China steals an unsavory global spotlight for the thick, noxious smog that often chokes its mega-cities.
Air pollution has become so bad in Beijing, for example, that Chinese officials aim to slash its local coal consumption by 30% in 2017.
Meanwhile, the US — which currently ranks eighth on the list of countries with the lowest air pollution — could be headed in the opposite direction.
President Donald Trump has said that he intends to fulfill his campaign promise of revitalizing the American coal industry, despite the criticism of fossil fuel industry analysts and the rise of affordable sources of renewable energy. Congress is also working to repeal numerous environmental and health regulations.
With these and other changes afoot, it's worth taking a look at current global rankings to see how China, the US, and other countries stack up when it comes to air quality, total energy use, and renewable contributions to power production.
Here the best and worst of 135 countries according to World Health Organization (WHO) and International Energy Agency data, which was shared with Business Insider by The Eco Experts, a UK-based solar energy comparison site.
There are many ways to measure air pollution, but a key indicator is called "PM 2.5" — one of the most harmful classes of airborne pollutants.
The "PM" stands for "particulate matter," and the "2.5" stands for 2.5 microns in diameter or smaller — roughly the size of a single bacterium. Such pollution, as Business Insider's Lydia Ramsey explained in 2016, "is especially dangerous because it can get lodged in the lungs and cause long-term health problems like asthma and chronic lung disease."
When PM 2.5 levels go above roughly 35 micrograms per cubic meter of air, it can become a major health problem. The WHO recommends keeping PM 2.5 levels to about 10 micrograms per cubic meter.
While Chinese cities have recently hit more than 500 micrograms of PM 2.5 per cubic meter, Saudi Arabia, on a per-country average, has the most toxic air in the world.
Air pollution levels are one thing, but deaths attributed to them are another.
Take China, for instance. The country isn't in the top 10 for highest average levels of air pollution, in terms of PM 2.5 (Saudi Arabia wins that contest, thanks in part to its oil industry). However, it ranks fifth for having the most deaths per capita due to air pollution, in part because if its high population density.
The US currently has one of the lowest death rates attributed to air pollution.
Decades of scientific investigation across multiple lines of evidence corroborate a powerful yet inconvenient truth: Human-caused global warming and climate change is real, and it's briskly accelerating as we dump more carbon into the atmosphere.
Looking at per-person average emissions of carbon dioxide, a persistent greenhouse gas emitted by burning fossil fuels, the US ranks as the eighth-highest contributor in the world.
Less developed nations, which lack robust and power-hungry infrastructure, rank among the lowest contributors to carbon dioxide emissions.
The main reason the US ranks so poorly on carbon dioxide emissions is because its per-person consumption rate of electricity is so high; all of that energy comes primarily from fossil fuels.
As with carbon dioxide emission rankings, less developed nations tend to score better on electricity consumption because access to electrical power is not as widely available.