| Chemical Abstract Number (CAS #) |
132649
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| Synonyms | Dibenzofuran |
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| Analytical Method |
EPA Method 8250A |
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| Molecular Formula | C12H8O |
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| Apparent Color | LEAF OR NEEDLES FROM ALCOHOL; WHITE CRYSTALS; CRYSTALLINE
SOLID
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| Boiling Point | 287 DEG C AT 760 MM HG
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| Melting Point | 86-87 DEG C
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| Molecular Weight | 168.19
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| Density | 1.0886 AT 99 DEG C/4 DEG C
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| Odor Threshold Concentration | Odor low= 0.7752 mg/cu m; odor high= 1.6150 mg/cu m
Odor detection in air= 1.2x10-1 ppm, purity= chemically pure.
Odor detection in air= 2.5x10-1 ppm, purity= chemically pure.
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| Environmental Impact | Dibenzofuran is released to the environment in atmospheric emissions involved with the
combustion of coal, biomass, refuse, and diesel fuel. Wastewater emissions can occur from coal
tar, coal gasification, and shale oil operations. If released to the atmosphere, dibenzofuran will
exist primarily in the gas-phase where it will degrade relatively rapidly by reaction with
photochemically produced hydroxyl radicals (estimated half-life of 11.3 hr in average air). A small
percentage of the dibenzofuran released to air will exist in the particulate phase which may be
relatively persistent to atmospheric degradation. Physical removal from air can occur by both wet
and dry deposition. If released to water, dibenzofuran may partition significantly from the water
column to sediments and suspended material. Volatilization from the water column may be
important; however, sorption to sediment may diminish the potential importance of volatilization.
If released to soil, dibenzofuran is not expected to leach significantly in most soil types. Biological
screening studies have shown that dibenzofuran is biodegraded readily by adapted microbes in the
presence of sufficient oxygen. However, in various groundwaters or aquatic sediments where
oxygen is limited or lacking, biodegradation may occur very slowly resulting in long periods of
persistence. The general population is primarily exposed to dibenzofuran through inhalation of air
which has been contaminated by a variety of combustion sources.
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| Environmental Fate | TERRESTRIAL FATE: Biological screening studies have demonstrated that
dibenzofuran is biodegraded readily by adapted microbes from subsurface regions in the presence
of sufficient oxygen. However, in groundwater regions where oxygen may be limited or lacking,
biodegradation may occur very slowly resulting in long periods of persistence. The estimated Koc
values of 4600-6350(1,SRC) indicate that dibenzofuran should have very low to no soil mobility.
Monitoring of leaching in soil associated with creosote contamination has indicated that leaching
may proceed somewhat faster than predicted by Koc, although this leaching was monitored in a
very low organic content soil in the presence of co-contaminants. No data are available to suggest
that dibenzofuran is chemically degraded in soil.
AQUATIC FATE: The estimated Koc values of 4600-6350(2,SRC) indicate that adsorption to
aquatic sediments and suspended material may be significant for dibenzofuran. The detection of
dibenzofuran in various aquatic sediments worldwide tends to confirm this indication. When
existing in the dissolved phase in the water column, dibenzofuran may be susceptible to significant
volatilization; however, the effect of adsorption can limit removal via volatilization. For example,
a computer simulation considering an environmental pond has predicted volatilization half-lives of
136.5 days(1,SRC) with the effect of adsorption and 7.1(1,SRC) days without adsorption.
Biological screening studies have demonstrated that dibenzofuran is biodegraded readily by
adapted microbes in the presence of sufficient oxygen. However, in aquatic sediments where
oxygen is limited or lacking, biodegradation may occur very slowly resulting in long periods of
persistence. Bioconcentration studies have shown that dibenzofuran can bioaccumulate
significantly in aquatic organisms. Aquatic hydrolysis is not important.
ATMOSPHERIC FATE: Monitoring of ambient air has shown that dibenzofuran exists primarily
in the gas-phase in the atmosphere with a small fraction (several percent) existing in the
particulate phase(1,2). Gas-phase dibenzofuran reacts relatively rapidly with photochemically
produced hydroxyl radicals; the half-life for this reaction can be estimated to be 11.3 hr in an
average atmosphere. Data are not available to predict the rate at which particulate phase
dibenzofuran may degrade in air; however, the rate is likely to be much slower than in the
gas-phase. Monitoring of rainwater has shown that both gas-phase and particulate dibenzofuran
are physically removed from air via wet deposition(1,2) The particulate phase may also be
physically removed via dry deposition.
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| Drinking Water Impact | DRINKING WATER: Dibenzofuran was qualitatively identified in drinking water
collected from Cincinnati, OH in Oct 1978 and Philadelphia, PA in Feb 1976 . Samples of
Japanese tap water have been found to contain dibenzofuran levels of 1.0-56.2 ng/l . Various
samples of Nordic tap water contained levels of 0.43-18 ng/l .
GROUNDWATER: Dibenzofuran concns ranging from 0.8-424.7 ppb have been detected in
groundwater sampled from various sites beneath an abandoned creosote facility in Conroe, TX
during 1982-1983 monitoring . Similar monitoring beneath a wood-preserving facility in
Pensacola, FL found levels of 0.01-0.49 ppm . Dibenzofuran was detected in upper level
groundwater beneath a coal-tar distillation facility in St. Louis Park, Minn
SURFACE WATER: Dibenzofuran has reportedly been detected in the surface waters of Lake
Erie .
RAIN/SNOW: The concn of dibenzofuran in the dissolved phase of rain collected in Portland,
OR in Feb 1984 was 9.9-26 ng/l ; the particulate phase concn in the rainwater was 0-2.1
ng/l .
EFFL: Dibenzofuran was identified in fly ash collected from a municipal incinerator in Ontario,
Canada . Concn in effluents from a sewage treatment plant in Norway was <57-359 ng/l during
1979-80 . Wastewater from a coal gasification facility estimated to contain 0.5 ppm
dibenzofuran . Concns in wastewater effluents from coal gasification facilities in Gillette, WY
and Morgantown, WV were 0.1 and 72 ppb, respectively ; concn in a shale oil wastewater was
29 ppb .
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