No, fortunately we did not. A lady from our group had purchased face mask for all of us but none of us ever needed it. A month or so after our return there was an article in the Dallas Morning News regarding how bad the smog was in China and they were advising people not to go outside. I can understand it - wall to wall people and wall to wall cars everywhere. We did see a very few people wearing mask but we were there a little over a month and you could probably count them on both hands. No one in our group ever had any problems with breathing.
I think the river gorge must be completed as we saw very little construction and visited some replaced folks. Amazing! The food was wonderful and plentiful. We were told to take snacks with us to supplement the food they served but we never needed it. There was always something for everyone to choose from. We loved the restaurants we visited. Only a few things I decided not to try.