Community gardens are popular in urban American neighborhoods, but new research suggests the soil in many is tainted with toxic lead — a brain-damaging heavy metal that can contaminate plants and vegetables.
Wayne State University researchers noted the sites of many garden plots in urban areas were previously occupied by residences or industrial buildings that disposed of toxic chemicals on site, creating potential health hazards from the use of lead in paint, gasoline, and industrial activities. To gauge the risk of soil contamination in urban gardens, they analyzed the lead content in soil in one Detroit garden plot.
The results showed soil concentration measured at the sites was highly variable across the plot, but that 2 percent of 80 samples tested exceeded the 400 parts per billion safety threshold set by the U.S. Environmental Protection Agency.
The study — conducted by WSU student Lauren Bugdalski, geology professor Lawrence D. Lemke, and Shawn P. McElmurry, assistant professor of civil and environmental engineering — was reported in the journal Risk Analysis, published by the Society for Risk Analysis.
Lemke said that the findings highlight the need for soil sampling in community gardens to identify the presence of lead and other contaminants.
"The highest risk of exposure generally comes from dust and soil sticking to unwashed vegetables, not from direct uptake into the vegetable plants themselves,” he said. “The easiest way to reduce this risk is to thoroughly wash fresh vegetables, especially leafy plants, before eating them."
The researchers also recommend that garden organizers interested in an untested plot check local libraries for historical maps and records that indicate how the land was used going back 100 years. Lemke said gardeners should also check with local Cooperative Extension services or universities to provide assistance with cost-effective soil sampling.
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