The worst air quality ever in Beijing was recorded during the period of time between the end of 2012 and the beginning of 2013, according to research published recently.

Most of the polluted days occurred in January and February, according to the 2013 annual report on Beijing society-building conducted by Beijing University of Technology.

Coal consumption, rapid industrialization and urbanization in the city contributed to the pollution. Among the hazardous weather warnings that Beijing residents received last year, smoggy weather warnings topped the list.

Low-quality oil, an overwhelming number of vehicles on the roads, and urban construction contributed to the emissions.