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Chemical Sampling Information |
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| Trimethylbenzene (mixed isomers) |
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General Description
Isomers and Synonyms: Trimethyl benzene; 1,2,3-Trimethylbenzene; 1,2,4-Trimethylbenzene; 1,3,5-Trimethylbenzene; Hemimellitene; Pseudocumene; Mesitylene; Methylxylene; Diesel Exhaust Component
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 (RTECS) Identification Number: DC3220000, DC3300000 , DC3325000 , & OX6825000
Department of Transportation Regulation Number (49 CFR 172.101) and Guide: 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: chemical description, physical properties, potentially hazardous incompatibilities, and more
Exposure Limits
OSHA Permissible Exposure Limit (PEL) for Construction Industry: 29 CFR 1926.55 Appendix A -- 25 ppm, 120 mg/m3 TWA (PEL listed under Trimethyl benzene)
OSHA Permissible Exposure Limit (PEL) for Maritime: 29 CFR 1915.1000 Table Z-Shipyards -- 25 ppm, 120 mg/m3 TWA (PEL listed under Trimethyl benzene)
American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV): 25 ppm, 123 mg/m3 TWA
National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL): 25 ppm, 125 mg/m3 TWA
Health Factors
Potential symptoms: Irritation of eyes, skin, respiratory tract; cough, sore throat, chronic bronchitis; headache, dizziness, drowsiness, confusion, fatigue, feeling of nervous tension; nausea, vomiting; dry skin.
Health Effects: Irritation - Eye, Nose, Throat, Skin---Moderate (HE15) Cumulative CNS effects (HE7); Anemia (HE12)
Affected organs: Eyes, skin, respiratory system, CNS, blood, liver
Notes:
- Among the trimethylbenzene isomers in gasoline, 1,2,4-trimethylbenzene is the most abundant (>3.0%). Second most abundant is the 1,3,5-isomer at approximately 1.0%, and least is the 1,2,3-isomer at approximately 0.75%.
- Metabolism of trimethylbenzene occurs primarily via hydroxylation, followed by dimethylbenzoic acid formation and/or conjugation reactions.
- Due to interindividual variation in urinary excretion of single isomers of dimethylhippuric acid (DMHA, a glycine conjugate of dimethylbenzoic acid isomers), 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.
- In 2001, the California Department of Health Services established a notification level for 1,2,4- and 1,3,5-trimethylbenzene of 0.33 milligrams per liter of drinking water.
- In pregnant rats exposed to individual trimethylbenzenes by inhalation on gestational days 6-20, the NOAEL for maternal toxicity (decrease in body weight gain) of 1,3,5-trimethylbenzene (mesitylene) was 100 ppm and for 1,2,4-trimethylbenzene (pseudocumene) was 300 ppm. The NOAEL for developmental toxicity (low fetal body weight) was 300 ppm for each isomer.
Date Last Revised: 11/30/2005
Literature Basis:
- International Chemical Safety Cards (WHO/IPCS/ILO): Trimethyl benzene (mixed isomers).
- California Department of Health Services-Drinking Water Program: Drinking Water Notification Levels, 2005.
- No author: Identifying hydrocarbons. In, Forensics Primer: An Introduction to Environmental Forensic Geochemistry. ZymaX Forensics, Division of ZymaX™ Envirotechnology, Inc.
- 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.
- Pohanish, R.P. (editor): Trimethyl Benzenes. In, Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens, Fourth Ed., Vol. 2. Norwich, NY: Noyes Publications, William Andrew Publishing, 2002, pp. 2277-2279.
- Saillenfait, A.M., Gallissot, F., Sabate, J.P. and Morel, G.: Developmental toxicity of two trimethylbenzene isomers, mesitylene and pseudocumene, in rats following inhalation exposure. Food Chem. Toxicol. 43(7): 1055-1063, 2005.
Monitoring Methods used by OSHA
Laboratory Sampling/Analytical Method:
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sampling media: Charcoal Tube (100/50 mg sections, 20/40 mesh)
analytical solvent: Carbon Disulfide
maximum volume: 10 Liters maximum flow rate: 0.1 L/min
current analytical method: Gas Chromatography; GC/FID
method reference: OSHA Analytical Method (OSHA PV2091)
method classification: Partially Validated
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