Is it safer for health to use regular A/C or recirculating air (MAX A/C) when commuting?

Question

Inevitably some auto exhaust pollution will pregnate the car interior no matter the conditions, conceded, but by running on recirculate, wouldn't this cause you to breathe in that same, stagnating air.. again, and again, and again...? Or is there some mechanism that stops this?

If you switched to regular A/C, although some of the incoming air will no doubt be polluted, won't you be getting plenty enough fresh air to reach your lungs and thereby prevent any cellular damage or bioaccumulation from occurring on part of the auto exhaust emissions?

Is there essentially no difference at all, and both options are equally safe (and hazardous?)

My vehicle is a 2007 Ford Ranger, if that's relevant.

Answer 1

If you drive in stop-and-go traffic, you're getting lots of carbon monoxide no matter whether the vents are open or closed.  The big problem is particulates.  Your Ranger has a filter on the cabin air intake:

http://www.thepartsbin.com/guides/ford/r...

so make sure it gets changed regularly.  Also, even with the filter, if you are stopped, or driving, behind something with a diesel engine, in my opinion it's a good idea to shut off the external airflow.  Diesel exhaust contains some nasty stuff, I personally don't trust the cabin air filter to remove it.  However, I freely admit that shutting off the vent around diesels probably does little to minimize my exposure to particulates while driving.  

Sadly, there really is nothing you can do to improve the air quality in your car, aside from not driving:

http://www.icta.org/doc/In-car%20polluti...