1,1-difluoroethylene

Endpoint summary

Description of key information

The acute inhalation toxicity of vinylidene fluoride is low. The LC50 in rats is established to be >130000 mg/m3.

Additional information

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.

Several acute inhalation toxicity tests have been performed, which are more or less comparable to LC50 studies.

In a series of acute inhalation experiments, the lethal concentration for rats and mice after 1-hour exposure was greater than 200000 ppm. Animals were observed for 7 days post exposure. Only the mice showed some minor behavioral changes (Pennwalt, 1974; 1982). In another test, rats were exposed to levels up to 80% (+20% oxygen) for up to 19 hours. No mortality was observed. At exposures to a concentration of 80%, some minor CNS effects were noted. No pathological changes were reported (Lester et al. 1950). Other test reports mentioned mortality of mice at 128000 ppm after a four-hour exposure but results are difficult to interpret because of variable exposure periods and the possibility of inadequate oxygen supply (Carpenter et al, 1949).

In an acute hepatotoxicity test with Holtzman rats, animals were exposed to concentrations of 0, 500, 15000 and 25000 ppm for 4 to 6 hrs. No mortality was observed. Only animals pretreated with polychlorinated biphenyls showed increased liver weights, increased serum sorbital dehydrogenase activity and hepatocellular damage at VF2 concentrations of 500 ppm VF2 and above (Conolly et al, 1979).

Although none of the mentioned studies were performed according to currently prescribed standard protocols, the Pennwalt data indicate clearly that the substance has a low acute toxicity. The other acute studies corroborate the weight of evidence for low acute toxicity.

 

As the classification and labelling according to EU Directive 67/548/EEC should be based on 4 hours exposure, a time extrapolation is required in this case. According to Chapter R.8 of REACH Technical Guidance Document, 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 exposure based on the Pennwalt studies with rats is established to be > 50000 ppm.

 

Dogs and cats survived exposure to 50% in air without cardiac sensitizing effects (Burgison, 1955).

Justification for classification or non-classification

Based on the 4 hours LC₅₀of > 50000 ppm (130000 mg/m³) in rats and the absence of other major significant effects, vinylidene fluoride does not need to be classified 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.