May 1994

Documentation for Immediately Dangerous To Life or Health 

Concentrations (IDLHs)

Toluene-2,4-diisocyanate

CAS number: 584–84–9

NIOSH REL: None established; NIOSH considers toluene-2,4-diisocyanate to be a potential 

occupational carcinogen as defined by the OSHA carcinogen policy [29 CFR 1990].

Current OSHA PEL: 0.02 ppm (0.14 mg/m ) CEILING

1989 OSHA PEL: 0.005 ppm (0.04 mg/m ) TWA, 0.02 ppm (0.15 mg/m ) STEL

1993-1994 ACGIH TLV: 0.005 ppm (0.036 mg/m ) TWA, 0.02 ppm (0.14 mg/m ) STEL

Description of substance: Colorless to pale-yellow solid or liquid (above 71°F) with a sharp, 

pungent odor.

LEL: . . 0.9% (10% LEL, 900 ppm)

Original (SCP) IDLH: 10 ppm

Basis for original (SCP) IDLH: For this draft technical standard, it is assumed that 

individuals who have developed a sensitivity to TDI will not be allowed to work in a TDI 

atmosphere. In these sensitized individuals, even concentrations below the OSHA PEL are 

capable of triggering the allergic response. Therefore, the IDLH has not been based on data 

obtained from the exposures of individuals or animals sensitized to TDI. The chosen IDLH is 

based on the 4-hour LC50 values for different species of animals, ranging from 9.7 to 13.9 ppm 

[Duncan et al. 1962 cited by AIHA 1967 and NIOSH 1973].

Short-term exposure guidelines: None developed

ACUTE TOXICITY DATA:

Lethal concentration data:

Species Reference

LC50

(ppm)

LCLo

(ppm) Time Adjusted 0.5-hr

LC (CF) Derived value

Rat Duncan et al. 1962 14 ----- 4 hr 28 ppm (2.0) 2.8 ppm

3

3 3

3 3

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G. pig

Mouse

Rabbit

Duncan et al. 1962

Duncan et al. 1962

Duncan et al. 1962

13.9 

9.7 

11 

-----

-----

-----

4 hr

4 hr

4 hr

28 ppm (2.0)

19 ppm (2.0)

22 ppm (2.0)

2.8 ppm

1.9 ppm

2.2 ppm

Other animal data: RD50 (mouse), 0.39 ppm [Alarie 1981].

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

Revised IDLH: 2.5 ppm

Basis for revised IDLH: The revised IDLH for toluene-2,4-diisocyanate is 2.5 ppm based 

on acute inhalation toxicity data in animals [Duncan et al. 1962]. Since in sensitized 

individuals, even concentrations below the OSHA PEL are capable of triggering the allergic 

response, the revised IDLH has not been based on data obtained from the exposures of 

individuals or animals sensitized to TDI. [Note: NIOSH recommends as part of its carcinogen 

policy that the "most protective" respirators be worn for toluene-2,4-diisocyanate at any 

detectable concentration.]

REFERENCES:

1. AIHA [1967]. Toluene diisocyanate. In: Hygienic guide series. Am Ind Hyg Assoc J 28:90-94.

2. Alarie Y [1981]. Dose-response analysis in animal studies: prediction of human responses. 

Environ Health Perspect 42:9-13.

3. Duncan B, Scheel LD, Fairchild EJ, Killens R, Graham S [1962]. Toluene diisocyanate 

inhalation toxicity: pathology and mortality. Am Ind Hyg Assoc J 23:447-456.

4. NIOSH [1973]. Criteria for a recommended standard: toluene diisocyanate. Cincinnati, OH: 

U.S. Department of Health, Education, and Welfare, Public Health Service, National Institute 

for Occupational Safety and Health, DHEW Publication No. HSM 73-11022.

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