Reference summary — not medical advice or a personal risk estimate.
Dioxin (2,3,7,8-TCDD)
Quick answer
Classified as Group 1 — carcinogenic to humans, based on sufficient evidence in humans. Eaten. Bioaccumulates in animal fat, so dietary exposure (meat, dairy, fish) dominates. Historical industrial accidents produced very high exposures in some communities.
Summary
An environmental pollutant byproduct of industrial processes. Associated with multiple cancers.
Detail
2,3,7,8-Tetrachlorodibenzo-para-dioxin is Group 1 with sufficient evidence for cancer at all sites combined, and limited evidence for soft tissue sarcoma and non-Hodgkin lymphoma. It bioaccumulates in food chains.
What's not established
This classification is based on sufficient evidence in humans that this factor can cause cancer. It does not establish a safe exposure threshold, your personal risk, or how this factor's risk compares in size to other Group 1 agents — hazard classifications are not ranked by magnitude.
Regional relevance
global
Evidence sources
Every claim on this page traces back to one of these. Click through to read the primary document yourself.
Primary sources
IARC
IARC Monographs — Classifications by Cancer Site, Vols 1–140
Supporting sources
ACS
ACS — Known and Probable Human Carcinogens
EPA
US EPA — Integrated Risk Information System (IRIS) carcinogen assessments
NTP
NTP — Report on Carcinogens (US National Toxicology Program)
Last reviewed: October 2026
Official reference list
A government list some readers use alongside the primary evidence. Meyron is not affiliated with it. A chemical being listed does not by itself describe a risk from any particular product.
- California Prop 65 list
State of California's list of chemicals known to cause cancer or reproductive harm.