What’s deadlier than malaria, four times as deadly as HIV/AIDS and flies under the radar for most policymakers worldwide? Air pollution.

That’s the finding of a new report by the World Bank and the Institute for Health Metrics and Evaluation. The culprits are particles of dirt, smoke, gases, microscopic liquid droplets and heavy metals and are the fourth highest cause of death, the study found, with sub-Saharan Africa and South Asia accounting for more than half of the estimated 5.5 million lives lost to diseases associated with pollution in 2013.

Some 20,000 people in South Africa alone will die each year from dirty air, warned the World Bank in its call-to-action report titled, “Air Pollution: Strengthening the Economic Case for Action.”

“Air pollution is a challenge that threatens basic human welfare, damages natural and physical capital and constrains economic growth,” said Laura Tuck, the vice president for sustainable development at the World Bank. “By supporting healthier cities and investments in cleaner sources of energy, we can reduce emissions, slow climate change and save lives.”

Risks to life are especially increasing in heavily populated, fast-urbanizing regions, and deaths related to cooking and heating homes with solid fuels have remained constant, despite development gains and improvements in health services.

Writing for Quartz Africa, Lily Kuo highlighted the case of Lagos, a city and surrounding metropolitan area of more than 21 million people, where smog has become another aspect of city life.

“The majority of residents live near industrial plants, breathing in exhaust from thousands of cars and millions of generators providing power to the city…” she wrote. “There’s little monitoring of pollution, no emissions inventories, or statistical information on things like fuel consumption. Researchers say that they struggle to find funding to study the issue.”

Kuo cited a study by Nature, a scholarly journal, that warned, “Not only is pollution in these cities killing local residents… [but] these emissions may even be altering the climate along the coast of West Africa, leading to changes in the clouds and so potentially to rainfall with devastating effects.” 

As much as 94 percent of Nigeria’s population is exposed to levels of air pollution that exceed what the World Health Organization deems as safe. And pollution within homes, often from fuel stoves and diesel generators, is believed to have contributed to as many as 600,000 deaths in Africa in 2012, the highest deaths per capita from indoor pollution of any region in the world. 

“This report and the burden of disease associated with air pollution are an urgent call to action,” said Dr. Chris Murray, director of IHME. “Policy makers in health and environment agencies, as well as leaders in various industries, are facing growing demands—and expectations—to address this problem.”