Assessment of tire-derived additives and their metabolites into fruit, root and leafy vegetables and evaluation of dietary intake in Swiss adults.

Abstract

Tire wear particles, released at an estimated 6 million tons annually worldwide, introduce various chemical substances into agricultural environments through atmospheric deposition, road runoff, and reclaimed wastewater. These tire-derived compounds are known to impact ecosystem health. This study investigates the transfer of such additives and their metabolites into vegetables, assessing human dietary intake. Using UPLC-MS/MS, eleven tire-related compounds were analyzed in 100 vegetable samples from nine Swiss retailers, including leafy (lettuce, cabbage, spinach), root (onion, potato, carrot), and fruit (tomato, bell pepper, zucchini, pumpkin) vegetables. Contamination was detected in all vegetable varieties. 31 % of the 100 samples contained benzothiazole (BTH), 1,3-diphenylguanidine (DPG), 6-PPD, or 1,3-dicyclohexylurea (DCU) at levels exceeding the limit of quantification (LOQ) whereas blank values remained below LOD. DPG was most frequently detected (18 %, n = 100), followed by 6-PPD (15 %, n = 100), DCU (10 %, n = 100), and BTH (3 %, n = 100). Spinach comprised 78 % of DPG-positive leafy samples. Daily intakes of 6-PPDQ, DCU, 6-PPD, and DPG from vegetables were estimated at 0-18.7, 0-57.7, 0-42.3, and 0-42.4 ng/person/day, respectively. While current toxicological data suggest no immediate health concerns, significant knowledge gaps remain regarding long-term toxicity. This study offers critical insights into the presence of tire-derived substances in agriculture and underscores the need for further research to better assess environmental and human health risks.