung cancer) to be 308 000 (113 300-497 000, 5th to 95th percentile uncertainty range) for monthly varying residential emissions and 517 000 (192 000-827 000) when residential carbonaceous emissions are doubled. Mortality due to residential emissions is greatest in Asia, with China and India accounting for 50 % of simulated global excess mortality. Using an offline radiative transfer model we estimate that residential emissions exert a global annual mean direct radiative effect between −66 and +21 mW m −2 , with sensitivity to the residential emission flux and the assumed ratio of BC, OC, and SO 2 emissions. Residential emissions exert a global annual mean first aerosol indirect effect of between −52 and −16 mW m −2 , which is sensitive to the assumed size distribution of carbonaceous emissions. Overall, our results demonstrate that reducing residential combustion emissions would have substantial benefits for human health through reductions in ambient PM 2.5 concentrations.
Vegetation fires across the tropics emit fine particulate matter (PM2.5) to the atmosphere, degrading regional air quality and impacting human health. Extensive vegetation fires occur regularly across the Amazon basin, but there have been no detailed assessments of the impacts on air quality or human health. We used updated exposure-response relationships and a regional climate-chemistry model, evaluated against a comprehensive set of observational data, to provide the first in-depth assessment of the potential public health benefits due to fire prevention across the Amazon Basin. We focused on 2012, a year with emissions similar to the 11-year average (2008 to 2018). Vegetation fires contributed >80% of simulated dry season mean surface PM2.5 in the western Amazon region particularly in Bolivia and Brazilian states of Rondônia, Acre, and Mato Grosso. We estimate that the prevention of vegetation fires would have averted 16 800 (95UI: 16 300–17 400) premature deaths and 641 000 (95UI: 551 900–741 300) disability adjusted life years (DALYs) across South America, with 26% of the avoided health burden located within the Amazon Basin. The health benefits of fire prevention in the Amazon are comparable to those found in Equatorial Asia.
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