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 a family of organic 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 dioxins.

The dibenzofuran TCDF (2,3,7,8-tetrachlorodibenzofuran) is the dibenzofuran analog of the dibenzodioxin and the poison responsible for the Seveso disaster, TCDD (2,3,7,8-tetrachlorodibenzodioxin).

Environmental and Health Consequences

Probable places of origin It is a white crystal-like solid created from production of coal tar¹. 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 dibenzofuran². 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 tars³. It also is a by-product of smoking and affects both the smoker and second hand smokers⁴.

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^5,6.

General Population Exposure: Fish and diary intake also have been studied to be related with body burden of dibenzofuran in pregnant women⁷. Consumption of contaminated water and food are the primary sources of exposure⁸.

Excretion: Dibenzofuran is excreted 22% the daily intake of dioxins from meals is excreted from feces and 29% from sebum⁹

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)⁴.

Testing process No medical test to identify dibenzofuran¹⁰. 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^11,12.

REFERENCES:

1.http://www.epa.gov/epawaste/hazard/wastemin/minimize/factshts/dibenzof.pdf

2.Elvers, B., Hawkins, S. , Ravenscroft, M., Rounsaville, J.F. & Schulz, G., eds. (1989) Ullmann’s Encyclopedia of Industrial Chemistry. 5th ed., vol A12, NY, VCH Publishers, pp130-131

3.ATSDR (1990) Toxicological Profile for Creosote (TP-90-09). Atlanta, GA, Agency for Toxic Substances and Disease Registry, pp 1-4, 9, 63-68

4.http://ntp.niehs.nih.gov/ntp/htdocs/Chem_Background/ExSumPdf/Dibenzofuran.pdf

5.U.S. Department of Health and Human Services. Hazardous Substances Data Bank (HSDB, online database).

6.Polychlorinated dibenzo-p-dioxin and dibenzofuran concentrations in serum samples of workers at intermittently burning municipal waste incinerators in Japan. Occupational and Environmental Medicine 2002;59:362-368

7.Associations of diet with body burden of dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs): observations on pregnant women from central Taiwan. Food Addit Contam. 2007 Jul;24(7):784-91

8.Congener-Specific Levels of Dioxins and Dibenzofurans in U.S. Food and Estimated Daily Dioxin Toxic Equivalent Intake. The National Institute of Environmental Health Sciences (NIEHS).

9.Balance of Intake and Excretion of 20 Congeners of Polychlorinated Dibenzo-p-dioxin, Polychlorinated Dibenzofuran and Coplanar Polychlorinated Biphenyl in Healthy Japanese Men. J Health Sci. VOL.47; NO.2; PAGE.145-154(2001)

10.New Jersey Department of Health and Senior Services. Hazardous Substance Fact Sheet: Dibenzofuran - http://nj.gov/health/eoh/rtkweb/documents/fs/2230.pdf

11.http://www.osha.gov/dts/chemicalsampling/data/CH_231985.html

12.Determination of OCDD and OCDF in soils and biological samples by GC/ECD. Waste testing and quality assurance. 3rd Vol. ASTM STP 1075. D.Friedman. American society for testing and materials.