Registration Dossier

Administrative data

Description of key information

Ethylene has low acute inhalation toxicity, the LC50 in rats is > 57,000 ppm (equivalent to >65,400 mg/m3). Anaesthesia in humans is seen at concentrations of 80% ethylene (800,000 ppm or 917,000 mg/m3). In accordance with Section 2 of REACH Annex XI, studies via the oral and dermal route do not need to be conducted as the substance is a gas at room temperature.

Key value for chemical safety assessment

Additional information

There are limited but adequate data for the assessment of the acute inhalation toxicity data of ethylene. It is not technically feasible to dose via the oral or dermal route since the substance is a gas at room temperature.

Non-human information

Acute toxicity: Oral and dermal

No data are available


Acute toxicity: inhalation

Non-human information

Standard inhalation acute toxicity studies have not been conducted on ethylene, but two rodent studies add to the overall weight of evidence for low toxicity via the inhalation route. Guest (1981) exposed rats via inhalation to 10,000 ppm ethylene for 5 hrs. No clinical signs or deaths were reported within the first 36 hrs (when the animals were terminated) and there were no histopathological effects in the liver.

The acute inhalation LC50 (5h) of ethylene in rats is > 10,000 ppm (equivalent to >11,473 mg/m3). Also the NOAEC for histopathological effects on the liver is 10,000 ppm (equivalent to >11,473 mg/m3).

The acute toxicity of ethylene via the inhalation route (4hrs) was also assessed by Connolly (1978) following high dose exposure at 10,000, 25,000, or 57,000 ppm (11,473, 28,700 or 65,400 mg/m3). In all cases exposure was preceded by 3 days of oral gavage pre-treatment with Arochlor 1254. No deaths occurred within the first 24 hrs in any dose group following exposure which suggests that the LC50 (4h) is greater than 57,000 ppm (65,400 mg/m3). No clinical signs of toxicity are reported. The authors report that rats that were exposed to ethylene, but not pre-treated with Aroclor, showed no observable changes in the liver. 

The acute inhalation LC50 (4h) of ethylene in rats is > 57,000 ppm (65,400 mg/m3).


Human information

Livingstone (1945) reviewed ethylene’s wide use as an anaesthetic from 1923 onwards. The standard mixture administered was 80% ethylene and 20% oxygen. This concentration was reported to have good anaesthetic properties whilst providing adequate oxygen for patients, but not enough to allow the mixture to explode. Ethylene proved to be an effective anaesthetic, relaxation was moderate but the authors reported no increase in mucous secretions or sign of irritation in the pulmonary endothelium. Post-operative mortality was 1.5%; none of the deaths being considered to be directly due to the anaesthetic agent. Incidences of postoperative nausea and/or vomiting occurred only on the day of surgery.

Anaesthesia in humans was induced by 80% ethylene, equivalent dose of 800,000 ppm or 917,857 mg/m3.

Justification for classification or non-classification

There is lack of exposure to ethylene via the oral or dermal routes because the substance is a gas at room temperature. It has a very low acute hazard following inhalation exposure, and no classification or labelling is required with respect to this end-point under Dir 67/548/EEC or GHS/CLP.

Although ethylene has been used historically as an anaesthetic at high concentrations (800,000 ppm) a NOAEC for acute narcosis has not been established. In 2001 the European Commission added an R67 classification.

It is proposed that ethylene is classified under Dir 67/548/EEC as R67 "vapours cause drowsiness" and Category 3 H336 under GHS/CLP “May cause drowsiness and dizziness”.