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Chemical Sampling Information (CSI)
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General Description

Synonyms: CI-2; Combustion Improver-2; Manganese tricarbonylmethylcyclopentadienyl; 2-methylcyclopentadienyl manganese tricarbonyl; MMT

OSHA IMIS Code Number: 1767

Chemical Abstracts Service (CAS) Registry Number: 12108-13-3

Other Chemical Abstracts Service (CAS) Registry Numbers: 7439-96-5 (Manganese compounds (as Mn))

NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) Identification Number: OP1450000

NIOSH Pocket Guide to Chemical Hazards, Methyl cyclopentadienyl manganese tricarbonyl (as Mn): chemical description, physical properties, potentially hazardous incompatibilities, and more

Exposure Limits

OSHA Permissible Exposure Limit (PEL):

General Industry: 29 CFR 1910.1000 Z-1 Table -- 5 mg/m3 Ceiling (PEL listed under Manganese compounds (as Mn))

Construction Industry: 29 CFR 1926.55 Appendix A -- 5 mg/m3 Ceiling (PEL listed under Manganese compounds (as Mn))

Maritime: 29 CFR 1915.1000 Table Z-Shipyards -- 5 mg/m3 Ceiling (PEL listed under Manganese compounds (as Mn))

American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV): 0.2 mg/m3 TWA; Skin; (TLV listed under 2-Methylcyclopentadienyl manganese tricarbonyl, as Mn)

National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL): 0.2 mg/m3 TWA; Skin

Health Factors

Potential Symptoms: Eye irritation; dizziness, giddiness, nausea, headache; cough, sore throat, labored breathing (dyspnea); in animals: tremor, severe clonic spasms, lassitude (weakness, exhaustion), slow respiration; lung, liver, kidney injury; SKIN ABS: skin redness, burning sensation.

Health Effects: Acute CNS effects (HE4); Cumulative liver and kidney damage (HE3) Irritation-Eye---Moderate (HE15)

Affected Organs: Eyes, CNS, liver, kidneys


  1. The acute injection of MMT into rats causes pulmonary edema localized to the lung alveoli, which is thought to be produced by a toxic metabolite formed in the lungs, possibly by cytochrome P450 2B1. It is not known whether this bioactivation occurs in human lungs.
  2. Compounds emitted from the vehicular combustion of MMT as a gasoline additive include manganese oxide, phosphate and sulfate. Studies in rats report that these compounds, upon inhalation, can be taken up by olfactory nerve endings in the nose and retrogradely transported back into the brain, causing endogenous manganese levels in some areas (e.g., globus pallidus, striatum) to be more than doubled.
  3. It has been suggested that the convulsive effect of MMT in mice is due to an inhibitory effect at the GABA(A) receptor-linked chloride channel.

Literature Basis:

  • NIOSH Pocket Guide to Chemical Hazards: Methyl cyclopentadienyl manganese tricarbonyl (as Mn).
  • International Chemical Safety Cards (WHO/IPCS/ILO): Methylcyclopentadienyl manganese tricarbonyl.
  • Blanchard, K.T., Clay, R.J. and Morris, J.B.: Pulmonary activation and toxicity of cyclopentadienyl manganese tricarbonyl. Toxicol. Appl. Pharmacol. 136(2): 280-288, 1996.
  • Fishman, B.E., McGinley, P.A. and Gianutsos, G.: Neurotoxic effects of methylcyclopentadienyl manganese carbonyl (MMT) in the mouse: basis of MMT-induced seizure activity. Toxicology 45(2): 193-201, 1987.
  • Normandin, L., et al. : Manganese distribution in the brain and neurobehavioral changes following inhalation exposure of rats to three chemical forms of manganese. Neurotoxicology 25(3): 433-441, 2004.
  • Pohanish, R.P. (editor): Manganese, Tricarbonyl Methylcyclopentadienyl. In, Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens, Fourth Ed., Vol. 2. Norwich, NY: Noyes Publications, William Andrew Publishing, 2002, pp. 1450-1451.
  • Verschoyle, R.D., Wolf, C.R. and Dinsdale, D.: Cytochrome P450 2B isozymes are responsible for the pulmonary bioactivation and toxicity of butylated hydroxytoluene, O,O,S-trimethylphosphorothioate and methylcyclopentadienyl manganese tricarbonyl. J. Pharmacol. Exp. Ther. 266(2): 958-963, 1993.

Date Last Revised: 06/10/2005

Monitoring Methods used by OSHA

Primary Laboratory Sampling/Analytical Method (SLC1):

  • sampling media: XAD-2 Tubes (80/40 mg sections)
    maximum volume: 10 Liters   
    maximum flow rate: 0.2 L/min
    current analytical method: Gas Chromatography; GC/ECD
    method reference: OSHA Salt Lake Technical Center In-House File
    method classification: Not Validated

Articles: "Analyst", February 1992, Vol 117, pp 161-164.

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