The Status Quo

In the previous post, I have looked at the ambient air quality standards which regulate the types of pollutants monitored and their limit values. So naturally, the next question is: how exactly is the air quality in China?

Collecting data has not been easy. Although China has now established a large monitoring system with 1521 sites in 369 cities reporting hourly via the internet, most archived data is not publicly available. The China National Environmental Monitoring Centre (CNEMC) releases a report on air quality in 74 major cities every month since January 2013 (with the report from February 2013 and December 2014 missing). Only part of the aggregated quarterly and semi-annual reports is published and annual reports are not accessible. There are also third party observations, among which the monitoring programme by the US embassy is the best known. However, it only measures the PM_2.5 concentration in 5 cities.

In this post, I will first examine the CNEMC reports and then present data from two papers for current and historical situations. The aim is to provide not an extensive review of different sources of data, but rather an overall image of the scale of air pollution in China. I will, however, continue collecting and update useful data in future posts.

In the monthly reports by CNEMC, a 74 city-average is calculated for PM_2.5, PM₁₀, NO₂ and SO₂ from the monthly average concentration of individual cities (for CO and O₃ a 74 city-average is not calculated):

Data source: China National Environmental Monitoring Centre.

As can be seen from the diagram, all four pollutants demonstrate seasonal patterns. I will get back on this when I write about the causes of air pollution in China. At this point, what we are most interested in is probably an annual average and how far it is below or above the limit. As data for February 2013 and December 2014 are missing, data from March 2013 to February 2014 are taken to calculate the annual average:

	annual average (μg/m3)	annual average limit (class 2) (μg/m3)
PM2.5	70	35
PM10	116	70
NO2	44	40
SO2	38	60

Data source: China National Environmental Monitoring Centre.

The annual average concentration of all pollutants except SO₂ exceeds the corresponding limit, among which that of two sizes of particulate matter lie far beyond.   

Due to lack of aggregated data, Rohde andMuller (2015) collect real-time (hourly) data during a four month period from April to August 2014 and apply Kriging interpolation to derive pollution maps for Eastern China (east of 95°E, which includes 97% of the population), as little monitoring is done in Western China. The following figure presents the average concentration of PM_2.5, PM₁₀ and O₃ during the study period for Eastern China (top) and the Beijing to Shanghai corridor (bottom), which contains the highest concentrations and major sources of pollution. The colour coding is not based on the Chinese, but the US EPA AQI categories:

                                                Source: Rohde & Muller (2015).  

For PM_2.5 concentration, areas containing approx. 38% of the population are classified as “unhealthy” (>55.5 μg/m³). Another 45% of the population is living in areas classified as “unhealthy for sensitive groups” (>35.5 μg/m³). PM₁₀ concentration shows similar but less severe patterns, with most of China averaging “moderate” (>150 μg/m³). Ozone concentration level is “good” for most of China, except for some Northeastern cities.

These two maps for SO₂ and NO₂ show “good” levels throughout the country:

 Source: Rohde & Muller (2015). 

As the first figure shows, the air pollution in China is most severe during winter months and modest from late summer to early fall. This study period from April to August lies somewhere in between; hence the concentration values should be similar to or slightly lower than the long-term average.

The next two diagrams illustrate annual concentration of pollutants in 31 major cities from 1995 to 2009 based on official yearbook data. The pollutants measured are particulate matter (total suspended particulates (TSP) until 2000, PM₁₀ thereafter), SO₂ and nitrogen oxides (NO_x until 1999, NO₂ thereafter). As can been seen from these graphs, the level of SO₂ concentration declined consistently from 1995 to 2009, with steep drop prior to 2000. By contrast, PM₁₀ level decreased only slightly since 2003 and NO₂ concentration remained stable during this time period.

Source: Nielson & Ho (2013).

In short, air pollution is extensive in China and affects the majority of the population. Pollution of particulate matter is most severe with average concentrations exceeding both domestic and international standards.