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General Description

Synonyms: H7CDF; HpCDF; 1,2,3,4,6,7,8-Heptachlorodibenzofuran; 1,2,3,4,6,7,9-Heptachlorodibenzofuran; 1,2,3,4,6,8,9-Heptachlorodibenzofuran; 1,2,3,4,7,8,9-Heptachlorodibenzofuran; synonyms vary depending upon the isomer

OSHA IMIS Code Number: H327

Chemical Abstracts Service (CAS) Registry Number: 38998-75-3

Other Chemical Abstracts Service (CAS) Registry Numbers: 55673-89-7 (1,2,3,4,7,8,9-HpCDF); 67562-39-4 (1,2,3,4,6,7,8-HpCDF); 69698-58-4 (1,2,3,4,6,8,9-HpCDF); 70648-25-8 (1,2,3,4,6,7,9-HpCDF)

Chemical Description and Physical Properties:

molecular weight: 409.31
molecular formula: C12HCl7O

Health Factors

Potential Symptoms: Headache, nausea, vomiting, diarrhea; chloracne (acneform skin lesions); hyperpigmentation (of skin, gingivae, conjunctivae, and nails); swollen eyelids with discharge; peripheral neuropathy (sensory and motor), numbness, paresthesia of the limbs; anemia; increased serum triglycerides; decreased serum IgA and IgM, increased susceptibility to respiratory infections

Health Effects: Chloracne (HE3); Nervous System Disturbances---Peripheral Neuropathy, Reduced Nerve Conduction Velocities, Delayed Neurobehavioral Development (HE7); Anemia (HE12)

Affected Organs: Skin, eyes, CNS, PNS, immune system


  1. OSHA does not have a PEL for any of the four heptachlorodibenzofuran (HpCDF) isomers, which have no commercial use but may occur mixed with other toxic contaminants of chlorinated chemicals or may be formed during the heating of such chemicals.
  2. The mean level of 1,2,3,4,6,7,8-HpCDF found in the blood plasma lipid of nine magnesium production plant workers was six times that found in a control group.
  3. Increases of 2-5 fold were also reported for workers at three sawmills exposed to a wood preservative product contaminated with HpCDF, when measured 5-9 years after use of the product was discontinued.
  4. Serum concentrations of HpCDF in workers at municipal incinerators were reported to increase with duration of employment or exposure, indicating long-term bioaccumulation.
  5. In mass poisonings in Japan (Yusho) and Taiwan (Yu-Cheng) via consumption of food cooked in rice-bran oil contaminated with polychlorinated biphenyl and other polychlorinated impurities, HpCDF comprised only a small fraction of the total polychlorinated dibenzofuran congeners found in the Yu-Cheng oil and in liver tissue from a deceased patient, which were proposed to be the major source of toxicity.
  6. Multiple-dosing studies of HpCDF-induced immunosuppression in mice indicated that the 1,2,3,4,6,7,8- and the 1,2,3,4,7,8,9 isomers were approximately 100-fold more potent than the other two isomers and approximately one-tenth as potent as 2,3,7,8-tetrachlorodibenzo-p-dioxin, an exceptionally potent agonist of the aryl hydrocarbon receptor (AhR). The AhR is thought to mediate many of the toxic effects of polychlorinated aryl chemicals, as well as the induction of cytochrome P450 1A1.

Literature Basis:

  • Agency for Toxic Substances and Disease Registry (ATSDR): Toxicological profile for chlorodibenzofurans. Atlanta: ATSDR, 1994, 226 pp.
  • Chen, P.H., Wong, C.-K., Rappe, C. and Nygren, M.: Polychlorinated biphenyls, dibenzofurans and quaterphenyls in toxic rice-bran oil and in the blood and tissues of patients with PCB poisoning (Yu-Cheng) in Taiwan. Environ. Health Perspect. 59: 59-65, 1985.
  • Dickerson, R., Howie, L., Davis, D. and Safe, S.: The structure-dependent effects of heptachlorodibenzofuran isomers in male C57BL/6 mice: immunotoxicity and monooxygenase enzyme induction. Fundam. Appl. Toxicol. 15(2): 298-307, 1990.
  • Hansson, M., Grimstad, T. and Rappe, C.: Occupational exposure to polychlorinated dibenzo-p-dioxins and dibenzofurans in a magnesium production plant. Occup. Environ. Med. 52(12): 823-826, 1995.
  • Kontsas, H., Rosenberg, C., Tornaeus, J., Mutanen, P. and Jappinen, P.: Exposure of workers to 2,3,7,8-substituted polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) compounds in sawmills previously using chlorophenol-containing antistain agents. Arch. Environ. Health 53(2): 99-108, 1998.
  • Kumagai, S., Koda, S., Miyakita, T., Yamaguchi, H., Katagi, K. and Yasuda, N.: Polychlorinated dibenzo-p-dioxin and dibenzofuran concentrations in the serum samples of workers at continuously burning municipal waste incinerators in Japan. Occup. Environ. Med. 57(3): 204-210, 2000.
  • Kumagai, S., Koda, S., Miyakita, T. and Ueno, M.: Polychlorinated dibenzo-p-dioxin and dibenzofuran concentrations in serum samples of workers at intermittently burning municipal waste incinerators in Japan. Occup. Environ. Med. 59(6): 362-368, 2002.

Date Last Revised: 01/10/2006

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