Assessment of Levels and Possible Health Implications of Heavy Metals in Vegetables from Selected Irrigable Wetlands in Lagos and Ogun States, Nigeria

Vegetables are widely consumed foods for their supply of important nutrients required for body metabolism and healthy living. However, contamination of vegetables by heavy metals (HMs) from the soil where they are grown may pose serious and irreversible health problems. Present study estimated the levels and health risks of HMs in vegetables collected from irrigable wetlands at twelve locations in Lagos and Ogun states, Southwestern Nigeria. Thirty-six composite vegetable samples were collected and analyzed for HMs (beneficial—Co, Fe, Zn, and Ni, and non-beneficial—Cd, Cr, and Pb) using the atomic absorption spectrometric method. HM data were analyzed using SPSS for Windows (version 23) for descriptive and inferential statistics. Health risk metrics such as non-carcinogenic Hazard Quotient (HQ), Hazard Index (HI), and Cancer Risk (CR) were assessed. Fe was most abundant heavy metal observed in the vegetable samples, ranging from 147.4 ± 52.2 to 867.7 ± 607.7 mg/kg. The distribution pattern of HMs in vegetables followed a decreasing order of Fe > Zn > Cu > Cd > Pb. The concentrations of Cd at two monitoring sites in Lagos were higher than the acceptable limit of 1.0, indicating adverse health effects. CR values for Co and Cd (at some sampling sites) exceeded the threshold limit of 1 × 10⁻⁴ (equivalent to one person in a population of 10,000), thereby indicating a potential risk of cancer development for consumers.