Bis(dodecylthio)dioctylstannane

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.024 mg/L

Assessment factor:

1 000

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.241 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.002 mg/L

Assessment factor:

10 000

Extrapolation method:

assessment factor

PNEC marine water (intermittent releases):

0.024 mg/L

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

1 mg/L

Assessment factor:

100

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

963 000 000 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

96 300 000 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

25 100 000 000 000 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

Read-across Justification

The target substance Bis(dodecylthio)dioctylstannane (DOT SLau CAS: 22205-30-7, EC: 244-841-3) is a mono-constituent organotin substance that consists of a tin as central metal element with two octyl-ligands. The source substances DOTE (Dioctyltin bis(2-ethylhexyl thioglycolate)) (CAS 15571-58-1) and DOTI (Diisooctyl 2,2'-[(dioctylstannylene)bis(thio)]diacetate) (CAS 26401-97-8) are also organotin compounds and have the identical structure elements as the target substance in respect of the tin-alkyl moiety.

According to WHO IPCS CIRCAD (2006) organotin compounds are characterized by a tin–carbon bond and have the general formula RxSn(L)(4−x), where R is an organic alkyl or aryl group and L is an organic (or sometimes inorganic) ligand. The organotin moiety is significant toxicologically. The anionic ligand influences physicochemical properties but generally has little or no effect on the toxicology.

Since the target substance and the source substances share the identical organotin moiety, and the organotin moiety is generally recognized as the relevant toxophore of organotins and the toxicity estimates (AE) respectively toxicity limits for organotins are expressed as tin, the overall ecotoxicity/systemic toxicity of the target can be interpolated by assessing the (eco-)toxicity of the source (WHO IPCS CIRCAD, 2006, BAUA AGS TRGS 900, 2014, Summer KH, Klein D and Greim H, 2003).

The purity of the source and target substance are expected to be high, based on the manufacturing method. The impurity profile is not expected to have strong effects on substance properties and any impurity of (eco-)toxicological relevance of the source substances is expected to be present in the target substance. Consequently, the hazard profiles of the source substances, including those of their impurities, are intrinsically covered. Differences in impurities are not expected and thus do not have an impact on the (eco-)toxic properties.

The bioavailability of all substances varies in a predictable manner and is assumed to be dependent on the water solubility. The prediction of the effects of the target substance is based on the relationship between solubility and (eco-)toxicity or on a worst-case basis.

The result of the simulated gastric hydrolysis study on our substance shows close similarities with the hydrolysis study conducted on DOTE, in that both materials breakdown to form the monochloride versions of the substance as the only breakdown products, which further backs up their similarities and the read across.

 

References

BAUA (Bundesanstalt für Arbeitsschutz und Arbeitsmedizin (Federal Institute for Occupational Safety and Health)) AGS (Ausschuss für Gefahrstoffe (Committee on Hazardous Substances)) TRGS (Technical Rules for Hazardous Substances) 900 (2014). Begründung zu n-Octylzinnverbindungen, April 2014.

Summer KH, Klein D, Griem H (2003). Ecological and toxicological aspects of mono- and disubstituted methyl-, butyl-, octyl-, and dodecyltin compounds - Update 2002. GSF National Research Center for Environment and Health, Neuherberg, for the Organotin Environmental Programme (ORTEP) Association.

World Health Organization (WHO) International Programme on Chemical Safety (IPCS) Concise International Chemical Assessment Document (CICAD) 73 Mono- and disubstituted methyltin, butyltin, and octyltin compounds (2006). Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organization, and the World Health Organization, and produced within the framework of the Inter-Organization Programme for the Sound Management of Chemicals. World Health Organization ISBN 978 92 4 153073.

 

Conclusion on classification

Based on read-across to structurally similar substance DOTE (CAS NO 15571-58-1), it is expected this substance is not readily biodegradable and is not anticipated to be bioaccumulative based on a BCF test. The ecotoxicity results are as follows:

 

Fish: LC50 (96h) > 100 mg/L (WSF)

Algae: ErC50 (72h) > 100 mg/L (WSF)

Daphnia: EC50 (48h): 24.12 mg/L

 Based on the results of acute toxicity to daphnia study and the lack of ready biodegradability of the substance, according to CLP classification criteria the substance is classified Aquatic Chronic Category 3 – H412: Harmful to aquatic life with long lasting effects.