EVEN the darkest cloud may have a silver lining. The sharp drop in air pollution that accompanied Greece's economic crisis could be a boon to the nation's health.
Mihalis Vrekoussis of the Cyprus Institute in Nicosia and colleagues used three satellites and a network of ground-based instruments to measure air pollution over Greece between 2007 and 2011. Levels of nitrogen dioxide fell over the whole country, with a particularly steep drop of 30 to 40 per cent over Athens. Nitrogen monoxide, carbon monoxide and sulphur dioxide also fell (Geophysical Research Letters, DOI: 10.1002/grl.50118).
Pollution levels have been falling since 2002, but the rate accelerated after 2008 by a factor of 3.5, says Vrekoussis. He found that the drop in pollution correlated with a decline in oil consumption, industrial activity and the size of the economy. "This suggests that the additional reported reduction in gas pollutant levels is due to the economic recession," he says.
In Athens, a combination of heavy car use and lots of sunshine have created serious health problems, so city dwellers should see real benefits. Sunlight triggers chemical reactions that make the car exhaust pollution more harmful, for instance by forming small particulates that cause respiratory diseases. "Hospital admissions for asthma should decline," says Dwayne Heard of the University of Leeds in the UK.
It's not all good news: despite the drop in pollutants, levels of ground-level ozone - another cause of respiratory disease - have risen. Ozone would normally be suppressed by nitrogen oxides, but those have declined. That will take the edge off the benefit, says Heard.
Greece isn't the only country where air pollution has dropped. Nitrogen oxide levels fell across Europe after the 2008 financial crisis (Scientific Reports, doi.org/j74). In the US, nitrogen dioxide levels fell between 2005 and 2011, with the sharpest fall at the height of the recession (Atmospheric Chemistry and Physics, doi.org/j75).
Such declines can be one-offs, or governments can help make them permanent, says Ronald Cohen of the University of California, Berkeley, who led the US study. "A time of crisis is a real opportunity to initiate change." After the 2008 financial downturn, for instance, the US and Europe committed to pollution cuts. "In 10 years, there will be an end to air pollution in the US and Europe," says Cohen. "It's an incredible success story."
Greece, however, is not seizing the current opportunity, says Vrekoussis. "Investments in clean technologies and low-carbon green strategies have been abandoned," he says. "I'm afraid that in the long run the negative effects will override the positives."
Global greenhouse gas emissions initially fell in the wake of the financial crisis, but not by much. Emerging economies like China and India continued their economic growth, so a small emissions drop in 2009 was followed by a huge rise in 2010 which continued in 2011.
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