Enhanced residual risk of abamectin induced by 6PPD: in water, soil, and vegetables†

Abamectin, one of the most widely used pesticides globally, is known for its effectiveness in protecting crops and animal health. However, the residual risk of abamectin in agricultural products and the environment may be exacerbated by other pollutants, posing greater potential hazards. One such emerging environmental pollutant is N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD), a common tire antioxidant found in various environments, including agricultural products and human urine. Our study is the first to reveal the co-existence of 6PPD and abamectin in water and soil, and it demonstrated that 6PPD significantly enhances the residual persistence of abamectin in environmental media and vegetables. Specifically, 6PPD extended the half-life of abamectin by 79% in pak choi and by 70% in cabbage. Additionally, 6PPD increased the photolysis half-life of abamectin by 191% in water and by 50% on soil surfaces. Furthermore, 6PPD also prolonged the photolysis half-life of four other macrolides in water. This study reveals the mechanism through which 6PPD extends the half-life of abamectin: by scavenging free radicals and inhibiting hydroxylation and oxidation, thus slowing its degradation. And this paper highlights that 6PPD significantly exacerbates the environmental risks and food safety issue associated with abamectin. Moreover, it provides valuable insights for studying the safe use of pesticides in complex environments with multiple contaminants.