Take a deep breath — but maybe not too deep.
According to the Health Effect Institute's 2018 State of Global Air Report, more than 95 percent of the world's population is breathing in air that exceeds pollution levels deemed safe by the World Health Organization. Developing countries are bearing the bulk of this burden as economic development outpaces environmental safeguards.
Relying on satellite data and air monitoring systems from around the world, the report highlights the density of outdoor polluted air, or ambient air, with a particular focus on air particulate matter less than or equal to 2.5 micrometers in diameter. Worldwide exposure to this particulate matter contributed to 4.1 million deaths in 2016 — the year from which the most recent data is available — making it the sixth leading cause of death around the world behind high blood pressure, smoking and various diet-related causes, according to the report.
Household air pollution generated by solid burning fuel sources like coal and wood led to another 2.6 million deaths.
China and India accounted for about 51 percent of ambient air deaths. Both countries are making changes to their air quality, but they have a long way to go. (The picture above shows the Chinese city of Hong Kong shrouded in smog.)
A separate study published in December 2018 shows that 1.24 million people in India died from air pollution in 2017 — a staggering one out of eight people in the country. What's even more sobering is more than 51 percent of those deaths were people younger than 70. Indoor air pollution from cooking fuels claimed 480,000 lives.
"There are reasons for optimism, though there is a long way to go," Bob O’Keefe, vice president of the institute, told The Guardian. "China seems to be now moving pretty aggressively, for instance in cutting coal and on stronger controls. India has really begun to step up on indoor air pollution, for instance through the provision of LPG [liquefied petroleum gas] as a cooking fuel, and through electrification."
China and India aren't the only nations that are suffering from air pollution. The American Lung Associated released its own State of the Air report. Their study found that four out of 10 people living in the United States live in counties with unhealthy levels of ozone and air pollution.
Editor's note: This article has been updated since it was originally published in April 2018.