The air quality of several cities in Hebei province failed to reach the national Level 2?????] standard in the first half of 2013, ranking the top among 74 major cities in China, according to the Environmental Protection Ministry’s national air quality report.

The Ministry published its report on 74 major cities in June and a summary of the first six months, on July 31, saying the air quality of the Beijing-Tianjin-Hebei area was the worst.

The air quality of 26 percent of the days in this region was below standard, and had tumbled to the serious level, with the major pollution being PM 2.5 (particulates less than 2.5 micrometers in diameter). Vehicle exhaust emissions, industries, and coal burning boilers were among the major causes.

The lingering air pollution put seven Hebei cities among the 10 with worst air quality in the first half, including Shijiazhuang, the provincial capital, Handan, Baoding and Tangshan.