Notice of Intent to List Pentachlorophenol and By-Products of its Synthesis (Complex Mixtures)

The California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA) intends to list “pentachlorophenol and by-products of its synthesis (complex mixture)” as known to the state to cause cancer under the Safe Drinking Water and Toxic Enforcement Act of 1986.

 

Chemical (CAS No.) Endpoint Reference Occurrence and Uses
Pentachlorophenolaand by‑products of its synthesisb(complex mixture)

Pentachlorophenol (87-86-5), and Pentachlorophenol, sodium salt (131-52-2) 

Cancer NTPc(2014) The commercially available complex mixture of pentachlorophenol and by-products of its synthesis is a restricted-use pesticide and registered as a heavy-duty wood preservative for utility poles, cross arms, pilings, fence posts, and construction. It is also used as a competitive inhibitor of sulfotransferase in the laboratory. The complex mixture was used in the past as a biocide in ropes, paints, adhesives, leather, canvas, insulation, and brick walls. Indoor uses were cancelled in 1984. Non-wood preservative uses were cancelled and restricted in 1987.

 

a Pentachlorophenol is currently listed as known to the state to cause cancer under Proposition 65. This listing includes the by-products of pentachlorophenol synthesis, which are found in varying amounts in pentachlorophenol and the sodium salt formulations.

 

b The commonly found by-products of pentachlorophenol synthesis include polychlorinated phenols (trichlorophenols and tetrachlorophenols), hexachlorobenzene, polychlorinated dibenzofurans (hexachlorodibenzofurans, heptachlorodibenzofurans, and octachlorodibenzofuran), polychlorinated dibenzo-p-dioxins (hexachlorodibenzo-p-dioxins, heptachlorodibenzo-p-dioxins, and octachlorodibenzo-p-dioxin), whereas 2,3,7,8-tetrachlorodibenzo-p-dioxin is a less commonly found by-product. Among them, 2,4,6-trichlorophenol, hexachlorobenzene, hexachlorodibenzodioxin, polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzofurans are listed as known to the state to cause cancer under Proposition 65.

 

c NTP = National Toxicology Program

 

OEHHA has determined that pentachlorophenol and by‑products of its synthesis (complex mixture)meet the criteria for listing as known to the state to cause cancer under Proposition 65, based on the findings of NTP (2014). In 2014, NTP published the Thirteenth Edition of the Report on Carcinogens (NTP, 2014). This report satisfies the formal identification and sufficiency of evidence criteria in the Proposition 65 regulations for pentachlorophenol and by‑products of its synthesis (complex mixture). NTP concluded that “The complex mixture pentachlorophenol and by‑products of its synthesis is reasonably anticipated to be a human carcinogen based on limited evidence of carcinogenicity from studies in humans and sufficient evidence of carcinogenicity from studies in experimental animals” (emphasis in original). Additionally, NTP states that “People exposed to pentachlorophenol are also exposed to its by‑products; therefore, the listing is for this complex mixture,” and that “the evidence from studies in experimental animals indicates that the observed carcinogenicity cannot be fully explained by either the presence of by-products alone or pentachlorophenol alone.”

OEHHA is relying on NTP’s discussion of data and conclusions in the report that pentachlorophenol and by‑products of its synthesis (complex mixture) causes cancer. Evidence described in the report includes studies showing that pentachlorophenol and by‑products of its synthesis (complex mixture) increased the incidences of malignant liver tumours in male mice, combined malignant and benign liver tumours and combined malignant and benign adrenal-gland tumours in male and female mice, malignant tumours of the blood vessels of the spleen and/or liver in female mice, malignant tumours in the tunica vaginalis of the testes in male rats, and malignant tumours of the nose to an unusual degree with respect to tumour type in male rats. OEHHA is requesting comments as to whether pentachlorophenol and by‑products of its synthesis (complex mixture) meets the criteria set forth in the Proposition 65 regulations for authoritative bodies listings. In order to be considered comments by be submitted to OEHHA by 30 November 2015. Further information is available at: Notice of Intent to List Pentachlorophenol and By-Products of its Synthesis (Complex Mixture)

OEHHA, 30 October, 2015 ;http://www.oehha.ca.gov ;