Strontium sulphide

Endpoint summary

Description of key information

In a weight of evidence approach the LD50 for strontium sulfide based on strontium nitrate and sodium sulfide data is calculated to 233.5 mg SrS/kg bw.

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

233.5 mg/kg bw

Quality of whole database:

Data are in accordance with current requirements and read across is fully justified (see discussion).

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Acute toxicity, oral:

According to regulation (EC) 1907/2006 Annex VII column 2 the study does not need to be conducted since the substance is classified as corrosive to the skin by worst case (pH 12.6 of a 1% solution). However, it is proven that the Sr²⁺causes no toxic effects when administered via oral route (see robust study summary: “Stitzinger 2010”). Furthermore, there are reliable data available which shows that the sulfide ion is responsible to cause toxic effects in rats when administered orally. Hence, the classification of SrS is based on studies performed with Na₂S.

Read across from Na2S:

The toxicity of SrS is based on the concentration of S^2-in solution. Read across to Na₂S (water solubility: 178 g/L; pH 12.8) is considered to be justified due to worst case considerations.

Conclusion on studies performed with Na2S:

For sodium sulfide, two reliable acute oral toxicity studies (RL=2, Ullmann_1986 and Mason_1998) are available.

However, the resulting LD₅₀values vary markedly (factor seven) between both studies:

Mason (1998): LD₅₀ = 1122 mg/kg bw for Na₂S (anhydrous)

Ullmann (1986): LD₅₀= 254 mg/kg bw for ca. 60% Na₂S that is recalculated with the following formula to 152.3 mg Na₂S/kg bw.

100 / ATE(mix) = Sum(n) C(i) / ATE(i)

 

Ci = concentration of ingredient i

i= the individual ingredient from 1 to n

n= the number of ingredients

Recalculation from Na₂S to SrS resulted in 233.5 mg SrS/kg bw (Ullmann_1986) and 1720.7 mg Sr/kg bw. (Mason_1998).

The Ullmann (1986) study would lead to a classification as toxic if swallowed according to the criteria specified by Directive 67/548/EC, Regulation (EC) No 1272/2008 and subsequent regulations. The Mason (1998) study would lead to a classification as harmful if swallowed according to the criteria specified by Directive 67/548/EC, Regulation (EC) No 1272/2008 and subsequent regulations.

However, for safety reasons it is proposed to use the lower LD₅₀from the Ullmann (1986) study report for classification of the substance.

Conclusion on studies performed with Sr(NO₃)₂:

The LD₅₀of strontium nitrate via the oral route is > 2000 mg/kg bw (> 1124 mg SrS/kg bw).

Respiratory irritation:

The classification as respiratory irritant is normally covered under the endpoint specific target organ toxicity- single exposure and repeated exposure. For substances and mixtures classified as skin corrosive, the additional labeling EUH071: Corrosive to the respiratory tract should be used due to the fact that no acute inhalation test data are available and which may be inhaled.

Justification for selection of acute toxicity – oral endpoint
One study conducted with strontium dinitrate and two studies conducted with sodium sulfide are available. In a weight of evidence approach based on read across to strontium dinitrate and sodium sulfide, strontium sulfide is considered as toxic if swallowed.

Justification for classification or non-classification

According to Regulation (EC) 1272/2008, the substance has to be classified as toxic if swallowed (H301) due to the fact that mortality was observed at a dose level of < 300 mg/kg bw (LD50 233.5 mg SrS/kg bw).

According to 67/548/EEC barium sulfide has to be classified as harmul if swallowed (LD50 >200 and < 2000 mg/kg bw) and labelled with Xn; R22.