India tops the list of countries with the highest annual average concentration of PM2.5, at 90.9 µg/m3. This is followed by Saudi Arabia and China. All the countries that reached Japan's annual average environmental standard (15 µg/m3 or less) were developed countries, with the respective figures as follows: Japan (11.7 µg/m3), the United States (7.4 µg/m3), the United Kingdom (10.5 µg/m3), and Germany (12.0 µg/m3). Looking at the last two years, Saudi Arabia in the Middle East has deteriorated at a faster rate than the others, with a 4.1% increase. On the other hand, Vietnam, the Philippines, the United Kingdom, and South Korea are on a downward trend.

Reference The World Bank "World Development Indicators" ”PM2.5 air pollution, mean annual exposure (micrograms per cubic meter)” Retrieved December 23, 2020, from http://bit.ly/3hbSb7q