Heavy metal concentration in tomatoes grown in wastewater irrigated sites in Dodoma District, Tanzania

The study was conducted in October 2011 in peri-urban area of Dodoma region, specifically in Dodoma district where wastewater utilization in agriculture was practiced by majority of farmers cultivating different crops close to Waste Stabilization Ponds (WSPs). Heavy metals concentrations were determined in tomato plants irrigated with effluent from WSPs. Findings from this study have shown that as concentration of heavy metals in irrigating water increases, the metal concentrations in plant tissues also increases. The study has also shown that concentrations of heavy metals in roots are much higher compared to the leaves and fruits. Results of the chemical analysis in tomato fruits have demonstrated low concentration of heavy metals compared to the standard given by World Health Organization (WHO) for irrigation sites after the maturation ponds, and higher levels of heavy metals for irrigation site near to the anaerobic pond. On this basis it can be concluded that there is an indication of health risk to the consumers of tomatoes cultivated near to the anaerobic pond.