Lead in Leafy Vegetables from Organic and Conventional Production Systems: Systematic Review and Meta-Analysis

Lead (Pb) is one the 10 chemicals of major public health concern listed by the World Health Organization. One reason for Pb occurrence in food is agricultural practices. In this context, organic production systems are highlighted for not using pesticides, which may result in less chemical contamination in food. Considering that, this systematic review (SR) and meta-analysis was conducted aiming to investigate if there are differences in Pb levels in organic (OLV) and conventional leafy vegetables (CLV). This SR and its protocol (PROSPERO CRD42022306048) were based on PRISMA. Only analytical, cross-sectional studies which reported data on the analysis of Pb in OLV and CLV were included. Searches were conducted in 12 electronic databases besides manual searches in articles, directory, and archives of thesis and dissertations. No restrictions regarding language or publication period were applied. After the selection stages, 24 studies were included, of which 22 (91.67%) presented low risk of bias, while two (8.33%) presented medium risk. Significant difference (p = 0.008) was observed in the meta-analysis considering results in fresh weight (mean difference = 0.01 mg/kg), indicating an inferior concentration of Pb in OLV, being classified as evidence of ‘moderate certainty’, which answers our research question.