To Örebro University

Humans are chronically exposed to mixtures of environmental contaminants. Exposure to endocrine-disrupting chemicals (EDCs) contributes to increased health impairment observed globally. This study aimed to evaluate the endocrine-disruptive and oxidative stress potential of a human-relevant, complex chemical mixture in vitro. By testing chemical class subgroup mixtures, the identity of toxicological drivers and mixture additivity could be investigated. A 50-component mixture was compiled based on Swedish human blood concentrations (xHBC), consisting of six subgroup mixtures: polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (PCB mixture), brominated flame retardants (BFR mixture), per- and polyfluoroalkyl substances (PFAS mixture), pesticide mixture, synthetic phenolic contaminants (phenol mixture), and phthalate mixture. These were tested in four chemically activated luciferase gene expression (CALUX) assays: dioxin responsive (DR-), estrogen receptor α (ERα-), androgen receptor. (AR-), and nuclear factor erythroid 2-related factor 2 (Nrf2)-CALUX, along with an adipocyte cell assay. The total mixture caused significant agonistic activity in DR- and ER-, and antagonistic activity in AR-CALUX at 0.1-15 xHBC, depending on the assay. Mixture additivity was assessed in ERα-, DR-, and anti-AR-CALUX using subgroup mixtures and the concentration addition (CA) model. The total mixture followed the CA model in ERα-, anti-AR- and DR-CALUX. The toxicological drivers of these activities were mainly the PCB and phenol mixture. A significant increase in differentiated adipocytes was observed at 100 xHBC. These results raise concerns regarding potential health effects on the endocrine system. The additive effects at human-relevant concentrations observed in this study motivate considering mixtures in regulatory contexts to protect the well-being of future generations.