Urban gardening has long been seen as a kind of antidote to the pollution and congestion of city life, but as the trend continues to soar, a concerned response (backlash is too strong a word here) seems to be forming in a spate of recent articles detailing the ways growing vegetables in your yard or on your roof may do harm. A post on Grub Street today alerted us to a refreshingly honest review in the New Yorker that pointed out that the rooftop-grown lettuce from Manhattan restaurant Bell Book & Cradle couldn't escape the "smoky aftertaste of city exhaust fumes." 

Most city restaurants don't serve produce grown amid the urban fray, not because they're worried about the funny taste but because it's just not available widely enough. But the Associated Press today reported that the trend toward DIY food production, which became popular during the recent recession, is still going strong. That means you're probably going to be eating more and more produce grown in backyards, rooftops, and vacant lots throughout your city, suburb, or small town. 

Last week, Edward Glaeser made the case in a Boston Globe op-ed that, depending on where you are, imported food can potentially stay cheaper and pose less of a threat to the environment than locally grown alternatives, because of the need for importing fertilizer and other gardening implements. 

One recent UK report found that the greenhouse gas emissions involved in eating English tomatoes were about three times as high as eating Spanish tomatoes. The extra energy and fertilizer involved in producing tomatoes in chilly England overwhelmed the benefits of less shipping. Even New Zealand lamb produced less greenhouse gases than English lamb.

Of course, urban gardening is not purely an environmental, or even economic, pursuit. There are all kinds of feel-good aspects to eating your own crops, and even Glaeser concedes, "there is something wonderful about eating something you’ve grown yourself." But there's the very real worry that plants grown among the air and soil pollution of the city may actually be dangerously toxic, even as gardeners deliberately avoid chemical fertilizers, insecticides, and herbicides. The AP last month reported that lead had routinely been found in the soil in cities nationwide. 

[Soil researchers] point to cities like Indianapolis, where nine out of 10 urban gardens tested by one researcher had problems with lead in the soil. Or the Boston area, where a recent study suggests that even clean, trucked-in soil can end up contaminated, perhaps by windblown dust or dirt splattered by rain, in a few short years.

A 2009 report from the University of California at Davis looked at the possible toxins that can make their way into crops grown in the city or suburbs. Lead, which flowed out of the exhaust pipes of cars for decades before leaded gas was banned in the 1980s, can stay in soil for years. In city environments, it frequently also comes from buildings constructed before the ban of lead-based paint. Cadmium from the wear of tires can coat the leaves of plants near roadsides, and even arsenic can hide in soil, especially in newly built suburbs where orchards once drained pesticides into the earth. Fortunately, the report has some easy-to-follow tips to keep toxic trace elements to a minimum. And once you've reduced the toxicity of your garden as much as possible, you may want to check out the large list of actual growing tips for the urban gardener on Gothamist today. Because dealing with a little exhaust is a small price to pay for growing your own greens. Just make sure you wash them thoroughly.