Disodium-3,3´-{Oxybis[2,1-ethanediyloxy(1-oxo-2,1-ethanediyl)imino]}bis(2,4,6-triiodobenzoate)

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:

Dec 2002 to Jan 2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Schering AG, Bergkamen, Germany (61703003)
- Purity: 99.5 %

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Solubility and stability of the test substance in the solvent/vehicle: S20°c> 546 g/L (according to Schering report A09525)

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Amount of substance in test solution (nominal) : 321 mg/L

OTHER SPECIFICS:
Vapor pressure: P25 < 10·3 Pa (according to Schering report A07301)
Hydrolytical stability: t½ > 1 year at 25°C (according to Schering report A08129)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): The activated sewage sludge for the inoculum was collected on the day before the start of the experiment from a well-operated municipal sewage treatment plant ("Klaranlage Berlin Ruhleben"), predominantly dealing with domestic sewage. Upon arrival at the laboratory, the activated sludge was stirred and aerated for approximately two hours. Thereafter, the sludge was homogenized in a blender. Then it was allowed to settle for approximately 30 minutes. 3 mL corresponding to 9 to 15 mg suspended solids were taken from the supernatant for each test vessel. The nutrient solution (mineral medium) was prepared according to the OECD guideline 301F (1).

Duration of test (contact time):

29 d

Initial conc.:

200 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: 200 mg ThOD/L:
- Test temperature: 21 to 22°C
- pH: 7.7 to 7.8
- pH adjusted: no

TEST SYSTEM
- Method used to create aerobic conditions: For the determination of the 02 consumed, an electronical manometric device, mounted on the top of each bottle was employed (WTW OxyTop C6).
- Details of trap for CO2 and volatile organics if used: The produced CO2 was absorbed by an absorbing agent (soda lime) installed inside. The resulting negative pressure was recorded by the electronical rnanometric device and calculated as mg 02/L consumption. The recorded values were transmitted to a portable controller instrument by infrared technique (WTW OxyTop OCl 10) and subsequently transferred to a laboratory computer by a serial connection cable. The percentage calculation of the degradation rate from the transferred data were performed by Microsoft Excel.


CONTROL AND BLANK SYSTEM
- Toxicity control: Iotroxic acid disodium salt +sodium acetate (100 mg + 100 mg ThOD/L) (single set)
- Blank control: 0mgThOD/L (triplicate)

Reference substance:

acetic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

29 d

Results with reference substance:

The reference compound sodium acetate was degraded to 89 % on day 29 (28 days of incubation). 60% degradation was reached between day 2 and 6.
In the toxicity control, the reference compound (sodium acetate) plus the test compound iotroxic acid disodium salt, was degraded to 44 % on day 29 (28 days of incubation), which reflected the degradation in the individual sets.

Biological degradation (cumulative) in percent (corrected for blank 02 consumption) of iotroxic acid, disodium salt (ZK 232105)
Test compound	Conc. expressed in theoretical O2 demand	Day of sampling
		2	6	10	14	18	22	26	29
Iotroxic acid, disodium salt	200 mg/L	0.0	0.0^(1)	0.0^(1)	0.0^(1)	0.0^(1)	0.0	0.0	0.0
Reference (sodium acetate)	200 mg/L	17.5	70.7	84.2	85.5	86.2	87.5	88.3	88.5
Toxicity control (iotroxic acid disodium salt+ sodium acetate)	100 mg/L + 100 mg/L	19.5	39.7	41.8	43.3	44.0	44.0	43.8	44.0
(1) negative values are considered as 0% degradation

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The test compound iotroxic acid disodium salt was not degraded up to day 29 (28 days of incubation).

Executive summary:

In a 28 day study on the biodegradability of iotroxic acid, disodium salt in the manometric respiration test, iotroxic acid disodium salt was incubated in an freshwater aqueous solution including nutrients with microorganisms from a municipal sewage treatment plant for 28 days (start of treatment= day 1). The biological degradation of the test and reference substances was evaluated by measurement of the 02 consumption during the test period. The test substance iotroxic acid, disodium salt was incubated at a concentration of 200 mg theoretical oxygen demand (Th OD) per litre. Additionally, a reference substance (sodium acetate) was tested in a single set according to the same procedure, in order to verify the viability and activity of the degrading microorganisms. One further set was incubated with sodium acetate at 100 mg ThOD/L (reference substance) plus iotroxic acid disodium salt at 100 mg ThOD/L representing a toxicity control. Furthermore, a blank control was tested in triplicate without any test or reference substance.

 

The test compound iotroxic acid disodium salt was not degraded up to day 29 (28 days of incubation). The reference compound sodium acetate was degraded to 89 % on day 29 (28 days of incubation). 60% degradation was reached between day 2 and 6.

 

In the toxicity control, the reference compound (sodium acetate) plus the test compound iotroxic acid disodium salt, was degraded to 44 % on day 29 (28 days of incubation), which reflected the degradation in the individual sets. In accordance with the OECD 301F (1), the test compound iotroxic acid disodium salt is not readily biodegradable under the conditions of the test and it was not toxic to the microbes of activated sludge. 

Description of key information

The test compound iotroxic acid disodium salt was not degraded up to day 29 (28 days of incubation).

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater