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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

Discussions on bioaccumulation potential

Key value for chemical safety assessment

BCF (aquatic species):
1 754.04 L/kg ww

Additional information

The substance is a UVCB material with a wide variety of potential structures. As such, in order to gain a measure of the propensity towards bioaccumulation, an assessment of 50 potential structures that could be present was undertaken. These were selected at random for the purposes of the exercise.

The assessment was undertaken utilizing recognised QSAR derivation software as follows:

·       BCF model (CAESAR) (version 2.1.11)

·       BCF model (Meylan) (version 1.0.0)

·       BCF Read-Across (version 1.0.0)

·       US EPA On-Line EPI Suite™ v4.0 model BCFBAF

 

It is understood that Annex  XI, section  1.3  allows  adaptation of the standard testing requirements by making use of (Q)SAR only if the following conditions are met:

(i) results are derived from a (Q)SAR  model  whose scientific validity has been established,

(ii) the substance falls within the applicability domain of the (Q)SAR model,

(iii) results are adequate for the purpose of classification and labelling and/or risk assessment, and

(iv) adequate and  reliable documentation of  the  applied method is  provided.

 

Within the four models used, the conditions (i) through (iv) are considered to be met for two of the models:

 

·       US EPA On-Line EPI Suite™ v4.0 model BCFBAF

·       BCF Read-Across (version 1.0.0)

The structures assessed with these models were deemed to mainly fall within the applicability domain of the model, and this is demonstrated within the relevant QPRF’s. The models are recognized, and are referenced within ECHA’s own guidance and/or have relevant QMRF’s which are also detailed. Due to the fact that QSAR is utilised, these were assigned as Klimisch 2 level studies.

 

Within the four models used, the conditions (i), (iii) and (iv) are considered to be met for two of the models:

 

·       BCF model (CAESAR) (version 2.1.11)

·       BCF model (Meylan) (version 1.0.0)

Within these models, conditions (i) through (iv) where only fulfilled for certain molecules. For other molecules, condition (ii) was not fulfilled for a number of reasons. These included:

 

- no similar compounds with known experimental value in the training set were found
- accuracy of prediction for similar molecules found in the training set was not optimal
- similar molecules found in the training set had experimental values that strongly disagreed with the target compound predicted value
- the maximum error in prediction of similar molecules found in the training set had a high value, considering the experimental variability
- some atom centered fragments of the compound had not been found in the compounds of the training set or are rare fragments
- descriptors for certain compound had values outside the descriptor range of the compounds of the training set

These studies were therefore assigned as Klimisch 3 level studies. They were considered suitable for inclusion in a weight of evidence approach in that where these did provide a value within the applicability domain, this was utilised for the calculation of the geometric mean.

 

As a result of these applications, the QSAR’s conducted all generally agree with each other that the substance is not bioaccumulative.

 

Overall

On the basis of a weight of evidence approach, there is sufficient information available to state that the substance is not bioaccumulative. Whilst it is not possible to provide a definitive BCF value for the substance, due to the variation in the results, none of the values determined via QSAR are above the threshold value quoted in the Regulation of 2000 or 5000 which indicates the potential to bioaccumulate. In order to derive a BCF for the purposes of dossier preparation, it is considered appropriate to utilise a geometric mean across the data set. The document “Guidance on information requirements and chemical safety assessment Chapter R.10: Characterisation of dose [concentration]-response for environment”states under section“R.10.2.2 Evaluation and interpretation of data”that:

 

Where there is more than one set of data on the same species, (strain if known), endpoint, duration, life stage and testing condition the greatest weight is attached to the most reliable and relevant one. When there is more than one set of data with the same reliability rating, it might be necessary tolook into more detail at the study reports to see whether a specific reason could explain the difference. If no explanation can be found and the results are for the same species and endpoints and are not more than one order of magnitude apart, they can be harmonised by a geometric mean.

 

A geometric mean BCF is therefore applied for the purposes of hazard assessment.

 

Endpoint study

Result (BCF) [geometric mean]

EPIWIN BCFBAF Results [L/kg]

36.60

BCF Read-Across (version 1.0.0) [L/kg]

348.83

BCF model (CAESAR) (version 2.1.11) [L/kg]

1274.0

BCF model (Meylan) (version 1.0.0)

95.0

Geometric Mean BCF overall

1754.04

 

Whilst this mean result is presented as only a general indication, this supports the overall conclusion that the substance is not considered to be bioaccumulative. The substance is not considered to be “bioaccumulative” or “very bioaccumulative” on the basis of the available data.