Academic journal article Environmental Health Perspectives

Pentachlorophenol and Cancer Risk: Focusing the Lens on Specific Chlorophenols and Contaminants

Academic journal article Environmental Health Perspectives

Pentachlorophenol and Cancer Risk: Focusing the Lens on Specific Chlorophenols and Contaminants

Article excerpt

OBJECTIVE: Pentachlorophenol, a fungicide widely used as a wood preservative, was classified in 1999 by the International Agency for Research on Cancer as a possible human carcinogen. We reviewed currently available data to determine the extent to which recent studies assist in distinguishing the effect of pentachlorophenol from that of its contaminants (e.g., dioxins and other chlorophenols).

DATA SOURCES AND EXTRACTION: We performed a systematic review of published studies pertaining to cancer risk in relation to pentachlorophenol exposure, focusing on results pertaining specifically to all cancer sites and specific hematopoietic cancers, and data pertaining to risks associated with other types of chlorophenols, dioxins, or furans.

SYNTHESIS: The pentachlorophenol studies presented considerable evidence pertaining to hematopoietic cancers, with strong associations seen in multiple studies, in different locations, and using different designs. There is little evidence of an association between these cancers and chlorophenols that contain fewer than four chlorines. The extension of a large cohort study of sawmill workers, with follow-up to 1995, provided information about risks of relatively rare cancers (e.g., non-Hodgkin lymphoma, multiple myeloma), using a validated exposure assessment procedure that distinguishes between exposures to pentachlorophenol and tetrachlorophenol. In contrast with dioxin, pentachlorophenol exposure has not been associated with total cancer incidence or mortality.

CONCLUSIONS: The updated cohort study focusing on pentachlorophenol provides increased statistical power and precision, and demonstrates associations between hematopoietic cancer and pentachlorophenol exposure not observed in earlier evaluations of this cohort. Contaminant confounding is an unlikely explanation for the risks seen with pentachlorophenol exposure.

KEY WORDS: cancer, childhood leukemia, chlorophenols, dioxins, furans, multiple myeloma, non-Hodgkin lymphoma, pentachlorophenol, soft-tissue sarcoma. Environ Health Perspect 116:1001-1008 (2008). doi:10.1289/ehp.11081 available via http://dx.doi.org/ [Online 11 April 2008]

Pentachlorophenol (CAS Registry no. 87-86-5; also referred to as penta, pentachlorofenol, 2,3,4,5,6-pentachlorophenol, and chlorophen) is a chlorinated aromatic compound that has been used extensively as a fungicide. Impurities comprise approximately 10% of technical or commercial grade pentachlorophenol and consist of several congeners of the chlorophenols, primarily the higher chlorinated congeners of dibenzo-p-dioxins and dibenzofurans [National Toxicology Program (NTP) 1989; Schwetz et al. 1974]. Pentachlorophenol was first registered as a wood preservative in the United States in 1936 (Ahlborg and Thunberg 1980) and has also been used in ropes, paints, adhesives, canvas, insulation, and brick walls [Agency for Toxic Substances and Disease Registry (ATSDR) 2001; Proudfoot 2003]. Use by the general public was restricted in 1984, and pentachlorophenol application was limited to industrial areas (e.g., utility poles, railroad crossties, fence posts). The 95th percentile of urinary pentachlorophenol concentration was approximately 1.0-2.0 [micro]g/L in the 1999-2002 National Health and Nutrition Examination Survey III [Centers for Disease Control and Prevention (CDC) 2005]. The comparable figure from a population-based study in Germany in 1998 was 3 [micro]g/L (Schulz 2007); in that study, levels had decreased since 1990.

Case reports (Bishop and Jones 1981; Greene et al. 1978) and case-control studies of hematopoietic cancers published in the 1980s and 1990s (Hardell et al. 1981, 1994, 1995; Kogevinas et al. 1995; Pearce et al. 1986b; Smith and Christophers 1992; Smith et al. 1984; Woods et al. 1987) raised concerns about the risk of non-Hodgkin lymphoma and soft-tissue sarcoma in relation to pentachlorophenol exposure. Other studies examined the carcinogenic effect of pentachlorophenol in experimental animals. …

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