Key findings from the research, which looked at causes of disease and premature death in 130 countries:

• In 2015, an estimated 6.5 million people died from heart disease, stroke, lung cancer and other respiratory conditions tied to air pollution. Water pollution was responsible for 1.8 million deaths.
• 92% of pollution-related deaths were seen in low-income and middle-income countries, per an accompanying article. The most deaths were in India (2.5 million) and China (1.8 million).
• Economic impact: The report estimated a 1.3% reduction in GDP in low-income countries versus 0.5% in developed ones. But "reducing the pollution quantified in the report might impact production, and so would not likely translate into gains equal to the $4.6 trillion in economic losses," writes the AP's Katy Daigle.

"It doesn't have to [get worse]. It's not an inevitable outcome," Landrigan told the Washington Post. "Pollution control is a winnable battle."