Assessment of the concentration of heavy metals in two vegetables in selected urban metropolises (Ilorin and Osogbo), Nigeria

Abstract

This study analyzed heavy metal contamination in commonly consumed leafy vegetables grown on peri-urban farms in Osogbo and Ilorin, Nigeria. Across five neighborhoods in each city, fresh vegetable samples were collected and assessed for lead (Pb), copper (Cu), zinc (Zn), iron (Fe), and manganese (Mn) using atomic absorption spectrophotometry. Alarming Pb levels were discovered, with mean concentrations ranging from 0.01 to 0.26 mg/kg depending on the sampling site, up to 4 times above the WHO safety limit (0.05 mg/kg). Average Cu levels also exceeded guidelines at 0.17 mg/kg in Osogbo and 0.13 mg/kg in Ilorin. Likewise, average Fe surpassed recommended thresholds at 0.54 mg/kg and 0.52 mg/kg in the two cities, respectively. Chronic dietary exposure to these metals poses risks of lung, kidney, neurological and other organ damage among consumers. The contamination likely results from industrial emissions and vehicular pollution. Further research should identify specific entry points across the food production pipeline to guide targeted interventions. Additionally, alternative cultivation methods and consumer health advisories are needed to reduce toxicant exposures from urban-grown greens that many Nigerians rely on. Urgent multi-sectoral action must decrease heavy metal accumulation in vegetables from farms encircled by expanding cities.