United States
Environmental Protection
Agency
Office of Water
4601
EPA 811-F-95-004b-T
October 1995
National Primary Drinking
Water Regulations
Benzene
CHEMICAL/ PHYSICAL PROPERTIES
CAS NUMBER: 71-43-2
COLOR/ FORM/ODOR: Clear, colorless
aromatic liquid; highly flammable
M.P.: 5.5° C B.P.: 80.1° C
VAPOR PRESSURE: 100 mm Hg at 26.1 ° C
OCTANOL/WATER PARTITION (Kow):
LogKow = 2.13
DENSITY/SPEC. GRAV.: 0.8787 at 15° C
SOLUBILITIES: 1.8 g/L of water at 25° C;
Slightly soluble in water;
SOIL SORPTION COEFFICIENT: Koc estimated
at 98; high to very high mobility in soil
ODOR/TASTE THRESHOLDS: Taste threshold
in water is 0.5 to 4.5 mg/L
BIOCONCENTRATION FACTOR: 3.5 to 4.4 in
fish; not expected to bioconcentrate in
aquatic organisms.
HENRY'S LAW COEFFICIENT:
0.0053 atm-cu m/mole;
TRADE NAMES/SYNONYMS: Benzol 90,
Pyrobenzol, Polystream, Coal naphtha,
Phene
DRINKING WATER STANDARDS
MCLG: Zero
MCL: 0.005 mg/L
HAL: 1 to 10 day: 0.2 mg/L
Longer-term: 0.2 mg/L
HEALTH EFFECTS SUMMARY
Acute: Acute exposure to high levels of benzene
produces central nervous system (CMS) effects and
death. At lower levels, above the MCL, mild CMS effects
appear to be concentration dependent and rapidly re-
versible. Other effects include immune system depres-
sion and bone marrow toxicity leading to aplastic anemia.
Drinking water levels which are considered "safe" for
short-term exposures: For a 10 kg (22 Ib.) child consum-
ing 1 liter of water per day: upto a ten-day exposure to 0.2
mg/L.
Chronic: Benzene has the potential to cause chromo-
somal aberrations in people who are chronically exposed
at levels above the MCL.
Cancer: Benzene has the potential to cause cancer
from a lifetime exposure at levels above the MCL.
USAGE PATTERNS
Production of benzene in the USA in 1993 was over 12
yillion Ibs.
Used for' printing & lithography, paint, rubber, dry
cleaning, adhesives & coatings, detergents, extraction
and rectification, preparation and use of inks in the
graphic arts industries, as a thinner for paints and as a
degreasing agent. In the tire industry and in shoe
factories, benzene is used extensively.
Used primarily as a raw material in the synthesis of
styrene (polystyrene plastics and synthetic rubber), phe-
nol (phenolic resins), cyclohexane (nylon), aniline, ma-
leic anhydride (polyester resins), alkylbenzenes (deter-
gents), chlorobenzenes, and other products used in the
production of drugs, dyes, insecticides, and plastics.
In future, coal will increasingly replace petroleum &
Toxic RELEASE INVENTORY -
RELEASES TO WATER AND LAND:
1987 TO 1993
TOTALS (in pounds)
Water
583,210
Top Releases by State*
TX 1,446
AL 199,892
LA 138,268
CO 0
NM 0
IL
Major Industries
Petroleum refining 141,876
Industrial chemicals 103,239
Steelworks, blast furn. 146,594
Alkalies, chlorine 150,934
Land
1,566,900
1,136,681
0
4,413
40,793
38,699
34,110
1,240 777
287,305
21,022
988
* Water/Land totals only include facilities with releases
greater than a certain amount - usually 1000 to 10,000 Ibs.
October 1995
Technical Version
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natural gas as a source of hydrocarbons both for fuel &
petrochemicals. Processes such as USA Steel
Corporation's Clean Coke process, which yields 38%
coke & 20% chemical by-products compared to 73%
coke & 2% chemical by-products in conventional coking
technology, should soon be used commercially. New
coking, liquefaction, & gasification processes for coal are
all potential sources of benzene.
RELEASE PATTERNS
Benzene will enter the atmosphere primarily from
fugitive emissions and exhaust connected with its use in
gasoline. Another important source is emissions associ-
ated with its production and use as an industrial interme-
diate. In addition, there are discharges into water from
industrial effluents and losses during spills. Benzene is
also released from its indirect production in coke ovens;
from nonferrous metal manufacture, ore mining, wood
processing, coal mining and textile manufacture. Al-
though most public drinking water supplies are free of
benzene or contain <0.3 ppb, exposure can be very high
from consumption of contaminated sources drawn from
wells contaminated by leaky gasoline storage tanks,
landfills, etc..
From 1987 to 1993, according to the Toxics Release
Inventory, releases of benzene to water totalled 583,210
Ibs. Releases to land totalled 1,566,900 Ibs. As indicated
in the Table below, these releases were primarily from
petroleum refining industries, with the greatest releases
occuring in Texas and Alabama.
ENVIRONMENTAL FATE
If benzene is released to soil, it will be subject to rapid
volatilization near the surface and that which does not
'evaporate will be highly to very highly mobile in the soil
and may leach to groundwater. It 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 soil in 1 and 10 weeks, respectively. It may
be subject to biodegradation in shallow, aerobic
groundwaters, but probably not under anaerobic condi-
tions.
If benzene is released to water, it will be subject to rapid
volatilization; the half-life for evaporation in a wind-wave
tank with a moderate wind speed of 7.09 m/secwas 5.23
hrs; the estimated half-life for volatilization of benzene
from a model river one meter deep flowing 1 m/sec with
a wind velocity of 3 m/sec is estimated to be 2.7 hrs at 20
degC.
It will not be expected to significantly adsorb to sedi-
ment, bioconcentrate in aquatic organisms or hydrolyze.
It may be subject to biodegradation based on a re-
ported biodegradation half-life of 16 days in an aerobic
river die-away test. In a marine ecosystem biodegrada-
tion occurred in 2 days after an acclimation period of 2
days and 2 weeks in the summer and spring, respec-
tively, whereas no degradation occurred in winter. Ac-
cording to one experiment, benzene has a half-life of 17
days due to photodegradation which could contribute to
benzene's removal in situations of cold water, poor
nutrients, or other conditions less conductive to microbial
degradation.
If benzene is released to the atmosphere, it will exist
predominantly in the vapor phase. Gas-phase benzene
will not be subject to direct photolysis but it will react with
photochemically produced hydroxyl radicals with a half-
life of 13.4 days calculated using an experimental rate
constant for the reaction. The reaction time in polluted
atmospheres which contain nitrogen oxides or sulfur
dioxide is accelerated with the half-life being reported as
4-6 hours. Products of photooxidation include phenol,
nitrophenols, nitrobenzene, formic acid, and peroxyacetyl
nitrate.
Benzene is fairly soluble in water and is removed from
the atmosphere in rain. The primary routes of exposure
are inhalation of contaminated air, especially in areas
with high traffic, and in the vicinity of gasoline service
stations and consumption of contaminated drinking wa-
ter.
OTHER REGULATORY INFORMATION
MONITORING:
FOR GROUND/SURFACE WATER SOURCES:
INITIAL FREQUENCY- 4 quarterly samples every 3 years
REPEAT FREQUENCY- Annually after 1 year of no detection
TRIGGERS - Return to Initial Freq. if detect at > 0.0005 mg/L
ANALYSIS:
REFERENCE SOURCE
EPA 600/4-88-039
METHOD NUMBERS
502.2; 524.2
TREATMENT:
BEST AVAILABLE TECHNOLOGIES
Granular Activated Charcoal and Packed Tower Aeration
FOR ADDITIONAL INFORMATION:
4 EPA can provide further regulatory and other general information:
• EPA Safe Drinking Water Hotline - 800/426-4791
* Other sources of toxicological and environmental fate data include:
• Toxic Substance Control Act Information Line - 202/554-1404
Toxics Release Inventory, National Library of Medicine - 301/496-6531
• Agency for Toxic Substances and Disease Registry - 404/639-6000
October 1995
Technical Version
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