Anti-smog gains marred by rising ozone levels

China's air quality improved slightly in the first half of 2014 compared with the same period in 2013, but aggravated ozone pollution became a prominent problem across the country, according to Environmental Protection Ministry figures released on Monday.

In 74 major cities, air quality was good 60.3 percent of the time from January to June. The figure was 58.7 percent during that period in 2013. In addition, the frequency, duration and pollution concentration of severely polluted days all decreased this year.

A ministry official who wished to remain anonymous said the improvement came from tougher policies adopted after the Airborne Pollution Prevention and Control Action Plan was issued in September 2013, and more favorable weather conditions.