Trizinc dicitrate

Endpoint summary

Description of key information

The key acute oral study reports an LD50 value of >2000mg/kg (Safepharm 1991; rel 1). The only available key study for dermal toxicity was read across from citric acid, which reports an LD50 value of 2000mg/kg (Safepharm, 2006; rel 1). Weight of evidence from other zinc metals  (zinc distearate and zinc sulphate) support the key findings (EU RAR, 2008; rel 2).

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Acute toxicity: via dermal route

Endpoint conclusion

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Additional information

There were no available data for acute dermal toxicity and inhalation toxicity for trizinc dicitrate. The data for inhalation toxicity is waived, since reliable read across is available via the dermal route and a key study is present for acute oral toxicity for trizinc dicitrate. The existing key data read across from citric acid indicates that the citrate is not acutely toxic following dermal exposure. Limited data for acute dermal toxicity are available for other zinc salts. However, the EU risk assessment Report (RAR) for zinc sulphate (EU 2004) reports an acute dermal LD50 value of >2000 mg/kg for rats treated with zinc sulphate heptahydrate, and the RAR for zinc distearate (EU 2008) also reports LD50 (rat, dermal) >2000 mg/kg. No details are available regarding the study with distearate. For zinc sulphate heptahydrate, local signs of irritation were reported, but there was no evidence of systemic toxicity reported in the RAR.

 

The LD50 value of >2000 mg/kg for ZnSO4x7H20/kg bw was converted into trizinc dicitrate in the following steps:

2000x0.18*= >360 mg Zn/kg bw

369x2.9** = >1070 mg trizinc dicitrate/kg bw

the conversion factors are obtained by taking into consideration the MW of the substance:

*the conversion from ZnSO4x7H20 into Zn is: MW Zn/MW ZnSO4x7H20=65/352=0.185

**the conversion from Zn to trizinc dicitrate is: MW trizinc dicitrate / (MW Zinc*3)=547 / (65*3)= 2.9

The LD50 value, when converted into trizinc dicitrate is therefore >1070mg/kg bw, which alone is not sufficient for classification purposes. The conversion of the result from zinc distearate into trizinc dicitrate yields a lower value than zinc sulphate. It is therefore unlikely that a limit test on trizincdicitrate itself would yield an LD50 above classification cut off point. Furthermore, the LogKow of <0 of trizinc dicitrate indicates that dermal uptake is unlikely. Based on the evidence available from citric acid and the other zinc compounds, together with the physico chemical properties of trizinc dicitrate it is therefore concluded that toxicity of the test substance via the dermal route is likely to be low.

Justification for classification or non-classification

The data available for other zinc compounds indicating low acute dermal toxicity/no classification, the physico chemical properties of trizinc dicitrate and the lack of classification of citric acid make classification or labelling to be an unlikely requirement for the acute dermal toxicity for trizinc dicitrate. The acute oral toxicity data for trizinc dicitrate do not trigger classification in accordance with current EU Directive 67/548/EEC or Regulation 1272/2008.