Part One · The Library
Known & probable carcinogens.
The International Agency for Research on Cancer (IARC) classifies agents into Group 1 (carcinogenic to humans), Group 2A (probably carcinogenic) and Group 2B (possibly carcinogenic). Each entry below identifies common sources, hidden synonyms used on ingredient labels, and the strength of evidence. Sign in to bookmark, add private notes, or ask questions on any entry.
Note on classification
IARC classifications describe the strength of evidence that something can cause cancer, not the size of the risk. A "Group 1" listing means the evidence is strong; it does not mean every exposure causes cancer. Real-world risk depends on dose, duration, individual susceptibility, and co-exposures. Always consult a healthcare provider for individual guidance.