Hexachlorocyclopentadiene

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

other: Expert assessment

Adequacy of study:

weight of evidence

Study period:

2017

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: An assessment was performed based on QSAR ToolBox predictions and available data on the biodegradability of the substance.

Qualifier:

no guideline required

Version / remarks:

Expert assessment

Principles of method if other than guideline:

An assessment was performed based on QSAR ToolBox predictions and available data on the biodegradability of the substance.

- Software tool(s) used including version: QSAR Toolbox 3.3.5.17
- Model(s) used: BIOWIN

Oxygen conditions:

not specified

Inoculum or test system:

not specified

Remarks on result:

other: see 'details on results'

Details on results:

The results from BIOWIN profiling of Hexachlorocyclopentadiene using QSAR Toolbox show that Hexachlorocyclopentadiene is not expected to be readily biodegradable in the aquatic environment.

Interpretation of results:

not readily biodegradable

Conclusions:

Hexachlorocyclopentadiene is not expected to be readily biodegradable in the aquatic environment.

Executive summary:

This expert assessment concludes that Hexachlorocyclopentadiene is not expected to be readily biodegradable in the aquatic environment. The REACH Centre has assessed all available information regarding the biodegradability of the substance, alongside BIOWIN predictions using the OECD QSAR Toolbox for the Grouping of Chemicals. A weight of evidence approach has been adopted to determine the endpoint in question. While the studies outlined in the EU Risk Assessment Report (2007) may have deficiencies and inadequacies which mean they are not acceptable for use by themselves, they can be used collectively, alongside QSAR predictions, to describe the REACH endpoint through weight of evidence, in accordance with Chapter R.4 of ECHA’s guidance (2011).

 

While it is believed that Hexachlorocyclopentadiene may be inherently biodegradable – a “worst case assumption” as described in the EU Risk Assessment Report (2007) – it can be concluded that the substance is not readily biodegradable. No further testing for this endpoint is required.

Description of key information

Hexachlorocyclopentadiene is not expected to be readily biodegradable in the aquatic environment. It is believed that the substance may be inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Additional information

An expert assessment was carried out which aimed to determine the ready biodegradability of Hexachlorocyclopentadiene. This was conducted on the basis of biodegradability studies cited in the EU Risk Assessment Report (2007) on the substance, combined with BIOWIN predictions from the OECD QSAR Toolbox for the Grouping of Chemicals. It was concluded that the substance is not expected to be readily biodegradable in the aquatic environment. However, it is believed that Hexachlorocyclopentadiene may be inherently biodegradable.