BEIJING, July 3  -- Beijing breathed cleaner air in the first half of this year as the Chinese capital's average PM 2.5 reading dropped 15.2 percent from the same period a year earlier, environmental watchdog said on Friday.

The average PM 2.5 reading registered in the first six months stood at 77.7 micrograms per cubic meter, which is still more than double the national standard of 35 micrograms per cubic meter, said Beijing Municipal Environmental Protection Bureau.

In the first six months, Beijing residents had to endure 16 days of heavily polluted air as PM2.5 readings shot up to more than 300 micrograms per cubic meter, according to the bureau, seven days less than the same period a year earlier.

Other air pollutants have also been reduced. Sulfur dioxide dropped by 41 percent, nitrogen dioxide by 15 percent and PM 10 by13 percent, according to the bureau.