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Toxicological information

Endpoint summary

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Administrative data

Description of key information

Across species, there are no adverse effects reported of acute inhalational exposure of propene, below concentrations of about 40% (688,000 mg/m3), when anaesthesia occurs. As the lower flammability limit for propene is 2% (34,400 mg/m3), the explosive range of airborne concentrations for propene is reached long before acute toxicity may be manifested.

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion
Endpoint conclusion:
no study available

Acute toxicity: via inhalation route

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Acute toxicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

The acute toxicity of propene has been studied in several non-guideline experimental animal studies and because of its potential use as an anaesthetic, there are also literature reports of the acute effects at high concentrations in humans. From the available data it is clear that there is no significant difference, across species, in the effects of propene or at the concentrations at which anaesthesia occurs (approx 40% propene: 688,000 mg/m3). Overall sufficient data exist to adequately assess the acute toxicity of propene.

In accordance with section 1.1 and 1.2 of REACH Annex XI, further testing does not appear scientifically necessary. The available animal studies (not performed in accordance with currently regulatory guidelines) in combination with the human data on acute inhalation toxicity are considered sufficient to cover the endpoint acute toxicity by inhalation.

Non-human studies

As early as 1924 it was known that propene had anaesthetic properties on cats: concentrations of 37% propene (637,000 mg/m3) in oxygen or air induced narcosis. Signs of anaesthesia occurred within 2 minutes of exposure at 70% propene (1200,000 mg/m3) but the cats recovered quickly with no apparent lasting effects (Brown, 1924). Additional acute inhalation studies were conducted with propene in cats. No toxic signs were observed when anaesthesia was maintained at propene concentrations of 20% to 31% (344,000 to 534,000 mg/m3). Some subtle effects were observed at concentrations ranging from 40% to 50% (688,000 to 861,000 mg/m3) and blood pressure decreases and rapid pulse occurred at a concentration of 70% (1,200,000 mg/m3). In summary, in this study cats were narcotised with propene concentrations of 688,000 to 861,000 mg/m3 and killed at concentrations of 1,200,000 to 1,380,000 mg/m3 (Brown, 1924).

Similarly, dogs could tolerate 50% (861,000 mg/m3) for hours without apparent depression of circulation or respiration, and the lethal dose in dogs (as in cats) was between 70 and 80% (1,200,000 to 1,380,000 mg/m3) (Halsey et al., 1926).

Acute rodent inhalation studies were conducted with propene (Halsey et al., 1926). In these studies propene concentrations of 30 to 40% (516,000 to 688,000 m/m3) were minimally anaesthetic whilst concentrations of 55 to 65% (947,000 to 1,120,000 m/m3) propene were lethal to mice. In a later group of rat studies, inhalation of 50, 000 ppm (86,000 mg/m3) for four hours also did not produce death or hepatotoxicity, unless the Sprague-Dawley rats were pre-treated with the PCB Arochlor 1254, in which case liver toxicity after Arochlor pre-treatment was manifested by increased liver weights, areas of macroscopic haemorrhage, and elevated liver enzymes (Osimitz and Conolly, 1985). NTP sighting-studies in rats and mice reported no effects following inhalation of up to the highest dose level tested 10,000 ppm (17,200 mg/m3) (half the lower explosive limit) propene for 14 days (NTP, 1985).

Although some of the earliest studies may not be reported to the standards expected today, nevertheless, the number of individual studies reporting a similar concentration for the onset of, and recovery from, anaesthesia together with the reported lack of side effects, across species, indicates a significant degree of correlation across all these weight of evidence studies. Furthermore the later group of studies reported by Osimitz and Conolly, and NTP, report results consistent with these earlier studies.

Human information

Khan and Riggs (1931) reported clinical studies with propene. In every case the anaesthesia was maintained for a period of a few minutes, and in the last experiment it lasted 16 minutes. The following series of exposures were reported: 40% propene (688,000 mg/m3), 20% oxygen, 40% nitrogen (experiments 1 and 2); 50% propene (862,000 mg/m3), 20% oxygen, 36% nitrogen (experiments 3,4 and 5); 75% propene (1,300,000 mg/m3), 25% oxygen (experiment 6), 50% propene (862,000 mg/m3), 20% oxygen, 30% nitrogen (experiments 7, 8 and 9). A human volunteer submitted himself to general anaesthesia two or three times each day for a total of 9 experiments at weekly intervals. The anaesthetic was administered two or more hours after a light meal.

The respirations were regular during inhalation of propene except in experiment 9 when subject ceased to breathe for 40-60 seconds, gasped and recovered consciousness. After the first few breaths, there was usually slight reddening of the eyelids with some lacrimation and flushing of the face. This was more marked with a high concentration of the anaesthetic. Sometimes coughing would occur from pharyngeal irritation. Just before the subject became unconscious there was noted contraction of the left leg and sometimes also flexion of the right leg which quickly subsided and the legs would remain entirely limp. Otherwise the progress of the anaesthesia was uneventful and gradual, and after an average period of eight inhalations anaesthesia was complete (pinching or sticking the subject with a pin indicated complete insensitiveness). Anaesthesia was achieved within 27.6 to 77.2 seconds of starting inhalation. There was no further lacrimation, nor any movement of skeletal muscles until the commencement of recovery. Recovery from the anaesthesia was prompt in each experiment (< 2 minutes). There was no feeling of nausea or vomiting during any of the experiments, and no feeling of any illness. Electrocardiography: the heart remained uninfluenced by the anaesthetic except for a diminution of sinus arrhythmia during complete narcosis. The pulse rate and the character of the pulse as well as the electrocardiogram remained unchanged.

Hasley (1926) reported 2 subjects anaesthetised to unconsciousness with 35 & 40% (602,000 -688,000 mg/m3) propene. Blood pressure was measured and symptoms described. Additionally shorter inhalations were undertaken and effects described. Recovery of the subjects from anaesthesia was rapid. Mild symptoms were reported, for example vomiting. Despite the high concentrations required for anaesthesia, there were no significant side effects reported.

Justification for classification or non-classification

In both human and animal studies propene is of low acute toxicity by the inhalation route with LC50 values exceeding the concentrations that would warrant classification under DSD or CLP.

Since propene is a gas at room temperature and pressure oral and dermal toxicity is not considered relevant in this context.