Chlorinated dibenzofurans (CDFs) are a family of chemical that contain one to eight chlorine atoms attached to the carbon atoms of the parent chemical, dibenzofuran. The CDF family contains 135 individual compounds (known as congeners) with varying harmful health and environmental effects. Of these 135 compounds, those that contain chlorine atoms at the 2,3,7,8-positions of the parent dibenzofuran molecule are especially harmful. Other than for laboratory use of small amounts of CDFs for research and development purposes, these chemicals are not deliberately produced by industry. Most CDFs are produced in very small amounts as unwanted impurities of certain products and processes utilizing chlorinated compounds. Only a few of the 135 CDF compounds have been produced in large enough quantities so that their properties, such as color, smell, taste, and toxicity could be studied. (2)
belongs to the class of organic compounds known as polychlorinated dibenzofurans. These are organic compounds containing two or more chlorine atoms attached to a dibenzofuran moiety.
Halogenated dibenzofurans (PCDFs and PBDFs) bind the aryl hydrocarbon receptor (AhR), which increases its ability to activate transcription in the XRE (xenobiotic resoponse element) promoter region. Specifically AhR binds to the PCDF, translocates it to the nucleus and together with hydrocarbon nuclear translocator (ARNT) and xenobiotic responsive element (XRE) increases the expression of CYP1A1 and aryl hydrocarbon hydroxylase (CYP1B1). AhR signaling also increseases conversion of arachidonic acid to prostanoids via cyclooxygenase-2, alters Wnt/beta-catenin signaling downregulating Sox9 and alters signaling by receptors for inflammatory cytokines. AhR signalling also alters proteasomal degradation of steroid hormone receptors, alters cellular UVB stress response and changes the differentiation of certain T-cell subsets. The resulting AhR mediated activation and alteration leads to body weight loss, cancer and thymic atrophy (characteristic of immune and endocrine disruption) which are common toxic responses to PCDFs and related toxic halogenated aryl hydrocarbons.
Metabolism
No information on the metabolism of dibenzofuran in mammalian organisms was found in the available literature. The bacteria Sphingomonas, Brevibacterium, Terrabacter, and Staphylococcus auricularis degrade dibenzofuran to 2,2',3-trihydroxybiphenyl via dibenzofuran 4,4a-dioxygenase. (2)
3, not classifiable as to its carcinogenicity to humans. (1)
Uses/Sources
CDFs are created from production of coal tar and during incineration. They are used as insecticides, in the production of PVC, and in industrial bleaching. (2)
Minimum Risk Level
Not Available
Health Effects
CDFs cause vomiting and diarrhea, anemia, more frequent lung infections, numbness and other effects on the nervous system, and mild changes in the liver. However, there were no permanent liver changes or definite liver damage found in people who ingested CDFs. (2)
Symptoms
Skin and eye irritations, especially severe acne, darkened skin color, and swollen eyelids with discharge are the most obvious health effects of the CDF poisoning. (2)
