Reaction mass of 2-(1,1-dimethylpropyl)anthraquinone and 2-(1,2-dimethylpropyl)anthraquinone

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1991

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

no

Principles of method if other than guideline:

- The test compound is poorly soluble and therefore the test compound was tested in the presence of silicagel to guarantee the availability of the compound to the micro-organisms.
- The test was prolonged to 56 days because at day 28 the biodegradation has started but the plateau was not yet reached.

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: RWZI Horstermeer, Nederhorst den Berg, the Netherlands. This is an activated sludge plant treating
predominantly (>85%) domestic waste water.
- Pretreatment: The sludge was preconditioned to reduce the endogenous respiration rate. The diluted sludge (200 mg dry weight/litre) was aerated for a period of one week.
- Concentration of sludge: the sludge was diluted to a concentration of 2 mg dry weight/l in the test bottles.
- Water filtered: no.

Duration of test (contact time):

56 d

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral salt solution prepared in distilled water.
- Solubilising agent (type and concentration if used): the test compound was dissolved in dichloromethane (1 gram/litre). Hereafter 0.56 ml was added to 2 g silicagel (100 - 200 mesh). The solvent was evaporated and transferred into the BOD bottles.
- Test temperature: 20°C.
- pH: 7.0 (mineral salt solution), 7.1 (test solution)
- pH adjusted: no
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 280 ml BOD bottles
- Number of culture flasks/concentration: 7 bottles per treatment

SAMPLING
- Sampling frequency: on Day 0, 5, 15, 28 and 56.
- Sampling method: the oxygen content was measured in the bottle.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes.
- Abiotic sterile control: no
- Toxicity control: no

Reference substance:

acetic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Value:

17

Sampling time:

56 d

Details on results:

The following biodegradation was observed during the study: 30% (5 days), 23 % (15 days), 18% (28 days) and 17% (56 days).

Results with reference substance:

The biodegradation of sodium acetate showed that the activity of the inoculum was sufficient.
The compound bis(2-ethylhexyl)phtalate (BEF) was used in this study as a reference compound which is poorly soluble in water, of which the biodegradability is known. The biodegradability of BEF found in this study was in good correspondence with the results from the literature.

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Ready biodegradability of 2-amylanthraquinone in a closed bottle test for 56 days. The initial concentration of the test substance was 2 mg/L. The sludge was diluted to a concentration of 2 mg dry weight/l in the test bottles. The following biodegradation was observed during the study: 30% (5 days), 23 % (15 days), 18% (28 days) and 17% (56 days). It is concluded that the test substance is not readily biodegradable under conditions applied in this test.

Description of key information

Several ready biodegradability studies were performed with 2-amylanthraquinone, according to OECD guideline 301D and 301F, all showing that the substance is to be considered not readily biodegradable. Although no significant ultimate biodegradation was observed in the available screening tests it has been shown that 2 -amylanthraquinone is primary biodegradable. Other anthraquinone derivates, like 2 -ethylanthraquinone, are inherently biodegradable. Furthermore the UM-BBD Pathway Prediction System indicates that several aerobic biodegradation pathways of 2 -amylanthraquinone are likely. This biodegradation pathway prediction system has been developed by the University of Minnesota (Fishbach et al., 2011).

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

The test substance is considered not (readily) biodegradable based on several performed OECD studies, 0 -30% degradation was seen after 14 -56 days:

 

A ready biodegradability study of 2-amylanthraquinone in a closed bottle test was performed for 56 days (OECD 301D). The initial concentration of the test substance was 2 mg/L. The sludge was diluted to a concentration of 2 mg dry weight/L in the test bottles. The following biodegradation was observed during the study: 30% (5 days), 23 % (15 days), 18% (28 days) and 17% (56 days). It is concluded that the test substance is not readily biodegradable under conditions applied in this test.

In a manometric respirometry biodegradability study (OECD guideline 301F), under aerobic circumstances activated sludge, domestic, non-adapted (30 mg/l) was exposed to 20 and 50 mg/l test substance for 56 days. Oxygen consumption was measured as parameter for biodegradation estimation. This study incorporated the REACH technical guidance for assessing the biodegradability of poorly water soluble compounds. For example surfactants, silica gel and silicone oil were used to increase the bioavailability of 2-amylanthraquinone. The substance is considered not biodegradable as less than 11% degradation was observed after 56 days of inoculum exposure.

In a supporting study, limited described but from a reliable source, the substance is assessed to be non- biodegradable in an OECD guideline 302C study (0% after 14 days).

Ready biodegradability of 2-amylanthraquinone was also studied in modified Sturm test for 28 days (OECD301B). The initial concentration of the test substance was 10 and 20 mg/L. The sludge was present in a concentration of 30 mg of solid substance per L medium. The test substance did not dissolve to any visually detectable extent and was still visible on the bottom of the flasks at the end of the test. Therefore, this study was disregarded.

A study was conducted according to OECD 301F with modifications for poorly water soluble substances and enhancements. Oxygen consumption of the sludges was extremely large, which resulted in no useful information on ready biodegradation.

However HPLC measurements of the 2-amylanthraquinone concentration generated useful information on the primary biodegradation of the substance. With adapted sludge the primary degradation was about 98 % after 2 weeks, while a primary degradation of 70 % has been found after 2 months when non-adapted sludge was used.

The lack of a mass balance does not allow for the calculation of half-lives nor does it confirm that the dissipation of the parent compound is only the result of biodegradation. The study is considered supportive.