Whether you’re growing an herb garden several dozen feet away from the road or several city blocks away, there’s a good chance that the grime and gunk emitted by the high volume of cars and trucks will reach your herb garden. This is one of the inevitable downsides of urban gardening. In my own “resi-dustrial” Brooklyn neighborhood that’s home to heavy truck traffic and a busy cruise ship terminal where luxury liners sit idle while spewing diesel fumes (although not for much longer), there’s also several vibrant community gardens and even a full-fledged organic farm. And from what I gather, the food produced in my own neighborhood is totally edible and safe to eat.

Often, the biggest safety concern facing urban gardeners revolves around not what’s in the air but what’s in the soil itself. In Boston and Indianapolis for example, many urban gardeners have struggled with high levels of lead contamination in the ground and perform soil tests regularly.

There aren’t any special ways to prevent outdoor air pollution from reaching your herbs that I know of, other than growing them indoors where the levels of pollutants like formaldehyde could be even higher than outside, but that’s why we have air-cleansing houseplants. Some plants are more susceptible to unhealthy outdoor air than others so you’ll need to submit to a bit of trial and error. Try growing two identical edibles at the same time and place, one on your fire escape and one indoors, on the windowsill. Check to see if the plant grown outdoors appears at all discolored or damaged compared to the one grown indoors — bleached out or burnt-looking leaves are a telltale sign of ozone damage. Wash them both thoroughly, examine them and perform a taste test. Does the herb or vegetable grown outdoors, on the fire escape, taste off or inferior compared to the one grown indoors?

Also, it doesn’t hurt to pick the brains of other urban gardeners in your own neighborhood. Do you know any of the tenants living in the buildings with the lush backyards that you mentioned? Pay them a visit (or just give ‘em a holler from your fire escape) and ask if they’ve noticed any effects that the dirty air has on their plants. Do any varieties of herbs or vegetables seem to grow better?

Above, I briefly mentioned an action that is key to growing and eating your own plants in the city: washing them and washing them well. If any dirt, debris or airborne crud from the road does reach your plants, which it very well could, a thorough wash will take it right off. If you’re paranoid about tap water not doing the trick, there are numerous produce washes available, while some folks concoct their own DIY washes with white vinegar. Allrecipes.com has a helpful guide on how to clean and prepare herbs and leafy greens with nothing more than cold H2O. And for general inspiration and advice on growing your own food in the city (including on fire escapes) check out Urban Organic Gardener.

Finally, you mention your concern over the safety of eating plants grown on a fire escape that’s not too far from a busy city street. Now that we’ve pretty much covered that, I should point out something else that’s safety-related. As noted in a 2009 Gothamist post, although everyone and their mother is doing it, container gardening on a fire escape in New York City is technically illegal, as placing anything, a plant or otherwise, on a fire escape is a fire hazard. So that’s certainly something to consider. I wouldn’t want you or your landlord getting slapped with a steep fine all over a couple containers of mint.

That said, if you decide to go ahead with your criminal fire escape herb garden and things go successfully, remember that I’m always available for salad-tasting house calls as long as you don’t finger me as an accomplice when the FDNY comes a knockin’…

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.

How can I protect my urban herb garden from air pollution?
Q: I'm an avid cook and like nothing more in the spring and summer than lots of salads and fresh herbs. I live in the city where the front of my apartment build