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WASHINGTON — Pollution around the globe contributed to an estimated 9 million premature deaths annually in 2015 — or roughly one in six of all premature deaths, according to a new in-depth study by an international team of researchers.
That means pollution kills more people each year than all war and violence in the world, and three times more than HIV/AIDS, tuberculosis, and malaria combined, the study said.
Most of those deaths occur in poor and developing countries, from such pollution sources as dirty air in India and China, tainted water in sub-Saharan Africa, and toxic mining and smelter operations in South America.
‘‘Going into this, my colleagues and I knew that pollution killed a lot of people. But we certainly did not have any idea of the total magnitude of the problem,’’ said Philip Landrigan, dean of global health at the Icahn School of Medicine in New York and cochairman of the commission behind the report.
The two-year project, which relied on data from researchers in more than 130 countries documenting the causes of disease and premature deaths in recent decades, found that poor air quality was the most significant pollution-related killer.
That includes both outdoor pollution tainted by mercury, arsenic, and other harmful particulates, and household air dirtied by the burning of wood, dung, and other organic materials. The result: An estimated 6.5 million deaths in 2015 from heart disease, strokes, lung cancer, and other respiratory problems.
Water pollution, which includes everything from unsafe sanitation to contaminated drinking water, accounted for an additional 1.8 million annual deaths from gastrointestinal diseases and other infections, researchers found.
Pollution in the workplace also took a heavy toll on some of the world’s poorest workers. From bladder cancer in dye workers to the lung disease pneumoconiosis in coal miners, researchers found that occupational exposure to various carcinogens and toxins was linked to about 800,000 deaths annually.
In 2015, the largest number of deaths attributable to pollution occurred in India and China, with an estimated 2.5 million and 1.8 million deaths, respectively, or about 24 and 19 percent of deaths worldwide. Other severely affected countries include Pakistan, Bangladesh, and Kenya.
Air pollution levels in India’s capital soared Friday as millions of Indians burst fire crackers to celebrate Diwali, the Hindu festival of lights, despite a court ban on the sale of fireworks in the region.
Already one of the world’s most polluted cities, New Delhi saw its air quality index hit 1,031 Friday morning, according to the US embassy. A reading of more than 300 is considered hazardous.
Beyond the massive human toll, the authors of the report, which appeared Thursday in the British medical journal the Lancet, also focused on the financial toll caused by pollution-related health problems.
It said about $4.6 trillion in annual losses can be attributed to the early deaths and illnesses.
‘‘Until now, people haven’t recognized what an incredible hit pollution makes on the economy of a country,’’ Landrigan said. ‘‘Pollution control can stimulate the economy because it reduces death and disease.’’
The study estimated the effect on national budgets at about 1.3 percent of gross domestic product in low-income countries, compared with about 0.5 percent in developed, high-income countries. In addition, nations facing crippling pollution tend to spend much more on health care to treat diseases related to the problem.
‘‘When you’re looking at developing countries, you really have to address this challenge if you want to move people out of poverty and into the middle class,’’ said Gina McCarthy, a former Environmental Protection Agency administrator who was not involved in the study.
Global warming is expected to fuel more deaths in the absence of international action, she said.
‘‘Climate change is going to exacerbate the very problems that are identified in this article. There will be more contagious and infectious diseases. There will be more lives lost, more injuries, if we don’t identify a path that gets us out of the hole that we’re in,’’ McCarthy said.
‘‘What people don’t realize is the instability that results from poverty, the instability that results from migration as a result of climate change,’’ she said.
The study stating pollution accounts for about 16 percent of deaths worldwide builds on previous studies, including a 2016 report from the World Health Organization.
McCarthy said the Lancet study was based on the most complete epidemiological data available. “Even if they’re off by a factor of 10, you’re still talking about huge, huge impacts. But they’re not off by a factor of 10,’’ she said.
‘‘It’s very clear if you go to other countries and it’s clear if you go to some of our own communities that they are being held back because of the impact of pollution on their kids and their elderly,’’ McCarthy said.
Landrigan said there is a prevailing belief that developing countries have to suffer through pollution and disease on their way to becoming more prosperous. But he and the study’s other authors said countries should do much to reduce pollution and improve the health of their citizens — and that they will reap economic benefits for doing so.
In addition, Landrigan said developed nations can play a meaningful role in helping poorer countries slash pollution, and major nonprofit foundations that have largely steered clear of the problem must be convinced that it is a global priority.
‘‘It’s not an inevitable outcome,’’ Landrigan said of the annual death toll. ‘‘Pollution control is a winnable battle.’’