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Diss Factsheets

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Justification for grouping of substances and read-across

There are no data available on the hydrolysis of zinc O,O,O',O'-tetrabutyl bis(phosphorodithioate). In order to fulfil the standard information requirements set out in Annex VIII-IX, Section 9.2.2.1, in accordance with Annex XI, Section 1.5 of Regulation (EC) No 1907/2006, read-across from a structurally similar substance is conducted.

In accordance with Article 13 (1) of Regulation (EC) No 1907/2006, "information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI are met.”

Having considered the general rules for grouping of substances and read-across approach laid down in Annex XI, Item 1.5, of Regulation (EC) No 1907/2006, whereby physicochemical, toxicological and ecotoxicological properties may be predicted from data for reference substance(s) by interpolation to other substances on the basis of structural similarity, the substance Phosphorodithioic acid, mixed O,O-bis(iso-Bu and pentyl) esters, zinc salts (CAS 68457-79-4) is selected as reference substances for assessment of hydrolysis.

Having considered the general rules for grouping of substances and read-across approach laid down in Annex XI, 1.5, of Regulation (EC) No 1907/2006, whereby substances may be predicted as similar provided that their physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity.

The read-across is based on structural similarity as both chemicals belong to the substance class of Zinc alkyldithiophosphates (ZDDP) which are produced by a chemical reaction of Phosphorous pentasulfide with low molecular weight alcohols followed by a subseuqent reaction with zinc oxide. A detailed analogue approach justification is provided in the technical dossier (see IUCLID Section 13).

Environmental fate of the target substance Zinc O,O,O',O'-tetrabutyl bis(phosphorodithioate) and the source substance Phosphorodithioic acid, mixed O,O-bis(iso-Bu and pentyl) esters, zinc salts is presented in the following table.

 

Target substance

Source substance

CAS No.

6990-43-8

68457-79-4

Chemical name

zinc O,O,O',O'-tetrabutyl bis(phosphorodithioate)

Phosphorodithioic acid, mixed O,O-bis(iso-Bu and pentyl) esters, zinc salts

Hydrolysis

RA: CAS 68457-79-4

Experimental result:

Hydrolytically stable

Biodegradation

Experimental result:

7% after 28 days

Experimental result:

1.5 % after 28 days

Bioaccumulation

Waiving: negligible potential since log Kow < 3

negligible potential since log Kow < 3

Adsorption

Waiving: low potential since log Kow < 3

low potential since log Kow < 3

The above mentioned substances are considered to be similar on the basis of the structural similar properties and/or activities. The available endpoint information on hydrolysis is used to predict the same endpoint for Zinc O,O,O',O'-tetrabutyl bis(phosphorodithioate).

Discussion

Based on this read across Zinc O,O,O',O'-tetrabutyl bis(phosphorodithioate) (CAS 6990-43-8 ) is considered to be hydrolytically stable and therefore abiotic hydrolysis is not a relevant pathway in water.

Furthermore, the substance is not readily biodegradable. Under the chosen test conditions less than 10% biodegradation was observed. Hence the substance has to be considered as poorly biodegradable in water. Based on the experimental result for ready biodegradation and stability towards hydrolysis, the substance is assessed as very persistent (vP). The substance has a log Kow <3 indicating negligible potential to adsorb to soil and sediment particles. Due to its high water solubility (>= 1700 mg/L in aqua bidest), low potential for adsorption to soil and sediment particles and low vapour pressure (< 1 Pa at 20°C) the target compartment for environmental distribution will be the aquatic environment.

Zinc O,O,O',O'-tetrabutyl bis(phosphorodithioate) (CAS 6990-43-8 ) is not bioaccumulative, based on the criteria given in Regulation (EC) No. 1907/2006, Annex XIII, 1.1.2 since the log kow is <3.