eek...
I hope this post isn't coming too late to deter some of you from using liquid smoke. I just finished reading some of the raves about the Vegan Bacon, which I'm anxious to try- definitely minus the liquid smoke however. I've done some reseach on the topic, and for a group of health conscientious, eco and body-friendly individuals, im surprised how many are eager to leapfrog their own health for a classic bacon taste. Carcinogenic materials and substances are one of the main causes of cancer. So considering that there is a debate whether liquid smoke filters ALL carcinogenic materials (and I highly doubt it does), using it, even in moderation, seems pretty reckless to me. Anyways, not trying to preach, just posting a friendly heads-up to everyone to do some investigating of your own, and  maybe try something else to get that 'bacon-y' taste! :). cheers.

I read a science article somewhere that said most of the carcinogens that would usually would be present in the liquid-smoke making process don't actually go into the liquid smoke. Something about the evaporation... anyway, the stuff is FAR from liquid cigarettes; :P so I'd say half a teaspoon won't kill you.

It's not just Liquid Smoke.  Anything that is smoked has PAHs. 

I don't know too much about food-related PAHs, I mainly deal with it related to fuel.  I've come across a couple of tidbits I stored away somewhere in my mind.

Mesquite and hot smoking top the PAH list, so if you're going to use something that's been smoked anyway and the label indiicates either of these choose a different variety, like a cold smoked hickory. 

A lot of it has to do with concentration of exposure and I don't know what that would be for veg*ns.  You can't escape it, PAHs are a by-product of "modern civilization".  If you drive a gas-fueled car, you're adding PAHs to the environment.

A cool thing i discovered is lapsang souchong, which is a tea that has been smoked, and therefore tastes very smokey. In my opinion it's gross to drink, but replacing some or all of the liquid in a recipe with it has a nice effect, especially when trying to mimick some non-veg dishes. For instance it puts back the ham flavor in split pea soup, if you like that. Since it's been smoked, i guess there are still PHAs in it, but i'm guessing less than in some other smoked items, since you're not actually eating the tea leaves. I wonder how much goes into the tea while it's brewing...?

Where did you find it?  My DH is begging for something to add the "pork" flavor to his pinto beans.  That might work.  I was planning on looking at Whole Foods for a pigless "pork" bouillon as well.  I don't actually like "porky" tasting beans but he loves them.  I never ate beans very often before I returned to being a vegetarian and I think that's why.