Illegal Air Pollution

No, the pollution itself is not illegal. As often the case in China, disseminating information about pollution is illegal.

Xinhuanet

BEIJING, June 5 (Xinhua) -- A foreign embassy's monitoring and issuing of air quality data in China is technically inaccurate and goes against international conventions and Chinese laws, an environment official said Tuesday in Beijing.

Vice Minister of Environmental Protection Wu Xiaoqing said to monitor air quality and release results, which involves the public interest, is the duty of the Chinese government.

"Some foreign embassies and consulates in China are monitoring air quality and publishing the results themselves. It is not in accordance with the Vienna Convention on Diplomatic Relations and the Vienna Convention on Consular Relations, as well as environmental protection regulations of China," Wu told a press conference.

...

"According to international conventions, diplomats are obligated to respect and abide by the laws and regulations in their receiving states. In addition, they cannot interfere with the domestic issues of receiving states," said Wu.

I'm going to call bullsh*t on the Vienna Convention nonsense. I read elsewhere that the Chinese government said foreign embassies can collect air pollution data for their staff but not publish on the Internet. Really? The Vienna Convention regulates Twitter tweets?! Also, let's see this "environmental protection regulation"... I'll bet none of the actual polluters are in trouble, especially those with government connections. Since Twitter is blocked in China (there's probably no laws being followed there either), the US embassy is technically not publishing PM2.5 data in China anyway.