Essential and Nonessential Element Translocation in Corn Cultivated Under Sewage Sludge Application and Associated Health Risk

Sewage sludge has been used as a fertilizer in agriculture, but human exposure to toxins due to crop exposure has been reported. This study evaluated the uptake of essential and nonessential elements from soil (exposed to sewage sludge) to roots, shoots, and grains of corn, aiming to estimate the daily intake corn consumption to assess the associated health risk. Corn plants were grown in soil amended with 0, 5, 10, and 20 tons of sewage sludge per hectare (t/ha). Soil, root, shoot, and grain samples were analyzed by inductively coupled plasma mass spectrometry. In soil, sludge application at 10 and 20 t/ha enhanced the Zn, Cu, Mo, Cd, Pb, Hg, and Ni concentration compared to control soil. Normally, corn plants exhibited essential and nonessential element concentrations significantly higher in roots than in grains and shoots. Selenium was equally distributed in roots, shoots, and grains but Mo was preferentially stored in grains. Cadmium, As, and Pb were more efficiently trapped in roots than other elements. Considering the estimated daily intake, for Brazilians, the concentrations were below the toxicological or the dietary reference values. In conclusion, chemical elements were efficiently trapped in roots and therefore applying 5 t/ha proportion of sewage sludge might be a sustainable and cost-effective strategy, with a very lower risk of toxicity due to consumption of grains. In contrast, sewage sludge at 20 t/ha enhanced element levels in plant parts and in places with higher corn consumption, estimated daily intakes are expected to rise.