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Oxalic Acid

General Description

  • Synonyms: Oxalic acid dihydrate; Ethanedioic acid
  • OSHA IMIS Code Number: 1970
  • Chemical Abstracts Service (CAS) Registry Number: 144-62-7
  • NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) Identification Number: RO2450000
  • NIOSH Pocket Guide to Chemical Hazards, Oxalic Acid: chemical description, physical properties, potentially hazardous incompatibilities, and more

Exposure Limits

  • OSHA Permissible Exposure Limit (PEL):
  • American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV): 1 mg/m3 TWA; 2 mg/m3 STEL
  • National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL): 1 mg/m3 TWA; 2 mg/m3 STEL

Health Factors

  • NIOSH Immediately Dangerous To Life or Health Concentration (IDLH): 500 mg/m3
  • Potential Symptoms: Eye, mucous membrane, skin irritation; eye burns; local pain; cyanosis (blue lips, fingernails, skin); shock, collapse, convulsions; kidney damage; pulmonary edema (may be delayed); INGES: Sore throat, burning sensation, abdominal pain, vomiting; diarrhea and bloody stools; drowsiness; numbness of fingers and toes.
  • Health Effects: Irritation-Eyes, Nose, Throat, Skin---Marked (HE14); Lung edema (HE11); Acute systemic effects (HE4)
  • Affected Organs: Eyes, skin, respiratory system, kidneys
  • Notes:
    1. Oxalic acid is a normal minor metabolite of carbohydrates (e.g., fructose), glycine, and vitamin C, but it is produced in toxic amounts after ethylene glycol intoxication.
    2. Kidney dialysis patients may be particularly susceptible to oxalate-induced nephrotoxicity and neurotoxicity.
    3. Prolonged barbiturate sleeping time in rats treated with star fruit juice was attributed to its high oxalate content, indicating a possible inhibition of some drug-metabolizing cytochrome P-450s in the liver.
    4. Calcium oxalate crystals, which occur in certain plants, may cause irritant contact dermatitis in agricultural workers.
  • Literature Basis:
    • NIOSH Pocket Guide to Chemical Hazards: Oxalic Acid.
    • International Chemical Safety Cards (WHO/IPCS/ILO): Oxalic acid.
    • Chen, C.L., Chou, K.J., Wang, J.S., Yeh, J.H., Fang, H.C. and Chung, H.M.: Neurotoxic effects of carambola in rats: the role of oxalate. J. Formos. Med. Assoc. 101 (5): 337-441, 2002.
    • Pohanish, R.P. (editor): Oxalic Acid. In, Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens, Fourth Ed., Vol. 2. Norwich, NY: Noyes Publications, William Andrew Publishing, 2002, pp. 1763-1765.
    • Rofe, A.M., James, H.M., Bais, R., Edwards, J.B. and Conyers, R.A.: The production of (14C) oxalate during the metabolism of (14C) carbohydrates in isolated rat hepatocytes. Aust. J. Exp. Biol. Med. Sci. 58 (2): 103-116, 1980.
    • Salinas, M.L., Ogura, T. and Soffchi, L.: Irritant contact dermatitis caused by needle-like calcium oxalate crystals, raphides, in Agave tequilana among workers in tequila distilleries and agave plantations. Contact Dermatitis 44(2): 94-96, 2001.
    • Tse, K.C., et al.: Star fruit intoxication in uraemic patients: case series and review of the literature. Intern. Med. J. 33 (7): 314-316, 2003.
  • Date Last Revised: 10/28/2004

Monitoring Methods used by OSHA

Laboratory Sampling/Analytical Method:
  • glass fiber filter (37-mm, open face)
  • maximum volume: 100 Liters
  • maximum flow rate: 1.0 L/min (TWA)
  • current analytical method: Ion Chromatography; IC
  • method reference: OSHA Analytical Method (PV2115)
  • method classification: Partially Validated
Wipe Sampling Method:
  • glass fiber filter (37-mm)
  • analytical solvent: Deionized water

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