Potentially Toxic Elements in Urban-Grown Lettuce: Effectiveness of Washing Procedures, Risk Assessment, and Isotopic Fingerprint

Urban Farm DB summary

Sixty-four lettuce plants were collected from six urban garden sites in Santo André, Brazil, to measure potentially toxic elements and test household washing. Lead reached 0.77 mg/kg at the Capuava 1 site near an industrial complex, above the 0.1 mg/kg limit, with chromium and arsenic also elevated. Sodium-hypochlorite soaking worked best, removing 48% of lead, 46% of arsenic and 52% of vanadium, while plain water immersion removed about 30% of lead and arsenic and cadmium and chromium fell by under 10%. Total cancer risk for children exceeded acceptable thresholds at some gardens, and the authors conclude washing alone is insufficient and environmental source control is required. Roots were not analysed because gardeners did not want beds damaged.