By Richard Lenti
The deadly toll of breathing polluted air is now estimated to claim over two million people worldwide annually, a new study has found. Another 470,000 people die every year because of human-caused increases in ozone.
The main culprit, according to researchers at the University of North Carolina, is fine particulate matter; tiny particles suspended in the air that can penetrate deep into the lungs, causing cancer and other respiratory disease.
“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,” said co-author Jason West
The study, published online in the journal Environmental Research Letters, downplays the effect of climate change on air pollution, suggesting it only accounts for a small proportion of the deaths caused by air pollution.
It estimates that approximately 1,500 deaths annually are due to ozone and 2,200 deaths related to particulate matter are caused by climate change. Higher temperatures can increase the emission of organic compounds from trees, which can react in the atmosphere to form ozone and particulate matter.
“Very few studies have attempted to estimate the effects of past climate change on air quality and health. We found that the effects of past climate change are likely to be a very small component of the overall effect of air pollution,” said West.
That’s because studies indicate that climate change affects air pollution in different ways, leading to both increases and decreases in local air pollution.
Researchers used a number of climate models to simulate the concentrations of ozone and particulate matter in the years 2000 and 1850. A total of 14 models simulated levels of ozone and six models simulated levels of particulate matter.
Previous epidemiological studies were used to assess how the specific concentrations of air pollution related to global mortality rates.
The results were comparable to previous studies that analyzed air pollution and mortality.
“We have also found that there is significant uncertainty based on the spread among different atmospheric models. This would caution against using a single model in the future, as some studies have done,” said West. “Consequently, it cannot be clearly concluded that past climate change has increased air pollution mortality.”
Another study published last week in the Proceedings of the National Academy of Sciences found that life expectancy in northern China is five and a half years lower than in the southern China because of heavy air pollution.
In a Los Angeles Times article, researchers estimated that the 500 million residents of northern China in the 1990s collectively lost 2.5 billion years from their lives.
“It’s a huge loss. Air pollution in China is really damaging people’s health much more seriously than the findings in previous literature” would suggest, said Yuyu Chen of Peking University, one of the study’s authors.
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