Lithium hydride

CAS number: 7580–67–8

NIOSH REL: 0.025 mg/m³ TWA

Current OSHA PEL: 0.025 mg/m³ TWA

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 0.025 mg/m³ TWA

Description of substance: Odorless, off-white to gray, translucent, crystalline mass or white powder.

LEL :. . Noncombustible Solid

Original (SCP) IDLH*: 55 mg/m³ [*Note: "Effective" IDLH = 50 mg/m³ -- see discussion below.]

Basis for original (SCP) IDLH: The chosen IDLH of 55 mg/m³ is based on the statement by Patty [1963] that "animals exposed to 5 to 55 mg/m³ for periods up to 4 hours experienced intense irritation, coughing and sneezing, inflammation of the conjunctiva, partial sloughing of mucosal epithelium of trachea, and some pulmonary emphysema. No mortality occurred (however) as a result of any level of exposure [Spiegl et al. 1956]." Spiegl et al. [1956], however, found that 2 of 10 animals died from a 4-hour exposure at 22 mg/m³; Spiegl et al. [1956] stated, though, that the mortality among rats, rabbits, guinea pigs, and mice exposed to levels of from 5 to 55 mg/m³ for 1 day was low and probably unrelated to the exposure. A statement by ACGIH [1971] (i.e., that industrial experience has shown that a reduction in atmospheric concentration to 25 µg/m³ is required to attain just a sneezing level), indicates that 22 mg/m³ is too low to be the IDLH. Respirators have been selected on the basis of the assigned protection factor afforded by each device up to 2,000 ´ OSHA PEL of 0.025 mg/m³ (i.e., 50 mg/m³); only the "most protective" respirators are permitted for use in concentrations exceeding 50 mg/m³.

Short-term exposure guidelines: None developed

ACUTE TOXICITY DATA:

Lethal concentration data:

Species	Reference	LC50	LCLo	Time	Adjusted 0.5-hr LC (CF)	Derived value
Rat	Spiegl et al. 1956	LC20: 22 mg/m3	-----	4 hr	44 mg/m3 (2.0)	4.4 mg/m3

Human data: It has been recommended that 0.5 mg/m³ is the maximum tolerable concentration for brief period of exposure [AIHA 1964].

Revised IDLH: 0.5 mg/m3 Basis for revised IDLH: The revised IDLH for lithium hydride is 0.5 mg/m3 based on acute inhalation toxicity data in humans [AIHA 1964].

REFERENCES:

1. ACGIH [1971]. Lithium hydride. In: Documentation of the Threshold Limit Values for Substances in Workroom Air, 3rd edition. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, p. 147.

2. AIHA [1964]. Lithium hydride. In: Hygienic guide series. Akron, OH: American Industrial Hygiene Association.

3. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., p. 1070.

4. Spiegl CJ, Scott JK, Steinhardt H, Leach LJ, Hodge HC [1956]. Acute inhalation toxicity of lithium hydride. AMA Arch Ind Health 14:468-470.