The study also warned that with no changes in air pollution, deaths per capita from air pollution would increase 20 to 30 per cent during the next 15 years in India and China.
The researchers found that meeting the World Health Organisation's (WHO) particulate air quality guidelines could prevent 2.1 million deaths per year related to outdoor air pollution worldwide.
Joshua S Apte of the Cockrell School of Engineering at The University of Texas Austin and his team looked at outdoor air pollution from particulate matter (PM) smaller than 2.5 microns.
Those particles can enter deep into the lungs. Breathing PM is associated with increased risk of heart attack, stroke and other cardiovascular disease; respiratory illnesses such as emphysema; and cancer.
"We wanted to determine how much cleaner different parts of the world would need to be in order to substantially reduce death from particulate matter," said Apte, lead author of the study published in the journal Environmental Science & Technology.
The study used the Institute of Health Metrics and Evaluation's Global Burden of Disease 2010 database; estimates of PM concentrations derived from ground-based measurements, satellite observations and air pollution models; and WHO's air quality guidelines.
Worldwide, most people live in areas with PM concentrations far above WHO's air quality guideline of 10 microgrammes per cubic metre, with some parts of India and China experiencing levels that exceed 100. The study demonstrated major potential to reduce mortality from PM in the world's most polluted regions.
One of the study's unexpected findings was that cleaning air in less polluted parts of the world, including in North America and Western Europe, can have as much health benefit as similar measures taken in the most polluted areas.
The study determined that meeting WHO's air quality guidelines could prevent up to 1.4 million premature deaths per year in polluted areas such as China and India.
Meeting WHO guidelines in clean regions could reduce premature deaths from outdoor pollution by more than half a million deaths per year. Another important finding is that because of ageing populations, health risks in many countries will increase even if pollution levels are constant.
The study found that with no changes in air pollution, deaths per capita from air pollution would increase 20 to 30 per cent during the next 15 years in India and China. If also accounting for population growth, the increase in deaths would be even greater if those countries experience no change in air pollution, researchers said.