Pentachlorophenol is a human carcinogen, Group 1

In October 2016 18 scientists met at IARC for evaluation of pentachlorophenol (PCP) as a human carcinogen. The panel classified PCP as ‘carcinogenic to humans’ Group 1. PCP is a persistent organic pollutant under the Stockholm Convention. Chlorophenols, mostly PCP, have been used as wood preservatives. The use was banned in Sweden in 1978 with few exceptions. Wood impregnated with PCP may still entail a health hazard. In case-control studies we associated use of chlorophenols, as well as phenoxy herbicides, with increased risk for soft-tissue sarcoma (1979) and malignant lymphoma, both Hodgkin’s disease and non-Hodgkin lymphoma (1981). These results were the first studies in the world showing a carcinogenic potential of these agents, and further discussed in an article published in 1982.

Our results associated exposure to chlorophenols and the weed-killers phenoxy herbicides, with contaminating TCDD, with increased risk for soft-tissue sarcoma and malignant lymphoma. The results were soon questioned by industry and its allied experts including scientists with their own hidden agenda, even with funds from the Swedish Cancer Society aimed at preventing cancer, see


The lesson is that it took 37 years from the first publication showing PCP as a human carcinogen to establish causation, years that were lost for cancer prevention.