Dissipative behavior, residual pattern, and risk assessment of four pesticides and their metabolites during tea cultivation, processing and infusion

Abstract

Background: In recent years, metabolic products of pesticides have gained much attention due to their substantial characteristics as organic pollutants. So far, the behavior and metabolite levels of pesticide metabolites in crops have not been characterized well. In the present study, four registered pesticides (imidacloprid, diafenthiuron, malathion and chlorothalonil) were applied on tea plants in Fujian and Sichuan to characterize their metabolites residue pattern and dietary risk.Results: Four pesticides dissipated first-order kinetics in the fresh tea leaves with the half-lives of 1.4-3.8 days. Nine metabolites were detected in the fresh tea leaves and green tea after processing. The metabolites residues showed an increasing trend first and then declined after treatment, and reached the maximum near the half-lives of pesticide. Compared with the parent pesticide, the total residue and acute risk (included the metabolites) increased by 1.7-105.2 times. Some metabolites, especially those whose parent pesticides have high water solubility and low Log Kow, will be more easily transferred to tea infusion. Conclusion: Pesticides were metabolized rapidly on tea plants after application, but the production of metabolites increased the health risk of tea consumption. These results could provide insights to use the pesticides in tea gardens and risk monitoring after application.

Traceable and Integrated Pesticide Screening (TIPS), a Systematic and Retrospective Strategy for Screening 900 Pesticides and Unknown Metabolites in Tea

“…However, the metabolites of imidacloprid (desnitro-imidacloprid, desnitro-olefin-imidacloprid) were detected in this study instead of the parent pesticide. Some researches have shown that several metabolites of neonicotinoids are as toxic as the parent pesticides . Triazole fungicides, toxic to a wide range of nonspecific organisms, easily accumulate in soil due to their hydrophobicity and low molecular weight and therefore may change physicochemical properties and affect the balance of the ecological system .…”

“…These metabolites accumulate in the lung and liver, thereby threatening human health . Wu et al indicated that the chronic hazard quotient of diafenthiuron and its metabolites was high and caused an unacceptable health risk to tea consumers due to the high residue and low ADI, even though there was a lower transfer rate in tea infusion. In addition, these metabolites could be detected after 21 days, revealing that they were persistent in tea plants .…”

“…Wu et al indicated that the chronic hazard quotient of diafenthiuron and its metabolites was high and caused an unacceptable health risk to tea consumers due to the high residue and low ADI, even though there was a lower transfer rate in tea infusion. In addition, these metabolites could be detected after 21 days, revealing that they were persistent in tea plants . It is worth mentioning that these metabolites of diafenthiuron were not specifically regulated in routine analysis but could be monitored in our study.…”

“…False-negative detection in screening may be observed due to the complexity of the tea matrix. 41 There is an obviously broad and highintensity peak at R t 6.22 min in the total ion chromatogram acquired in positive mode in the blank sample (Figure S4). False-negative detection would occur at relatively low concentrations because of serious ion suppression when the pesticides coelute with many matrix ions in the samples.…”

“…Some researches have shown that several metabolites of neonicotinoids are as toxic as the parent pesticides. 41 Triazole fungicides, toxic to a wide range of nonspecific organisms, easily accumulate in soil due to their hydrophobicity and low molecular weight and therefore may change physicochemical properties and affect the balance of the ecological system. 47 Difenoconazole, fenbuconazole, and tebuconazole, widely used triazole fungicides, were detected in our tea samples and found in other studies.…”