China_pollution_Beijing.jpgThe 13m residents of Beijing can at last breath more easily — but for how long? Air pollution in the capital over the last six months reached its lowest level in the decade, officials report.

So far this year, Beijing has had 23 more “blue sky days” than during the same period last year, according to the Beijing Environmental Protection Bureau.

Meanwhile, the average pollution readings for five of the last six months were the best since 2000.

Of course, there is much scepticism about the accuracy of these official data. Critics have long accused Beijing of manipulating the data, particularly in the run-up to last year's Olympics, when some star athletes threatened a boycott because of Beijing's notorious high levels of air pollution.

As it turns out, they were right to be concerned.

Researchers from Peking University and the Oregon State University (OSU) have just published the results of a comparative study of atmospheric particulate pollution before and after last year's Olympics.

The team found that the concentration of PM10 particles — those smaller than 10 micrometres — in Beijing during the Olympic period were 2.9, 3.5, and 1.9 times higher than when the Olympics games were held in Atlanta, Sydney, and Athens, respectively.

The size of the particle is a main determinant of where in the respiratory tract the particle will come to rest when inhaled, and thus possible health risks. Particles larger than 10 micrometres generally do not cause health problems as they get filtered by the nose.

Below 10 micrometres, particles are small enough to enter the bronchi of lungs. In addition, the researchers measured the concentration of PM2.5 particles, which are less than 2.5 micrometres in diameter. At this size, particles are more dangerous as they can penetrate deeper into the gas exchange regions of the lungs.

China has been criticised for not including the PM2.5 measure in its air quality index, although a Beijing official said that the city was considering more comprehensive air quality measurements

The OSU researchers found that PM2.5 and PM10 concentrations during the Olympic period exceeded the World Health Organisation's guideline 100% and 81% of the time, respectively.

When the the research team repeated the measurements in the last three months of 2008, they found that particle concentrations decreased by between 9% and 27% over the year-earlier same period.

That suggests that Beijing's much-vaunted anti-pollution measures — closing factories, restricting traffic — introduced for the Olympics did indeed have some effect, albeit too late to effect pollution levels while the games were taking place.

But the researchers noted that the weather was often the greatest ally in Beijing's attempt to reduce air pollution. Staci Simonich, associate professor of environmental and molecular toxicology at OSU, said:

Considering the massive efforts by China to reduce air pollution in and around Beijing during the Olympics, this was the largest scale atmospheric pollution experiment ever conducted. Despite all that, it was some evening rains and favourable shifts in the winds that provided the most relief from the pollution. This demonstrates how difficult it is to solve environmental problems on a short-term, local basis.”

The researchers argue that the economic downturn might also have been responsible for the reduced pollution levels at the end of 2008 — and presumably this may also explain the continuing low levels reported in the official figures for the first six months of 2009.

Summing up, Simonich said that there is no scientific evidence so far of any health problems that have been linked to the short-term exposure of athletes or spectators to this pollution during the Olympics. She said:

The athletes and visitors were only exposed for a very short time. Millions of other people there face this air quality problem their entire lives. It was unlike anything I've ever seen – you could look directly at the sun and not have a problem, due to the thickness of the haze.”

Food for thought for expats who are about to relocate to Beijing.

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