Since 1936, when U.S. production began, 2,3,4,5,6-pentachlorophenol (PCP) has been widely used as an industrial wood preservative, fungicide, insecticide, and general herbicide. All U.S. PCP production workers (n=2166) in the National Institute for Occupational Safety and Health Dioxin Registry, exposed to PCP and to dioxin and furan contaminants of PCP production, were followed from first employment through 2005. A subcohort of 764 was also exposed to 2,4,5-trichlorophenol and 2,3,7,8-tetrachlorodibenzodioxin (classified by the International Agency for Research on Cancer as "carcinogenic to humans") during production of 2,4,5trichlorophenoxyacetic acid. A priori hypotheses based on animal and human studies were that the cohort would have elevated standardized mortality ratios (SMRs) for liver, adrenal, thyroid, and parathyroid cancer, soft-tissue sarcoma, lymphatic and hematopoietic cancers, and aplastic anemia in life-table analyses, compared to the U.S. population. Statistically significant excess mortality occurred for all causes (1139 deaths, SMR 1.06,95% confidence interval [CI] 1.00-1.13), all cancer (324 deaths, SMR 1.21, CI 1.08-1.35), respiratory cancer (130 deaths, SMR 1.36, CI 1.14-1.61), and non-Hodgkin's lymphoma (17 deaths, SMR 1.77, CI 1.03-2.83) but not from other a priori causes of death. In race- and sex-specific analyses, nonwhite males had increased leukemia mortality (four deaths, SMR 7.03, CI 1.92-18). A cancer incidence study might clarify interpretation of results, especially for cancers of a priori interest such as soft-tissue sarcoma, lymphomas, and leukemia.
Avima Ruder, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DSHEFS, Cincinnati, OH 45226
American Journal of Epidemiology. Abstracts of the 42nd Annual Meeting society for Epidemiologic Research Anaheim, California, June 23-26, 2009