3,5-diiodothyronine

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, adapted

Details on inoculum:

Activated sludge from a biologic sewage treatment plant was used as inoculum. The cho-sen plant treats mostly domestic sewage.
The sludge was taken from the activation basin of the sewage treatment plant, In den Seewiesen, 67480 Edenkoben.
Date of collection: 29. Jun. 2018, batch no: 20180629.
Pre-Treatment:
The sludge was filtrated, washed with test medium (2x) and re-suspended in test medium. It was then aerated until use. The dry matter was determined to contain 4060 mg of suspended solids/L.

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

TOC

Details on study design:

Inoculum concentration: 25.0 mg/L
Temperature: 20.3 – 23.0 °C
Duration: 28 days

Reference substance:

aniline

Key result

Parameter:

% degradation (CO2 evolution)

Remarks:

Test 1

Value:

4.8

Sampling time:

28 d

Key result

Parameter:

% degradation (CO2 evolution)

Remarks:

Test 2

Value:

5.3

Sampling time:

28 d

Key result

Parameter:

% degradation (CO2 evolution)

Remarks:

mean value

Value:

5.1

Sampling time:

28 d

Table 2: Degradation values in %

Day	Positive Control 1	Positive Control 2	Positive Control Mean	Test 1	Test 2	Test Mean	Abiotic Control	Toxicity Control
2	1.0	-1.3	-0.1	1.5	1.0	1.2	0.4	0.1
4	6.1	10.0	8.1	0.3	0.3	0.3	0.5	11.8
7	38.4	31.2	34.8	1.2	1.6	1.4	0.9	21.6
9	67.7	50.5	59.1	1.1	1.7	1.4	0.5	30.7
11	73.7	59.7	66.7	3.0	2.2	2.6	0.4	36.0
14	75.1	64.4	69.8	3.0	2.2	2.6	0.5	36.5
18	75.0	67.1	71.0	5.8	3.4	4.6	-0.2	38.4
23	81.9	77.1	79.5	6.7	5.0	5.9	0.2	42.9
29	78.7	73.7	76.2	5.8	4.8	5.3	-0.3	39.5

 

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

10-day-window: not detected
degradation at the end of 10-day-window: none
degradation at the end of the test: 5 %

Therefore, when applying the 10-day-window, the test item L-Tyrosine, O-(4-hydroxyphenyl)-3,5-diiodo- is not readily biodegradable following OECD 301B and EU C.4-C respectively. As degradation missed 60% in the course of the test, L-Tyrosine, O-(4-hydroxyphenyl)-3,5-diiodo- is considered as not ultimately biodegradable.

Executive summary:

All validity criteria were met.

Degradation behaviour of positive control and toxicity control was normal. Abiotic degrada-tion was not observed. Both replicates of the test item showed very good correspondence.

If degradation in the toxicity flask is below 25 % after 14 days, the test item can be considered as toxic towards the inoculum. As degradation in the toxicity flask was 36.5 % after 14 days, the test item can be stated as “not toxic towards the inoculum in a concentration of 59.6 mg/L”.

Ready biodegradability is defined in the guidelines as degradation surpassing 60% within 10 days after reaching a level of 10 %. The 10-day-window was not detected.

Therefore, the test item L-Tyrosine, O-(4-hydroxyphenyl)-3,5-diiodo- can be considered as “not readily biodegradable”. Degradation missed 60 % within 28 days, though. Therefore, the test item is considered as “not ultimately biodegradable within 28 days”, as well.

No observations were made which might cause doubts concerning the validity of the study outcome.

The result of the test can be considered valid.

Description of key information

One study was performed according to OECD 301B.

Due to the low degradation (5% in 28 d) the substance is classified as not readily biodegradable and not inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater