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Boron oxide

May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)

CAS number: 1303-86-2

NIOSH REL: 10 mg/m3 TWA

Current OSHA PEL: 15 mg/m3 TWA

1989 OSHA PEL: 10 mg/m3 TWA

1993-1994 ACGIH TLV: 10 mg/m3 TWA

Description of Substance: Colorless, semitransparent lumps or hard, white, odorless crystals.

LEL: Noncombustible Solid

Original (SCP) IDLH*: No Evidence [*Note: “Effective” IDLH = 7,500 mg/m3 — see discussion below.]

Basis for original (SCP) IDLH: No evidence exists in the available toxicological data that an acute exposure to a high concentration of boron oxide would impede escape or cause any irreversible health effects within 30 minutes. For this draft technical standard, therefore, respirators have been selected on the basis of the assigned protection factor afforded by each device. However, for some particulate substances for which no evidence of an IDLH exists, the determination of allowable respiratory protection based on protection factors may result in the assignment of respirators for concentrations that are not likely to be encountered in the occupational environment. Therefore, for all such particulate substances it has been arbitrarily determined that only the “most protective” respirators are permitted for use in concentrations exceeding 500 x the OSHA PEL; in the case of boron oxide, 500 x the OSHA PEL of 15 mg/m3 is 7,500 mg/m3.

Short-term exposure guidelines: None developed


Lethal dose data:

LL50 LCLo Derived
Species Reference Route (mg/kg) (mg/kg) Adjusted LD Value
Mouse Izmerov et al. 19825 oral 3,163 —– 22,141 mg/m3 2,214 mg/m3

Other animal data: Rats exposed for 6 hours/day, 5 days/week for 10 weeks to a concentration of 470 mg/m3 showed no signs of intoxication other than mild nasal irritation [Wilding et al. 1959].

Human data: None relevant for use in determining the revised IDLH.


  1. Izmerov NF, Sanotsky IV, Sidorov KK [1982]. Toxicometric parameters of industrial toxic chemicals under single exposure. Moscow, Russia: Centre of International Projects, GKNT, p. 27.
  2. Wilding JL, Smith WJ, Yevich P, Sicks ME, Ryan SG, Punte CL [1959]. The toxicity of boron oxide. Am Ind Hyg Assoc J 20:284-289.