Fossil fuels behind a quarter of PM deaths

Burning of coal, oil and gas caused most of the fine particle (PM_2.5) related deaths in industralised countries, shows a new study. Shipping and farming had higher impacts than are widely recognised.

Fossil fuel combustion was the major source of air pollution and contributed to more than a quarter of all deaths from outdoor fine particulate matter (PM_2.5), says a new report published by the Health Effects Institute (HEI). Coal combustion was responsible for half of those deaths, with natural gas and oil combustion accounting for the other half. The burning of solid biofuels, such as wood for indoor heating and cooking, was the second major source of PM_2.5, especially across South Asia and Sub-Saharan Africa.

HEI initiated the Global Burden of Disease from Major Air Pollution Sources (GBD MAPS) project to determine which air pollutant sources or fuels contribute most to outdoor PM2.5 concentrations and their associated mortality. The results can help to identify priorities for source-specific policies and interventions. McDuffie and colleagues started by expanding and updating the only publicly available global emissions inventory for seven key atmospheric pollutants (nitrogen oxides, carbon monoxide, sulphur dioxide, ammonia, non-methane volatile organic compounds, black carbon, and organic carbon), eleven anthropogenic sectors (including agriculture, energy, industry, and transportation), and four fuel categories (coal, biofuel, liquid fuel, and a remaining category that included such industrial processes as fugitive emissions). The investigators used the emissions data in a model and combined those results with satellite data to model outdoor PM_2.5 at a spatial resolution of 0.01° × 0.01° (about 1 km × 1 km at the equator). They compared the modelled concentrations with measurements of PM_2.5 from many stations in different countries to confirm the model results. They then calculated average outdoor PM_2.5 exposures for all the people living in different countries and world regions for all the source sectors and fuel categories. Finally, the investigators applied relationships between air pollution and health at different ages to calculate the mortality impact of the outdoor PM_2.5 sources. They assumed that all particles are equally toxic, which of course could have implications for e.g., windblown dust in the western sub-Saharan Africa region.

Energy generation, including electricity and residential cooking and heating, was the largest source sector. Agriculture was an important source contributor in some regions because of emissions of ammonia, which is a precursor to PM_2.5. Combustion of fossil fuels (coal, oil, and natural gas) contributed one fourth, and as much as one third in South Asia or East Asia, of all attributed deaths globally. Of the fossil fuels, coal contributed the highest emissions and related deaths. International shipping and agriculture sectors had higher impacts than are widely recognised. Biofuel and remaining emissions from fossil fuels and other sources also had substantial contributions. Windblown dust had a large variation in their contribution. The new report highlighted that major source of PM_2.5 vary by country and region, and different parts of the world were impacted by air pollution in different ways. While fossil fuel combustion made up most of the PM_2.5 across the industrialised nations of the global north, windblown dust was a major source of PM_2.5 in African countries. Overall, the report indicates that a majority of PM_2.5 in outdoor air comes from anthropogenic fuel combustion, suggesting that integrating air quality, energy, and climate policies is key to achieve health benefits from reducing air pollution.

Ebba Malmqvist

The research team has made all datasets, code, and visualisations publicly available (gbdmaps.med.ubc.ca).

Figure above: Premature deaths per 100,000 attributable to population-weighted mean ambient PM_2.5 mass from selected sectors in 2017.