Health Risk Assessment of Heavy Metals in Lettuce and Spring Onion on Human Health in Kumasi, Ghana

Introduction: The demand and consumption of vegetables are significantly increasing worldwide, which has resulted in urban farming on anthropogenic sites. This study assessed the concentrations of some selected heavy metals in lettuce and spring onion in line with the WHO/FAO required standard and its implications on human health. Methods: The study was carried out in Kumasi, within moist semi-deciduous forest vegetation, Ghana. The digested samples were analyzed for heavy metals (Cu, Cr, Fe, Mg, Ni, and Zn) using atomic absorption spectrophotometer (AAS Model AA 400p). Analysis of variance was used to test the level of significance at α = .05. Results: The study found mean concentrations of chromium and iron in lettuce and spring onion to be below detection level (BDL) in all study sites based on WHO/FAO permissible level. Also, while copper in lettuce was BDL at all the sites, there were higher mean concentration of copper in spring onion at BSGS (131.5 ± 0.31 mg/kg) and BSG (120.8 ± 0.01 mg/kg). The mean concentration of nickel in lettuce (137.15 ± 0.0231) and spring onion (173.55 ± 0.02 mg/kg) at BSGS were higher than WHO/FAO permissible level. Mean concentration of zinc in both lettuce and spring onion were higher than WHO/FAO permissible level in all the study sites, except zinc in spring onion at KT. The ANOVA test statistics showed no significant difference among the concentrations of heavy metals in all sites, except zinc in lettuce and nickel in spring onion. The study found cancer risk factor for nickel, which exceeded the benchmark of 1 × 10−6 for both lettuce and spring onion, indicating that long-term consumption could increase the risk of cancer in consumers. Conclusion: The study’s findings call for strict regulation and regular monitoring of heavy metals in vegetables cultivated at anthropogenic sites in urban areas to ensure food safety and consumer health. Plain language summary The study assessed the concentrations of some selected heavy metals in lettuce and spring onion in line with the WHO/FAO required standard and its implications on human health. Why was the study done? The WHO recommends consuming at least 400 g fruits and vegetables each day to reap health and nutritional benefits. This has resulted in increased advocacy for vegetable consumption and production. However, farmlands have become very scare due to proliferation of illegal mining activities in Ghana, making urban anthropogenic sites the idea sites for farming. Meanwhi