2 million a year die from air pollution

Estimate in study smaller than previous calculations

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LOS ANGELES -- Global air pollution contributes to the premature deaths of more than 2 million adults each year, according to new research.

In a study published Friday in the journal Environmental Research Letters, scientists used mathematical models to estimate the effects of fine particulate matter -- tiny particles, or soot, that penetrate deep into the lungs -- and ozone, the main component of smog.

The estimate is smaller than most previous calculations, which pegged pollution-related deaths at more than 3 million a year. The researchers also concluded that climate change has had only minimal effect on pollution-related deaths.

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

West and his colleagues concluded that about 470,000 people die each year from ozone produced by human industrial activities. (Unlike ozone high in the atmosphere, which provides protection from the sun's rays, ground level ozone is mostly caused by chemical reactions in urban and suburban regions.)

Authors also concluded that an additional 2.1 million deaths were caused by fine particulate matter resulting from human activity. Such particles measure smaller than 2.5 microns in width and are called PM 2.5. These particles have been linked to lung cancer and a variety of respiratory diseases.

The authors noted that climate change could affect air quality in a number of ways. Moist or wet regions, for example, might see less ozone production, while drier areas might see more.

Different climate models provided widely differing forecasts, the researchers said, with some models estimating an overall decrease in mortality. When these models were averaged together, the effects of climate change were determined to be small.