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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(ppm) LCLo(ppm) Time Adjusted 0.5-hrLC (CF) 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(mg/kg) LDLo(mg/kg) 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).