China's Provinces air pollution ranking from Jan to Jun 2014: Hebei, Hubei, Henan, Beijing, Shaanxi, Tianjin, Xinjiang & Shandong had more than 50-72% of exceedance days

Bubble pie map of provinces and municipalities over the first six months of 2014 

The 8 following regions and municipalities (see Figures 2 & 3) have had the highest population-weighted average urban air pollution (1^st quintile): Hebei, Hubei, Henan, Beijing, Shaanxi, Tianjin, Xinjiang & Shandong. They concern a population of 139 Mil. 

These regions and municipalities have had 90-149 exceedance days (50-72% of total 181 days) above the threshold of 100 (AQI) and 75 µg/m3 (PM2.5).

The best regions and municipalities (5th quintile) were Hainan, Yunnan, Fujian, Tibet and Guangdong with only 4-18% exceedance days. 

Figure 1 :  Air pollution provinces & municipalities urban air pollution ranking over the first 6 months of 2014 (Jan. to Jun. 2014: 181 days)

The 8 most polluted regions or municipalities are: Hebei (13Mil pop); Hubei (12 mil); Henan (12 Mil), Beijing (19 Mil); Shaanxi (17 Mil); Tianjin (11 Mil); Xinjiang (4 Mil)  & Shandong (50 Mil). AQI is around 120-160 and there are more than 55% of days with AQI>100 (90 on 181  days).

As explained in my post dated 22 Sep 2013, AQI is a random variable with a log normal distribution and the repartition of daily AQI above 50 or 100 AQI is more or less correlated with the average AQI value. 

The correlation is good for days with daily AQI>100,  less good for days with AQI>50 and more loose for days with 50< daily AQI <100.

Figure 2 : Correlation between average AQI and daily AQI repartition

Air pollution in China from Jan to Jun 2014 far exceeds all limits put forward by UE or US standards : out of the 190 major cities, the highest 38 air pollution ranked cities have a population of 113 Mil with 125 exceedance days (70% of days), above 100 AQI or 75µg/m3 (PM2.5)

Bubble pie map of cumulated number of daily AQI repartition over the first six month of 2014 (Jan. to Jun. 181 days)

During Q2-2014, there had been only a slight improvement of urban air pollution over Q1, but we still have AQI>100 over 31% of days (29 days over 81 days) for the 190 monitored cities by China’s Ministry of Environmental Protection (see June 2014 MEP Chinese city air quality ranking).

After the first 6 months of 2014: the first 38 air pollution ranked cities out of 190 main Chinese cities (1^st quintile) could be considered as the “core urban polluted area” comprising around forty cities - among them Jinan, Wuhan, Xi'an, Beijing, Chengdu. This core urban area population of 113 Mil, after 6 months, have had in average 125 cumulated exceedance days (70% of total 181 days), above 100 AQI or 75µg/m3 (PM2.5).

This is far exceeding the health exceedance limits put forward by EU and US air pollution standards where the maximum exceedance days permitted is around 35 days in one year!  

It means that the concerned population had been exposed to a harmful air pollution level 7 times more important than the level permitted by health regulations.   

Air pollution health standards 

Following our last post dated 21 July 2014, it is necessary to look more thoroughly at Chinese cities’ daily AQI inside the first six month period. This information– numbers of days with daily AQI>50 or AQI>100 - are provided each month by China’s Ministry of Environmental Protection (see June 2014 MEP Chinese city air quality ranking), along with the monthly average of the main pollutants and the resulting AQI

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Concerning human health issues we know that what really counts is not the average AQI over defined monthly, quarterly or 6 months periods - qualified as moderately polluted (50<AQI<100) or unhealthy for sensitive groups  (100<AQI<150)- but the number of cumulated days where daily AQI has been above a defined dangerous limit. The longer the cumulated effect the more dangerous it is.

There is a cumulative effect especially for fine particulate matter: after some days of exposure above this limit a high number of tiny particulate are entering the lung’s cells. In the coal mining industry the dust contained in the inhaled breath is transforming progressively the lungs in stone after days and years of continuous silicate inhaling (silicosis).

Even if AQI level is classified as lightly polluted following China's standards (or “Unhealthy for sensitive group” as denominated by US standards): maintaining this risk level for a lengthly period could be extremely harmful to health. This is the notion of exceedance days permitted by the air pollution standards:

-     For EU (2008-2010) over a yearly period, there should be less than 36 exceedance days (10% of days) having air pollution above 50 µg/m3 (PM10) or 50 (AQI);

-     For USA (2012) over a period of 3 years, there should be less than 2% exceedance days above 35 µg/m3 (PM2.5) or again 50 (AQI).

As fine particulate matter in China’s city are almost always the main air pollutant as explained in our previous surveys, the number of exceedance days above 50 - 100 (AQI)or 35-75 µg/m3 (PM2.5) thresholds are two risk levels to consider with a target of a maximum exceedance days permitted each year .

In the following survey - due to the extremely air polluted China’s situation- we are considering mainly an interim target of 36 exceedance days in a  year (10%) above 100 (AQI) or 75 µg/m3 (PM2.5).

Situation in China of daily AQI  over Q1 & Q2-2014 or 6 first months of 2014

Over Q1 and Q2- 2014, daily AQI had been above 100 during 40% of days (73.6 days over 181 days).

During Q2 there had been only a slight improvement on Q1, but we still have AQI>100 over 32% of days (29 days over 81 days).

These values are population weighted average over the monthly values of the 190 monitored cities.

Figure 1: Average population-weighted evolution of urban daily AQI over first 6 months 2014

The geographic repartition of urban air pollution is described in zoomed in Figure 2 below: the most polluted urban area or “core polluted area”concerns a urban population of 113 Mil people (2010 census) where 75% of days have been AQI>100!

Figure 2: Bubble pie map of daily urban air pollution in Northern, Middle and Southern China’s regions showing the “core polluted area” (half circle in red) of the 38 worst air polluted cities (first air pollution quintile ranking).

The detail evolution over the 6 first months of 2014 of this “core polluted area” is described in the following Figure 3:

-    38 cities with an overall population of 113 Mil had in average 125 exceedance days (70% of total), above 100 AQI or 75µg/m3 (PM2.5);

-    5 cities in Q1 and 10 cities in Q2 are not in the concerned 6 first months core polluted area;

-    Concerning the biggest cities improving their air quality: Xi’an (Shaanxi) N°12 in Q1 , N°25 on 6 months; Weinan (Shaanxi) N°16 in Q1, N°27 on 6 months; and Chengdu (Sichuan) N°24 in Q1, N°36 on 6 months;

-    The biggest cities reducing their relative ranking air quality: Beijing N°42 in Q1, N°30 on six months; Tangshan (Hebei) N°15 on Q1, N°9 on 6 months; Jinan (Shandong); Wuhan (Hubei) etc…

Figure 3 : First quintile air pollution ranking cities and cumulated days where daily AQI is > 100