I am guessing coal/charcoal/wood fired street food vendors. I doubt a yearly family picnic contributes enough to worry about.

I'm guessing public barbecues

Yes, I guess 'barbecue pit' isn't a good choice of words. I was referring to the street vendors who sell barbecue meat, etc. The ones near my home seem to be shut down.

http://inhabitat.com/chinese-government-bans-outdoor-bbqs-in...