Cumulative risk assessment of five phthalates in European children and adolescents

The European Human Biomonitoring Initiative (HBM4EU) assessed human biomonitoring data on phthalates in children and adolescents, that were sampled between 2014 and 2021, in a harmonised way. These so-called “HBM4EU Aligned Studies” revealed that almost all children and adolescents were exposed to multiple phthalates concurrently. Some phthalates have been shown to act in a dose-additive manner, thus, a mixture risk assessment is warranted. In our study, we determine the risk from combined exposure to five anti-androgenic phthalates, namely DEHP, DiBP, DnBP, BBzP and DiNP by making use of the hazard index (HI) approach. Toxicologically-based human biomonitoring guidance values (HBM-GVs) derived within the framework of HBM4EU served as basis. Our results show that exposures of 17% of children and adolescents from twelve European countries resulted in hazard indices (HI) > 1 with an HI of 1.77 at the 95th percentile (geometric mean, GM = 0.44). Main drivers for the mixture risk are DnBP and DiBP. Generalized Linear Model (GLM) analysis including four major exposure determinants (age, sex, European region, sampling year) simultaneously reveal differences for the European regions and between sampling years. Children and adolescents living in the Eastern region of Europe have on average, higher HIs (GM=0.58) than in the Southern region (GM = 0.36) and Western region (GM = 0.42). Moreover, participants from which urine samples were taken in the earlier years (2014–2016) seem to have higher average HI levels than participants from studies with later sampling periods. Strikingly, the majority (63%) of participants with HIs > 1 would have gone unnoticed in single substance risk assessments as individual phthalates levels were below corresponding HBM-GVs. Thus, our results underline the importance of mixture risk assessment approaches to adequately address risks from concurrent chemical exposure.