The Chinese capital was on the second-highest orange smog alert in the depth of winter on Tuesday but city officials said the air quality was improving overall, citing data for last year. Hundreds of flights were cancelled and highways closed across northern China over the New Year holiday as average concentrations of small breathable particles known as PM2.5 soared above 500 micrograms per cubic meter in Beijing and surrounding regions. Pollution alerts are common in northern China, especially during bitterly cold winters when energy demand, much of it met by coal, soars. But the Beijing Municipal Environmental Protection Bureau told state media that PM2.5 concentrations dropped 9.9 percent on the year to an average of 73 micrograms per cubic meter in the Chinese capital in 2016. The total number of "blue sky days" reached 198 in 2016, up 12 from the previous year. However, the average PM2.5 measure still exceeded national air quality standards by 109 percent, the bureau said. Despite a brief respite on Monday, smog returned to the Chinese capital on Tuesday, with PM2.5 readings again at "hazardous" levels. Smog is expected to last in the region until a cold front arrives on Jan. 8, state news agency Xinhua said. China's weather bureau also issued its first ever fog red alert on Tuesday, saying that visibility could fall below 50 meters across northern China. Three major ports in northern China suspended the loading of ships on Tuesday as a result of poor visibility, maritime safety agencies said.
