Supplementary Material for: Persistent organic pollutant exposure and thyroid function among 12-year-old children

Introduction Polychlorobiphenyls (PCBs), organochlorine pesticides (OCPs) and per- and polyfluoroalkyl substances (PFASs) are persistent organic pollutants (POPs) having numerous toxicological properties, including thyroid endocrine disruption. Our aim was to assess the impact of POPs on thyroid hormones among 12-years children, while taking puberty into consideration Methods Exposure to 7 PCBs, 4 OCPs and 6 PFASs (in µg/L), and free triiodothyronine (fT3, pg/mL), free thyroxine (fT4, ng/dL) and thyroid-stimulating hormones (TSH, mIU/L) were assessed through blood-serum measurements at age 12 in 249 boys and 227 girls of the PELAGIE mother-child cohort (France). Pubertal status was clinically rated using the Tanner stages. For each POP, associations were estimated using linear regression, adjusted for potential confounders. Results Among boys, hexachlorobenzene and perfluorodecanoic acid were associated with decreased fT3 (log-scale; β (95% Confidence Interval) =-0.07 (-0.12,-0.02) and β=-0.03 (-0.06,-0.00) respectively). Intermediate levels of perfluorohexanesulfonic acid (PFHxS) and PCB180 were associated, respectively, with increased and decreased fT4. After stratification on pubertal status, PCBs and OCPs were associated with decreased TSH only in the more advanced Tanner stages (3, 4 and 5) and with decreased fT3 among early Tanner stages (1-2). Among girls, PFHxS was associated with decreased TSH (log-scale; β=-0.15 (-0.29,-0.00)), and perfluorooctanoic acid was associated with decreased fT3 (β2nd_tercile=-0.06 (-0.10,-0.03) and β3rd_tercile=-0.04 (-0.08,-0.00), vs 1st tercile). Discussion / Conclusion This cross-sectional study highlights associations between some POPs and thyroid function disruption, which appears consistent with the literature. Considering that the associations were sex-specific and moderated by pubertal status in boys, complex endocrine interactions are likely involved.