Chloroethylene

Endpoint summary

Description of key information

The 4 hour LC50 of vinyl chloride in acute inhalation toxicity study with rats was established to be 195,000 mg/m3.

Key value for chemical safety assessment

Acute toxicity: via inhalation route

Endpoint conclusion

Dose descriptor:

LC50

Value:

195 000 mg/m³ air

Additional information

As vinyl chloride is a gas, oral and dermal routes of exposure are considered to be not relevant for human exposure and the performance of conventional studies via these routes is not necessary. Inhalation is considered to be the most relevant route of exposure. Prodan et al., 1975 studied the acute inhalation toxicity of vinyl chloride in rats, mice, rabbits and guinea pigs up to 2 hours of exposure. For rats, an LC50 of 390,000 mg/m³ was established. Death of animals was preceded by excitement, contractions, convulsions, and respiratory excitement followed by failure. Intensive salivation and lacrimation were noted. Gross necropsy indicated congestion of internal body organs. This is confirmed in studies with different species and with different exposure duration, as LC50 values were of the same order of magnitude.

As 4 hours exposure duration is required for classification and labelling, time extrapolation is required in this case. According to Chapter R.8 of the Guidance on information requirements and chemical safety assessment, if time extrapolation is considered valid, then the most appropriate approach is to make use of the modified Haber’s law (Cⁿx t = k, where ‘C’ is the concentration, ‘n’ is a regression coefficient, ‘t’ is the exposure time and ‘k’ is a constant) according to which the relationship between exposure concentration and exposure duration for a specific effect is exponential. A default value of n=1 is suggested for extrapolating from shorter to longer exposure durations. Therefore the recalculated LC50 for 4 hours of exposure to vinyl chloride in rats is established to be 195,000 mg/m³.

Inhalation at levels less than 8000 ppm for 5 minutes may be tolerated without developing symptoms of toxicity (Lester et al., 1963). Inhalation of concentrations ranging from 12000 to 20000 ppm for 5 minutes may produce slight anaesthetic effects including dizziness, headache and/or nausea (Lester et al, 1963).

Justification for classification or non-classification

Based on the LC50 value of 195,000 mg/m³/4 h for vinyl chloride in rats, classification of vinyl chloride for acute toxicity according to EU Directive 67/548/EEC and EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008 is not warranted.