Occurrence and toxicological risk characterization of 6-PPD, 6-PPDQ, and related rubber-associated chemicals in fruits and vegetables

Rubber-related antioxidants and vulcanisation accelerators are high-production-volume chemicals widely used in tire manufacturing. Through tire and road wear particles, these substances can enter the environment and contaminate crops via atmospheric deposition, irrigation, or soil uptake. This study reports the occurrence of six such compounds - N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6-PPD), its quinone transformation product (6-PPDQ), benzothiazole (BTH), diphenylguanidine (DPG), 1,3-dicyclohexylurea (DCU), and N,N'-diphenyl-p-phenylenediamine (DPPD) - in fresh fruits and vegetables. Using a QuEChERS-LC-MS/MS approach, the compounds were screened across multiple commodities, revealing DPG and BTH as the most frequently detected analytes, whereas 6-PPD was consistently below quantification limits. Estimated daily intakes (EDIs) were derived for adults and children, and a hazard quotient (HQ) approach was applied to characterize potential dietary risks. Across all scenarios, HQs remained well below 1.0, indicating negligible risk from fruit- and vegetable-mediated exposure. These findings highlight the low dietary relevance of these compounds compared with other exposure routes and support the need for integrated assessments that consider inhalation, dust, and other non-dietary pathways. Importantly, this study also demonstrates the practical value of applying a QuEChERS-LC-MS/MS workflow to this specific combination of analytes and food matrices, providing a robust basis for future monitoring and risk-assessment efforts.