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Chemical Sampling Information (CSI)
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General Description

Synonyms: (2,2,2-Trichloro-1-hydroxyethyl) dimethylphosphonate; (2,2,2-Trichloro-1-hydroxyethyl) phosphonic acid dimethyl ester; Trichlorphon

OSHA IMIS Code Number: T116

Chemical Abstracts Service (CAS) Registry Number: 52-68-6

NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) Identification Number: TA0700000

Chemical Description and Physical Properties:

white crystals
molecular weight: 257.4
vapor pressure: < 0.01 Pa @ 20°C
molecular formula: C4H8Cl3O4P
melting point: 83-84°C

Exposure Limits

American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV): 1 mg/m3 TWA - Inhalable fraction; see Appendix C, paragraph A. Appendix A4 - Not Classifiable as a Human Carcinogen; BEIA: see BEI® for Acetylcholinesterase Inhibiting Pesticides (TLV listed under Trichlorphon)

Health Factors

Carcinogenic Classification:

International Agency for Research on Cancer (IARC): Group 3, not classifiable as to its carcinogenicity to humans

Potential Symptoms: Miosis, blurring of vision, ocular pain; rhinorrhea; headache; chest tightness, labored breathing; excessive salivation; slurred speech; nausea, vomiting, abdominal cramps, diarrhea; sweating, muscle weakness, twitching, loss of muscle coordination; giddiness, dizziness; convulsions

Health Effects: Cholinesterase inhibition (HE6); Potential teratogen (HE5)

Affected Organs: Respiratory system, cardiovascular system, CNS, eyes, skin, blood cholinesterases


  1. OSHA does not have a PEL for trichlorfon.
  2. Although trichlorfon is a much more potent inhibitor of acetylcholinesterase than of neuropathy target esterase, a few cases of a delayed neuropathy following recovery from acute accidental ingestion have been reported. Occupational exposure includes both inhalation and dermal absorption.
  3. Trichlorfon underwent clinical trials under the generic drug name metrifonate (ProMed) for the treatment of Alzheimer's dementia, but was withdrawn by the sponsor after several cases involving muscle weakness and respiratory paralysis were reported. Metrifonate has also been used as an anthelmintic drug to treat schistosomiasis.
  4. Studies with human volunteers demonstrated some conversion of metrifonate to dichlorvos in the body and the urinary excretion of dichloroacetic acid as one of the metabolites. Dichlorvos is the active form of the chemical for inhibiting cholinesterases.
  5. Trichlorfon is teratogenic in animals and was associated with a cluster of cases of Down syndrome (trisomy 21) in a village where pregnant women ate fish contaminated with high levels (100 mg/kg) of organophosphate. Other studies have shown that trichlorfon can cause errors in chromosome segregation during meiosis.

Literature Basis:

  • International Chemical Safety Cards (WHO/IPCS/ILO): Trichlorphon.
  • Cukurcam, S., Sun, F., Betzendahl, I., Adler, I.D. and Eichenlaub-Ritter, U.: Trichlorfon predisposes to aneuploidy and interferes with spindle formatin in in vitro maturing mouse oocytes. Mutat. Res. 564(2): 165-178, 2004.
  • Czeizel, A.E., et al.: Environmental trichlorfon and cluster of congenital abnormalities. Lancet 341(8844): 539-542, 1993.
  • Dingemanse, J., Halabi, A., Kleinbloesem, C.H., Heinig, R. and Blume, H.: Pharmacokinetics and pharmacodynamics of the acetylcholinesterase inhibitor metrifonate in patients with renal impairment. Ther. Drug Monit. 21(3): 310-316, 1999.
  • Hu, X.H., Lu, Y.P., Xue, S.Z., Ling, Y.X. and Gu, X.Q.: Toxicity of dipterex: a field study. Br. J. Ind. Med. 43(6): 414-419, 1986.
  • King, C.H., et al.: Chemotherapy-based control of schistosomiasis haematobia. I. Metrifonate versus praziquantel in control of intensity and prevalence of infection. Am. J. Trop. Med. Hyg. 39(3): 295-305, 1988.
  • Pohanish, R.P. (editor): Trichlorfon. Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens, Fourth Ed., Vol. 2. Norwich, NY: Noyes Publications, William Andrew Publishing, 2002, pp. 2237-2239.
  • Vasilescu, C., Alexianu, M. and Dan, A.: Delayed neuropathy after organophosphorus insecticide (Dipterex) poisoning: a clinical, electrophysiological and nerve biopsy study. J. Neurol. Neurosurg. Psychiatry 47(5): 543-548, 1984.

Date Last Revised: 05/26/2005

Monitoring Methods used by OSHA

Primary Laboratory Sampling/Analytical Method (SLC1):

  • sampling media: OVS-2 Tube (270/100 mg sections XAD-2 preceded by 13 mm Glass Fiber Filter)
    analytical solvent: Toluene
    maximum volume: 400 Liters
    maximum flow rate: 1 L/min
    current analytical method: Gas Chromatography; GC/FPD
    method reference: OSHA (In-House File)
    method classification: Not Validated
    note: More than 100% was recovered from the sampling device. This needs to be investigated.