Terphenyl (o-, m-, p-isomers)

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

CAS number: 26140–60–3 (mixed isomers)

NIOSH REL: 5 mg/m3 (0.5 ppm) CEILING

Current OSHA PEL: 9 mg/m3 (1 ppm) CEILING

1989 OSHA PEL: 5 mg/m3 (0.5 ppm) CEILING

1993-1994 ACGIH TLV: 5 mg/m3 (0.53 ppm) CEILING

Description of substance: Colorless or light-yellow solid.

LEL : . Unknown

Original (SCP) IDLH*: Unknown [*Note: “Effective” IDLH = 900 mg/m3 — see discussion below.]

Basis for original (SCP) IDLH: According to Testa and Masi [1964], workers have been exposed to 280 mg/m3 without adverse effect. For this draft technical standard, however, respirators have been selected on the basis of the assigned protection factor afforded by each device up to 100 ´ the OSHA PEL of 9 mg/m3 (i.e., 900 mg/m3); only the “most protective” respirators are permitted for use in concentrations exceeding 900 mg/m3. This is a concentration unlikely to occur because of its low vapor pressure.

Short-term exposure guidelines: None developed


Lethal dose data:

Species Reference Route LD50




Adjusted LD Derived value
Mixed isomers Mouse Zhenjiang & Gengliang 1986 oral 13,200 ----- 92,400 mg/m3 9,240 mg/m3
o-Isomer Rat Cornish et al. 1962 oral 1,900 ----- 13,300 mg/m3 1,330 mg/m3
m-Isomer Rat Cornish et al. 1962 oral 2,400 ----- 16,800 mg/m3 1,680 mg/m3
p-Isomer Rat Cornish et al. 1962 oral >10,000 ----- >70,000 mg/m3 >7,000 mg/m3
p-Isomer Rat NRC 1953 oral ----- 500 3,500 mg/m3 350 mg/m3

Other animal data: In 30-day feeding studies involving doses of 250 or 500 mg/kg/day, rats fed o-terphenyl showed elevated liver and kidney weight ratios, rats fed m-terphenyl showed elevated kidney weight ratios only, and rats fed p-terphenyl showed no elevation in liver or kidney weight ratios [Cornish et al. 1962].

Human data: It has been reported that workers have been exposed to 280 mg/m3 without adverse effect [Testa and Masi 1964].

Revised IDLH: 500 mg/m3

Basis for revised IDLH: Based on health considerations and acute toxicity data in animals [NRC 1953], a value of about 2,000 mg/m3 would have been appropriate for terphenyl. However, the revised IDLH for terphenyl is 500 mg/m3 based on being 100 times the NIOSH REL of 5 mg/m3 (100 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 terphenyl).


1. Cornish HH, Bahor RE, Ryan RC [1962]. Toxicity and metabolism of ortho-, meta-, and para-terphenyls. Am Ind Hyg Assoc J 23:372-378.

2. NRC [1953]. Relationship between chemical structure and toxic action on rats. National Academy of Sciences, National Research Council, Chemical-Biological Coordination Center, Review 5:26.

3. Testa C, Masi G [1964]. Determination of polyphenyls in working environments of organic reactors by spectrophotometric methods. Anal Chem 36(12):2284-2287.

4. Zhenjiang L, Gengliang W [1986]. Development of hydroterphenyl for use as high temperature organic heat carrier. Shiyou Huagong (Petrochemical Technology) 15:305-308 (in Chinese).

Page last reviewed: December 4, 2014