During the Spring Festival of 20 14, Shijiazhuang suffered from severe smog weather, and the PM2.5 index was above 500. The following measures cannot reduce air pollution.

A, fireworks will produce harmful gases and dust, so reducing fireworks can reduce air pollution, so A is correct;

B, using natural gas instead of coal as fuel can reduce the generation of harmful gases and dust and reduce air pollution, so B is correct;

C. wearing a special PM2.5 mask can't reduce air pollution, so c is wrong;

D, driving less private cars and taking more public transport can reduce the generation of harmful gases and dust and reduce air pollution, so D is correct.

So choose: C.