Phytoavailability of Lead for Vegetables in Urban Garden Soils

Field studies are important to minimize human Pb exposure via urban gardening. This study assessed (1) the effect of the use of limestone and composted manure on soil–plant transfer of Pb and on in vitro Pb bioaccessibility in an urban garden contaminated (total Pb ∼ 200 mg kg–1) with gasoline emissions and other diffuse sources of Pb, (2) the effect of peeling on Pb in root crops, and (3) the significance of surface contamination of vegetables. In a field study, we planted lettuce, radish, carrots, and beetroots. The surface soil (0–15 cm) was loamy sand, had a low organic C content (1.2 %), and had a slightly acidic pH (5.92). The amendments did not affect Pb in vegetables or Pb bioaccessibility. Peeling reduced the concentration of Pb in radish by half. Removal of surface dust reduced the concentration of Pb in leafy vegetables by 40–50%. The daily Pb intake that could occur by consumption of both lettuce and carrot/beetroot in the garden was 1–2 times lower than the daily Pb intake allowed by the CODEX limits, but it was ∼1.5 times higher than the interim reference level of Pb intake proposed by the U.S. Food and Drug Administration.