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

CAS number: 100–00–5

NIOSH REL: None established; NIOSH considers p-nitrochlorobenzene to be a potential occupational carcinogen as defined by the OSHA carcinogen policy [29 CFR 1990] that may be absorbed through the skin.

Current OSHA PEL: 1 mg/m3 TWA [skin]

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 0.64 mg/m3 (0.1 ppm) TWA [skin]

Description of substance: Yellow, crystalline solid with a sweet odor.

LEL: . . . Unknown

Original (SCP) IDLH: 1,000 mg/m3

Basis for original (SCP) IDLH: No data on acute inhalation toxicity are available on which to base an IDLH for p-nitrochlorobenzene. The chosen IDLH, therefore, is based on an analogy with nitrobenzene, which has an IDLH of 200 ppm. [Note: A concentration of 200 ppm nitrobenzene is equivalent to about 1,000 mg/m3 p-nitrochlorobenzene.]

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50 LCLo Time Adjusted 0.5-hr


Derived value
Cat Watrous & Schultz 1950 164 mg/m3 ----- 7 hr 393 mg/m3 (2.4) 39 mg/m3

Lethal dose data:

Species Reference Route LD50




Adjusted LD Derived value
Rat Back et al. 1972 oral 812 ----- 5,684 mg/m3 568 mg/m3
Mouse Back et al. 1972 oral 1,414 ----- 9,898 mg/m3 990 mg/m3
Mouse Izmerov et al. 1982 oral 440 ----- 3,080 mg/m3 308 mg/m3
Rat Sziza & Magos 1959 oral 420 ----- 2,940 mg/m3 294 mg/m3

Other animal data: Exposures of cats and guinea pigs to 87 mg/m3 for 8 hours/day for 6 weeks resulted in methemoglobinemia and slight anemia [Watrous and Schultz 1950].

Human data: Workers exposed intermittently for 0.5 to 1 hour over many months to concentrations ranging from 7 to 400 mg/m3 (average of 90 mg/m3) had only vague complaints of tiredness, loss of appetite, headache, and afternoon fatigue [Watrous and Schultz 1950]. Because of the strong and disagreeable odor, these workers voluntarily wore respiratory protection when exposed to the higher concentrations [Watrous and Schultz 1950].

Revised IDLH: 100 mg/m3

Basis for revised IDLH: The revised IDLH for p-nitrochlorobenzene is 100 mg/m3 based on subchronic inhalation toxicity data in workers [Watrous and Schultz 1950] and animals [Watrous and Schultz 1950]. This may be a conservative value due to the lack of relevant acute toxicity data for workers exposed to concentrations above 100 mg/m3. [Note: NIOSH recommends as part of its carcinogen policy that the "most protective" respirators be worn for p-nitrochlorobenzene at any detectable concentration.]


1. Back KC, Thomas AA, MacEwen JD [1972]. Reclassification of materials listed as transportation health hazards. Wright-Patterson Air Force Base, OH: 6570th Aerospace Medical Research Laboratory, Report No. TSA-20-72-3, pp. A-270 to A-271.

2. Izmerov NF, Sanotsky IV, Sidorov KK [1982]. Toxicometric parameters of industrial toxic chemicals under single exposure. Moscow, Russia: Centre of International Projects, GKNT, p. 92.

3. Sziza M, Magos I [1959]. Toxikologische untersuchung einiger in der ungarischen industrie zur anwendung gelangenden aromatischen nitroverbindungen. Arch Gewerbepath Gewerbehyg 17:217-226 (in German).

4. Watrous RM, Schultz HN [1950]. Cyclohexylamine, p-chloronitrobenzene, 2-aminopyridine: toxic effects in industrial use. Ind Med Surg 19:317-320.