Assessments of lead levels and daily intakes from green leafy vegetables of southwest Nigeria

Abstract

PurposeThe aim of this paper is to assess the safety of commonly consumed green leafy vegetables in southwest Nigeria in relation to lead (Pb) contamination.Design/methodology/approachIn total, 585 samples of five species of commonly consumed green leafy vegetable samples were procured from 15 outdoor markets and selected farms in three major cities (Abeokuta, Ibadan and Lagos) in the region. Samples were fragmented to two portions (water‐washed and unwashed) and subjected to acid digestion. The Pb in the digests was measured using a flame atomic spectrophotometer. Relevant information was elicited from traders by the administration of a structured questionnaire. Acceptable daily intakes of the metal from the vegetables were estimated using the FAO/WHO total diet study.FindingsLead concentrations in all the vegetable samples (6.35‐20.85 mg/kg) exceeded the recommended value of 0.3 mg/kg for green leafy vegetables. The estimated daily intakes of the metal (1.11×10−2 to 2.02×10−2 mg/kg bw) were also higher than the FAO/WHO safety threshold of 3.0×10−3 to 4.0×10−3 mg/kg bw for Pb. Washing the vegetables with water reduced Pb concentrations and EDIs by 11.36 to 43.52 per cent but did not bring the values below the recommended limit.Research limitations/implicationsIt was impossible to evaluate the effect of distance from highways on metal concentration because traders were not restricted to a particular location in the outdoor markets in the country.Originality/valueThe study constitutes an evaluative probe into the degree of exposure of commonly consumed vegetables to Pb contamination, contributing to the database of knowledge on toxic metal daily intake from Nigerian foods and environmental contamination.