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

CAS number: 93-76-5

NIOSH REL: 10 mg/m3 TWA

Current OSHA PEL: 10 mg/m3 TWA

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 10 mg/m3 TWA

Description of substance: Colorless to tan, odorless, crystalline solid.

LEL :. . Unknown

Original (SCP) IDLH*: Unknown [*Note: “Effective” IDLH = 5,000 mg/m3 — see discussion below.]

Basis for original (SCP) IDLH: According to ACGIH [1971], “the toxicity of this compound appears to be similar to the somewhat better known 2,4-D. According to Rowe and Hymas [1954], the oral LD50 values fall in a range of 300 to 1,000 mg/kg for rats, mice, guinea pigs, and rabbits. Chronic exposure is not necessarily more hazardous. Drill and Hiratzka [1953] found that there were no deaths among dogs treated with 2, 5, or 10 mg/kg/day of 2,4,5-T (5 days/week for 13 weeks); some deaths occurred at 20 mg/kg/day. There are no reports of illness from occupational exposure. It appears that the TLV of 10 mg/m3 is justified on the basis of extrapolation from animal feeding studies and extensive use experience.” Based on the toxicological data cited above, 2,4,5-T is a relatively nontoxic compound. Because data on acute inhalation toxicology are not available for this substance and to be consistent with the IDLHs selected for similar, relatively nontoxic compounds, 5,000 mg/m3 (i.e., 500 ´ the OSHA PEL of 10 mg/m3) has been chosen as the concentration above which only the “most protective” respirators are permitted.

Short-term exposure guidelines: None developed


Lethal dose data:

Species Reference Route LD50




Adjusted LD Derived value
G. pig AAPCO 1966 oral 381 ----- 2,667 mg/m3 267 mg/m3
Rat Bailey & White 1965 oral 300 ----- 2,100 mg/m3 210 mg/m3
Hamster Grant 1979 oral 425 ----- 2,975 mg/m3 298 mg/m3
Mouse Senczuk & Pogorzelska 1980 oral 242 ----- 1,694 mg/m3 169 mg/m3

Other animal data: It has been reported that there were no deaths among dogs treated with 2, 5, or 10 mg/kg/day of 2,4,5-T (5 days/week for 13 weeks); some deaths occurred at 20 mg/kg/day [Drill and Hiratzka 1953].

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

Revised IDLH: 250 mg/m3

Basis for revised IDLH: No inhalation toxicity data are available on which to base an IDLH for 2,4,5-T. Therefore, the revised IDLH for 2,4,5-T is 250 mg/m3 based on acute oral toxicity data in animals [AAPCO 1966; Bailey and White 1965; Grant 1979; Senczuk and Pogorzelska 1980]. This may be a conservative value due to the lack of relevant acute inhalation toxicity data for workers.


1. AAPCO [1966]. Pesticide chemicals official compendium. Topeka, KS: Association of American Pesticide Control Officials, Inc., p. 965.

2. ACGIH [1971]. 2,4,5-T (2,4,5 trichlorophenoxyacetic acid). In: Documentation of the threshold limit values for substances in workroom air. 3rd ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, p. 242.

3. Bailey GW, White JL [1965]. Herbicides: a compilation of their physical, chemical, and biological properties. Residue Reviews 10:97-102.

4. Drill VA, Hiratzka T [1953]. Toxicity of 2,4-dichlorophenoxyacetic acid and 2,4,5-trichloro-phenoxyacetic acid. AMA Arch Ind Hyg Occup Med 7:61-67.

5. Grant WF [1979]. The genotoxic effects of 2,4,5-T. Mutat Res 65:83-110.

6. Rowe VK, Hymas TA [1954]. Summary of toxicological information on 2,4-D and 2,4,5-T type herbicides and an evaluation of the hazards to livestock associated with their use. Am J Vet Res 15(57):622-629.

7. Senczuk W, Pogorzelska H [1980]. Budowa chemiczna a toksykodynamiczne wlasciwosci pochodnych kwasow fenoksykarboksylowych. Roczniki Panstwowego Zakladu Higieny 31(4):373-377 (in Polish).

Page last reviewed: December 4, 2014