Detection of novel organophosphorus flame retardants and plasticizers in children urines: Associations with oxidative stress damage and thyroid nodule risk

Organophosphorus flame retardants and plasticizers (OPFRs) are prevalent and raise health concerns due to their endocrine-disrupting properties. Clinically detectable thyroid nodules are less common in children than in adults but pose a higher malignancy risk. The effects of OPFRs on children's thyroid nodules and their relation to oxidative stress remain unknown. This cross-sectional study analyzed concentrations of seven OPFRs and three oxidative stress biomarkers (OSBs), namely 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OHdG), malondialdehyde, and o, o'-dityrosine (diY) in 521 urine samples from children in a coastal urbanized region. Median creatinine-adjusted levels of the seven OPFRs ranged from 0.02 to 0.64 μg/g. Triphenyl phosphine oxide (TPPO) was detected for the first time in children urine. Diphenyl phosphate (DPHP) and isopropyl phenyl phosphate (ip-PPP) were frequently detected, with median levels of 0.46 μg/g and 0.64 μg/g, respectively. Multiple linear regression analyses and mixture models demonstrated that seven OPFRs were positively associated with three OSBs. Furthermore, logistic regression analysis revealed that urinary TPPO and tris(1-chloro-2-propyl) phosphate (TCIPP) were associated with thyroid nodule risk in children, and TPPO and TCIPP further demonstrated sex-dependent association with thyroid nodule risk particularly in girls, although OSBs did not show significant mediating effects. Overall, further studies are warranted to explore the potential mechanisms linking thyroid health with OPFRs exposure and oxidative stress, particularly in children.