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Biodegradation in water: screening tests

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biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
30/01/2003 - 5/03/2003
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP Compliant, guideline study, available as unpublished report, acceptable with restrictions
Justification for type of information:
See read across justification (Cross reference)
according to guideline
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
with the exception of the inoculum preparation which was performed ASTM D5864
Principles of method if other than guideline:
No protocol deviations occurred that would have affected the quality or integrity of the study data.
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
CAS Inventory Name: Naphtha, petroleum, light steam-cracked, debenzenized, C8-16 cycloalkadiene concentrate
DCPD/Codimer Concentrate is produced as a distillate from a C8+ fraction of thermally processed pyrolysis gasoline obtained from ethylene production (steam cracking process). The sample tested consisted of dicyclopentadiene (29%), methylcyclopentadiene dimer (13%), cyclopentadiene/methylcyclopentadiene codimer (13%), other codimers of cyclopentadiene - e.g. with 1,3-butadiene or isoprene (7%), other similar codimers of ethycyclopentadiene (22%), balance (16%).
Oxygen conditions:
Test conducted according to the guidelines
Inoculum or test system:
other: Activated Sludge supernatant
Details on inoculum:
activated sludge from the Clinton Sanitary Wastewater Treatment Plant, Annandale New Jersey
Duration of test (contact time):
28 d
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Triplicate test systems were used to evaluate the biodegradability of the test and positive control substances at mean concentrations of 49.00 mg/L and 47.39 mg/L, respectively. Blank test systems, which did not contain the test or positive control substance, were run concurrently in triplicate. The total suspended solids (TSS) of the activated sludge was determined to be 4.41 g/L. The inoculum was added at a 1% loading volume of sludge supernatant to test medium. The microbial count of the inoculum was 106 CFU/mL. One litre of test medium, which was aerated for 24 hours with carbon dioxide free air, was added to each one litre respirometer flask. The test substance was weighed in an airtight syringe and injected into the test medium. The test system was sealed immediately after addition of the test substance. An aliquot of the positive control stock solution was added to the appropriate test flasks. An unacclimated activated sludge inoculum was used in this study. The inoculum was obtained from the Clinton Sanitary Wastewater Treatment Plant, Annandale, NJ, USA. The treatment plant receives domestic sewage. All test systems were placed on a Coordinated Environmental Services (CES) automated respirometer which automatically recorded the oxygen uptake in general agreement with the OECD guideline. The 28-day study was conducted at a temperature range of 21.0°C to 22.2°C.
Reference substance:
other: Sodium Benzoate
Preliminary study:
no data
Test performance:
no data
Key result
% degradation (O2 consumption)
Sampling time:
28 d
Details on results:
No measurable biodegradation observed over a 28 day testing period.
DCPD/Codimer Concentrate cannot be considerd readily biodegradable
Results with reference substance:
Sodium benzoate biodegraded to >60% by day 2 and the average of the cumulative oxygen consumed in the blank systems was 22.35 mg/L.

No measurable biodegradation observed over a 28 day testing period. DCPD/Codimer Concentrate cannot be considerd readily biodegradable.

Validity criteria fulfilled:
Interpretation of results:
under test conditions no biodegradation observed
Under the test conditions used no biodegradation was observed. DCPD/Codimer had biodegraded by 0% in 28 days.
Executive summary:

This study was GLP compliant and followed guidelines. The study is considered adequate for assessment. Under the test conditions used no biodegradation was observed. DCPD/Codimer had biodegraded by 0% in 28 days. Therefore, based on the read across from the DCPD codimer (which did not degrade), DCDP is also considered not readily biodegradable.

Description of key information

DCPD is not readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

A study for DCPD/Codimer Concentrate (CAS 68478-10-4) was available for review (Exxon Mobil, 2004) and was considered suitable for read across. The ready biodegradability study using activated sludge following OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test) showed no biodegradation after 28 days. The DCPD/Codimer Concentrate consists of dicyclopentadiene and codimers of cyclopentadiene. The substance consists of DCPD along with lower concentrations of other codimers of cyclopentadiene which have similar structures to DCPD and are expected to have similar biodegradation properties. Therefore, read across of this conservative result to DCPD is considered robust.

Information from MITI Japan indicating that the substance was not readily biodegradable was unavailable for review. However, this study is from a regulatory source and has been used in the OECD SIDS and therefore is included as a supporting study.

The use of a QSAR to predict the biodegradability of 3a,4,7,7a-tetrahydro-4,7-methanoindene is an appropriate technique to use as part of a weight of evidence approach. The use of BioHCwin and Biowin is appropriate for 3a,4,7,7a-tetrahydro-4,7-methanoindene as this compound clearly falls within the applicability domains of these models as all substructures in 3a,4,7,7a-tetrahydro-4,7-methanoindene are included in the models. The results from both QSAR indicate that 3a,4,7,7a-tetrahydro-4,7-methanoindene is expected not to be readily biodegradable.