Reference summary — not medical advice or a personal risk estimate.
Polychlorinated biphenyls (PCBs)
Quick answer
Classified as Group 1 — carcinogenic to humans, based on sufficient evidence in humans. Eaten. Contaminated fish from affected waterways. PCBs were banned decades ago but persist in older transformers, sealants, and sediments.
Summary
Industrial chemicals banned for decades but persistent in the environment. Associated with melanoma and lymphoma.
Detail
PCBs are chlorinated industrial chemicals banned or restricted in most industrialised countries by the late 1970s and 1980s, and globally under the Stockholm Convention from 2001. They remain present in older transformers, sealants and contaminated sediments. Group 1 with sufficient evidence for melanoma and limited evidence for non-Hodgkin lymphoma and breast cancer. Today's exposure is largely through contaminated fish from affected waterways.
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
Documented in these products
Presence in a product category doesn't imply the product causes cancer. Click each to see the source and context.
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.