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General Description

Synonyms: o-DCB; 1,2-Dichlorobenzene; ortho-Dichlorobenzene; o-Dichlorobenzol

OSHA IMIS Code Number: 0867

Chemical Abstracts Service (CAS) Registry Number: 95-50-1

NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) Identification Number: CZ4500000

Department of Transportation Regulation Number (49 CFR 172.101) and Guide: 1591 152

NIOSH Pocket Guide to Chemical Hazards, o-Dichlorobenzene: chemical description, physical properties, potentially hazardous incompatibilities, and more

Exposure Limits

OSHA Permissible Exposure Limit (PEL):

General Industry: 29 CFR 1910.1000 Table Z-1 - 50 ppm, 300 mg/m3 Ceiling

Construction Industry: 29 CFR 1926.55 Appendix A - 50 ppm, 300 mg/m3 Ceiling

Maritime: 29 CFR 1915.1000 Table Z-Shipyards - 50 ppm, 300 mg/m3 Ceiling

American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV): 25 ppm, 150 mg/m3 TWA; 50 ppm, 301 mg/m3 STEL; Appendix A4 - Not Classifiable as a Human Carcinogen

National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL): 50 ppm, 300 mg/m3 Ceiling

Health Factors

Carcinogenic Classification:

International Agency for Research on Cancer (IARC): Group 3, not classifiable as to its carcinogenicity to humans [134 KB PDF, 54 pages]

NIOSH Immediately Dangerous To Life or Health Concentration (IDLH): 200 ppm

Potential Symptoms: Irritation of eyes, nose; cough, sore throat; dizziness, fatigue, headache, nausea; unconsciousness; liver, kidney damage; skin blisters; INGES. ACUTE: Burning sensation; nausea, vomiting, diarrhea

Health Effects: Irritation-Eye, Nose, Throat, Skin---Marked (HE14); Liver damage (HE4); Clastogen (HE2)

Affected Organs: Eyes, skin, respiratory system, liver, kidneys


  1. Urinary metabolites of o-dichloro-benzene include 4,5-dichlorocatechol, 3,4-dichlorocatechol, 2,3-dichlorophenol, and 3,4-dichlorophenol and their conjugates.
  2. The urinary conjugates, 2,3-dichloro-phenylmercapturic acid and 3,4-dichloro-phenylmercapturic acid, were reported to have mean excretion half-lives of 5.3 and 5.9 hours, respectively, in eight volunteers.
  3. The hepatotoxicity of o-dichlorobenzene may be due to production of reactive metabolites, possibly epoxides, which bind covalently to proteins and DNA, as well as to oxidative stress from the intracellular depletion of reduced glutathione (GSH).
  4. Chromosome studies of laboratory workers six months after they were accidentally exposed to o-dichlorobenzene showed four times as many aberrations (single and double strand chromosome breaks) as a control group performing comparable work elsewhere.
  5. Although a case of chloracne was recently attributed to low-level exposure to o-dichlorobenzene, chloracne was not mentioned as one of the symptoms in any of 26 accidentally exposed lab workers.
  6. EPA's oral reference dose (daily oral exposure likely to be without an appreciable risk of deleterious effects during a lifetime) of o-dichlorobenzene is 0.09 mg/kg/day.

Literature Basis:

  • NIOSH Pocket Guide to Chemical Hazards: o-Dichlorobenzene.
  • International Chemical Safety Cards (WHO/IPCS/ILO): 1,2-Dichlorobenzene.
  • U.S. EPA Integrated Risk Information System: 1,2-Dichlorobenzene (CASRN 95-50-1).
  • Hissink, A.M., Van Ommen, B., Krüse, J. and Van Bladeren, P.J.: A physiologically based pharmacokinetic (PB-PK) model for 1,2-dichlorobenzene linked to two possible parameters of toxicity. Toxicol. Appl. Pharmacol. 145(2): 301-310, 1997.
  • Kumagai, S. and Matsunaga, I.: Relations between exposure to o-dichlorobenzene and concentrations of urinary metabolites. J. Occup. Health 39(2): 124-129, 1997.
  • McDougal, J.N., Grabau, J.H., Dong, I., Mattie, D.R. and Jepson, G.W.: Inflammatory damage to skin by prolonged contact with 1,2-dichlorobenzene and chloropentafluorobenzene. Microsc. Res. Tech. 37(3): 214-220, 1997.
  • Pohanish, R.P. (editor): Dichlorobenzenes. In, Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens, Fourth Ed., Vol. 1. Norwich, NY: Noyes Publications, William Andrew Publishing, 2002, pp. 799-804.
  • Violante, F.S., Milani, S., Malenchini, G. and Barbieri, A.: Chloracne due to o-dichlorobenzene in a laboratory worker. Contact Dermatitis 52(2): 108, 2005.
  • Zapata-Gayon, C., Zapata-Gayon, N. and Gonzalez-Angulo, A.: Clastogenic chromosomal aberrations in 26 individuals accidentally exposed to ortho dichlorobenzene vapors in the National Medical Center in Mexico City. Arch. Environ. Health 37(4): 231-235, 1982.
  • Zenser, L.-P., Lang, A. and Knecht, U.: N-Acetyl-S-(dichlorophenyl)cysteines as suitable biomarkers for the monitoring of occupational exposure to 1,2-dichlorobenzene. Int. Arch. Occup. Environ. Health 69(4): 252-254, 1997.

Date Last Revised: 11/07/2005

Monitoring Methods used by OSHA

Primary Laboratory Sampling/Analytical Method (SLC1):

  • sampling media: Charcoal Tube (100/50 mg sections, 20/40 mesh)
    analytical solvent: Carbon Disulfide
    minimum time: 15 Minutes
    maximum flow rate: 0.2 L/min (Ceiling)
    current analytical method: Gas Chromatography; GC/FID
    method reference: NIOSH Analytical Method (NIOSH 1003 [113 KB PDF, 7 pages])
    method classification: Partially Validated

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