Reaction mass of m,alpha-dimethylstyrene and p,alpha-dimethylstyrene

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

08 Aug 2018 - 20 Dec 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Report date:

2019

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

m,α-dimethylstyrene

EC Number:

214-394-9

EC Name:

m,α-dimethylstyrene

Cas Number:

1124-20-5

Molecular formula:

C10H12

IUPAC Name:

1-isopropenyl-3-methylbenzene

Constituent 2

Reference substance name:

p,α-dimethylstyrene

EC Number:

214-795-9

EC Name:

p,α-dimethylstyrene

Cas Number:

1195-32-0

Molecular formula:

C10H12

IUPAC Name:

1-isopropenyl-4-methylbenzene

Test material form:

liquid

Details on test material:

Appearance: Clear colourless liquid
Storage conditions: At room temperature

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.
- Storage conditions: The freshly obtained sludge was kept under continuous aeration until further treatment.
- Pretreatment: Before use, the sludge was coarsely sieved (1 mm) and washed with mineral medium. After treatment, the concentration of suspended solids (SS) was determined to be 3 g/L in the concentrated sludge used for the test. The sludge was used as inoculum at a concentration of 6 mL per litre of mineral medium, leading to a final concentration SS of 18 mg/L.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial test substance concentration 1

Initial conc.:

25 mg/L

Based on:

test mat.

Initial test substance concentration 2

Initial conc.:

80 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral medium, according to OECD301
- Test temperature: 22 - 24 °C
- pH: 7.5 - 7.6 at start, 7.4 - 8.4 at day 28
- pH adjusted: no
- Continuous aeration: yes
- Continuous darkness: yes
- Other: The test solutions were continuously stirred during the test to ensure optimal contact between the test item and test organisms.

TEST SYSTEM
- Culturing apparatus: 500 mL brown colored glass bottles, fill volume 244 mL, in order to obtain the required headspace-to-volume ratio.
- Number of culture flasks/concentration: 4 containing test item and inoculum; 2 containing only inoculum (inoculum blank); 1 containing reference item and inoculum (procedure control); 1 containing test item, reference item and inoculum (toxicity control).
- Preparation of bottles: At the start of the test (day 0), mineral medium was inoculated with activated sludge. Test and/or reference item were added to the respective bottles. The volumes of suspensions were made up to 244 mL using inoculated mineral medium. Rubber gaskets containing two pellets of sodium hydroxide were inserted into each bottle. Subsequently, each bottle was sealed by screwing an automated respirometer head on top.
- Method used to create aerobic conditions: continuous aeration
- Respirometer/measuring equipment: Lovibond BD600-GLP manometric respirometry system, equipped with an inductive stirring system.
- Details of trap for CO2 and volatile organics if used: The CO2 produced in each test bottle reacted with the CO2 absorbent (Sodium hydroxide pellets) in the rubber gaskets. As gaseous O2 was converted into gaseous CO2 that was absorbed, the gas pressure in the test system slowly decreased. This decrease in air pressure was measured by the respirometer heads and automatically converted into oxygen consumption (mg O2/L).

MEASUREMENTS
- Measurements were recorded on day day 0-4-7-11-14-18-21-25-28. After recording the oxygen consumption on day 28, the pH was determined in all test vessels.

CONTROL AND BLANK SYSTEM
- Abiotic sterile control: no

Reference substance

Reference substance:

acetic acid, sodium salt

Results and discussion

% Degradation

Key result

Parameter:

% degradation (O2 consumption)

Value:

24

Sampling time:

28 d

Remarks on result:

other: Mean from 4 bottles, range: 16 - 35%

Details on results:

The relative biodegradation values calculated from the measurements performed during the test period revealed 16%, 35%, 20% and 24% biodegradation of test item based on ThOD, for bottle A through D. Thus, the criterion for ready biodegradability (at least 60% biodegradation within a 10-day window) was not met.
In the toxicity control, more than 25% biodegradation occurred within 14 days (47%, based on ThOD). Therefore, the test item was assumed not to be inhibitory to the inoculum.

BOD5 / COD results

Results with reference substance:

Functioning of the test system was checked by testing the reference item sodium acetate, which showed a normal biodegradation curve and 78% degradation within 14 days.

Any other information on results incl. tables

Table 1: Comparison of Biodegradation of the Test Item in Bottles A through D

Day	Biodegradation (%)
	Bottle A	Bottle B	Bottle C	Bottle D	Mean A - D	∆ A-D *
0	0	0	0	0	0	0
4	3	3	1	0	2	3
7	6	8	3	3	5	5
11	10	14	13	15	13	5
14	13	16	16	18	16	5
18	15	19	18	20	18	5
21	15	23	19	22	20	8
25	16	30	20	22	22	14
28	16	35	20	24	24	19
*: Difference in biodegradation between lowest and highest bottle.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

See 'overall remarks' for details on validity criteria

Interpretation of results:

not readily biodegradable

Conclusions:

The test substance was found to be not readily biodegradable in a manometric respirometry test.

Executive summary:

In a GLP-compliant Manometric Respirometry Test according to OECD guideline 301 F, the substance was assessed for its ready biodegradability. The substance was tested in quadruplicate at a target concentration of 25 mg/L, corresponding to a ThOD of 80 mg O2/L (based on the molecular formula of the substance). The exposure period was 28 days and two inoculum blanks, a positive control and a toxicity control were included. The substance was added directly into the test bottles. The test solutions were continuously stirred during the test to ensure optimal contact between the substance and test organisms. The substance was 16%, 20%, 24% and 35% biodegraded, in the 4 replicate bottles. Thus, the criterion for ready biodegradability (at least 60% biodegradation within a 10 -day window) was not met. The substance was found not to inhibit microbial activity. Based on the average biodegradation of 24%, the substance is classified as not readily biodegradable in the Manometric Respirometry Test. All validity criteria were met, thus the study was considered to be valid and reliable without restriction.