AFAIK an AQI feature was actually first introduced in iOS 10, but only for a very limited set of cities/geographic areas (only ones I heard named directly were

AFAIK an AQI feature was actually first introduced in iOS 10, but only for a very limited set of cities/geographic areas (only ones I heard named directly were in China, which of course is both a big market and has had horrendous air quality issues they've had to grapple with). I heard it briefly vanished in iOS 11.0 actually before being reintroduced in a point update. I never had cause to use it myself back then. Presumably in iOS 12 the feature is both more refined and Apple has also just plain worked to get more access to the necessary data streams and integrate them. From a brief glance around at some weather related APIs I've played with before it doesn't seem like AQI data, particularly sufficiently granular, has the kind of global support that is simply universal for other more common measures. I guess as knowledge of the health effects of small PM pollution and such start to become more widely known by the public, combined with worsening climate making it more common/worse in new areas we'll see sensors and data streams for that improve worldwide, at least in urban areas.