The Dark Side of Urban Farming

Your organic veggies could be growing in contaminated soil. Here's how to keep homegrown food safe.
(Photo: Zoran Milich/Getty Images)
Jul 21, 2015· 1 MIN READ
Katharine Gammon has written for Nature, Wired, Discover, and Popular Science. A new mom, she lives in Santa Monica.

Growing food at home is good for your health and the planet, but your vegetables could be sucking up toxins as well as sunshine.

So, Why Should You Care? All around the world, more people are getting their hands dirty and planting crops to harvest at home. More than a third of all households in America are growing food at home or in community gardens—a 17 percent jump in five years, according to the National Gardening Association. About 15 percent of the world’s food is produced in urban areas, according to the United States Department of Agriculture.

All of this urban farming raises questions about the safety of crops grown in cities, where soil may be contaminated with lead, arsenic, hydrocarbons, and other toxins.

A recent study considered how different gardening practices could reduce a plant’s uptake of potential soil toxins. The scientists grew tomatoes, collard greens, and carrots in city soils and measured their take-up of lead, arsenic, and compounds called polycyclic aromatic hydrocarbons, which are potential carcinogens.

They found that in the majority of examples, eating vegetables grown in the contaminated soils studied was safe. Levels of contaminants in root vegetables, such as carrots, were higher than in tomatoes and collard greens. But the researchers said there was no reason to avoid gardening in city soils, as long as precautions are taken.

“Washing hands thoroughly after gardening, covering pathways with woodchips or gravel, and keeping soil moist during dry and windy conditions to prevent dust generation are all effective preventative measures to ensure safe gardening,” said Ganga Hettiarachchi, a soil chemist at Kansas State University and lead author of the study.

She pointed out other ways to reduce plants’ uptake of heavy metals from the soil. Adding nutrients to the soil will make plants less likely to absorb toxins. For instance, she said, phosphorus—which is good for healthy root growth—will transform lead into a more stable, less toxic form.

Home gardeners can find out whether their soil contains lead by sending samples to a cooperative extension or a university lab, said Scott Kellogg, educational director at the Radix Ecological Sustainability Center, an urban environmental educational center in Albany, New York.

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“Based upon those results, you can make an informed decision about what to do,” said Kellogg. “If the levels are slightly elevated or higher, you may consider building a raised-bed garden, which keeps roots of most annual vegetables out of contaminated soil. You can also consider putting down ground cover and adding compost as well.”

Kellogg sees more people wanting to take part in a low-carbon diet, and home gardening is a big part of that trend. He encouraged everyone to participate, even those without backyards.

“Make use of what space you have access to—that could be rooftops, front stoops, window boxes, or small containers—anywhere that gets light you can plant something. Even if you don’t have any sunlight you can sprout plants on your kitchen counter or grow mushrooms.”