Dihydro-2,2-dioctyl-6H-1,3,2-oxathiastannin-6-one

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

no hazard identified

Marine water

Hazard assessment conclusion:

no hazard identified

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

124 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

no hazard identified

Sediment (marine water)

Hazard assessment conclusion:

no hazard identified

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

no hazard identified

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

Justification for Read-Across

By read across to DOTO, aquatic short-term and long-term effect concentrations of Dioctyltin mercaptopropionate are expected to exceed the water solubilty limit of the substance. According to the available data on DOTO, algae is the most sensitive taxonomic group to octyl tin compounds. Acute and chronic algae data (i.e. 72h EC50, EC10 and NOEC) show that Dioctyltin mercaptopropionate is not toxic to algae up to and including the highest attainable test concentration (measured 0.0092 mg/L, nominal 0.025 mg/L).

In summary of the studies, it is concluded Dioctyltin mercaptopropionate is not soluble enough to cause adverse effects in the aquatic environment.

Endpoint code	Description	Guideline	Effect	Value	Remark	Evaluation
6.1.1	Short term fish	OECD 203 EU Method C.1	96-hour LC50	> 0.09 mg/L meas. (geom. mean)	LC50 of the test material is greater than the limit of solubility of the test substance.	Based on read-across to Dioctyltin oxide, the LC50 of Dioctyltin mercaptopropionate is considered to be greater than the water solubility, corrected for molecular weight the 96 h LC50 was > 0.11 mg/L
6.1.3	Short term invertebrates	OECD 202 EU Method C.2	48-hour EC50	> 0.21 mg/L meas. (geom. mean)	EC50 of the test material is greater than the limit of solubility of the test substance.	Based on read-across to Dioctyltin oxide, the EC50 of Dioctyltin mercaptopropionate is considered to be greater than the water solubility, corrected for molecular weight the 48 h EC50 was > 0.26 mg/L.
6.1.3	Short term invertebrates	OECD 202	24-hour EC50	> 0.00067 mg/L meas. (geom. mean)	EC50 of the test material is greater than the limit of solubility of the test substance.	Supporting study confirming no effects at the limit of solubility. Based on read-across to Dioctyltin oxide, corrected for molecular weight the 24 h EC50 was > 0.000383 mg/L.
6.1.5	Growth inhibition algae	OECD 201 EU Method C.3	72-hour ErC50 72-hour NOEC	> 0.0092 mg/L meas. (geom. mean) 0.0092 mg/L meas. (geom. mean)	ErC50 of the test material is greater than the limit of solubility of the test substance.	There were no inhibitory effects on growth at the maximum attainable test material concentration of 0.0092 mg/L.

The target substance Dihydro-2,2-dioctyl-6H-1,3,2-oxathiastannin-6-one (Public name: Dioctyltin mercaptopropionate, CAS: 3033-29-2, EC: 221-218-4) is a mono-constituent organotin substance that consists of a tin as central metal element with two octyl-ligands and one 3-mercaptopropionate-ligand. The source substance dioctyltin oxide (Public name: DOTO, CAS: 870-08-6, EC: 212-791-1) is also an organotin compound and has 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. Applying this WHO characterization to target and source, they can be described (C8H32)2SnL, with L source = O2- and L target = (SCH2CH2COO)2-.

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). As the source has a higher relative amount of tin based on molecular weight (source 32.87%, target 26.42%) the read-across approach to DOTO can be assessed as conservative (worst case).

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 dominating intrinsic property of mercaptopropionic acid - which is as mercaptopropionate the moiety of the target substance, which is not covered by the source substance and thus may pose a source specific impurity - is its corrosivity. However this is a local effect covered by studies on the target substance itself and thus excluded from the read- across approach. In addition, mercaptopropionic acid and derivatives thereof are natural constituents of the environment and human nutrition.

The bioavailability of both 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 based on the relationship between solubility and (eco-)toxicity or on a worst-case basis. The respective ligands of source and target are expected to be of no (eco-)toxic importance based on intrinsic properties but may have an effect on solubility respectively bioavailability.

 

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

9.1.3 Short-term toxicity testing on fish: Hooftman & de Wolf (2004), OECD 203 and EU method C.1; LC50 > water solubility

9.1.1 Short-term toxicity on invertebrates: Hooftman & de Wolf (2004), OECD 202 and EU method C.2; EC50 > water solubility

9.1.2 Growth Inhibition Study on Aquatic Plants: Vryenhoef (2018), OECD 201; ErC50 > water solubility

In accordance with the criteria outlined in Regulation EC No. 1272/2008 (CLP) and Directive 67/548/EEC (DSD), the substance does not meet the critieria for classification as dangerous to the environment.