{"hq_id":"hq-c-org-000271","name":"2,3,7,8-TCDF (2,3,7,8-Tetrachlorodibenzofuran)","context":"human_adult","risk_level":"high","schema":"legacy","note":"Synthesis unavailable: compound lacks vectorizable regulatory classifications. Raw safety data returned.","data":{"risk_level":"high","summary":"2,3,7,8-Tetrachlorodibenzofuran (2,3,7,8-TCDF) is classified by IARC as Group 3 in Monographs Volume 69 (1997) and carries a WHO TEF of 0.1 in the 2005 WHO TEF scheme — the same TEF as 1,2,3,4,7,8-HxCDD. 2,3,7,8-TCDF has the highest TEF among tetrachlorodibenzofuran congeners and is the most potent member of the TCDF isomer group. Its lower TEF compared to TCDD (1.0) and 2,3,4,7,8-PeCDF (0.3) reflects the furan ring geometry: the oxygen bridge in dibenzofurans reduces coplanarity and AhR binding affinity slightly relative to the corresponding dibenzodioxin congener with the same lateral chlorine pattern. 2,3,7,8-TCDF is consistently detected in food samples from contaminated areas alongside TCDD and other PCDD/PCDF congeners; its concentrations in fatty fish, dairy, and meat are typically in the low-to-mid picogram-per-gram range, contributing a meaningful fraction of total dietary PCDF-TEQ alongside the higher-TEF 2,3,4,7,8-PeCDF. The Yusho and Yu-Cheng PCB-oil poisoning incidents (Japan 1968, Taiwan 1979) involved substantial 2,3,7,8-TCDF exposure alongside PCBs and other PCDFs; health studies of these cohorts have provided human data on TCDF toxicology including chloracne, immune effects, and reproductive outcomes, contributing to understanding of the dioxin-like PCB/PCDF hazard in humans. EFSA's TWI assessment includes 2,3,7,8-TCDF in the PCDD/F-TEQ sum that determines compliance with the 2 pg WHO-TEQ/kg bw/week target.","source_refs":["iarc_dioxins_v69_1997","efsa_dioxins_2018","r60-2026-09-24-d869-iarc-monographs-available","r60-2026-10-02-d983-stockholm-convention-text-2025","r60-2026-10-01-dd54-pops-all-pops","r60-2026-09-30-d918-oehha-prop65-list-csv-own-url","pubchem-exp-haz-map-information-on-hazardous-chemica-cid-39929","ctx_pred_dtxsid3052147"]},"meta":{"synthesis_version":"n/a","timestamp":"2026-10-28T18:59:15.494Z"},"_notice":"ALETHEIA output is reference data, not professional advice. Not a substitute for primary agency sources or qualified professionals. See https://aletheia.holisticquality.io/disclaimer.","_disclaimer_url":"https://aletheia.holisticquality.io/disclaimer","available_contexts":["human_adult","human_child","exposure_ingestion","human_teen","human_elderly","human_infant","human_pregnant","aquatic_life","exposure_dermal","exposure_inhalation","exposure_ocular","occupational_exposure"]}