Tiny particles and troublesome gases in the outdoor air are ultimately responsible for some 3.3 million premature deaths annually, according to a comprehensive new look at the health effects of air pollution.

The data suggest that globally, more people die from outdoor air pollution than from malaria and HIV/AIDS combined. And if there is no change to our current control measures, outdoor air pollution could cause around 6.6 million early deaths each year by 2050.

“Air pollution appears to be a very significant source of premature mortality,” the study’s lead author, Jos Lelieveld of the Max Planck Institute for Chemistry, said this week in a telephone press conference.

Low-altitude ozone and fine particulates in the air have been linked to heart disease, strokes, respiratory illnesses and lung cancer. But global data on this pollution has been lacking because air quality is not monitored in many parts of the world.

Lelieveld’s team combined atmospheric modeling with population data and health statistics to create estimates of air pollution levels, where it was coming from and how many people it was killing.

Particulates can come from natural sources such as dust as well as unnatural ones, including burning wood and charcoal, large-scale power generation, vehicles and agriculture. Agriculture may seem like an odd source of air pollution, but fertilizer and domesticated animals both produce ammonia, which mixes with other types of emissions in the atmosphere to produce particulates.

The source of the particulates—and thus deaths from air pollution—varies from region to region, the study demonstrates. In the United States, for instance, where air pollution accounts for some 55,000 deaths annually, traffic and power generation are big contributors. In the eastern half of the country, the combination of agricultural fields and dense cities and suburbs combines to produce many deaths, Lelieveld says.

But the majority of deaths from air pollution occur in China and India, mostly from residential heating and cooking, which is often inefficient and produces a lot of particle-filled smoke. Researchers already knew that this type of pollution, when breathed indoors, causes around 3.5 million deaths. But Lelieveld and his colleagues found this source is also a huge contributor to outdoor air pollution, responsible for killing another million people globally.

“You cannot stop people from eating and cooking, but you can provide better technologies,” Lelieveld said during the press conference. He noted, however, that though inventors have tried to lessen this source of pollution with more efficient cookstoves, it has often been difficult to convince people to give up their traditional methods.

Lelieveld admits that his group’s dataset is not perfect. For instance, there is some research that shows that black carbon—the main component in soot—is worse than other types of particulates. If that is true, than the scope of deaths from various sources of air pollution would change. But Lelieveld and his team hope that their research will help guide governments in creating better control measures.

Evidence that such measures can reduce deaths comes from another study published today in Nature Geoscience. Dominick Spracklen of the University of Leeds and colleagues looked at the health impact from a reduction in fires linked to Amazon deforestation. They estimate that fewer fires lessened airborne particulates enough to prevent some 400 to 1,700 premature deaths in South America each year.