Maybe more people than we thought long to be urban Martha Stewarts, or perhaps folks are just tired of spending an entire paycheck on high-priced organic food. Whatever the reason, city dwellers are embracing gardening en masse—but many aren't aware that the rich black soil they're dropping seeds into may contain toxic metals and chemicals.

Related

According to a recent study, urban gardeners aren’t prone to inspecting the soil they’re planting those tomatoes and pepper plants in—and that's a huge mistake, because toxins make their way into the produce.

Researchers at Johns Hopkins University’s Center for a Livable Future conducted surveys of 70 urban gardeners across Baltimore and found “low levels of concern and inconsistent levels of knowledge about heavy metal and organic chemical contaminants,” as well as limited knowledge about effective ways to reduce exposure.

The urban gardening movement has grown rapidly over the last five years, with 2 million new city gardeners getting their hands dirty, according to newly released figures by the National Gardening Association. That's a lot of potentially contaminated tomatoes.

Brent Kim, a program officer at the center, told NPR that once gardeners find a plot of land where they want to plant, it's important to learn its history:

What's now an empty plot or a backyard might once have been a parking lot, a gas station or the site of a chemical spill, he says. "Knowing the site history will give you some clues about what might be in that soil," he says.

Once you know the history, share it. After all, it is a “community” garden, right?

Inside Urban Green, a blog on modern methods of growing food, calls soil contamination a “dirty secret” of urban gardening unknown to city dwellers who are not in the inner circle of community gardeners:

“Who educates recent immigrants and low income people? From my experience the answer is no one.”

Heeding the warnings and taking precautions against soil contamination don't mean you shouldn't indulge a budding green thumb, however.

The Environmental Protection Agency has a thorough fact sheet on reusing potentially contaminated soil for growing a sustainable urban garden. It recommends using raised beds, adding a thick layer of organic matter that can provide a physical barrier to contamination, and removing all the contaminated soil and replacing it with a new batch before you begin.

You can even conduct a formal environmental assessment (called a brown field assessment), for which the government is willing to provide a monetary grant, according to the EPA.

Contact your regional United States Department of Agriculture Service Center to find out how to go about testing your soil. Though you can use home test soil kits, these aren’t as comprehensive when it comes to detecting chemicals found in urban soil. Local city officials can connect you with soil testing labs in your city that can provide detailed analysis of your soil. The Department of Agriculture also provides information on soil testing labs in your area.