Over two million deaths occur annually as a direct consequence of man-made air pollution, researchers from the University of North Carolina found in a study.

Air pollution is the cause of many diseases and health problems.  It is known to cause asthma, lung infections and even cancer. So how dangerous is air pollution? Scientists from the University of North Carolina found that over 2 million deaths annually are caused due to air pollution.

"Our estimates make outdoor air pollution among the most important environmental risk factors for health. Many of these deaths are estimated to occur in East Asia and South Asia, where population is high and air pollution is severe," Co-author of the study, Jason West, from the University of North Carolina, said in a press statement.

For the study, researchers used an ensemble of climate models to simulate the concentrations of ozone and PM2.5 in the years 2000 and 1850. A total of 14 models simulated levels of ozone and six models simulated levels of PM 2.5 (tiny particles suspended in the air that can penetrate deep into the lungs, causing cancer and other respiratory disease).

The research actually found that about 470,000 people die each year because of human-caused increases in ozone. In addition, the scientists discovered that 2.1 million deaths are caused by increases in particulate matter from human activities. Climate changes are known to affect air pollution in many ways. These changes can either increase or decrease the level of local air pollution. Nevertheless, researchers have found that the number of deaths caused due to climatic changes is relatively small. While climate change alone doesn't cause many deaths, scientists worry that it could exacerbate the effects of air pollution and increase death rates.

"Very few studies have attempted to estimate the effects of past climate change on air quality and health," said West. "We found that the effects of past climate change are likely to be a very small component of the overall effect of air pollution."

The findings are published in the journal Environmental Research Letters.