Ecological risk assessment of toxic elements, microbial loads, parasites and antinutritional factors in Telfairia occidentalis grown on sewage contaminated soil

Abstract

The aim of this study was to evaluate the ecological health risk assessment of toxic elements, microbial load, and anti-nutrient constituent build-up in vegetables, Talfairia occidentalis, grown on sewage contaminated soil. Samples of soil and vegetables were taken from farms near the dumpsites (sites A). As a control, samples were taken from an area with no dump sites (sites B). Atomic Absorption Spectrophotometry was used to determine the potentially toxic elements. The basic titrimetric method was used to estimate Phytate and Oxalate in the vegetables in order to assess anti-nutrient constituents. The content of cyanogenic glycosides, tannins, and alkaloids in vegetable samples was determine using a standard method. Total heterotrophic bacteria, E. coli, total coliform, faecal coliform, Staphylococcus aureus, Salmonella, and intestinal parasites were all determined using APHA standard methods. For all samples analyzed, the concentrations of metals – Cr, Zn, Pb, Cu, and Ni in site A were higher than those in site B. The soil and vegetable samples differed from the controls by a significant amount (P <0.05). Vegetable samples from site A were mainly infected with faecal coliform TO (9.7 × 105cfu/g) and other bacteria at levels higher than the recommended levels. In contrast to samples from site B, which were not infected with human intestinal helminth parasites, Ascaris lumbricoides ova and Entamoeba histolytica cryst were present in vegetables in site A samples. The majority of the values obtained for the sewage dumpsite were significantly higher than the values recorded by the World Health Organization (WHO). However, sewage wastes, anthropogenic sources, and atmospheric depositions cause higher concentrations of heavy metals, anti-nutrients, and microbial load around dumpsites, which bioaccumulate in vegetables through uptake from the soil and eventual entry into the food chain. The overall evaluation found that consumption of vegetables grown on sewage soil poses a risk of heavy metals, microbial loads, and anti-nutrients adversely affecting human health.