Taken together, air pollution caused 5.5 million deaths in 2013 and was the 4^th highest-ranking risk factor for death in the world.

The research, presented at the 2016 annual meeting of the American Association for the Advancement of Science (AAAS), found that despite efforts to limit future emissions, the number of premature deaths linked to air pollution will climb over the next two decades unless more aggressive targets are set.

Air pollution is the fourth highest risk factor for death globally and by far the leading environmental risk factor for disease. Reducing air pollution is an incredibly efficient way to improve the health of a population.

—Michael Brauer, a professor at the University of British Columbia’s School of Population and Public Health

Outdoor particulate air pollution specifically was the 7^th leading risk factor for death globally, with cardiovascular disease (ischemic heart disease and stroke) accounting for the majority of these deaths.

Additional deaths from air pollution were from lung cancer, chronic lung disease and respiratory infections. Of these 2.9 million deaths, 64% were in Asia, especially China and India. Even in the US, where air pollution levels are considerably lower than the global average, ambient air pollution was the 13^th highest ranked risk factor for deaths with 79,000 estimated in 2013.

Between 1990 and 2013, global exposure to particulate matter air pollution increased by 20%, driven by increases in South Asia, Southeast Asia, and China. These increases, combined with population growth, aging and increasing prevalence of diseases impacted by air pollution led to increases in both total deaths from air pollution and the rate of attributable deaths.

In China, burning coal is the biggest contributor to poor air quality. Qiao Ma, a PhD student at the School of Environment, Tsinghua University in Beijing, China, found that outdoor air pollution from coal alone caused an estimated 366,000 deaths in China in 2013.

Ma also calculated the expected number of premature deaths in China in the future if the country meets its current targets to restrict coal combustion and emissions through a combination of energy policies and pollution controls. She found that air pollution will cause anywhere from 990,000 to 1.3 million premature deaths in 2030 unless even more ambitious targets are introduced.

Our study highlights the urgent need for even more aggressive strategies to reduce emissions from coal and from other sectors.

—Qiao Ma

In India, a major contributor to poor air quality is the practice of burning wood, dung and similar sources of biomass for cooking and heating. Millions of families, among the poorest in India, are regularly exposed to high levels of particulate matter in their own homes.

India needs a three-pronged mitigation approach to address industrial coal burning, open burning for agriculture, and household air pollution sources.

—Chandra Venkataraman, professor of Chemical Engineering at the Indian Institute of Technology Bombay

The research is an extension of the Global Burden of Disease study, an international collaboration led by the Institute for Health Metrics and Evaluation (IHME) at the University of Washington that systematically measured health and its risk factors, including air pollution levels, for 188 countries between 1990 and 2013. The air pollution research is led by researchers at the University of British Columbia and the Health Effects Institute.

Additional facts about air pollution:

• World Health Organization (WHO) air quality guidelines set daily particulate matter at 25 micrograms per cubic meter.

• At this time of year, Beijing and New Delhi will see daily levels at or above 300 micrograms per cubic meter meter; 1,200 per cent higher than WHO guidelines.

• While air pollution has decreased in most high-income countries in the past 20 years, global levels are up largely because of South Asia, Southeast Asia, and China. More than 85% of the world’s population now lives in areas where the World Health Organization Air Quality Guideline is exceeded.