Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Adsorption/desorption:

Key study

Based on solubility data available for the test item, the batch equilibrium method for quantification of adsorption properties would not be feasible employing the procedure detailed within OECD Method 106. This was because of the limited water solubility of the test item.

The HPLC estimation method procedure detailed in OECD Method 121 also was considered not to be valid for this test item, due to potential non-partitioning interaction of the molybdenum containing functional group with the HPLC column stationary phase. In the absence of chemically related reference substances of known adsorption coefficient values with which to construct the calibration curve, it was considered that a valid adsorption coefficient based on HPLC retention time could not be determined for this test item.

As the experimental procedures detailed within the above referenced guidelines were concluded to be either unfeasible or invalid, due to the nature of this test item, alternative validated estimation methods have been employed.

Estimation of adsorption coefficient was performed using both a Quantitative Structure Activity Relationship (QSAR) method and a molecular connectivity index (MCI) method. Estimations were performed on an individual component basis, with no specific molybdenum correction factor employed. The calculation procedure undertaken was limited to the initial reaction products containing only a single coconut oil alkyl residue group as this was sufficient to demonstrate the theoretical immobility of this substance in soils. The estimated adsorption coefficient (log10 Koc) values were in the range of 3.52 to at least 5.43 for the dominant lauric acid and myristic acid reaction products. The remaining, less abundant fatty acids resulted in estimated adsorption coefficient (log10 Koc) values in the range of 2.44 to at least 6.47. The upper value of each range was reported as a limit value due to possible additional reaction of the organic subunits, resulting in higher molecular weight species containing multiple coconut oil alkyl residue groups.  A weighted average adsorption coefficient could not be generated for the substance due to the complexity of the substance composition.  The estimated adsorption coefficient (log10 Koc) value for the substance identified as Molyvan 855 is considered to be greater than 3.52. It is acknowledged, however, that majority of constituents that comprise this substance would present even higher adsorption coefficients, indicating the substance is immobile in soils.

Other distribution data:

Key study

Important differences are found between the behaviour of the substance in purified water compared with aqueous media containing biotic matter. The primary difference is that presence of biotic matters seems to eliminate organic molybdenum species in favour of molybdic acid and structurally modified organic species, and this leads to a compartmental distribution which predominates in the aqueous phase with negligible matter in the organic phase.

Proposed compartmental distributions:

Molyvan 855J: Water 100%, sludge 0%

Molybdic acid: Water 100%, sludge 0%

Structurally modified organic substances: Water 100%, sludge 0%