3,3'-dichlorobenzidine dihydrochloride

Endpoint summary

Description of key information

After single oral application of > 2000 mg/kg bw  to female rats no lethality was observed. 

Additional information

Single oral application of 2000 mg/kg bw 3,3'-dichlorobenzidine dihydrochloride to female rats in a reliable guideline study did not result in the death of any animal. This finding is supported by other studies, which were judged not to be reliable (RL 3) due to insufficient documentation: These studies reported rat oral LD50 values of 3820 mg/kg bw and 7070 mg/kg bw for the dihydrochloride and free base, respectively. Lower LD50 values (females: 488 mg/kg bw; males: 676 mg/kg bw) were only reported in a study performed with mice. The reliability of this study could not be evaluated, because results were only availably from a secondary source.

In an acute inhalation study with rats, which were exposed for 1 hour to concentrated dust of the submission substance no deaths were reported during the 14 day observation period. This study was judged not to be reliable (RL 3) due to insufficient reporting.

Data on acute toxicity after dermal application are only available from two studies using the free base of the submission substance.The results of these studies are contradictory: One of these studies reported an dermal LD50 value of > 8000 mg/kg bw for rabbits (study not reliable due to insufficient documentation; RL 3), whereas in the other study 4 of 5 rabbits died after single dermal application of 1000 mg/kg bw (results only available from secondary source; RL 4).

In summary, reliable data on the acute toxicity of the submission substance are only available after single oral application, indicating that the oral LD50 in rats is > 2000 mg/kg bw. Further studies, which were not reliable due to insufficient documentation, indicated that the submission substance has no or only very low acute toxicity after oral, inhalative or dermal exposure, not relevant for classification. Two studies, which were only available from secondary sources, pointed to some acute toxicity after single oral or dermal application. It is concluded that the submission substance has not to be classified for acute toxicity after oral, inhalative or dermal application according to Regulation (EC) No 1272/2008 and Council Directive 67/548/EEC.

Justification for classification or non-classification

Reliable data on the acute toxicity of the submission substance are only available after single oral application, indicating that the oral LD50 in rats is > 2000 mg/kg bw. Further studies, which were not reliable due to insufficient documentation, indicated that the submission substance has no or only very low acute toxicity after oral, inhalative or dermal exposure, not relevant for classification. Two studies, which were only available from secondary sources, pointed to some acute toxicity after single oral or dermal application. It is concluded that the submission substance has not to be classified for acute toxicity after oral, inhalative or dermal application according to Regulation (EC) No 1272/2008 and Council Directive 67/548/EEC.

For the existing classification given in Annex VI to Regulation (EC) No 1272/2008 (R21, H312), which deviats from the justification above, no rationale is available. In the absence of reliable contrary data and for precautionary reasons this classification is retained.