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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
10.02.-10.03.1989
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment
Reason / purpose:
reference to same study
Reference:
Composition 1
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)
Principles of method if other than guideline:
No details given
GLP compliance:
no
Test material information:
Composition 1
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
no details given
Oxygen conditions:
aerobic
Inoculum or test system:
not specified
Details on inoculum:
no details given
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
control: inoculum blank
Reference substance:
aniline
Test performance:
no data
Parameter:
% degradation (O2 consumption)
Value:
51
Sampling time:
4 d
Parameter:
% degradation (O2 consumption)
Value:
59
Sampling time:
6 d
Parameter:
% degradation (O2 consumption)
Value:
75
Sampling time:
10 d
Parameter:
% degradation (O2 consumption)
Value:
82
Sampling time:
18 d
Parameter:
% degradation (O2 consumption)
Value:
83
Sampling time:
28 d
Results with reference substance:
%degradation: 61 after 28 days (aniline)

Results table:

time

oxygen consumption [mg/L]

%biodegradation

day

test substance

aniline

blank control

test substance

aninline

2

-

-

-

-

-

4

136

9

14

51

0

6

155

129

14

59

48

8

-

-

-

-

-

10

194

165

15

75

62

12

200

167

16

77

63

14

205

167

17

79

62

16

-

-

-

-

-

18

214

167

19

82

61

20

216

167

19

83

61

22

-

-

-

-

-

24

218

167

20

83

61

26

218

167

21

83

61

28

219

167

21

83

61

 

Validity criteria fulfilled:
not specified
Interpretation of results:
readily biodegradable
Conclusions:
Under the experimental conditions used in the test, the test substance was readily biodegradable.
Executive summary:

The biodegradability of the test item was tested according to OECD guideline no. 301E. The test substance was tested in a concentration of 100 mg/L test medium. During the test period of 28 d, the oxygen consumption was measured every other day and the % biodegradation was then determined by using the following formula (according to OECD guideline 301):

% biodegradation = BOD (mg O2/mg test substance) / ThOD (mg O2/mg test substance) x 100

BOD = mg O2 uptake by the test substance - mg O2 uptake by blank / mg test substance in vessel

The ThOD (theoretical oxygen demand)-value used was 2.387 mg O2/mg test substance.

The pass level (according to OECD guideline no. 301) for ready biodegradability (60% ThOD to be reached within a 10-day window of the 28-d period) is fulfilled by the test substance in the tested concentration. Hence the substance is considered readily biodegradable.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to same study
Reference:
Composition 1
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Principles of method if other than guideline:
not applicable
GLP compliance:
yes
Test material information:
Composition 1
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Municipal activated sludge from laboratory wastewater treatment plant fed with municipal sewage and synthetic wastewater.
- Concentration of sludge: 30 mg/l
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Reference substance:
aniline
Preliminary study:
not applicable
Test performance:
not applicable
Parameter:
% degradation (O2 consumption)
Value:
0 - < 10
Sampling time:
3 d
Parameter:
% degradation (O2 consumption)
Value:
> 10
Sampling time:
4 d
Parameter:
% degradation (O2 consumption)
Value:
> 60 - 70
Sampling time:
12 d
Parameter:
% degradation (O2 consumption)
Value:
70 - 80
Sampling time:
21 d
Parameter:
% degradation (O2 consumption)
Value:
70 - 80
Sampling time:
28 d
ThOC mg/g = 742* 
COD mg/g = 2177
ThOD mg/g = 2527*

(* = at 99.7 % purity)
Interpretation of results:
readily biodegradable
Conclusions:
As the degradation of the test substance reached 70-80% within 28d based on O2 consumption, the substance is considered as ready biodegradable.
Executive summary:

The biodegradability of the substance was tested according to OECD guideline 301 F. The test substance was tested in a concentration of 100 mg/L test medium. During the test period of 28 d, the oxygen consumption was measured every other day and the % biodegradation was determined.

The pass level (according to OECD guideline no. 301) for ready biodegradability (60% ThOD to be reached within a 10-day window of the 28-day period) is fulfilled by the test substance in the tested concentration. Hence the test substance is considered readily biodegradable.

The target substance (CAS 71617 -10 -2) and the read-across substance (CAS 5466 -77 -3) are both esters of p-methoxycinnamic acid. Due to this close structural relationship, these two compounds are considered to show comparable ecotoxicological properties. Therefore, the present results are used in a read-across approach to support the findings made in the ready biodegradation study conducted with the target substance (CAS 71617 -10 -2).

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH

Scenario 2 of the Read Across Assessment Framework (RAAF) is appropriate because it is hypothesised that the target and source substances present similar physico-chemical, environmental and toxicological properties, as a result of their structural similarity (i.e. analogue approach). The source substance 2-ethylhexyl 4-methoxycinnamate (OMC) contains the same functional groups as Isopentyl p-methoxycinnamate (IMC), differing only in the length of the carbon chain originating from the alcohol.

Physico-chemical properties of the two substances are broadly similar. Both substances are liquids with low melting / freezing points. Both Isopentyl p-methoxycinnamate and 2-Ethylhexyl 4-methoxycinnamate are poorly soluble, with high partition coefficients and low vapour pressure. Relative density values of the two substances are within a narrow range of 1.0104 to 1.04. Boiling point, flash point and auto-ignition temperatures of the two substances are also similar.

Due to the similarity in chemical structure and physico-chemical properties, both substances are expected to behave in a similar manner when released into the environment.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)

Source: 2-ethylhexyl 4-methoxycinnamate
Target: Isopentyl p-methoxycinnamate

The target substance, Isopentyl p-methoxycinnamate is an organic mono-constituent substance used as a sunscreen agent in cosmetics. The target substance has a typical degree of purity of ≥ 96.5% ≤ 99.93% w/w. Impurities include 3-Methylbutyl (Z)-p-methoxycinnamate (≥ 0.01% ≤ 0.5% w/w); 3-Methylbutyl p-methoxy-dihydrocinnamate (≥ 0.01% ≤ 0.5% w/w); 3-Methylbutyl 3-isopropoxy-3-(p-methoxyphenyl)propionate (≥ 0.01% ≤ 0.5% w/w); 4,4’-Dimethoxystilbene (≥ 0.01% ≤ 0.5% w/w); Pentyl (E)-p-methoxycinnamate (≥ 0.01% ≤ 0.5% w/w); 3-Methylbutyl-3-methyl-p-methoxycinnamate (≥ 0.01% ≤ 0.5% w/w); 3-Methylbutyl p-methoxy-3-(3-methylbutoxy)cinnamate (≥ 0.01% ≤ 0.5% w/w). None of the impurities are considered relevant for the classification and labelling of the substance.

The source substance, 2-Ethylhexyl 4-methoxycinnamate, is also an organic mono-constituent substance used as a sunscreen agent in cosmetics. Details of the source substance purity are not publicly available. However, as a mono-constituent substance a purity ≥80% is required for OMC. Both esters of p-methoxycinnamic acid, IMC and OMC are close structural analogues, differing only in the length of the carbon chain originating from the alcohol. Consequently, the impurity profile is expected to be similar.

3. ANALOGUE APPROACH JUSTIFICATION

IMC and OMC are very structurally similar, and measured and predicted properties of the two substances also demonstrate similarity of behaviour in the environment. Both IMC and OMC are poorly soluble and are expected to partition to soil and sediment based on high measured partition coefficient values (log Kow 4.78 and >6, respectively) and predicted Koc values (log Koc 3.1 – 3.6 and 3.9 – 4.3, respectively). Based on the Henry’s law constant values predicted for each substance, and also considering the predicted Koc values, both substances are considered to be of low volatility and to be only slightly mobile in soil and sediments. Based on structurally similarity, both substances are likely to have similar degradation potential. Both substances contain the same functional groups, with only the length of the carbon chain differing. Solubility of the substances is similar, with OMC slightly less soluble as would be expected based on its slightly higher molecular weight. The available measured data for biodegradation potential supports read across between the two substances, although the available data for IMC can only be assigned a Klimisch score of 4 due to the lack of some critical method details in the report summary.

Results are available for a biodegradation study conducted with IMC (Bayer 1989). Only a results page is available, therefore it is not possible to fully assess the reliability of the study. However, it is stated to follow a standard test guideline, OECD 301E and the initial test substance concentration is reported as 100 mg L-1. Based on oxygen consumption, the study demonstrated 83% degradation of the test item after 28 days. As IMC was biodegraded by over 60% within the 10-day window, the substance is considered to be readily biodegradable.

A biodegradation study is available for OMC (BASF 1997), conducted according to OECD 301F. A test concentration of 100 mg L-1 was used and degradation was assessed based on oxygen consumption. After 28 days, 70 - 80% degradation was demonstrated and the 10-day window criterion was met, therefore OMC is considered to be readily biodegradable.

BIOWIN results for the two substances also predict similar biodegradation potential, although results for BIOWIN 4 (Primary biodegradation) are slightly different (days – weeks for IMC and hours – days for OMC) (see Read across justification report attached in the Robust Study Summary).

Neither IMC or OMC are PBT / vPvB. Both substances are considered to be readily biodegradable and are therefore not persistent. Although measured partition coefficient values are high for both substances, predicted BCF values for IMC and measured BCFs for OMC are all below the threshold for a bioaccumulative substance.

4. DATA MATRIX

See attached read across justification report attached in the Robust Study Summary.
Reason / purpose:
read-across source
Related information:
Composition 1
Test material information:
Composition 1
Parameter:
% degradation (O2 consumption)
Value:
0 - < 10
Sampling time:
3 d
Parameter:
% degradation (O2 consumption)
Value:
> 10
Sampling time:
4 d
Parameter:
% degradation (O2 consumption)
Value:
> 60 - 70
Sampling time:
12 d
Parameter:
% degradation (O2 consumption)
Value:
70 - 80
Sampling time:
21 d
Parameter:
% degradation (O2 consumption)
Value:
70 - 80
Sampling time:
28 d
Interpretation of results:
readily biodegradable
Conclusions:
As the degradation of the test substance reached 70-80% within 28d based on O2 consumption, the substance is considered as ready biodegradable.
Executive summary:

The biodegradability of the substance was tested according to OECD guideline 301 F. The test substance was tested in a concentration of 100 mg/L test medium. During the test period of 28 d, the oxygen consumption was measured every other day and the % biodegradation was determined.

The pass level (according to OECD guideline no. 301) for ready biodegradability (60% ThOD to be reached within a 10-day window of the 28-day period) is fulfilled by the test substance in the tested concentration. Hence the test substance is considered readily biodegradable.

The target substance (CAS 71617 -10 -2) and the read-across substance (CAS 5466 -77 -3) are both esters of p-methoxycinnamic acid. Due to this close structural relationship, these two compounds are considered to show comparable ecotoxicological properties. Therefore, the present results are used in a read-across approach to support the findings made in the ready biodegradation study conducted with the target substance (CAS 71617 -10 -2).

Description of key information

On the  basis of the available data with the test substance itself and a structurally similar read-across substance, it can be concluded that the test substance can be regarded as readily biodegradable fulfilling the 10-day-window.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The biodegradability of isopentyl p-methoxycinnamate was tested in a 28-d MITI test which was performed similar to OECD guideline 301E. The test substance was tested at a concentration of 100 mg/L test medium. After 28 days 83% of the test substance was degraded. The 10 -day-window was fulfilled (day 4: 51%; day 10: 75%). No details on the test procedure were reported, therefore the reliability of the study cannot be assessed and the data has been used in combination with the data from a read across substance, in a weight of evidence approach.

The biodegradability test with the read-across substance was done according to OECD guideline no. 301F under GLP conditions. The substance was tested in a concentration of 100 mg/L test medium. At the end of the test period of 28 d, the biodegradation was 70 to 80% fulfilling the 10-day-window, showing that the substance is readily biodegradable. This result is in line with the result for the test item itself.

The read across substance, 2-ethylhexyl 4-methoxycinnamate has a similar structure to isopentyl p-methoxycinnamate, and measured physico-chemical data for the two substances is also similar. The two substances are therefore likely to behave in a similar manner in the environment, and read across between the two is considered to be acceptable. The read across is confirmed by the available biodegradation data for the substance itself which, although its reliability cannot be fully assessed, determines the same conclusion of readily biodegradable. See attached read across justification report for full details of the read across approach

A weight of evidence approach is used to assess the biodegradation potential of isopentyl p-methoxycinnamate, based on available data for the substance itself and a read across substance. Based on the data from both studies, isopentyl p-methoxycinnamate is considered to be readily biodegradable.