Dibenzofuran

Dibenzofuran, is a heterocyclic organic compound with the chemical structure shown at right. It is an aromatic compound that has two benzene rings fused to one furan ring in the middle. All of the numbered carbon atoms have a hydrogen atom bonded to each of them (not shown in the image). Dibenzofuran is an aromatic ether having the chemical formula C12H8O.

Dibenzofurans
Dibenzofurans can also refer to polychlorinated dibenzofurans (PCDFs), a family of organic compounds which are polyhalogenated compounds which have atom or group substitutions made for the hydrogens on any of the numbered carbon atoms in the dibenzofuran structure. 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 below). Polychlorinated dibenzofurans are very toxic chemicals with properties and chemical structures similar to polychlorinated dibenzodioxins, often simply called dioxin.



The dibenzofuran TCDF (2,3,7,8-tetrachlorodibenzofuran) is the dibenzofuran analog of the polychlorinated dibenzodioxin TCDD (2,3,7,8-tetrachlorodibenzodioxin), the poison released in the Seveso disaster.

Environmental and health consequences
Probable places of origin It is a white crystal-like solid created from production of coal tar. It is used as an insecticide, in the production of PVC, industrial bleaching and incineration.

Production and Producers: Dibenzofuran is recovered from a wash oil fraction of coal tar that boils between 275 °C and 290 °C. Redistillation separates dibenzofuran from acenaphthene, which boils at a lower temperature. Crystallization of the redistilled fraction then produces technically pure dibenzofuran. Typical wood preservative creosote is approximately 3.5% dibenzofuran. Dibenzofuran occurs at levels of 0.19-1.50 wt % of dry tar in commercial coal tars. It also is a by-product of smoking and affects both the smoker and second hand smokers.

Pathways of exposure Occupational exposure to dibenzofuran may occur through inhalation and dermal contact, particularly at sites where coal tar, coal tar derivatives, and creosote are produced and used.

General Population Exposure: Fish and dairy intake also have been studied to be related with body burden of dibenzofuran in pregnant women. Consumption of contaminated water and food are the primary sources of exposure.

Excretion: Dibenzofuran is excreted 22% the daily intake of dioxins from meals is excreted from feces and 29% from sebum.

Regulatory Status: Dibenzofuran is cited in the 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).

Testing process No medical test exists to identify dibenzofuran. But if symptoms of eye, nose, throat or skin irritation occurs after exposure (accidentally / workplace) medical attention is recommended. EPA uses High Performance Liquid Chromatography (HPLC) to monitor samples.