Issue link: https://www.e-digitaleditions.com/i/1469783
38 June 2022 Inhalation and combining the models with observations to assess and improve model performance; and methods consistent with GBD methods to allow comparisons with previous GBD MAPS research. e reviewers also agreed with the investigators that "several sources of uncertainty likely vary in magnitude by location and source sector that warrant further investigation." ese include the assumption that all particle mix- tures have equal effects on mor- tality; the quality and quantity of emissions and air quality data in different regions; and the method to exclude emission from source sectors one by one. In particular, the assumption that all particles are equally toxic could have important implications for policy given that natural sources with high uncertainty in emissions estimates appear to dominate anthropogenic sources in several try." Study findings included the following: • Energy generation (including both electricity and residential cooking and heating) was the largest source sector. • Combustion of fossil fuels (coal, oil and natural gas) con- tributed to an estimated one million deaths globally in 2017 and 800,000 of those deaths were in South Asia or East Asia. • F o s s i l f u e l c o m b u s t i o n accounted for 27.3% of all deaths from outdoor PM 2.5 . Of that percentage, 50% was due to coal and the other 50% to a combination of liquid fuel and gas. • Biofuel and remaining emis- sions from fossil fuels and other sources also had sub- stantial contributions that exceeded those of fossil fuels in some places. • Agriculture was an import- ant contributor to health bur- dens from exposure to outdoor PM 2.5 in some regions due to emissions of ammonia, which is a precursor to PM 2.5 . • International shipping and ag- riculture sectors had higher impacts than are widely recognized. • Windblown dust was the source sector that had the most variation. Findings of an independent review panel HEI also had the investigator's report independently reviewed and included those findings in the summary statement. e review panel concluded the study's strengths were its global perspective, application of stan- dardized methods across coun- tries and the availability of data and code. Strengths of the approach included the most recent updated emissions data available; current methods for modeling air pollution sources has now published the study report and a summary statement, includ- ing findings about the study from an independent review panel. A multi-step process e HEI summary statement explained that McDuffie and her colleagues began by expanding and updating the only available global emissions inventory to generate monthly emissions data for 1970 to 2017 for seven key atmospheric pollutants (nitrogen oxides, carbon monoxide, sul- fur dioxide, ammonia, nonmeth- ane volatile organic compounds, black carbon and organic car- bon); eleven anthropogenic sec- tors (including agriculture, energy, industry and transportation); and four fuel categories (coal, biofuel, liquid fuel and a remaining cate- gory that included industrial pro- cesses such as fugitive emissions). Next, they used the emissions data in an updated global air quality model and combined those results with satellite data to model out- door PM 2.5 . ey also compared the modeled concentrations of outdoor PM 2.5 with measure- ments made at many stations in different countries to confirm the model gave realistic values. Fur- ther, they calculated average expo- sures to outdoor PM 2.5 for all the people living in different countries and world regions for the source sectors and fuel categories. Lastly, they applied relationships between air pollution and health at differ- ent ages to calculate the number of deaths that were related to the outdoor PM 2.5 sources. The first comprehensive estimates In describing the results, the HEI summary stated "the study provides the first comprehensive estimates of source contributions to PM 2.5 levels and cause- specific disease burden at global, regional and national levels to help inform policy." e summary also noted that, "major sources of PM 2.5 varied substantially by coun- e Health Effects Institute (HEI) is a nonprofit corpo- ration and an independent research organization. Estab- lished in 1980, it aims to provide "high-quality, impar- tial and relevant science on the effects of air pollution on health. Its research is selected, overseen and peer reviewed by leading subject matter experts on environment and health without involvement of HEI's public or private sponsors. It is jointly funded by the United States Environmental Protection Agency (EPA) and other public and private orga- nizations in the United States and around the world. HEI has funded more than 340 research projects in North America, Europe, Asia and Latin America, the results of which have informed decisions regarding carbon monoxide, air toxins, nitrogen oxides, die- sel exhaust, ozone, particulate matter and other pollutants."