road training

Q : We dont have much choices but to ride daily on a very busy highway and the fumes from cars & trucks is getting very bad. How bad is that for the health/training ?

I wouldn't be doing it if I could help it. The best stretch of road near me is busy and polluted as well, so I've found a shorter route with little traffic and some rolling hills mixed in. I prefer to do laps of this route, than train on the longer, busier, smellier roads. It's safer too .