Calming worries about car exhaust

Hello! Hoping some city permies can help me out here. I help manage a shared-harvest community garden - our garden members make planting decisions collectively and share all the labour and all the produce. Not always easy, but it works (and a handful of us are slowly converting the place to an urban cold-climate permaculture paradise, muwah-ha-ha-ha!).

Some of our gardeners are concerned about car exhaust from the adjacent parking lot, which is separated from the garden by a chain link fence. The parking lot actually sees relatively little use, and people seldom leave their cars idling, so I don't see any issue with using the area immediately inside the fence to grow food plants, and in fact I would like to use the fence as a trellis for some melons and squash. I figure a bit of car exhaust here and there is still going to add up to less contamination than, say, an "organic" monoculture farm that is using fossil-fuel powered machinery directly in the fields. I would be using containers filled with "clean" soil brought in from outside of town, so there would be no concern about exhaust contamination in the soil, just in the air.

So my question is, can anyone point me to studies or statistics that might help ease my fellow gardeners' concerns? Are there some food plants that are less likely to absorb airborne contaminants than others? Or are there any plants we could put in to mitigate potential exhaust issues? Is exhaust even an issue at all in this circumstance? It's really a very small parking lot, and our growing season is only about 5 months here in Newfoundland, so the exposure time is limited.

This is just my opinion, but I wouldn't be too concerned over a little car exhaust.
It has been a few decades since leaded gasoline has been outlawed, and the lead contamination was probably the worst contaminate in gasoline. Autos now have tighter restrictions on emissions, and fuel consumption has greatly improved. The contamination now is probably only a tiny fraction of what it was a few years ago.

Chain link fences do almost nothing to stop airborne intrusion. However, if you slide battens between the links, you could probably reduce about 90% of what a bare fence would allow. (Keep an eye out for free venetian blinds on Craig's List.) If the fence is on the north side of the garden, you have lost nothing. On any other side, the battens would reduce sunlight, which may be detrimental in a short season region.

While 'Big Rigs' blow their exhaust up into the atmosphere, most automobiles direct their exhaust towards the ground. The exhaust is heavier than air, so it will mostly stay low. Perhaps, a mid-calf dirt berm along the length of the fence would keep most from drifting into the garden. Tall grasses planted into this berm would also slow down intrusion.

Regardless, what you are growing will be a vast improvement over what supermarkets offer.

I don't think you have to worry either. I've seen "organic" farms right up against major highways, etc. Trees and woody shrubs will help clean the air. Your vining plants on the fence will work too. If people are really concerned, plant some sacrificial plants, or pollinator plant on the fence.

Whenever I hear this kind of concern, I remember that we are all living in a huge toxic soup of our own making (I know, not very uplifting) - the best thing we can do is create less pollution in general. However, that may be beyond our control. The second best thing we can do is mitigate pollution by planting trees and by creating our own compost from local waste streams.

Thanks, John and Jennifer. Very good points here - I hadn't thought about the angle of exhaust pipes, but that's quite reassuring. Definitely no big rigs in the parking lot, only the odd maintenance truck. And the Geoff Lawton video puts it all into perspective. At my own home I grow my vegetables right out on the sidewalk, and we get far more traffic than the parking lot at the garden. I had my blood lead levels tested a few years ago (as part of a strange government experiment, no joke) and I was way at the low end of normal, despite a lifetime of eating foraged food from roadsides and lead-laden soils. The human body is remarkably resilient!