It depends on how safely one can cycle elsewhere. I wouldn't know, so I won't recommend it (but if it is possible, definitely!). But there are other options, such as rowing, running, Nordic skiing, swimming, etc.

My area seems to average about a 30 AQI, which I guess is good (it's 28 today). But I stopped biking a long time ago do to safety after many incidents, there's just no safe place to ride a bike in most of the US. To be fair, riding a motorcycle is far more dangerous, and people still do that. So I guess it is up to your risk tolerance.