A major study published in a British medical journal, The Lancet, says pollution kills at least 9 million people a year and costs nearly $5 trillion annually.
The study, released on October 20, says one out of every six premature deaths in 2015 could be attributed to exposure to toxins in the air, water, or soil.
Although the estimate of 9 million deaths was described as "conservative," it is more than three times the number of people killed annually by AIDS, tuberculosis, and malaria combined and more than 15 times the number of people killed by wars and other forms of violence.
The Lancet study is the first of its kind to assemble data on disease and deaths caused by air, water, and soil pollution.
"Pollution is a massive problem that people aren't seeing because they're looking at scattered bits of it," epidemiologist Phillip Landrigan, a lead author of the study, told AP.
India was the country with the most premature deaths caused by pollution, with an estimated 2.5 million in 2015.
China was second, with some 1.8 million deaths by pollution-related causes.
Pakistan, Bangladesh, North Korea, South Sudan, and Haiti were also featured in the report.
With reporting by AP, BBC, and The Guardian