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

CAS number: 110–91–8

NIOSH REL: 20 ppm (70 mg/m3) TWA, 30 ppm (105 mg/m3) STEL [skin]

Current OSHA PEL: 20 ppm (70 mg/m3) TWA [skin]

1989 OSHA PEL: 20 ppm (70 mg/m3) TWA, 30 ppm (105 mg/m3) STEL [skin]

1993-1994 ACGIH TLV: 20 ppm (71 mg/m3) TWA [skin]

Description of substance: Colorless liquid with a weak, ammonia- or fish-like odor.

LEL :. . 1.4% (10% LEL, 1,400 ppm)

Original (SCP) IDLH: 8,000 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the statement by ILO [1972] that 1 of 6 rats died following an 8-hour exposure to 8,497 ppm. The chosen IDLH is also supported by Patty [1963] who reported that 1 hour was the maximum survival time for rats exposed to the saturated vapor (9,200 ppm); exposure of 6 rats to 8,000 ppm (calculated) for 8 hours resulted in no deaths [Smyth et al. 1954].

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50




Time Adjusted 0.5-hr


Derived value
Rat ILO 1972 LC17: 8,497 ----- 8 hr 21,243 ppm (2.5) 2,124 ppm
Mouse Toksikol Nov Prom Khim Vesh 1966 365 ----- 2 hr 584 ppm (1.6) 58 ppm

Lethal dose data:

Species Reference Route LD50




Adjusted LD Derived value
Mammal Bazarova & Miguekina 1975 oral 1,220 ----- 2,359 ppm 236 ppm
Mouse Patel et al. 1985 oral 525 ----- 1,015 ppm 102 ppm
Rat Smyth et al. 1954 oral 1,050 ----- 2,030 ppm 203 ppm

Other animal data: No deaths resulted from exposures of 6 rats to 8,000 ppm for 8 hours [Smyth et al. 1954].

Human data: Irritation of the nose has been reported after a 1-minute exposure to 12,000 ppm and coughing started after 1.5 minutes; it was suggested that this concentration would probable be intolerable for long periods [Shea 1939].

Revised IDLH: 1,400 ppm [LEL]

Basis for revised IDLH: Based on health considerations and acute inhalation toxicity data in humans [Shea 1939] and animals [ILO 1972; Smyth et al. 1954], a value of 2,000 ppm would have been appropriate for morpholine. However, the revised IDLH for morpholine is 1,400 ppm based strictly on safety considerations (i.e., being 10% of the lower explosive limit of 1.4%).


1. Bazarova LA, Miguekina NV [1975]. Comparative evaluation of the toxicity, hazard and effect of piperidine and morpholine. Toksikol Nov Prom Khim Vesh 14:90-95 (in Russian).

2. ILO [1972]. Morpholine. In: Encyclopaedia of occupational health and safety. 2nd ed. Vol. II (L-Z). Geneva, Switzerland: International Labour Office, pp. 915-916.

3. Patel VK, Venkatakrishna-Bhatt H, Patel NB, Jindal MN [1985]. Pharmacology of new glutarimide compounds. Biomed Biochim Acta 44(5):795-803.

4. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., pp. 2203-2204.

5. Shea TE Jr [1939]. The acute and sub-acute toxicity of morpholine. J Ind Hyg Toxicol 21(7):236-245.

6. Smyth HF Jr, Carpenter CP, Weil CS, Pozzani UC [1954]. Range-finding toxicity data: list V. AMA Arch Ind Hyg Occup Med 10:61-68.

7. Toksikol Nov Prom Khim Vesh [1966]; 8:60-70 (in Russian).