Confusing numbers on ambient air quality compliance in China

A few days ago, China’s Ministry of Environmental Protection released its annual State of the Environment report. I was struck in particular by the following statistic: the air quality in 88.5% of China’s 113 “key environmental protection cities” meets China’s air quality standard. Sounds pretty good, right? Unfortunately, there are a couple of problems with this number.

1) The first problem is that China’s current air quality standard, GB 3095-1996 (with revisions in 2000), is quite weak. Under this outdated standard, a city “in compliance” could still have an annual PM10 concentration as high as 100 µg/m^3 – a level 5 times higher than what’s recommended by the WHO. More importantly, the current standard doesn’t even include PM2.5 or ozone, the two ambient air pollutants of greatest long-term human health concern in urban megacities.

The good news is that last year, China adopted a new ambient air quality standard, GB 3095-2012. This new standard represents big progress in China by significantly tightening the acceptable limits for ambient air pollutant concentrations as well as adding standards for PM2.5 and ozone. Although the standard doesn’t enter into mandatory force until 2016, MEP’s 2012 annual report already reports compliance numbers according to the new standard. The numbers are bleak: just 23.9% of the 113 cities meet the new standard.

In other words, the introduction of the new standard causes the compliance rate of cities to drop from 88.5% to 23.9%. Although from a PR perspective this seems like a huge step backwards, I think MEP deserves tremendous credit for disclosing these data (and acknowledging the significant future challenges they imply).

2) The second problem with this statistic — % of cities in compliance — is that it ignores the significant variation in population among cities in China. Accordingly, it offers no indication of how many people in China are regularly breathing dangerous air — the key number we care about from a human health impacts perspective. The annual report doesn’t have a list of the cities along with their data, but it does include this graph, showing annual PM10 concentrations:

Map, PM10 in China cities, 2012

From this graph, it appears as though some really big cities – including Beijing (~20 million people), Tianjin (10 million), Chengdu (9 million), Xi’an (7 million), Urumqi (3 million), and Lanzhou (2.5 million) are not in compliance. (Plus, some of these may be far out of compliance — especially Urumqi, one of the few red dots on the map.) These six cities alone represent some 50 million people — similar to the populations of England or Spain — breathing air that doesn’t even meet China’s outdated, relatively loose air quality standard.

While this “% of cities in compliance” metric may be a useful gauge of general progress across the country, from a human health impacts perspective, a more meaningful statistic would be “urban population living in non-compliant areas.” The long-term goal of the Chinese government — indeed of all governments — should be to drive this number — evaluated according to global best practices ambient air quality standards — down to 0.

Clean air