Glyphosate residues in Chinese tea: a national survey, contamination pathway and risk assessment

BACKGROUND The health risks and the pathways of glyphosate pollution are of great significance for glyphosate risk management in tea. RESULTS A total of 1013 Chinese tea samples were assayed, with 27.4% contaminated by glyphosate and 0.9% exceeding the Chinese maximum residue limit (1.0 mg/kg). Field experiments suggested that spray drift and translocation within the tea plant are the main sources of glyphosate residues in tea. Following soil application, the initial glyphosate residual concentrations in young shoots and mature leaves derived from drift were 1.19 and 41.1 mg/kg, respectively. In young shoots, glyphosate declined rapidly during Day (D)1, but rebounded to a relatively high level by D7. The loss of glyphosate, owing to translocation and/or degradation, proceeded slowly in mature leaves. Upon low‐dose tea foliar application, glyphosate in young shoots and mature leaves had a relatively short residual period with half‐lives of 0.5 and 1.9 days, respectively. Glyphosate residues decreased during both green and black tea processing, and the loss rate was between 36% and 61%. Both the detection rate and measured concentrations of aminomethylphosphonic acid (AMPA) were markedly lower than those of glyphosate in commercial and experimental tea samples. The hazard quotient calculated from glyphosate residues in tea was several orders of magnitude below the level of concern. CONCLUSION Detectable glyphosate residues have been found in Chinese tea, whereas estimated consumer exposure remains far below accepted reference values. Nevertheless, careful application and management of glyphosate use in tea plantations is important for controlling its residues.