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Polychlorinated dibenzofurans (PCDFs) are a family of organic compounds with one or several of the hydrogens in the dibenzofuran structure replaced by chlorines. For example, 2,3,7,8-tetrachlorodibenzofuran (TCDF) has chlorine atoms substituted for each of the hydrogens on the number 2, 3, 7, and 8 carbons (see structure in the upper left corner of the second image). Polychlorinated dibenzofurans are much more toxic than the parent compounds, with properties and chemical structures similar to polychlorinated dibenzodioxins. These groups together are often inaccurately called dioxins. They are known teratogens, mutagens, and suspected human carcinogens. PCDFs tend to co-occur with polychlorinated dibenzodioxins (PCDDs). PCDFs can be formed by pyrolysis or incineration at temperatures below 1200 °C of chlorine containing products, such as PVC, PCBs, and other organochlorides, or of non-chlorine containing products in the presence of chlorine donors. Dibenzofurans are known persistent organic pollutants (POP), classified among the dirty dozen in the Stockholm Convention on Persistent Organic Pollutants.
Safety, toxicity, regulation
Occupational exposure to dibenzofuran may occur through inhalation and contact with the skin, particularly at sites where coal tar, coal tar derivatives, and creosote are produced or used.
Fish and dairy intake also have been studied in relation to the body burden of dibenzofuran in pregnant women. Consumption of contaminated water and food are the primary sources of exposure.
Dibenzofuran is excreted 22% the daily intake of dioxins from meals is excreted from feces and 29% from sebum.
Dibenzofuran is cited in the United States Clean Air Act 1990 Amendments -Hazardous Air Pollutants as a volatile hazardous air pollutant of potential concern. The Superfund Amendment Reauthorization Act (SARA) Section 110 placed dibenzofuran on the revised Agency for Toxic Substances and Disease Registry (ATSDR) priority list of hazardous substances to be the subject of a toxicological profile. The listing was based on the substance’s frequency of occurrence at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List sites, its toxicity, and/or its potential for human exposure. Dibenzofuran is also listed in the Massachusetts Substance List for Right-to-Know Law, the New Jersey Department of Health Hazard Right-to-Know Program Hazardous Substance List, and the Pennsylvania Department of Labor and Industry Hazardous Substance List. California’s Air Toxics “Hot Spots” List (Assembly Bill).