New China's AQI six month readings in 2013 is showing a stabilizationof PM10 pollutant at a high level (90 µg/m3) but also an increasedpollution resulting from fine particulate PM2.5

Figure 1: Heavy smog in Harbin on Oct. 21, 2013. (STR/AFP/GettyImages)

Winter brings the worst air pollution to Northeast Chinese cities due to a combination of bad weather conditions with the starting period of home and municipal coal heating. According to the China’s MEP published reading of PM2.5 - inaugurated in May 2013- Harbin showed the first measured value of 1000µg/m3 which is twice the maximum scale set for this type of pollutant.

China’s Government had long been thriving to increase production regardless on the environment impacts. Coal according to MEP statistics provided in 2011 around 68.4% of total energy while combustion facilities are far from respecting strict specifications for reduction of their dust, ashes and particulate matter outputs.

But this situation is rapidly changing as the population is becoming acutely aware of the huge toll of air pollution on public health. People are asking air quality standards more in line with the best worldwide practice. They want transparency and more reliable information to be made available to the public. 

New standard for China AQI in 2012

The 2007 standard concerning Air Pollution Index (API 2007) has been updated during 2012 to make it more comparable to the US AQI (see Figure 2).

Figure 2 : New China’s Air Quality Index 

Figure 3 : Comparison of the threshold pollution of the new China’s AQI with US AQI

Fine particulate matter pollutant has been introduced and other pollutant concentration thresholds as compared to the 2007 previous standard have been reduced (NO2, CO) or maintained (PM10, O3-1 hour).

If we look at the most dangerous pollutants- namely PM2.5, PM10 and O3 - when compared to the US AQI- the Chinese pollution levels are still much more important especially for PM2.5 (see above Figure 3).

But more insidiously -if the colour policy is exactely the same- the rhetoric behind the US or Chinese pollution index levels are not the same. The US "moderate pollution" is in China qualified as a "good situation" , or US "unhealthy pollution for sensitive groups" (children or elderly persons) is considered in China as a "light pollution"! 

Chinese cities new air quality ranking based on the 6 months mean AQI from May to Oct. 2013

Since May 2013 a synthetic document is  published monthly (see MEP November issue ) giving all the monthly mean values for 76 cities (May to September 2013) extended at 114 cities (October 2013).

The AQI ranking of the various 76 cities is presented in the following figure 4 based on the mean value for the period May to Oct. 2013.

Figure 4: First AQI ranking for 76 cities - May to Oct. 2013 (see www.ppm25.com)

The 3 best ranking cities during the 6 months period were island or coastal cities: Haikou in Hainan (38); Zhoushan in Zhejiang (45); Xiamen in Fujian(48) having an "excellent" AQI.

After these 3 best ranking cities there is a steady climb of air pollution – with Guangzhou (62), Shanghai (67), then Harbin (77), Chongqing (78)- before reaching a sharp air pollution acceleration in the tail of the ranking beginning with Beijing (112) and Tianjin (113).

The 2 worst ranking cities are both in Hebei:  Xingtai (184); Shijiazhuang  (172) ; all having a "moderately polluted" air quality  (in US very unhealthy!).

These are AQI mean values on a 6 month period which is averaging and thus  decreasing  the monthly variations.

If we look at the mean October AQI values the readings are more contrasted: there are altogether 12 cities which are either "moderately" or "heavily polluted" (US Unhealthy or Very polluted): 

G06_Xingtai:274; G06_Shijiazhuang:243; G06_Baoding:195; G08_Zhengzhou:192; G06_Handan:176; G10_Changsha:173; G10_Xiangtan:171; G06_Hengshui:164; G04_Harbin:161; G02_Xian:157; G10_Wuhan:155; G10_Zhuzhou:153. (See Figure 6 for the GO1 to G14 cities' clusters). 

If we could look further at the  cities' 24h mean values, variations could even be much contrasted. G04_Harbin which had a 6 months man value of 77 (good), was ranked 161 in October ("moderately polluted" or US Unhealthy) and had issued PM2.5 reading  around 1000µg/m3 around Oct. 20-21.

The cities’ conundrum in China

As explained in my post dated 10 Oct. 2013, to better understand China overall urban air pollution, it is convenient to group similarly located cities which are also behaving closely together as concerns their Air Quality Indexes. These cluster of relevant cities have been presented in a paper by W. J. Qu, R. Arimoto  & al (2010).

During the period June 2000 to Feb. 2007, we have past values of PM10 pollution concerning a set of 87 main cities clustered over 14+1 groups. For each of these grouping of cities we have 4 seasonal coefficients.

Figure 5 : The cluster of 14+1 group of cities from W. J. Qu, R. Arimoto  & al in 2010 

Moreover we explained that in order to provide systematic value of pertinent population exposure to air pollution, population weighted mean values were necessary.

The Figure 6 below is presenting the intersection of the various cities tracked under the PM10 concentration in this post:

• 86 main cities for which we have PM10 references on the period June 2000 - February 2007 from  W. J. Qu, R. Arimoto  & al (2010).
• 76 cities tracked by MEP (www.ppm25.com) since May 2013 increased at 114 (+38) in October 2013

Figure 6: The cities' conumdrun in China

We can see that 46+18= 64 cities documented by PEM monthly monitoring are already included in the 86 main cities and that additional 50 new cities had been supplied bringing up to 86 +50 = 136 the cluster of Chinese cities shown in Figures 6 and 7.

Figure 7: Cluster of Chinese 136 cities figuring either in the 200-2007 evaluations or in May to October 2013 new readings

Since May 2013, 46 cities which were around 53% of the 86 cities are documented by the Chinese Ministry of Environmental Protection (MEP), but population weighted these cities are amounting  to 218 Mil or 80% of the 86 cities total population (271 Mil). 

This distortion is due to heavy weight cities having a huge population such as G09_Shanghai (22 Mil), G06_Beijing (19 Mil), G06_Tianjin (11 Mil), G14_Guangzhou (11 Mil) or G14_Shenzhen (10 Mil).

A set of 22 cities (22=86-46-18) included in the 86 main cities are not yet documented by MEP. 
Altogether they have a population of 28 Mil on which 9 cities with urban population around 1.5 Mil: G11_Deyang: (3. 8 Mil); G11_Nanchong (1. 7 Mil); G13_Zhanjiang (1.6 Mil); G05_Anshan (1.6 Mil); G04_Qiqihar (1.5 Mil); G10_Zhangjiajie (1.5 Mil); G10_Changde (1.5 Mil) ; G09_Wuhu (1. 4 Mil); G11_Luzhou (1. 4 Mil).

As regards PM10 only: is it possible to assess whether the air pollution has improved or deteriorated over the past ten years?

As we have a set of PM10 mean values during Jun. 2000 to Feb. 2007 for each of the 86 cities (see my post dated 10 Oct. 2013) and the seasonal variations in each of the 14+1 cities’ groupings, it is then possible to evaluate the population weighted PM10 mean value during May to Oct. 2000-2007 (the median date is Sep.. 2003) and to assess the variation during the 10 years lead time period.

Figure 8 : Variation of PM10 for 46 cities during the 10 year between June 2000 - Feb. 2007 and May - Oct. 2013

A stabilization of PM10 during the last 10 years or even a 10%  reduction 

We found  during the six month period from May to Oct. 2013 a population-weighted PM10 mean value of 90 µg/m3, which is a reduction of 10% - or around 1% each year- since the reference period from Jun. 2000 to Feb. 2007 on the population-weighted PM10 mean values (100 µg/m3) for the same monitored cities (see Figure 8 with the cities’ detailed variations).

This apply only to 53% (and 80% population weighted) of the 86 main cities and does not permit to infer with certainty that there had been a reduction of PM10 pollution in the sample of 86 main cities. But a mere overall stabilization should seem plausible.

We have seen that the 47% (or 25% population weighted) of the 86 main cities are not yet documented by the MEP this including cities with an urban population around 1.5 Mil.

If we look at the 10 years' variations presented in the Figure 8 above:  

• 29 cities had seen their PM10 pollution level decreasing:

G11_Chongqing (7.5Mil):-40.2%; G10_Changsha (3.1Mil):-35.4%; G09_Shanghai (22.3Mil):-35.1%; G09_Hangzhou (6.2Mil):-33.4%; G01_Yinchuan (1.3Mil):-31.7%; G09_Suzhou (5.3Mil):-26.5%; G01_Lanzhou (2.5Mil):-26.4%; G06_Beijing (19.3Mil):-26.2%; G03_Taiyuan (3.4Mil):-24.5%; G05_Shenyang (6Mil):-23.6%; G14_Guangzhou (11.1Mil):-21.9%; G09_Ningbo (3.5Mil):-21.1%; G09_Huzhou (2.6Mil):-19.5%; G10_Wuhan (9.8Mil):-15.6%; G14_Fuzhou (2.9Mil):-15.6%; G04_Harbin (4.5Mil):-15.4%; G09_Nanjing (7.2Mil):-14.1%; G09_Nantong (2.3Mil):-13.9%; G13_Guiyang (3Mil):-13.7%; G11_Chengdu (7.7Mil):-13.4%; G10_Nanchang (2.4Mil):-12.8%; G01_Xining (1.2Mil):-12.6%; GXX_Lhasa (0.3Mil):-11.5%; G09_Yangzhou (2.4Mil):-11.0%; G12_Kunming (3.6Mil):-10.6%; G14_Wenzhou (3Mil):-10.4%; G06_Dalian (3.7Mil):-5.8%; G02_Xian (6.5Mil):-3.9%; G09_Shaoxing (0.9Mil):-2.6%

• 17 cities had seen their PM10 pollution level increasing:

G06_Shijiazhuang (2.9Mil):61.8%; G06_Qinhuangdao (1Mil):54.2%; G08_Zhengzhou(4.3Mil):46.9%; G07_Jinan (4.3Mil):30.5%; G07_Qingdao (4.6Mil):28.9%; G03_Hohhot (2Mil):25.5%; GXX_Ürümqi (3Mil):22.4%; G14_Shenzhen (10.4Mil):22.2%; G14_Zhuhai (1.6Mil):21.4%; G04_Changchun (3.5Mil):17.8%; G09_Zhenjiang (1.2Mil):14.8%; G13_Nanning (3.4Mil):13.0%; G14_Xiamen (3.5Mil):11.6%; G09_Hefei (3.4Mil):10.2%; G06_Tianjin (11.1Mil):9.3%; G13_Haikou (2Mil):8.8%; G07_Lianyungang (1Mil):4.4%

We see that there are many more heavily populated cities in the first group as compared to the second which explains the overall variation.

Monthly PM2.5 pollutant readings and how they compare to PM10 readings

The integration of PM2.5 pollution in the new AQI index is a significant change. 

It sheds a new and disturbing light on the overall air quality, including during the prior years, when this pollutant was not taken into account. We can see from the following Figure 9 than the PM2.5 content is the biggest component with a mean value of more than 50µg/m3.

Figure 9 : PM2.5 and PM10:  6 months' mean values for 46 cities 

The volatility of PM2.5 inside PM10 is generating new pollutions:

If we consider cities where PM2.5’s 6 month mean values are between 75 and 150µg/m3 (classified "lightly" or "moderately polluted"), we find the following 12 cities: 

G06_Xingtai: 127.2; G06_Shijiazhuang: 113.7; G06_Handan: 101.7; G06_Baoding: 97.9; G06_Tangshan: 97.2; G06_Hengshui: 96.0; G08_Zhengzhou: 91.3; G06_Langfang: 88.7; G07_Jinan: 86.7; G06_Tianjin: 83.1; G06_Cangzhou: 81.5; G06_Beijing: 78.5.

Then if we consider cities where PM10’s 6 month mean values are between 150 and 250µg/m3, we find the following 8 cities: 

G06_Xingtai: 249.3; G06_Shijiazhuang: 247.3; G06_Handan: 194.2; G06_Hengshui: 173.5; G06_Baoding: 169.0; G06_Tangshan: 166.2; G07_Jinan: 160.8; G06_Langfang: 156.0.

We find 1/3 of cities which are in the first group are not in the second:  G08_Zhengzhou: 91.3; G06_Tianjin: 83.1; G06_Cangzhou: 81.5; G06_Beijing:78.5. 

This means that there is not necessarily a proportional relationship between  PM2.5 and PM10, as we can see in Figure10 and that the volatility of PM2.5 inside PM10 could be generating additional air pollution.

G06  Beijing_Tianjin_Hebei group of cities are particularly concerned by PM2.5 high volatility pollution impact.

Days where PM2.5>35µg/m3:

Furthermore MEP monthly statistics  are providing for each city the number of days where PM2.5<35µg/m3. It is then easy to derive (see Figure 10 below) the number of days where PM2.5>35µg/m3 over the 6 months period May to Oct. 2013.

After factoring by the urban population then the overall proportion of days where PM2.5>35µg/m3 are population weighted around 21% of the days during the 6 months period May to Oct. 2013.

Figure 10 : Number of days where PM2.5 is greater than 35µg/m3 -6 months period May to Oct. 2013

During the 6 months period we have 16 cities which have more than 20% of days where PM2.5 is greater than 35µg/m3, including the following:

G06_Shijiazhuang (2.9 Mil):72.3%; G06_Tianjin (11.1 Mil):71.2%; G07_Jinan (4.3 Mil):57.6%; G08_Zhengzhou (4.3 Mil):47.3%; G06_Beijing (19.3 Mil):40.8%; G02_Xian  (6.5 Mil):33.7%; G06_Qinhuangdao (1 Mil):31.5%; G09_Zhenjiang (1.2 Mil):27.7%; G09_Hefei  (3.4 Mil):25.5%; G10_Changsha (3.1 Mil):23.9%; G10_Wuhan (9.8 Mil):22.8%; G09_Yangzhou  (2.4 Mil):22.3%; G03_Taiyuan (3.4 Mil):21.7%; G07_Lianyungang: (1 Mil):21.2%; G09_Shaoxing  (0.9 Mil):20.1%; G09_Suzhou: (5.3 Mil):20.1%.

Here again the G06: Beijing_Tianjin_Hebei and G09_Shanghai_Anhui_Jiangsu_Zhejiang 2 clusters of cities are especially concerned.

Of course that level of PM2.5 pollution is deadly dangerous. The minimum yearly intake of fine particulate matter at a concentration  > 35µg/m3 allowed under USA standard (see my post dated 22 Sep. Figure 2) is 2 percentiles (2% of days or 7 days during 1 year). So more than 20% of days is a huge impact implying afterward a high level of health hazard.