Community gardens provide city residents with many benefits, like healthy local produce, social connection and can even stress reduction. But pollution in urban areas, particularly ones with industrial histories, can potentially pose health risks to gardeners and the people who eat their produce.
How serious is the risk? It depends a lot on the gardener. A study conducted by researchers from the Johns Hopkins Urban Health Institute surveyed urban gardeners in Baltimore, to better understand their knowledge of potential soil contaminants and remediation techniques. The paper was published in the open-access journal PLOS.
With help from the Community Greening Resource Network, information was gathered from 70 gardeners through semi-formal interviews. In exchange for participating in the survey, the researchers offered to help gardeners get their soil tested.
The researchers found that gardeners had minimal concern about soil contaminants, and often assumed that if the garden was established then contamination issues had already been addressed. This could be a problem not only because contaminants may make their way into food grown at the garden, but also because contaminated soil may pose a risk to gardeners who touch it.
The most worrisome chemical to community gardeners was lead, and rightly so considering tests show higher levels of lead in Baltimore soils than other potential contaminants. However, the researchers write that knowing the history of a plot is key to testing for the right substances.
The most common method of avoiding polluted soil within the surveyed group was the use of raised beds with imported soil. However, raised beds can still become contaminated when dirt from outside of the beds is kicked up, from atmospheric particles settling into the beds, and when roots reach deeper than the beds. The community gardeners didn't mention some of the best practices for avoiding contact with chemicals of concern, like growing produce away from busy streets, application of soil amendments, removing shoes to avoid tracking contaminants into the home, washing produce, and peeling root crops.
Fortunately, a number of the study participants were quick to acknowledge their limitations and were eager to learn how to avoid contaminants.
"One theme that emerged from informant interviews was the need for a central repository where gardeners could access information about soil contamination," the authors write. This could be done by an organization that already has a relationship with community gardens or though the local government.
They also write that face-to-face information, through workshops or from master gardeners, is an important means of sharing information. Although 83 percent of the study participants had a bachelor's degree, getting information from fellow growers may be an important way of reaching less educated and lower income gardeners. The authors also suggest that some responsibilities such as soil testing could be handled by city governments.
Despite the dangers of soil contamination, the researchers emphasize the need to balance warnings with information about the benefits of gardening, so as to not discourage gardeners from planting altogether.