Not so much smog in LV rather...it is a desert and, just like Phoenix, there is always a lot of dust in the air. In addition right now, we are getting smoke blowing over from the CA wildfires. We have done a few staycations and don't have any worries, but I wouldn't recommend coming to town right now as the hotels haven't really discounted the rooms so you are paying relatively normal prices with far less services ranging from HK to limited restaurant hours and very crowded pools that, due to social distancing, are hard to access. Most strip casinos are not busy at all (Cosmo an exception) and Tropicana (who cares) and Mirage will be opening in the next two weeks.