Most of those deaths are concentrated among the world's poorest populations, according to a study published online October 19 in the Lancet that documents the health and economic toll of pollution in 2015.
Various kinds of airborne pollution - smog from power plants, factories or vehicles - proved to be the most fatal form, accounting for 6.5 million deaths in 2015.
Professor Landrigan said: "Despite its far-reaching effects on health, the economy and the environment, pollution has been neglected in the worldwide assistance and the global health agendas, and some control strategies have been deeply underfunded".
The study, published on Friday in the Lancet, warned that pollution is so unsafe it "threatens the continuing survival of human societies". That's more than the number of deaths caused by tobacco, three times as many deaths caused by AIDS, tuberculosis, and malaria combined, and 15 times as many deaths caused by war and other violence.
An overwhelming majority of pollution-related deaths - 92 percent - occur in less-developed countries.
About one in every six premature deaths worldwide is linked to dirty air, water and soil.More news: India rout Pakistan 4-0, face Malaysia in Asia Cup hockey final
"There's been a lot of study of pollution, but it has never received the resources or level of attention as, say, Aids or climate change", Landrigan said. In addition, the researchers note, across the board, the deaths are most prevalent among minorities and the marginalized.
China ranked second deadliest with over 1.8 million premature deaths recorded.
Switching to cleaner sources of energy has been recognized as the best way to control air pollution and the best way to sustain human health and planet's survival, said the report.
News agency PTI reported that the online indicators of the pollution monitoring stations in Delhi on Diwali nigh glowed red, indicating a "very poor" air quality as the volume of ultra fine particulates PM2.5 and PM10, which enter the respiratory system and manage to reach the bloodstream, sharply rose from around 7 pm. Other nations with deadly environments include Haiti, Bangladesh, South Sudan, Pakistan and North Korea.
Pollution, the report said, was also "costly", costing some United States dollars 4.6 trillion in annual losses - or about 6.2 per cent of the global economy.
The report also insists on the economic weight of these lives cut short for the countries concerned: over 4,600 billion dollars each year, or the equivalent of 6.2% of global economic wealth.
"Pollution-related diseases cause productivity losses that reduce gross domestic product (GDP) in low-income to middle-income countries by up to 2 per cent each year".