Smog and the challenges posed by China's coal-powered economy

Frequent winter smog in northern China has shown that the war on pollution will be arduous and calls for greater efforts. In a severe bout of smog last month, 40 cities in north China issued alerts for air pollution. Beijing, along with the cities of Baoding, Handan, Langfang and Xingtai in the neighboring Hebei province, issued red alerts, the most serious in the four-tier warning system.

Although the breakdown of the smog's sources - including weather conditions, motor vehicle exhaust and industrial waste - varies across China, growing winter coal consumption is one of the major factors in the haze.

Monitoring data showed substances directly related to coal burning, including sulfate and black charcoal, are major components of PM2.5, airborne particles smaller than 2.5 microns in diameter, that can penetrate deep into the lungs.