The Hidden Dangers of Lead in Urban Gardens
Click on image for larger file. Fig. 1. A vacant lot urban farm highlighting abiotic challenges of urban agriculture, including: elevated atmospheric concentrations of industrial pollutants (A), elevated atmospheric concentrations of greenhouse gases from traffic emissions (B), contaminated storm water runoff (C), Pb-contaminated soils adjacent to aging housing stock (e.g., paint chips) (D), soils contaminated by heavy metals and/or polycyclic aromatic hydrocarbons (E), unpredictable access to municipal water sources (F), potentially contaminated recycled water sources (e.g., rainwater harvesting) (G), reduced light and wind speed due to the built environment (H), increased mechanical heat (e.g., air conditioners) (I), and increased surface temperatures from pavement and rooftops (J). Credits: This illustration from Sam Worman’s study shows the myriad challenges of urban gardeners, including lead sources.
When Ryan Kuck’s young twins both tested positive for elevated lead levels in their blood he was worried — but not surprised.
By Karen Pinchin
July 28, 2014
When it comes to remediation, there are a few ways to deal with the problem. One is cap-and-fill (covering over an existing lot with cement, then trucking in soil and building a garden overtop), which is preferred by many municipal governments, simply because it buries the problem, says Wortman. There is also phytoremediation, in which plants slightly better at absorbing lead, like mustards and sunflowers, are planted on vacant land, then harvested and disposed of over a long period of time. While this technique is trendy right now, probably because it feels like “using nature to heal nature,” Wortman says it isn’t practical or effective.
Instead, planting ground cover and building up the amount of organic matter in the soil, where soil carbon binds to and stabilizes lead, is probably more efficient and cheaper, says Wortman. But he doesn’t know for sure, and without more scientific studies, the urban farming community is left guessing. Not only is more research needed, but urban farmers need to get out in front of the issue, he says.
“I think urban farmers and policy advocates need to be proactive about making sure that the food is just as — if not more safe — than food that folks can get at the grocery store or rural farms. It’s a health issue, [and] also a self-preservation and [public relations] issue,” says Wortman.
If urban farmers and local food advocates ignore the issue, says Wortman, they do so at their peril. That’s why, he says, it’s in their best interests to advocate soil testing, careful washing of produce, and, particularly, more scientific studies.
“It wouldn’t take long for the local news to do their own investigation, and it could show that lead levels are twice as high on this lettuce than lettuce from the grocery store. And that type of press could really destroy the movement.”