First comparing anything to the USA is a pretty low bar. Second when it comes to issues that affect health trending is great but it's not as important as the current conditions when it comes to traveling to or living in a place. Our lives are too short to accept 'trending' for these kinds of issues.

Is it though? Have you been there or lived in a place with high smog and low air quality? Do you or your child have asthma? I made the comment simply as a note of the current condition - you sometimes literally can have a hard time seeing the city skyline in Beijing and I've never been to places like Hotan and other more industrial areas where it is worse.

Living or even visiting a place and saying it's the trend that matters sounds like politician speak. Tell that to your lungs and brain while you sit in the pollution.