The International Agency for Research on Cancer (IARC), a specialized agency of the World Health Organization, held a Working Group meeting in October to assess the carcinogenicity of pentachlorophenol, 2,4,6-tricholorphenol, aldrin, dieldrin, and 3,3′,4,4′-tetrachloroazobenzene.
The Working Group determined that the insecticide and wood preservative pentachlorophenol is carcinogenic to humans (Group 1), and causes non-Hodgkin lymphoma. Pentachlorophenol is a persistent organic pollutant and its use has been restricted since the 1990s.
Aldrin and dieldrin are organochlorine pesticides. Their use has been widely restricted since the 1970s, but they are persistent in the environment. 3,3′,4,4′-Tetrachloroazobenzene is a contaminant formed in the production of some herbicides. All three compounds were classified as probably carcinogenic to humans (Group 2A).
2,4,6-Trichlorophenol was classified as possibly carcinogenic to humans (Group 2B). It is a pesticide used for wood preservation and for treating animal pelts and leather.