Dose effect of Zn and Cu in sludge-amended soils on vegetable uptake of trace elements, antibiotics, and antibiotic resistance genes: Human health implications

Abstract

The application of sewage sludge to agricultural fields reduces the need for mineral fertilizers by increasing soil organic matter, but may also increase soil pollution. Previous studies indicate that zinc and copper, as the most abundant elements in sewage sludge, affect plant uptake of other contaminants. This paper aims to investigate and compare the effect of increasing amounts of Zn and Cu in sludge-amended soils on the accumulation of trace elements (TEs), antibiotics (ABs), and antibiotic resistance genes (ARGs) in lettuce and radish. The vegetables were grown under controlled conditions, and the influence on plant physiology and human health were also evaluated. The results show that the addition of Zn and Cu significantly increased the concentration of TEs in the edible tissue of both vegetables. According to the hazard quotient (HQ) of the TEs, the human health risk increased 2 to 3 times and was 3-4 times greater in lettuce than in radish. In contrast to the TEs, the occurrence of ABs and most of the ARGs was higher in radish roots than lettuce leaves. ABs were not detected in lettuce leaves, and the amount of all ARGs except bla TEM was 10 times lower than in radish roots. On the other hand, the addition of Zn and Cu had no significant effect on the occurrence of ABs and ARGs in the edible part of the vegetables, and no damage was found to plant productivity or physiology. The results show that the consumption of lettuce and radish grown in sewage-sludge-amended soils under tested doses of Cu and Zn does not pose an adverse human health effect, as the total HQ value was always less than 1, and the presence of ABs and ARGs was not found to have any potential impact. Nevertheless, further studies are needed to estimate the long-term effect on human health of crops grown under frequent application of biosolids in arable soil.

A Review on Occurrence and Spread of Antibiotic Resistance in Wastewaters and in Wastewater Treatment Plants: Mechanisms and Perspectives

“…More and more studies are linking the application of biosolids to higher levels of resistant bacteria and genes in agricultural soil ( Ross and Topp, 2015 ; Gondim-Porto et al, 2016 ; Burch et al, 2017 ; Lau et al, 2017 ; Murray et al, 2019 ). However, the resistance levels decrease with time after application ( Marti et al, 2014 ; Rahube et al, 2014 ; Ross and Topp, 2015 ; Burch et al, 2017 ; Lau et al, 2017 ; Murray et al, 2019 ), and the current evidence for gene transfer to crops and animals remains inconclusive ( Marti et al, 2013b ; Rahube et al, 2014 ; Lau et al, 2017 ; Murray et al, 2019 ; You et al, 2020 ). Current regulations in the US and the EU do include time restrictions from application to harvesting and/or grazing ( United States Environmental Protection Agency, 1994 , 2003 ; Eur-Lex, 2018 ; Collivignarelli et al, 2019 ).…”

An Overview of Antibiotic Resistance and Abiotic Stresses Affecting Antimicrobial Resistance in Agricultural Soils

“…Considering the interactions between antibiotics, heavy metals, and ARGs in sewage sludge, the use of sewage sludge in agricultural soils is controversial [201], though it meets the demands of farm soils for organic matter and nutrients [202]. The long-term consequences of sewage sludge containing pharmaceutical compounds on soil attributes are not entirely realized.…”

Applying animal derived organic fertilizers increases the transmission of antibiotic resistance genes in the soil-onion system

“…Trace elements present in both soil and fertilizers play a crucial role in various metabolic and developmental processes throughout a plant's growth. Essential micronutrients such as boron (B), iron (Fe), zinc (Zn), manganese (Mn), magnesium (Mg), copper (Cu), selenium (Se), and molybdenum (You et al, 2020) are indispensable for plant growth (Mishra et al, 2023). Previous studies have indicated that varying copper (Cu) and zinc (Zn) concentrations signi cantly in uence the occurrence of ARGs in edible parts of lettuce (leaves) and radishes (roots).…”