Benzene

71-43-2

Manufacturing styrene, phenol, detergents, organic chemicals, 
pesticide, plastics and resins, synthetic rubber, aviation 
fuel, pharmaceuticals, dye, explosives, PCB gasoline, tanning, 
flavors and perfumes, paints and coatings; nylon intermediates; 
food processing, photographic chemicals; as a solvent and a 
fuel additive; intermediate (25%); byproduct.

Colourless liquid.

Threshold Odour Concentration (T.O.C.):
0.516 mg/m3 = 0.160 ppm (Stockham et al. 1969)
43 mg/m3 = 13.3 ppm (Stockham et al. 1969)
1 - 300 ppm (Verschueren 1983)
4.68 ppm (Verschueren 1983)
1 ppm (Verschueren 1983)
60 ppm (Verschueren 1983, Summer 1971)
100 ppm (Verschueren 1983)
320 ppm (Verschueren 1983)
180 mg/m3 = 60 ppm (Verschueren 1983)
100.7 mg/m3 = 31.0 ppm (Verschueren 1983)
2.8 mg/m3 = 0.86 ppm (Verschueren 1983)
recognition: 105 - 210 mg/m3 (Leonardos 1969)

Population Identification Threshold 50 %: 2.14 ppm
Population Identification Threshold 100 %: 4.68 ppm
distinct odour: 310 mg/m3 = 90 ppm (Verschueren 1983).

Human odour perception: 3.0 mg/m3 = 1 ppm
Animal chronic exposure: adverse effect: 3.2 mg/m3
(Stern 1968).

Threshold odour concentration in water: 2 - 31 mg/l
(Fawell & Hunt 1988).

78.12

Relative volatility (nBuAc=1) = 6.91

Equilibrium distribution:
        mass %
air     99.34
water    0.65
solid    0.02
(Anon 1988).

Koc Woodburn silt loam:
31         (Chiou et al. 1983)
31.7 - 143 (Sabljic 1984)
83         (Kenaga 1980).

Benzene leaches in soil, passing through soil during bank 
infiltration (Green et al. 1981) (Piet & Morra 1983).

Photochemical reaction; estimated lifetime under photochemical
smog conditions in SE England: 28 hours (Verschueren 1983).

Gas-phase benzene will not be subject to direct photolysis but
will react with photochemically produced hydroxyl radicals with
a half-life of 13.4 days calculates using an experimental rate
constant for the reaction. 
The reaction time in polluted
atmospheres that contain nitrogen oxides or sulfur dioxide is
accelerated with the half-life being reported as 4-6 hours with
50% mineralization toCO2 in approximately 2 days. 
Products of
photooxidation include phenol, nitrophenols, nitrobenzene,
formic acid and peroxyacetal nitrate (Korte & Klein 1982).

Since gas-phase benzene or benzene dissolved in cyclohexane
does not absorb light of 290 nm or longer, it will not be
expected to directly photolyze in sunlight in these media.

However, shight shifts in wavelength of absorption might be
expected in more representative environmental media, such as
water; e.g., a half-life of 16.9 days was reported for
photolysis of benzene dissolved in deionized water saturated
with air exposed to sunlight (Howard & Durkin 1974) (Hustert
et al. 1981).

Photodegradation, which according to one experiment has a 
half-life of 17 days, could contribute to benzene's removal in 
situations of cold water, poor nutrients, or other conditions 
less conductive to microbial degradation (Hustert et al. 1981).

Hydrolysis is not a significant process for benzene (Lyman et 
al. 1982).

Biodegradation to CO2 in estuarine water:
Conc.          incubation    Degradation rate    Turnover
mg/l   Month   time (hr)     (mg/l/day) x 1000   time (days)
0.006  June    24            0.2                 30
0.012  June    24            0.26                46
0.024  June    24            0.33                75
(Verschueren 1983).

Biodegradation half-lives of 28 and 16 days were reported in
die-away for degradation of up to 3.2 µl/l benzene tests using
ground water and Lester river water, respectively, under
aerobic conditions (Vaishav 1986).

Complete biodegradtion in 16 days was reported under simulated
aerobic ground water conditions at 20°C (Delfino & Miles 1985).

If benzene is released to soil it will be subject to rapid
volatilization near the surface, and which does not evaporate
will be highly to very highly mobile in soil and may leach to
the ground water (Howard 1990).

The effective half-lives for volatilization without water
evaporation from soil to benzene uniformly distributed to 1 and
10 cm in soil were 7.2 and 38.4 days, respectively (Jury et al
1984).

Benzene may be subject to biodegradation based on reported
biodegradation of 24% and 47% of the initial 20 ppm benzene in
a base-rich para-brownish silt in 1 and 10 weeks, respectively
(Haider et al. 1974).

The estimated half-life for volatilization of benzene from a 
river 1 m deep flowing i m/sec with a wind velocity of 3 m/sec 
is estimated to be 2.7 hr at 20°C. 
It will not be expected to 
significantly addorb to sediment, bioconcentrate in aquatic 
organisms, or hydrolyze. 
It may be subject to biodegradation 
based on a reported biodegradation half-life of 16 has in an 
aerobic river die-away test (Wakeham et al. 1983).

Biodegradation:
39-41% by BOD (on the upward trend)
period: 14d
substance: 100 mg/l
sludge: 30 mg/l
(MITI 1992).

phenol
unidentified phenols * using pure cultures of microorganisms
(Smith & Rosazza 1974).

catecol
cis-1,2-dihydroxy-1,2-dihydrobenzene * using pure cultures of 
microorganisms (Gibson et al. 1968).

Confirmed to be biodegradable (Anon. 1987).

*-------------------------------------------------------------*
ENVIRONMENT    INITIAL CONC   REDOX-  TEMP   DEGRADATION  REF
               mg/l           COND.   °C     %/day
*-------------------------------------------------------------*
water          1 - 3        aerobic   20     100/16       a
water          1 - 3        aerobic   20       0/41       a
water            5          aerobic   25      49/7        b
water           10          aerobic   25      37/7        b
water (adapted)  5          aerobic   25     100/7        b
water (adapted) 10          aerobic   25     100/7        b
water          0.295        aerobic   -       92/17       c
groundwater    0.0041       aerobic   13     100/8        d
sludge         appr. 50     anaerob.  35       0/56       e
sludge         appr. 50     anaerob.  35       0/56       e
soil           0.613       methanogen 17      72/280      f
soil           0.613       methanogen 17     >99/840      f
sterile soil   0.613       methanogen 17       0/280      f
sterile soil   0.613       methanogen 17      30/840      f
*-------------------------------------------------------------*
a) Delfino & Miles 1985         d) Jamison et al. 1976
b) Tabak et al. 1981            e) Horowitz et al. 1982
c) Battermann 1984              f) Wilson et al. 1986
(Anon 1987b).

The half-life of benzene in estuarine water was 6 days (Lee &
Ryan 1979).

In a marine ecosystem biodegradation occurred in 2 days after
an application period of 2 days and 2 weeks in the summer and
spring, respectively, whereas no degradation occurred in winter
(Wakeham et al. 1983).

Benzene at 50 ppm was 90% degraded by industrial wastewater
seed incubated at 23 °C for 6 hours (Davis et al. 1981).

No information appears to be available with regard to the
gastrointestinal absorption of benzene, though a value of
around 40 - 50 % has been reported in several studies for
respiratory absorption in humans. 
Percutaneous absorption has
been demostrated to occur slowly in man and rhesus monkey.

Autoradiographic and pharmacokinetic studies have shown that
benzene has an affinity for nervous and adipose tissue, with
high levels also found in the bone marrow, liver, spleen and
blood.

Benzene is metabolized primarily in the liver to phenol,
catechol, quinol and hydroxyquinol and subsequently to
conjugates of ester sulfates and glucuronides. 
In bone marrow,
phenol appears to be the major metabolite shortly after
exposure, though catechol and hydroquinone predominate
subsequently. 
It is thought that secondary metabolites of the
latter two compounds are probably responsible for the toxic
effects of bentzene in the bone marrow.

The elimination of benzene by the lungs has been reported to be
around 12 % of the retained dose in humans but up to 70 % in
the experimental animals. 
Excretion in the urine as free or
conjugated phenols accounts for 50 - 87 % of retained benzene
in humans, but only 23 % is elimated in this way by rodents 
(Fawell & Hunt 1988).

Based on the reported and estimated BCF, benzene will not
expected to bioconcentrate in aquatic organisms (Howard 1990).

Both epidemiological and animal studies have shown that 
pancytopenia is the most common effect of chronic exposure to 
benzene (Fawell & Hunt 1988).

Man:
severe toxic effects: 1500 ppm, 60 min
symptoms of illness: 500 ppm
unsatisfactory: 50 ppm
(Verschueren 1983).

There is good evidence that benzene can cause leukemia in man
and some indication that it does also in experimental animals.

This carcinogenic action of benzene also appears to be
consistent with that of tumour promotion. 
There is no evidence
of anyother benzene-related tumours, apart from zymbal gland
carcinomas and mammary carcinomas reported in one rat study
(Fawell & Hunt 1988).



Carcinogen (IARC).

Benzene has been reported to cause chromosomal abnormalities in 
vitro and in vivo in mammals, but has not yet been shown to be 
mutagenic in bacterial assays (Fawell & Hunt 1988).

Embryotoxicity through inhalation: CF-1 mice and New Zealand
white rabbit were exposed to 0 or 500 ppm of benzene to 7 hr
per day from days 6 through 15 (mice) and 6 through 18
(rabbits) of gestation. 
Little evidence of maternal toxicity
was seen in either species. 
Although some signs of embryonal
toxicity were observed in both mice and rabbits, a teratogenic
effect was not discerned in either spicies inhaling 500 ppm of
benzene (Verschueren 1983).

Benzene can cause retardation of foetal development at high
doses, but does not appear to be teratogenic (Fawell & Hunt 
1988).

Mexican axoloth (3 - 4 weeks after hatching): LC50 48 hr: 
370 mg/l; clawed toad (3 - 4 weeks after hatching) LC50 48 hr: 
190 mg/l (Slooff & Baerselman 1980).

Toxicity threshold (cell multiplication inhibition test):
bacteria (Pseudomonas putida): 92 mg/l (Bringmann & Kühn 1980a).

Removal/secondary treatment 44% - 100%,
removal percentages based upon data from continuous activated 
sludge biological treatment simulators (Howard 1991).

Herring and anchovy larvae (Clupea pallasi; Engraulis mordex):
35 - 45 ppm caused delay in development of eggs and produces
abnormal larvae; 10 - 35 ppm caused delay in development of
larvae; decrease in feeding and growth, and increase in
respiration (Verschueren 1983).

Toxicity threshold (cell multiplication inhibition test):
algae (Microcystis aeruginosa): > 1400 mg/l
(Bringmann & Kühn 1976).

green algae (Scenedesmus quadricauda): > 1400 mg/l
protozoa (Entosiphon sulcatum): > 700 mg/l
protozoa (Uronema parduczi): 486 mg/l
(Bringmann & Kühn 1980).

Chlorella vulgaris: 50 % reduction of cell numbers vs controls,
after 1 day incubation at 20 °C: at 525 ppm (Verschueren 1983).

Inhibition of photosynthesis of a freshwater, non axenic
uni-algal culture of Selenastrum capricornutum:
10 mg/l: 95 % carbon-14 fixation (vs. controls)
100 mg/l: 84 % carbon-14 fixation (vs. controls)
1000 mg/l: 5 % carbon-14 fixation (vs. controls)
(Verschueren 1983).

Ciliate (Tetrahymena pyriformis): 24 hr LC100: 12.8 mmol/l
(Schultz et al. 1978).

Minnows: min. lethal dose: 5 - 7 mg/l; 6 hr (McKee & Wolf 1963).

Young Coho salmon: no significant mortalities up to 10 ppm
after 96 hours in artificial sea water at 8 °C; mortality:
12/20 at 50 ppm after 24 up to 96 hours in artificial sea water
at 8 °C; mortality 30/30 at 100 ppm after 24 hours in
artificial sea water at 8 °C (Verschueren 1983).

LC50, 48hr, >320 mg/l, Tubificidae
LC50, 48hr, 100 mg/l, Chironomus gr. thummi
LC50, 48hr, >320 mg/l, Erpobdella octoculata
LC50, 48hr, 230 mg/l, Lymnaea stagnalis
LC50, 48hr, 74 mg/l, Dugesia cf. lugubris
LC50, 48hr, 34 mg/l, Hydra oligactis
LC50, 48hr, 48 mg/l, Corixa punctata
LC50, 48hr, 10 mg/l, Ischura elegans
LC50, 48hr, 130 mg/l, Nemoura cinerea
LC50, 48hr, 34 mg/l, Cloeon dipterum
(Slooff 1983)

Manufacturing source: petroleum refinery; solvent recovery
plant; coal tar distillation; coal processing; coal coking
(Anon. 1975).

The major source of atmospheric benzene is vehicle echausts.

Benzene is found in many foodstuffs and beverages at
significant levels. 
Exposure to waterborne benzene at current
levels is almost insignificant in comparison to exposure from
other sources (Fawell & Hunt 1988).