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

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. Meanwhile, these sites can have adverse effect on human health since it may contain heavy metals in the soil used for planting and this could be easily absorbed into the food chain, particularly for leafy vegetables such as lettuce and spring onion.

What did the research do? The research team selected samples of lettuce and spring onion for laboratory analysis. The digested samples were analyzed for heavy metals; copper (Cu), chromium (Cr), iron (Fe), magnesium (Mg), nickel (Ni) and zinc (Zn); using atomic absorption spectrophotometer (AAS Model AA 400p) so that we can determine the presence of heavy metals in the leafy vegetables.

What did the research find? The study found permissible level of chromium and iron in both lettuce and spring onion in all the study sites. Also, while copper in lettuce was within the permissible limit at all the sites, there were higher concentration of copper in spring onion at BSGS and BSG. Nickel concentration in lettuce and spring onion at BSGS were higher than WHO/FAO permissible level, however, in AH and KT, they were less than the permissible limit. There was high concentration of zinc in both lettuce and spring onion in all the study sites, except zinc in spring onion at KT. The ANOVA test statistics showed a significant difference among the concentrations of zinc in lettuce and nickel in spring onion.

Keywords: Heavy metals, leafy vegetables, health risk, hazard quotient, anthropogenic activities