A man wears a facial mask in Shenyang, Liaoning Province. A swathe of China was blanketed with dangerous acrid smog yesterday after levels of the most dangerous particulates reached almost 50 times World Health Organization maximums. Levels of PM 2.5, the tiny airborne particles considered most harmful to health, reached 860 micrograms per cubic meter in Changchun, the capital of the northeastern province of Jilin, yesterday. PM 2.5 levels reached 1,157 micrograms per cubic meter in Shenyang, capital of neighboring Liaoning, on Sunday.  SD-Agencies