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Boric acid

General Description

  • Synonyms: Basilit B; Boracic acid; Borofax; Boron trihydroxide; Orthoboric acid; Trihydroxyborone
  • OSHA IMIS Code Number: B141
  • Chemical Abstracts Service (CAS) Registry Number: 10043-35-3
  • NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) Identification Number: ED4550000
  • Chemical Description and Physical Properties:
    • odorless, colorless crystals or white powder
    • molecular weight: 61.84
    • molecular formula: BH3O3
    • melting point: 171°C

Exposure Limits

  • American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV): 2 mg/m3* TWA; 6 mg/m3* STEL; Appendix A4 - Not Classifiable as a Human Carcinogen *Inhalable fraction, see Appendix C, paragraph A. (TLV listed under Borate compounds, Inorganic)

Health Factors

  • Potential Symptoms: Irritation of eyes, skin, respiratory tract; cough, sore throat; skin rash; kidney damage, diminished urinary output; metabolic acidosis; Acute ingestion: Abdominal pain, nausea, vomiting, diarrhea; neurologic symptoms (headache, tremulousness, irritability, delirium, seizures); skin redness on palms, soles and buttocks followed by peeling.
  • Health Effects: Irritation-Eyes, Nose, Throat, Skin---Mild (HE16); Acute toxicity (CNS, kidney) (HE4); Potential developmental and reproductive hazards (HE5).
  • Affected Organs: Eyes, skin, respiratory system, kidneys, CNS (In animals: testes)
  • Notes:
    1. In animals, developmental toxicity included a decreased fetal weight and increased incidence of "short rib XIII," whereas reproductive toxicity included inhibition of spermatogenesis and testicular atrophy. Boron accumulates in bone, but not in testes.
    2. Boric acid is excreted unchanged in the urine with a plasma half-life in the range of 12 to 27 hours in humans. Boron in bone, however, remained elevated eight months after the end of exposure of rats to boric acid in their feed. The role in these processes of a recently characterized borate transporter in cell membranes remains to be elucidated.
    3. A study of workers exposed to boric acid and boron oxide dust (which reacts with water to form boric acid) concluded that significant symptoms of upper respiratory tract and eye irritation occurred at dust levels less than 10 mg/m3.
    4. EPA's oral reference dose (daily oral exposure likely to be without an appreciable risk of deleterious effects during a lifetime) of boron is 0.2 mg/kg/day (based mainly on animal studies with boric acid).
    5. The FDA has a 5% maximum limit for boric acid concentrations in consumer goods applied to the skin and hair (e.g., cosmetics and personal care products).
    6. The California Department of Health Services established a notification level for boron of 1 milligram per liter of drinking water.
  • Literature Basis:
    • California Department of Health Services-Drinking Water Program: Drinking Water Notification Levels, 2005.
    • U.S. EPA Integrated Risk Information System: Toxicological Review of Boron and Compounds (CAS 7440-42-8), 2004 (EPA 635/04/052).
    • Chapin, R.E., et al.: The effects of dietary boron on bone strength in rats. Fundam. Appl. Toxicol. 35(2): 205-215, 1997.
    • Garabrant, D.H., Bernstein, L., Peters, J.M. and Smith, T.J.: Respiratory and eye irritation from boron oxide and boric acid dusts. J. Occup. Med. 26(8): 584-586, 1984.
    • Ku, W.W. and Chapin, R.E.: Mechanism of the testicular toxicity of boric acid in rats: in vivo and in vitro studies. Environ. Health Perspect. 102(Suppl. 7): 99-105, 1994.
    • Moore, J.A., et al.: An assessment of boric acid and borax using the IEHR evaluative process for assessing human developmental and reproductive toxicity of agents. Reprod. Toxicol. 11(1): 123-160, 1997.
    • Pahl, M.V., Culver, B.D. and Vaziri, N.D.: Boron and the kidney. J. Ren. Nutr. 15(4): 362-370, 2005.
    • Park, M., Li, Q., Shcheynikov, N., Zeng, W. and Muallem, S.: NaBC1 is a ubiquitous electrogenic Na+-coupled borate transporter essential for cellular boron homeostasis and cell growth and proliferation. Mol. Cell 16(3): 331-341, 2004.
    • Pohanish, R.P. (editor): Boron, Boric Acid and Borax. In, Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens, Fourth Ed., Vol. 1. Norwich, NY: Noyes Publications, William Andrew Publishing, 2002, pp. 355-357.
  • Date Last Revised: 12/06/2005

Monitoring Methods used by OSHA

Primary Laboratory Sampling/Analytical Method (SLC1):
  • tared 37-mm diameter low-ash polyvinyl chloride filter
  • maximum volume: 960 Liters
  • maximum flow rate: 2.0 L/min
  • current analytical method: Gravimetric
  • method reference: OSHA Analytical Method (OSHA PV2121)
  • method classification: Partially Validated
  • note: OSHA personnel can obtain tared sampling media from the Salt Lake Technical Center (SLTC).
  • note: If the sample is considered PNOR, it is analyzed gravimetrically. When analysis of this compound is requested, an elemental analysis for boron is performed and the results are reported as the compound.
Wipe Sampling Method:
  • Whatman smear tab
  • analytical solvent: Deionized water

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