Realize we suck exhaust enough as it is on any given ride that takes you with the flow of the traffic. Whether the air is "green" or not, having car exhaust being blown at you at what I'd consider point blank range I'm sure isn't good over the long run. But hey, we ride ROAD bikes right? I wouldn't worry all too much unless you are in the sensitive group, it's a "red" warning, and like 100+ outside.

Get out and ride!