Agroecosystem contamination with heavy metals due to road transportation: A global threat to safe food security

Abstract

Road transportation significantly contributes to heavy metals (HMs) in the atmosphere. The introduction of HMs into the environment is a major global ecotoxicological concern. The proliferation of road networks, coupled with the escalating vehicular volume, has exacerbated the presence of HMs, including lead (Pb), cadmium (Cd), manganese (Mn), mercury (Hg), copper (Cu), chromium (Cr), in agricultural soil and crops proximate to transportation arteries, thereby imperilling global food security. The current review focused on the significant contamination of HMs in agroecosystems worldwide due to road transportation. It highlights the various pathways through which HMs are transported to agroecosystems and their impact on nearby ecosystems. The review also evaluates the degree of HMs contamination and its subsequent transfer into soil and crops such as geoaccumulation index (Igeo), enrichment factor (EF), translocation factor (TF), and bioaccumulation factor (BAF). Recent studies have shown that harmful HMs can be absorbed by edible parts of crops, which are then consumed directly by humans. A study conducted near the National Highway in Jhansi, India found high levels of HMs in the edible parts of tomato plants (Cu – 4.77 mg/kg, Cd- 0.14 mg/kg, nickel (Ni) – 0.89 mg/kg, and Mn – 14.46). Similar studies conducted in various parts of the world have also observed increased HMs in agricultural soil and crops near roads. The current review aims to investigate HMs contamination in agroecosystems caused by road transportation and to suggest directions for future research to reduce HMs emissions from the sources. © 2024 The Institution of Chemical Engineers