Lead and cadmium contents in a medicinal plant/spice grown in an urban city of Nigeria

Human exposure to heavy metals is a growing concern across Nigerian urban settings due to potential danger from consuming plants grown on contaminated soils. This study assessed the contents of lead and cadmium in soil and basil (Ocimum basilicum Lamiaceae) grown by vegetable farmers in Ojo Local Government Area of Lagos State, Nigeria. Using grid method, 36 points were located to collect soil samples at 0–15 and 15–30 cm depths, while plant samples were also collected simultaneously. The contents of lead and cadmium in soil and plants were determined and results were subjected to descriptive statistics while the transfer factor (TF) was calculated. Lead ranged from 1.85 mg kg−1 at the topsoil to 2.54 mg kg−1 at subsoil. Cadmium varied from 0.99 mg kg−1 at the topsoil to 1.41 mg kg−1 at subsoil. Average TF were 0.21 for Pb and 0.35 for cadmium. Distribution of lead and cadmium increased in order leaf < stem < root indicating that the root of basil may be useful in bioremediation of metal-contaminated soils. Although, the levels of lead and cadmium contents in the basil leaf are lower than other parts, there could be accumulation of these metals through long-term consumption of the leaf.