Trace Elements Elevate Health Risks: Heavy Transport Intensifies Soil Contamination in Selected Areas of Dar es Salaam City

Urban soil contamination is a growing concern due to increasing human activities and expanding transportation systems. This study assessed the effects of heavy traffic on soil quality and human health in selected areas of Dar es Salaam City via the consumption of leafy vegetables grown near the traffic roads. The study used laboratory tests, statistical analyses, pollution indices, and health risk assessments. We used two pollution indices, the geo‐accumulation index and soil‐to‐plant transfer coefficient, to determine the contamination levels and trace element absorption by leafy vegetables, respectively. We collected 58 soil samples from selected roadside areas and 11 leafy vegetable samples grown near roads. The analysis of irrigation water used for selected farms was also conducted. The parameters analyzed in this study were pH, organic matter, and trace elements (Pb, Cd, Cr, Cu, and Zn). Results showed varying trace element levels near roads, with Zn > Pb > Cu > Cr > Cd as the dominant order, primarily linked to vehicle emissions. Elevated trace element levels in soil and leafy vegetables confirmed the influence of traffic on the quality of studied leafy vegetables. Health risk assessments revealed that Pb posed the greatest risk, followed by Cr, Cd, Zn, and Cu, highlighting serious health concerns for consumers of the studied roadside leafy vegetables. This study recommends public health campaigns to raise awareness on roadside vegetable farming and further research to develop remediation for contaminated farms in the Dar es Salaam.