It doesn’t take a germaphobe to worry about food grown on urban lots, roots sprouting through metals and leaves drenched in traffic smog. Are those dusty tomatoes safe to eat? The answer: probably. But first, some context.
Taking an alarmist look at toxicity levels of urban soils can falsely skew how we look at the practices of urban farming. Such an alarmist story looks a lot like the one printed in November, 2014 by The New York Post (an easy target, I know, I know). Titled, “Root of all evil: Vegetables in New York City gardens are toxic,” the story began: “Herbs and vegetables grown in New York City community gardens are loaded with lead and other toxic metals, a startling state study shows.”
This story fails on two major levels. First, looking solely at soil or vegetable toxicity levels ignores all of the irrefutably healthy aspects of community gardens. To name just a few, urban agriculture improves nutritional health while strengthening local economies, communities, food security, and the mental well-being of surrounding populations. Some of the diverse benefits of urban farming are neatly collected in a 2016 publication, Sowing Seeds in the City, which looks at the positive impacts of urban agriculture on a range of ecosystem services including soil and water conservation, waste recycling, climate change mitigation, habitat, and food production. Putting urban agriculture in its appropriate context — acknowledging the range and multiple scopes of its benefits — is good medicine against fear-dredging stories about soil toxicity.
The Post’s story also fails because it completely misrepresents the Cornell University-led study it uses as its main reference. As opposed to The Post’s opening statement, the study summarizes its findings like this: “Overall, the study found that levels of lead, cadmium and barium in urban garden produce were generally below health-based guidance values.” This study suggests that levels of toxics vary plot by plot and crop by crop. Toxicity depends on what and where you’re growing, how you’re growing it, and crucially, what measures you’re using to prevent harmful exposures.
Rather than blanketly portraying urban produce as toxic, it’s more useful to assess how we’re exposed to toxics and what we can do to prevent or reduce exposures. In addition to the Cornell study and Sowing Seeds in the City, a recent mass of literature — academic and other — is providing an increasingly full sense of the risks of urban farming and how to do it safely.
One example of such literature is a 2016 published in the Journal of Environmental Quality and titled, “Lead in Urban Soils: A Real or Perceived Concern?” The study suggests that although urban soils may contain high concentrations of lead, the most common pollutant in urban soils, these concentrations are unlikely to result in elevated blood lead levels of children, or the most vulnerable population living in those areas. In other words, soils contain lead, but that’s no reason to freak out. The study also suggests that the majority of crops don’t uptake significant concentrations of lead (exceptions are root vegetables like radishes, beets, and carrots). Just as importantly, other studies have shown that eating lead in root vegetables does not necessarily mean our bodies will absorb it. Consuming lead with food significantly limits absorption. The study concludes that “benefits associated with urban agriculture far outweigh any risks posed by elevated lead.” While this study is limited to one heavy metal — and while other toxics (PAHs and cadmium, say) come with their own safety and management concerns — the study’s conclusions aren’t alone.
The collective mass of recent literature on urban farming suggests a stark but hopeful assessment of urban soil quality. Rounds of industrialization and deindustrialization have heavily degraded and contaminated city soils. We shouldn’t dismiss the concern of working around, and ingesting, toxics. Rather, growing food in contaminated soils is a responsibility that requires attention and care.
A number of resources provide simple best practices that can help gardeners minimize exposures to toxics. In addition to Sowing Seeds in the City — an academic publication that can be expensive and difficult to access — two good free resources are Johns Hopkins’ University’s Urban Soil Safety Guide and EPA’s concise Guidelines for Safe Gardening Practices.
For me, three common and simple pieces of gardening advice stand out from these resources. First, wash your hands and produce after digging in contaminated dirt. Washing hands eliminates the most direct route toxins can take into your body. Second, add organic soil amendments (ie. compost or biosolids) to the soil. Adding soil amendments, especially those that include soluble phosphate, reduces uptake of heavy metals like lead while also improving the physical and biological quality of your soil. Third, if you’re at all worried about soil quality, grow crops in raised beds using clean soil.
If you can, learn the history and composition of the soil you’re working with. You may also be able to get testing help from local health or environmental agencies or even local universities. Also, city planning offices can help provide records of past land uses.
Turning contaminated land into productive gardens is a beautiful way to reclaim space while bolstering community and environmental health. Like almost anything fun, urban gardening comes with health concerns and responsibilities. Rather than shy away from these responsibilities out of an irrational fear of what lurks beneath the dirt, we should embrace ways to garden better.