Air pollution exceeded guidelines set by the World Health Organization (WHO) and was about one third higher than reported by Chinese officials during the Games.


Hepeng Jia/Beijing, China

A study suggesting Beijing’s air pollution during the 2008 Olympics may have been worse than official figures has been challenged by environmental chemists.

In the 17 July issue of the journal Environmental Science and Technology (EST), Tao Shu from Peking University, Staci Simonich from Oregon State University, US, and colleagues published research based on the air particulate matter (PM) samples collected over a two-week period prior to the 2008 Olympics, the two weeks of the Games, and during a four-week period following the event1.

According to the team’s figures, air pollution exceeded guidelines set by the World Health Organization (WHO) and was about one third higher than reported by Chinese officials during the Games.

Hu Fang

© Hbh |

Official figures questioned

In response to international concerns about the air pollution in Beijing, local governments cooperated to improve the environment for the Olympics. Hundreds of chemical, cement and steel factories were shut down, half the cars were taken of Beijing’s roads during the Games and construction activities were slowed down.

The measures did have some effect according to the study, which focused on measurements of air-borne particles with a diameter of less than 10mu.gifm (PM10 measurements) and less than 2.5mu.gifm (PM2.5 measurements) collected on a site on the Peking University campus. Both types of particle are major pollutants in the Chinese cities, though the finer particles are more harmful to health. The Beijing Environmental Protection Bureau (EPB) takes daily measurements of PM10 but not PM2.5.

According to the study, the average concentration of PM2.5 and PM10 were 31 per cent and 35 per cent lower respectively during the Olympic period compared to the non-Olympic period. PM10 concentrations in October, November, and December 2008 were also found to be 9-27 per cent down on the same months in 2007.

However, when the authors compared their data with the average figures released by the EPB and those recorded by the EPB in nearby sample collection sites, they found their observed PM10 concentrations were 1.3 times higher than those measured at nearby sites by EPB.

While cautioning that such differences could be down to the different measurement methods used, the study also found PM10 concentrations in Beijing during the Olympic period were 2.9, 3.5, and 1.9 times higher than those in Atlanta, Sydney, and Athens when those cities hosted the Olympics in 1996, 2000 and 2004.

The researchers also found that PM2.5 and PM10 concentrations during the Olympic period exceeded WHO 24-hour guidelines 100 per cent and 81 per cent of the time respectively, while according to Beijing EPB average figures, only 44 per cent of days surpassed the WHO guidelines.

The authors also found 40 per cent of the variation was down to meteorological factors, while efforts to control emission sources only accounted for 16 per cent.

Results challenged

The Olympics air study seems to upset other environmental scientists both in China and overseas. Two comments published in the 3 September issue of EST aired serious concerns about the study, ranging from the methodology, accuracy of equipment, and collection sites to the definition of the control measures taken by Beijing authorities.
In one comment, Yao Xiaohong from the University of Toronto and colleagues from both China and the United States say the filter-based measurements used in the study are vulnerable to large margins of error because the filters used were not suitable for tiny particles like PM2.52.

The comment also says the authors’ interpretation of the modeling results may be inappropriate.

In another comment, Tang Xiaoyan from Peking University and colleagues from the Chinese Academy of Sciences, and the US-based University of Medicine and Dentistry of New Jersey point out the monitoring site used by the study was close to a main roadway with high traffic density, which could cause higher concentration of pollutants3.

In addition, the control measures designed and implemented to improve the air quality for the Beijing Olympics were rather complex, according to Tang, and the air study has incorrectly set some periods of time as controlled and others as non-controlled. Therefore, the conclusion that the climate factors may have played a bigger role in improving the air quality than the source control measures could be questioned.

The debate seems to be sensitive.

The commenting authors either did not respond to Chemistry World’s inquiries, or refused to comment. 

Simonich, author of the original study, published her responses to the two comments in EST, but she also refused to talk to Chemistry World.

Olympics for the future

In her response, Simonich insisted her methods work for tiny particles, and that as the sample collection site was 25 metres above the traffic level, it represented a ’conservative measure of what athletes and spectators experienced at traffic level near [Peking University] because of dilution’. She also stresses that the study defined ’source control’ and ’non-source control’ time periods with respect to restrictions in automobile traffic, as information about other emission control measures were not available and thus not taken into consideration.4

’Our data indicate that some of the highest PM concentrations occurred during the source control periods, while some of the lowest PM concentrations occurred during the non-source control time periods,’ Simonich writes. ’Clearly, this suggests that variables other than source control measures, including meteorology, played a significant role in the resulting PM concentrations.’

On the other hand, Zhuang Guoshun, chair of the Research Centre for Atmospheric Chemistry of Shanghai-based Fudan University, says only evaluating the PM concentration cannot clearly reveal the air quality change during the Beijing Olympics.

In his unpublished study, the total concentration of air-borne particles in Beijing during the Olympics did not show a dramatic change compared to the pre-Olympics period. ’But when comparing PM2.5 in two individual weeks before and during the Olympics with similar meteorological status, [concentrations of] some harmful particles, such as  carbon black, most elements and ions, as well as the aerosol mass clearly decreased during Olympics,’ Zhuang told Chemistry World.

According to Zhuang, however, concentrations of some particles rose again after the Olympic Games, mainly due to long-range transport from eastern China.

’Our studies have shown most of the reduction comes from the automobile controls, indicating this could be the most powerful measure to improve air quality,’ he adds.


1. W Wang et al, Environ. Sci. Technol., 2009, 43, 6440 (DOI: 10.1021/es901953s)
2. X Yao, Environ. Sci. Technol., 2009, DOI: 10.1021/es902276p
3. X Tang, Environ. Sci. Technol., 2009, DOI: 10.1021/es902217x
4. S Simonich, Environ. Sci. Technol., 2009, DOI: 10.1021/es902531w