Beijing air pollution

Why is Beijing so polluted?

Beijing's air pollution is mainly caused by heavy construction, coal combustion, booming industry and growing private car ownership. In December 2009, state media reported that there were 4 million cars in Beijing.

The city is also ringed by mountains that trap all these harmful gases. Coal power stations are among the worst culprits. See our research last year on how deadly coal is in China.  

Beijing air pollution by the numbers

Air quality is measured by the air pollution index (API), also called the air quality index (AQI). The higher the number – it ranges from 0 to 500 – the more severe the pollution.

"Good" air is defined between 0 and 50, while numbers above 100 are considered unhealthful for sensitive groups. An API of over 150 is unhealthful for everyone, while readings over 300 are hazardous. A full explanation of the scale can be found here. 

The US embassy in Beijing has an air-quality monitor, which measures ozone and particulate matter (PM) 2.5. PM2.5 is widely considered to be the most dangerous for human health, as its particles are tiny enough to penetrate into lungs and the bloodstream.

You can see the air-quality monitor's hourly updates via Twitter. Those without a proxy or VPN can get readings delivered using RSS. 

Pollution standards

China has set air-quality objectives for its urban areas, called National Grade II standard.

If we compare these to World Health Organisation air-quality standards – including both ideal targets and an interim standard geared for developing countries – China's standards are lower than both.

China has previously said it will reform these standards.