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Dibenzofuran
CASRN 132-64-9
Contents
0429
Dibenzofuran; CASRN 132-64-9
Health assessment information on a chemical substance is included in IRIS only
after a comprehensive review of chronic toxicity data by U.S. EPA health
scientists from several Program Offices and the Office of Research and
Development. The summaries presented in Sections I and II represent a
consensus reached in the review process. Background information and
explanations of the methods used to derive the values given in IRIS are
provided in the Background Documents.
STATUS OF DATA FOR Dibenzofuran
File On-Line 10/01/1990
Category (section) Status Last Revised
----------------------------------------- -------- ------------
Oral RfD Assessment (I.A.) no data
Inhalation RfC Assessment (I.B.) no data 05/01/1992
Carcinogenicity Assessment (II.) on-line 10/01/1990
_I. CHRONIC HEALTH HAZARD ASSESSMENTS FOR NONCARCINOGENIC EFFECTS
__I.A. REFERENCE DOSE FOR CHRONIC ORAL EXPOSURE (RfD)
Substance Name -- Dibenzofuran
CASRN -- 132-64-9
Not available at this time.
__I.B. REFERENCE CONCENTRATION FOR CHRONIC INHALATION EXPOSURE (RfC)
Substance Name -- Dibenzofuran
CASRN -- 132-64-9
Not available at this time.
_II. CARCINOGENICITY ASSESSMENT FOR LIFETIME EXPOSURE
Substance Name -- Dibenzofuran
CASRN -- 132-64-9
Last Revised -- 10/01/1990
Section II provides information on three aspects of the carcinogenic
assessment for the substance in question; the weight-of-evidence judgment of
the likelihood that the substance is a human carcinogen, and quantitative
estimates of risk from oral exposure and from inhalation exposure. The
quantitative risk estimates are presented in three ways. The slope factor is
the result of application of a low-dose extrapolation procedure and is
presented as the risk per (mg/kg)/day. The unit risk is the quantitative
estimate in terms of either risk per ug/L drinking water or risk per ug/cu.m
air breathed. The third form in which risk is presented is a drinking water
or air concentration providing cancer risks of 1 in 10,000, 1 in 100,000 or 1
in 1,000,000. The rationale and methods used to develop the carcinogenicity
information in IRIS are described in The Risk Assessment Guidelines of 1986
(EPA/600/8-87/045) and in the IRIS Background Document. IRIS summaries
developed since the publication of EPA's more recent Proposed Guidelines for
Carcinogen Risk Assessment also utilize those Guidelines where indicated
(Federal Register 61(79):17960-18011, April 23, 1996). Users are referred to
Section I of this IRIS file for information on long-term toxic effects other
than carcinogenicity.
__II.A. EVIDENCE FOR CLASSIFICATION AS TO HUMAN CARCINOGENICITY
___II.A.1. WEIGHT-OF-EVIDENCE CLASSIFICATION
Classification -- D; not classifiable as to human carcinogenicity
Basis -- Based on no human data and no animal data for dibenzofuran alone.
___II.A.2. HUMAN CARCINOGENICITY DATA
None. There are no data on the possible carcinogenicity of dibenzofuran
alone in humans. Studies have evaluated exposure to a mixture of
polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs) and
polychlorinated quinones (PCQs) by consumption of contaminated rice oil
(Yusho incident) (reviewed in U.S. EPA, 1986, 1987). However, these studies
have limited value because they do not assess dibenzofuran or correlate
exposure with cancer risk. Additionally, because of the multiple exposures,
the extent to which the various components contributed to the increase in
cancer mortality cannot be determined.
___II.A.3. ANIMAL CARCINOGENICITY DATA
None. No animal carcinogenicity data on dibenzofuran are currently
available. U.S. EPA (1986) noted that the biological activity of PCDFs varies
greatly, so that risk assessment of dibenzofuran by analogy to any of these
more widely studied compounds would not be recommended.
___II.A.4. SUPPORTING DATA FOR CARCINOGENICITY
Dibenzofuran is not mutagenic with or without metabolic activation in
several strains of Salmonella typhimurium assay (Schoeny, 1982).
In a comparison of Toxic Equivalency Factor (TEF) values for chlorinated
dibenzofurans, mono-, di- and tri-chlorinated dibenzofuran had TEF values of
O (U.S. EPA, 1989). Based on these results and the fact that toxicity of
polychlorinated dibenzofurans (PCDF) depends on the number of chlorine
SUBSTituents and their position (U.S. EPA, 1986), the TEF for dibenzofuran,
with no chlorine SUBSTituents, is set equal to O.
__II.B. QUANTITATIVE ESTIMATE OF CARCINOGENIC RISK FROM ORAL EXPOSURE
None.
__II.C. QUANTITATIVE ESTIMATE OF CARCINOGENIC RISK FROM INHALATION EXPOSURE
None.
__II.D. EPA DOCUMENTATION, REVIEW, AND CONTACTS (CARCINOGENICITY ASSESSMENT)
___II.D.1. EPA DOCUMENTATION
Source Document -- U.S. EPA, 1986, 1987, 1989
The 1986 Health Assessment for Polychlorinated Dibenzofurans is an external
draft for review purposes only and does not constitute Agency policy.
The 1987 Health Effects Assessment Document for Dibenzofuran has been reviewed
in accordance with the U.S. Environmental Protection Agency's peer and
administrative review policies and has been approved for publication.
___II.D.2. REVIEW (CARCINOGENICITY ASSESSMENT)
Agency Work Group Review -- 10/05/1989
Verification Date -- 10/05/1989
___II.D.3. U.S. EPA CONTACTS (CARCINOGENICITY ASSESSMENT)
Please contact the Risk Information Hotline for all questions concerning this
assessment or IRIS, in general, at (513)569-7254 (phone), (513)569-7159 (FAX)
or RIH.IRIS@EPAMAIL.EPA.GOV (internet address).
_VI. BIBLIOGRAPHY
Substance Name -- Dibenzofuran
CASRN -- 132-64-9
Last Revised -- 10/01/1990
__VI.A. ORAL RfD REFERENCES
None
__VI.B. INHALATION RfD REFERENCES
None
__VI.C. CARCINOGENICITY ASSESSMENT REFERENCES
Schoeny, R. 1982. Mutagenicity testing of chlorinated biphenyls and
chlorinated dibenzofurans. Mutat. Res. 101: 45-56.
U.S. EPA. 1986. Health Assessment Document for Polychlorinated
Dibenzofurans. Prepared by the Office of Health and Environmental Assessment,
Environmental Criteria and Assessment Office, Cincinnati, OH for the Office of
Air Quality Planning and Standards, Research Triangle Park, NC. EPA 600/8-
86/018A. NTIS PB86-221256/AS.
U.S. EPA. 1987. Health Effects Assessment for Dibenzofuran. Prepared by
the Office of Health and Environmental Assessment, Environmental Criteria and
Assessment Office, Cincinnati, OH for the Office of Emergency and Remedial
Response, Washington, DC. ECAO-CIN-H088.
U.S. EPA. 1989. Interim Procedures for Estimating Risks Associated with
Exposures to Mixtures of Chlorinated Dibenzo-p-Dioxins and -Dibenzofurans
(CDDs and CDFs) and 1989 Update. Risk Assessment Forum, Washington, DC.
EPA/625/3-89/016.
_VII. REVISION HISTORY
Substance Name -- Dibenzofuran
CASRN -- 132-64-9
-------- -------- --------------------------------------------------------
Date Section Description
-------- -------- --------------------------------------------------------
10/01/1990 II. Carcinogen assessment on-line
10/01/1990 VI. Bibliography on-line
01/01/1992 IV. Regulatory Action section on-line
05/01/1992 I.B. Inhalation RfC now under review
VIII. SYNONYMS
Substance Name -- Dibenzofuran
CASRN -- 132-64-9
Last Revised -- 10/01/1990
132-64-9
(1,1'-BIPHENYL)-2,2'-DIYL OXIDE
2,2'-BIPHENYLENE OXIDE
2,2'-BIPHENYLYLENE OXIDE
DIBENZOFURAN
DIBENZO(B,D)FURAN
DIPHENYLENE OXIDE
HSDB 2163
NSC 1245
Last updated: 5 May 1998
URL: http://www.epa.gov/iris/SUBST/0429.HTM
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