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
|j|/_4-- _
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 MMJ
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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