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Trimethylbenzene (mixed isomers)

General Description

  • Synonyms: Trimethyl benzene; 1,2,3-Trimethylbenzene; 1,2,4-Trimethylbenzene; 1,3,5-Trimethylbenzene; Hemimellitene; Pseudocumene; Mesitylene; Methylxylene
  • OSHA IMIS Code Number: 2505
  • (IMIS Name History: Trimethylbenzene ONLY prior to 11/20/06)

  • Chemical Abstracts Service (CAS) Registry Number: 25551-13-7
  • Related Chemical Abstracts Service (CAS) Registry Number: 95-63-6 (1,2,4-Trimethylbenzene); 108-67-8 (1,3,5-Trimethylbenzene); 526-73-8 (1,2,3-Trimethylbenzene)

  • NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) Identification Number: DC3220000, DC3300000 (1,2,3-Trimethylbenzene), DC3325000 (1,2,4-Trimethylbenzene), and OX6825000 (1,3,5-Trimethylbenzene)
  • Department of Transportation Regulation Number (49 CFR 172.101) and Emergency Response Guidebook: 2325 129 (1,3,5-Trimethylbenzene)
  • NIOSH Pocket Guide to Chemical Hazards - 1,2,3-Trimethylbenzene, 1,2,4-Trimethylbenzene, and 1,3,5-Trimethylbenzene: Physical description, chemical properties, potentially hazardous incompatibilities, and more

Exposure Limits

Exposure Limit Limit Values HE Codes Health Factors and Target Organs
OSHA Permissible Exposure Limit (PEL) - General Industry Not established
OSHA PEL - Construction Industry
See 29 CFR 1926.55 Appendix A
25 ppm
(120 mg/m3) TWA
HE7 Central nervous system changes, including nervousness, tension, anxiety
HE9 Asthmatic bronchitis
HE12 Blood changes
OSHA PEL - Shipyard Employment
See 29 CFR 1915.1000 Table Z-Shipyards
25 ppm
(120 mg/m3) TWA
HE7 Central nervous system changes, including nervousness, tension, anxiety
HE9 Asthmatic bronchitis
HE12 Blood changes
National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL) 25 ppm
(125 mg/m3)
HE7 Central nervous system changes, including nervousness, tension, anxiety
HE11 Respiratory failure
HE15 Skin irritation
American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) (2001) 25 ppm
(125 mg/m3) TWA
HE7 Central nervous system depression
HE9 Asthmatic bronchitis
HE12 Blood dyscrasias
HE15 Eye, nose, and respiratory irritation
CAL/OSHA PELs 25 ppm
(125 mg/m3) TWA
HE7 Central nervous system depression
HE9 Asthmatic bronchitis
HE12 Blood dyscrasias
HE15 Eye, nose, and respiratory irritation

National Toxicology Program (NTP) carcinogenic classification: Not listed

International Agency for Research on Cancer (IARC): Not listed

U.S. Environmental Protection Agency (EPA) carcinogenic classification: Not listed

EPA Inhalation Reference Concentration (RfC): Not established

Agency for Toxic Substances and Disease Registry (ATSDR) Inhalation Minimal Risk Level (MRL): Not established

Notes on Other Potential Health Effects and Hazards

  1. Explosive vapor/air mixtures may be formed above 44°C (NIOSH/IPCS 2002).
  2. Due to interindividual variation in urinary excretion of single isomers of dimethylhippuric acid (DMHA), it has been suggested that using the sum of DMHA isomer excretion may more closely reflect exposure to trimethylbenzene than monitoring any single isomer in the urine (Järnberg et al. 1997).
  3. Significant body burden accumulation is expected following repeated occupational exposures to trimethylbenzene (Jones et al. 2006).

Date last revised: 09/06/2012

Literature Basis

  • ACGIH: Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) - Trimethyl Benzene Isomers. 2001.
  • Järnberg, J., Ståhlbom, B., Johanson, G. and Löf, A.: Urinary excretion of dimethylhippuric acids in humans after exposure to trimethylbenzenes. Int. Arch. Occup. Environ. Health 69(6): 491-497, 1997.
  • Jones, K., Meldrum, M., Baird, E., Cottrell, S., Kaur, P., Plant, N., Dyne, D., Cocker, J.: Biological monitoring for trimethylbenzene exposure - a human volunteer study and a practical example in the workplace. The Annals of Occupational Hygiene. 50 (6): 593-598, 2006.
  • NIOSH: Recommendations for Occupational Safety and Health - Compendium of Policy Documents and Statements. January 1992.
  • NIOSH/IPCS: International Chemical Safety Cards - Trimethyl Benzene (Mixed Isomers). June 3, 2002.

Monitoring Methods used by OSHA

Laboratory Sampling/Analytical Method:
  • Charcoal Tube (100/50 mg sections, 20/40 mesh)
  • analytical solvent: (99:1) Carbon Disulfide:N,N-Dimethylformamide
  • maximum volume: 12 Liters
  • maximum flow rate: 0.05 L/min
  • current analytical method: Gas Chromatography; GC/FID
  • method reference: OSHA Analytical Method (OSHA 1020)
  • method classification: Fully Validated
  • Diffusive Sampler (SKC 575-002 Passive Sampler)
  • analytical solvent: (99:1) Carbon Disulfide:N,N-Dimethylformamide
  • minimum time: < or = 240 minutes (TWA)
  • minimum time: > 15 minutes
  • current analytical method: Gas Chromatography; GC/FID
  • method reference: OSHA Analytical Method (OSHA 1020)
  • method classification: Fully Validated

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