Estimated 2013 annual average PM2.5 concentrations (μg/m3). The estimates are generated from the grid cell average of satellite-based estimates and TM5-FASST simulations and calibrated with a prediction model incorporating surface measurements. Credit: ACS, Brauer et al. Click to enlarge.

The Global Burden of Disease (GBD) 2013 provided important estimates of the global health impacts attributable to ambient air pollution. Ambient particulate matter air pollution (PM_2.5, particulate matter with aerodynamic diameter 2.5 μm or smaller) was identified as a leading risk factor for global disease burden with an estimated 2.9 million attributable deaths in the year 2013. An additional 217,000 deaths were attributable to long-term ozone exposure. These two pollutants were selected as indicators of exposure to ambient air pollution based on extensive epidemiologic and mechanistic evidence indicating independent adverse health impacts.

… In the context of the most recent update of the Global Burden of Disease (GBD 2013) we developed updated and revised global exposure estimates for PM_2.5 and ozone (O₃). We incorporated improvements in satellite-based estimation of PM_2.5, internally consistent emissions inventories spanning 2.5 the 1990−2010 period and a substantially increased number of ground measurements of particulate matter, compared to those utilized previously.

—Brauer et al.

For the study, the researchers combined satellite-based estimates; chemical transport model simulations; and ground measurements from 79 different countries to produce global estimates of annual average fine particle (PM_2.5) and ozone concentrations at 0.1° × 0.1° spatial resolution for five-year intervals from 1990 to 2010 and the year 2013.

They then applied these estimates to assess population-weighted mean concentrations for 1990–2013 for each of 188 countries.

Half of the 79 countries were high income countries in North America (25%), Western (32%), and Central (12%) Europe. Aided by a major expansion of China’s air quality monitoring network, 10% of the ground measurements were from East Asia, and 5% were from South Asia.

Countries in 11 regions (Andean Latin America; Australasia; Central Asia; Eastern Europe; High-income Asia Pacific; North Africa and Middle East; Southeast Asia; Southern Latin America; Southern Sub-Saharan Africa; Tropical Latin America; Western Sub-Saharan Africa) each contributed less than 3% of the measurement data. No measurements came from the other four regions (Caribbean, Central Latin America, East, and Central sub-Saharan Africa) of the world.

The highest measured annual average PM_2.5 concentration in the assembled measurement database was 194 μg/m³ in Shijiazhuang, the capital of Hebei Province in China, while the lowest was <1 μg/m³, measured in Soldotna, Alaska.

Among the general findings:

• The highest concentrations of PM_2.5 were evident in northern Africa and the Middle East due to emissions of windblown mineral dust; and in South and East Asia—especially in northern India and eastern China—due to combustion emissions from multiple sources including household solid fuel use, coal fired power plant emissions, landscape fires, industrial and transportation-related emissions.

• Ozone concentrations were less variable spatially, but relatively higher in parts of the US, the Amazon Basin, sub-Saharan Africa, and throughout much of southern Europe, the Middle East, and Asia.

• 35% of global population resided in areas with concentrations above the WHO Interim Target 1 of 35 μg/m³ annual average PM^2.5 with nearly all of the most extreme (>65 μg/m³) concentrations experienced by populations in China and India.

• 87% of the global population resided in areas above the WHO guideline of 10 μg/m³, with essentially none of the population of China (0.4%) or India (0.01%) living in areas meeting this level.

• Large relative decreases in estimated PM_2.5 concentrations between 1990 and 2013 at the 0.1° x 0.1° grid cell level were evident in the Eastern US, Europe, Russia and in parts of Southeast Asia.

• Large relative increases were apparent in Western Canada, parts of South America, the Middle East, India and China. Somewhat similar patterns were also evident for ozone.

• Between 1990 and 2013, decreases in population-weighted mean concentrations of PM_2.5 were evident in most of high income countries—in contrast to consistent increases in South Asia, much of Southeast Asia, and in China.

• There were modest decreases in population-weighted ozone levels in the US, Mexico, and Canada as well as parts of Europe, likely due to implementation of air quality management programs, and several countries in southeast Asia.

Resources

• Michael Brauer, Greg Freedman, Joseph Frostad, Aaron van Donkelaar, Randall V. Martin, Frank Dentener, Rita van Dingenen, Kara Estep, Heresh Amini, Joshua S. Apte, Kalpana Balakrishnan, Lars Barregard, David Broday, Valery Feigin, Santu Ghosh, Philip K. Hopke, Luke D. Knibbs, Yoshihiro Kokubo, Yang Liu, Stefan Ma, Lidia Morawska, José Luis Texcalac Sangrador, Gavin Shaddick, H. Ross Anderson, Theo Vos, Mohammad H. Forouzanfar, Richard T. Burnett, and Aaron Cohen (2015) “Ambient Air Pollution Exposure Estimation for the Global Burden of Disease 2013” Environmental Science & Technology doi: 10.1021/acs.est.5b03709

• Forouzanfar, Mohammad H et al. (2015) “Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks in 188 countries, 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013” The Lancet, Volume 386, Issue 10010, 2287 - 2323 doi: 10.1016/S0140-6736(15)00128-2