Relative effect potency estimates of dioxin-like activity for dioxins, furans, and dioxin-like PCBs in adults based on cytochrome P450 1A1 and 1B1 gene expression in blood.

•TEFs for assessment of health risks from dioxin-like compounds are regularly updated.•Besides TEFs based on animal studies, we derived REPs based on human health outcomes.•We used thyroid and cytochrome P450 (CYP) 1A1 and 1B1 gene expression endpoints in PBMC of exposed adults.•REPs from CYP1A1 correlated with REPs derived from thyroid volume and serum FT4 outcomes.•REPs based on chronic, low-dose exposure sustain validity of dioxin TEFs and reflect most human exposure scenarios.