In this context, it means that the chemicals that evaporate from it contribute to smog.
I believe you are correct. Its right above, Hazardous to Children, and it doesn't say anything about drying, in or out of the sun. So I guess I'm contributing to the smog here in Chicago [:'(] And of course the warning label is a novel.... Why it it that the stuff that works so good is so dangerous? (no need to answer that, just an out loud observation)
Thanks again to all!
Joe