TUESDAY, March 3, 2020 (HealthDay News) -- Worldwide, air pollution may be shortening people's life expectancy by an average of three years, according to new estimates.

Researchers calculate that air pollution actually has a bigger impact on life expectancy than tobacco smoking, HIV/AIDS or violence.

While that might sound surprising, it reflects the ubiquity of air pollution, said study co-author Jos Lelieveld of the Max Planck Institute for Chemistry in Mainz, Germany.

Smoking is a greater threat to any one person's life, he said. But since everyone is exposed to some degree of outdoor air pollution -- consistently, over a lifetime -- dirty air has a bigger impact on life expectancy across the population, Lelieveld said.

How does air pollution take its toll? Deaths from heart disease and stroke are the biggest culprit, the researchers said, accounting for 43% of the loss in life expectancy worldwide.

The study, published March 3 in Cardiovascular Research, is far from the first to highlight the public health consequences of air pollution. Smog is known to worsen lung disease and to increase the risks of heart attack and stroke in vulnerable people. And previous research has linked air pollution exposure to premature death.

"There's very little question that air pollution is responsible for deaths and disease," said Dr. John Balmes, a volunteer medical spokesman for the American Lung Association.

In fact, he noted, the World Health Organization (WHO) has estimated that air pollution causes around 7 million deaths each year.

The new study looks at the issue through a "different lens," Balmes said. It estimates lost life expectancy and compares the impact of air pollution with other global killers.

To do that, researchers used a couple of statistical "models." One simulated atmospheric chemical processes and the way they interact with land, water and chemicals churned out from natural and human-made sources, such as road traffic and factories.

The other estimated the impact of air pollution on non-accidental deaths -- based on 41 studies from 16 countries.

Worldwide, the researchers said, air pollution may take an average of three years from people's life expectancy. The impact is smallest in Australia, South America and North America -- where dirty air accounted for around one year of life lost, give or take a few months.

At the other end of the spectrum is East Asia, where air pollution shortens people's lives by an estimated four years. Meanwhile, people in South Asia, Africa and Europe face two to three years of lost life expectancy, the study found.

By comparison, exposure to tobacco smoke shortens life expectancy by an average of 2.2 years globally, the researchers noted. Air pollution also beats out major global killers like HIV/AIDS, malaria and all forms of violence, including wars, which each reduce life expectancy by less than a year globally.

In the United States, air quality has been improving, said Balmes, who is also a professor of medicine at the University of California, San Francisco.

But, he said, much could still be gained from more improvements -- fewer deaths from heart disease being a prime one.

Moving away from fossil fuels could not only address climate change, but also help everyone breathe cleaner air, Balmes said.

In fact, the study estimates, eliminating fossil fuel emissions could add more than a year to average life expectancy worldwide.

Study co-author Dr. Thomas Münzel pointed to the particular impact of dirty air on heart health.

Air pollution should be included in guidelines on heart disease prevention, said Münzel, a cardiologist at the University Medical Center of the Johannes Gutenberg University, in Mainz.

Right now, he said, prevention guidelines from the American College of Cardiology/American Heart Association "do not mention air pollution as a risk factor at all."

"That's hard to understand," Münzel said.

According to the WHO, 91% of the world's population lives in places where outdoor air pollution exceeds the group's recommended limits.

More information

For more on the health effects of air pollution, visit the American Lung Association.