Underestimate of human exposure to p-phenylenediamine derived quinones in diet: Evidence from a cross-country survey of contaminants in chicken eggs

p-Phenylenediamine-derived quinones (PPD-Qs) are recognized as new types of transformation products from ubiquitous tire rubber additives of p-phenylenediamines (PPDs) in the environment. Although emerging evidence indicates that these contaminants could enter human body via dermal absorption, air inhalation and consumption of contaminated water, there is a paucity of research on the exposure scenario of these xenobiotics via diet. The present study sought to address this by conducting a cross-country survey to characterize the contamination levels of PPD-Qs with their parent compounds in chicken eggs from 13 countries/regions. Alarmingly, both PPD-Qs and their parent PPDs were detected in egg samples. Specifically, PPD-Q concentrations in egg yolk ranged from 132 to 857 ng/kg ww, accounting for 40.1 % of the total PPD-Q burden of these anthropogenic contaminants, demonstrating their distinct metabolic behavior and bioaccumulative potential. Furthermore, dietary intake assessments based on national per capita egg consumption rates and the WHO recommended dietary guidelines revealed a 1.1–4.8–fold regional difference in human exposure to these contaminants via dietary egg intake. Of note, European countries exhibit higher levels of PPD-Qs contamination in eggs, ranging from 91.9 to 1843 ng/kg ww, with a median value of 521 ng/kg ww. The findings underscore diet as a significant and previously overlooked route for human exposure to these emerging contaminants, supplementing the well-established relevance of inhalation and dermal routes.