United States
Environmental Protection
Agency
Office of Water
4601
EPA 811-F-95-004e-T
October 1995
National Primary Drinking
Water Regulations
o-Dichlorobenzene
CHEMICAL/ PHYSICAL PROPERTIES
CAS NUMBER: 95-50-1
DENSITY/SPEC. GRAV: 1.31 g/L at 20° C
SOLUBILITY: 0.14 g/L of water at 25° C;
Slightly soluble in water
COLOR/ FORM/ODOR:
Colorless liquid with pleasant, aromatic SOIL SORPTION COEFFICIENT:
ocjor Koc measured at 280 to 320 for loam
soils; low to moderate mobility in soil
M.P.: -17° C B.P.: 180.5° C
ODOR/TASTE THRESHOLDS: N/A
VAPOR PRESSURE: 1.47 mm Hg at 25° C
OCTANOL/WATER PARTITION (Kow):
Log Kow = 3.38
BlOCONCENTRATION FACTOR.'
BCF measured at 270 to 560 in fish;
expected to bioconcentrate in aquatic
organisms.
HENRY'S LAW COEFFICIENT:
. 0.0012 atm-cu m/mole at 20° C
TRADE NAMES/SYNONYMS:
ortho Dichlorobenzol, Dilantin,
Dowtherm E, Chloroben, Dilatin DB
DRINKING WATER STANDARDS
MCLG: 0.6 mg/L
MCL: 0.6 mg/L
HAL: 1 to 10 day: 9 mg/L
Longer-term: 9 mg/L
HEALTH EFFECTS SUMMARY
Acute: EPA has no data on the acute toxicity of o-
dichlorobenzene which is relevant to the drinking water
cellaneous uses, 5%.
The greatest use of o-dichlorobenzene is as a chemi-
cal intermediate for making agricultural chemicals, pri-
marily herbicides.
Other present and past uses include: solvent forwaxes,
gums, resins, wood preservatives, paints; insecticide for
termites and borers; in making dyes; as a coolant, de-
odorizer, degreaser.
I^UMlCAl.
Drinking water levels which are considered "safe" for
short-term exposures: Fora 10-kg (22 Ib.) child consum-
ing 1 liter of water per day: upto a 7-year exposure to 9
mg/L.
Chronic: EPA has found o-dichlorobenzene to poten-
tially cause damage to the nervous system, liver, kidneys
and blood cells from long-term exposure at levels above
the MCL.
Cancer: There is inadequate evidence to state whether
or not o-dichlorobenzene has the potential to cause
cancer from lifetime exposures in drinking water.
USAGE PATTERNS
Production of o-dichlorobenzene has decreased since
the 1970's: from 54.6 million Ibs. in 1975 to an estimated
43 million Ibs. in 1991. In 1987 it was estimated that
industries consumed o-dichlorobenzene as follows: Or-
ganic synthesis (mainly for herbicides), 90%; toluene
diisocyanate processing solvent, 5%; solvent and mis-
Toxic RELEASE INVENTORY -
RELEASES TO WATER AND LAND: 1987
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wafer
TOTALS (in pounds) 75,967
Top Five States*
NJ 19,602
WV 39,653
OR 7,260
SC 1,502
TX 1,418
Major Industries
Industrial Organics 15.416
Cyclic crudes, dyes 7,639
Alkalis, chlorine 38,029
Paper mills 7,260
Gum, wood chems. 250
TO 1993
1 MM«J
Land
171,663
165,661
0
0
4,628
1,000
98,092
67,418
0
0
4,378
* 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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RELEASE PATTERNS
1,2-Dichlorobenzene's use in manufacturing and sol-
vents may be significant sources of discharges into
water. Dichlorobenzenes also enter the water systems
(raw and contaminated water) from the use of 1,2-DCB as
a deodorant in industrial wastewater treatment. Chemi-
cal waste dump leachates and direct manufacturing
effluents are reported to be the major source of pollution
of the chlorobenzenes (including the dichlorobenzenes)
to Lake Ontario. The major source of 1,2-dichloroben-
zene emission to the atmosphere has been reported to
be solvent applications which may emit 25% of annual
production to the atmosphere.
From 1987 to 1993, according to EPA's Toxic Chemi-
cal Release Inventory, o-dichlorobenzene releases to
land and water totalled over 240,000 Ibs., of which nearly
172,000 Ibs. was to land. These releases were primarily
from organic chemicals manufacturing industries which
use it as an intermediate in herbicide production. The
largest releases occurred in New Jersey.
ENVIRONMENTAL FATE
If released to soil, 1,2-dichlorobenzene can be moder-
ately to tightly adsorbed. Experimental Koc values of 280
to 320 were determined in silt loam soils containing less
than 2 percent organic matter. In equilibrium batch stud-
ies, a relatively strong adsorption of 1,2-dichlorobenzene
to collected aquifer material was observed. However, the
detection of 1,2-dichlorobenzene in various groundwaters
indicates that leaching can occur. Volatilization from soil
surfaces may be an important transport mechanism. It is
possible that 1,2-dichlorobenzene will be slowly biode-
graded in soil under aerobic conditions. Chemical trans-
formation by hydrolysis, oxidation or direct photolysis are
not expected to occur in soil.
If released to water, adsorption to sediment will be a
major environmental fate process based upon extensive
monitoring data in the Great Lakes area and Koc values.
Analysis of Lake Ontario sediment cores has indicated
the presence and persistence of 1,2-dichlorobenzene
since before 1940. 1,2-Dichlorobenzene is volatile from
the water column with an estimated half-life of 4.4 hours
from a model river one meter deep flowing 1 m/sec with
a wind velocity of 3 m/sec at 20 deg C; adsorption to
sediment will attenuate volatilization. It has been sug-
gested that the three dichlorobenzene isomers may
undergo slow biodegradation in natural water. The di-
chlorobenzenes are not expected to be biotransformed in
anaerobic water conditions found in aquifers.
1,2-Dichlorobenzene is not expected to undergo sig-
nificant hydrolysis in environmental waters. It is reported
to be resistant towards oxidation by peroxy radicals in
aquatic media. In an isooctane solvent, 1,2-dichloroben-
zene absorbs virtually no radiation above 300 nm; there-
fore, direct photolysis in the environment should not be
significant.
If released to air, 1,2-dichlorobenzene will exist pre-
dominantly in the vapor-phase and will react.with photo-
chemically produced hydroxyl radicals at an estimated
half-life rate of 24 days in a typical atmosphere. Direct
photolysis in the troposphere is not expected to be
important. The detection of 1,2-dichlorobenzene in rain-
water suggests that atmospheric removal via wash-out is
possible.
In a study of a representative green alga, the Iog10
bioconcentration factors (BCF) for 1,2-dichlorobenzene
was 4.17. Experimental BCF values of 66-560 have been
reported and 1,2-dichlorobenzene has been detected in
trout from Lake Ontario. General population exposure to
1,2-dichlorobenzene may occur through oral consump-
tion of contaminated drinking water and food (particularly
fish) and through inhalation of contaminated air since 1,2-
dichlorobenzene has been detected in widespread am-
bient air.
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:
* 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
Page 2
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