The study, published in Environmental Science and Technology, was done before, during and after the 2008 Olympics by scientists from Oregon State University and Peking University.
Particulate matter air pollution in the Beijing Olympics were about double the levels of recent games in Athens, triple those of Atlanta and 3.5 times higher than the games in Sydney. However due to massive control efforts, Beijing had the most significant decrease in particulate air pollution compared to the other Olympic sites around the time of their games.
Nevertheless unacceptable levels were found in Beijing 100 percent of the time for particulate matter smaller than 2.5 microns that causes the most serious health problems. The smaller, most harmful particulate matter was the least affected by government pollution reduction efforts -- even though some favorable weather conditions did help reduce the problem.
Oregon State's Staci Simonich describes Beijing during the Olympics as the largest scale atmospheric pollution experiment ever conducted.
"Despite all that, it was some evening rains and favorable shifts in the winds that provided the most relief from the pollution," Simonich said in a statement.