Sustainability, Vol. 12, Pages 2910: Dynamic Trends of Fine Particulate Matter Exposure Across 190 Countries: Analysis and Key Insights (Sustainability)

Despite the fact that fine particulate matter (PM2.5) causes serious health issues, few studies have investigated the level and annual rate of PM2.5 change across a large number of countries. For a better understanding of the global trend of PM2.5, this study classified 190 countries into groups showing different trends of PM2.5 change during the 2000–2014 period by estimating the progress ratio (PR) from the experience curve (EC), with PM2.5 exposure (PME)–the population-weighted average annual concentration of PM2.5 to which a person is exposed—as the dependent variable and the cumulative energy consumption as the independent variable. The results showed a wide variation of PRs across countries: While the average PR for 190 countries was 96.5%, indicating only a moderate decreasing PME trend of 3.5% for each doubling of the cumulative energy consumption, a majority of 118 countries experienced a decreasing trend of PME with an average PR of 88.1%, and the remaining 72 countries displayed an increasing trend with an average PR of 110.4%. When two different types of EC, classical and kinked, were applied, the chances of possible improvement in the future PME could be suggested in the descending order as follows: (1) the 60 countries with an increasing classical slope; (2) the 12 countries with an increasing kinked slope; (3) the 75 countries with a decreasing classical slope; and (4) the 43 countries with a decreasing kinked slope. The reason is that both increasing classical and kinked slopes are more likely to be replaced by decreasing kinked slopes, while decreasing classical and kinked slopes are less likely to change in the future. Population size seems to play a role: A majority of 52%, or 38 out of the 72 countries with an increasing slope, had a population size of bigger than 10 million inhabitants. Many of these countries came from SSA, EAP, and LAC regions. By identifying different patterns of past trends based on the analysis of PME for individual countries, this study suggests a possible change of the future slope for different groups of countries.