The Cumberland County Soil and Water Conservation District (CCSWCD), in partnership with the EPA, is working to test plant tissue to better identify lead risks for gardeners in urban areas. Initial results of 14 plant tissue samples in Portland, Maine have shown a possible link between plant texture and lead concentration.

Results from the sampling found a correlation between plant tissue lead concentration and surface area. “High surface area” edible plants include texture herbs such as mint, radish greens, and rhubarb, while “low surface area” plants include cherry tomatoes, apples, and garlic. As is indicated below, most high surface area edibles contained higher concentrations of lead in plant tissue, independent of the concentration of lead in the contaminated soil they were grown in.

These findings indicate that the highest risk of consuming lead from produce grown in and around lead contaminated soils is from the dust adhering to the surface of the plants. Plants with higher surface area often have a “fuzzy” texture, making it difficult to remove all particulate matter from plants prior to consumption. The discrepancy in lead concentration between daikon radishes and greens illustrates this hypothesis.

The sample size of plant tissues was not statistically significant, so no conclusions can be made at this time. However, this information can be useful in developing future research on the matter and providing advice to gardeners in areas with high soil lead concentrations. It is strongly encouraged that all gardeners take a soil test to determine lead concentration levels in their soil. Gardeners who wish to grow in proximity to contaminated soil are urged to take precautionary measures to prevent unintentional exposure and consumption. It is important to thoroughly wash your hands and clothes immediately after gardening, as well as anything grown in your garden to remove all dirt. Based on the findings of plant tissue sampling, it is highly recommended to avoid planting leafy and root vegetables, and instead grow fruiting plants, such as tomatoes, peppers, cucumbers, and apples.

More information on soil lead contamination and best gardening practices is available here.