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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Administrative data

Description of key information

ENB has a relatively low degree of acute toxicity in several species via oral and dermal but has significant toxicity by the inhalation route of administration.

Oral LD50: All rat.  male: 2276mg/kg, female: 5071mg/kg, sex not specified: 2.83, 3.08, 3.125ml/kg

Inhalation LC50: Rat male: 6.23, 13.5mg/l, female: 11.25, 15.1mg/l.  Mouse: male 5.5 mg/l, female 3.7mg/l.  Rabbit male: 15.5mg/l.  Guinea pig male: 14.4mg/l

Dermal, rabbit LD50: 5.66 ,>8, 9.17ml/kg

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion
Dose descriptor:
LD50
Value:
2 200 mg/kg bw

Acute toxicity: via dermal route

Endpoint conclusion
Dose descriptor:
LD50
Value:
5 000 mg/kg bw

Additional information

There are a number of acute toxicity studies on ENB by the inhalation route, the oral route and the dermal route. The data described in Ballantyne et al (1997) were selected as the key studies since the analytical purity of the ENB was specified and because they are well reported studies. The acute oral LD50value was 2276 mg/kg for male rats and 5071 mg/kg for female rats. The acute inhalation LC50values were 13.3 mg/L (2717 ppm) for male rats and 14.8 mg/L (3015 ppm) for female rats. The dermal LD50value was greater than 7168 mg/kg for male and female rabbits.

Justification for classification or non-classification

Based on the available animal data, there is sufficient information available to determine that no classification is required for the oral and dermal routes of acute exposure.

For the inhalation route, the data available indicates that classification as acute toxicity category 4 is required base on data from the rat (3 of 4 studies including the LT50 studies), rabbit and guinea pig (average of results from all studies and sexes). The data on mice suggests a more severe effect. A classification based on the response in the majority of species and the preferred species for this end point, therefore a classification of harmful seems most appropriate. This is supported by the observation that the range of LC50 values span the range 13 -56% of the saturated vapour concentration at 20C.