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

CAS number: 1321–65–9

NIOSH REL: 5 mg/m3 TWA [skin]

Current OSHA PEL: 5 mg/m3 TWA [skin]

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 5 mg/m3 TWA [skin]

Description of substance: Colorless to pale-yellow solid with an aromatic odor.

LEL: . . Unknown

Original (SCP) IDLH*: Unknown [*Note: “Effective” IDLH = 50 mg/m3 — see discussion below.]

Basis for original (SCP) IDLH: No toxicological data are available concerning the effects of acute exposures to trichloronaphthalene. For this draft technical standard, however, an analogy with other chloronaphthalenes was used, and the respirators were selected on the basis of the assigned protection factor afforded by each device up to 10 ´ the OSHA PEL of 5 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


Animal data: Rats and mice exposed to a single 2-hour exposure to 200 mg/m3 had no adverse effects [Shakahnovskava 1953].

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

Revised IDLH: Unknown [Unchanged]

Basis for revised IDLH: Due to a lack of relevant acute toxicity data, the IDLH for trichloronaphthalene remains "Unknown." The "most protective" respirators will continue to be recommended for concentrations exceeding 50 mg/m3 based on being 10 times the NIOSH REL and OSHA PEL of 5 mg/m3 (10 is an assigned protection factor for respirators and was used during the Standards Completion Program for deciding when the "most protective" respirators should be used for trichloronaphthalene). This may be a conservative value due to the lack of relevant acute toxicity data for workers at concentrations above 50 mg/m3 for trichloronaphthalene.


1. Shakahnovskava FB [1953]. Toxicology of chlorinated naphthalenes. Farmakol Toksikol 16:43-47 (translated).

Page last reviewed: December 4, 2014