Thanks to widespread public information campaigns, most of us know that ingesting lead is harmful to our health. We’ve likely heard that lead exposure is especially serious for young children. It can damage the still-developing brain and nervous system, slowing an exposed child’s overall growth and capacity to learn.
It can also cause hearing and speech problems in children and cardiovascular issues in adults.
Over the years, we may have heard warnings about potential lead exposure from flaking lead paint or old lead plumbing fixtures. But what about lead (and other heavy metal) that may be present in our garden soil? Turns out, surprisingly little guidance exists when it comes to the lead content in the garden.
In a recent study published in the American Geophysical Union’s journal GeoHealth, researchers examined soil safety policies from more than 40 of the most populous U.S. cities. They uncovered a host of inconsistencies. Sara Lupolt, a public health scientist at Johns Hopkins University, served as the lead author on “Urban Soil Safety Policies: The Next Frontier for Mitigating Lead Exposures and Promoting Sustainable Food Production.”
“What we found is that just more than half of the 40 most populous cities that we looked at had any sort of policy pertaining to soil safety and urban agriculture,” Lupolt says. “A lot of the cities didn’t have any sort of guidance whatsoever.”
The researchers found just 10 policies dealing with lead-contaminated soil, in particular. And the “acceptable” levels of lead in soil varied widely—from 34 to 400 parts per million (ppm).
Some of the cities that do have soil safety policies also provide soil-related services, such as soil testing for urban farms. They include Austin, Texas; Columbus, Ohio; Denver, Colorado; Los Angeles, California; Louisville, Kentucky; Milwaukee, Wisconsin; Minneapolis, Minnesota; New York, New York; Philadelphia, Pennsylvania; Phoenix, Arizona, and Washington, DC.
Los Angeles, California; Phoenix, Arizona; Philadelphia, Pennsylvania; and Tucson, Arizona also offered urban farmers some site history/assessment services.
No Federal Policy
Our cities and states offer a hodgepodge of soil safety policies, but what about something official from the federal government?
“We have guidelines for the EPA Superfund Program, which is about redevelopment of sites that are known to be contaminated,” Lupolt explains. “Those are guidelines for industrial or residential kinds of land uses. But there’s really not guidance out there at the federal level for soils that are used to grow food in urban areas or rural areas coming down from EPA or FDA.”
In 2014, the U.S. Environmental Protection Agency’s Office of Solid Waste and Emergency Response did release special recommendations to help gardeners reduce their lead exposure. However, the GeoHealth study authors noted, “[The guidance] does not consider that urban growers may be exposed to urban soils at greater frequencies (e.g., 5 or more days a week) and for longer durations (e.g., 8 or more hours each day) than hobby gardeners. Consequently, the recommendations may not be adequate to protect urban growers from lead exposure.”
What You Can Do
Whether your city has safe soil policies in place or not, you can still take action to reduce your exposure to lead and other soil contaminants in the garden.
“One thing that we always recommend to anybody starting out is to familiarize themselves with the history of the site that they’re growing on,” Lupolt says. “Conduct a site history to learn a little bit more about past land uses. That site history can be particularly helpful in understanding which potential chemicals to look for. So depending on how the land was used previously, lead might not be the particular thing to be looking for. It could be something else.”
You may be able to turn to local government agencies to learn more about your property or simply start by asking your neighbors what they may recall. She continues, “Was there a demolition of a home built before 1970 on the site? Those sorts of things can just kind of give you some clues.”
Next, conduct a soil test. Many USDA extension offices can perform soil testing, and here is a great online guide for testing soil for heavy metals.
Depending on your results, you may need to grow in raised beds with clean soil, rather than farming the area’s native soil. To further reduce your potential lead exposure, Lupolt recommends thoroughly washing your hands after time in the garden and removing gardening clothes and shoes before entering your home.
“Thoroughly wash all of your produce before you consume it,” she says. “And peel any vegetables that can be peeled just to be sure that any kind of soil splash or soil adherence is completely removed.”