A Meta-Analysis and Risk Assessment of Heavy Metal Uptake in Common Garden Vegetables.

Peer reviewed literature was searched to identify research pertaining to the uptake of heavy metals (As, Cd, Pb and Zn) by vegetables (cabbage, carrot, lettuce, and radish). The objectives of this research were to 1) determine the relationship between heavy metal concentrations in the soil and heavy metal concentrations in vegetables, and 2) determine the level of risk associated with exposure to heavy metals through ingestion of contaminated vegetables. Highly variable estimates and biologically implausible regression equations resulted from this meta-analysis. Exposure to arsenic through the ingestion of lettuce grown on contaminated soil significantly increases cancer risk, especially in children. Highly variable hazard quotients prevent strong statements concerning toxic effects from exposure to Pb, Cd, or Zn. A more in-depth meta-analysis (multiple-regression and nonlinear curve-fitting) and an upgrade in data reporting standards are recommended