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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: read-across from a guideline study
Justification for type of information:
The information is derived from read across. The rationale is presented in the Endpoint summary biodegradation in water:screening section.
Reason / purpose:
read-across source
Key result
Parameter:
% degradation (O2 consumption)
Value:
86
Sampling time:
28 d
Remarks on result:
other: read-across from Methacrylic acid
Validity criteria fulfilled:
yes
Remarks:
Annex XI criteria for using read across are all fulfilled
Interpretation of results:
readily biodegradable
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
Justification for type of information:
The information is used for read across to Fragarone.
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
other: activated sewage sludge bacteria
Details on inoculum:
Aeration stage of the HRC Limited sewage treatment plant treating predominantly domestic sewage
Duration of test (contact time):
28 d
Initial conc.:
3 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
other: Percent biodegradation determined by comparing oxygen depletion value with the corresponding ThOD
Details on study design:
Sampling at 0, 5, 15 and 28 days
20°C
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
86
Sampling time:
28 d
Remarks on result:
other: Oxygen depletion = 4.325 mg O2/L; ThOD = 5.01 mg O2/L
Details on results:
Oxygen depletion in the inoculated and non-inoculated control series were within prescribed limits.
The substance passed the "time window" criterion (60% degradation within 10 days of attaining the 10% level)
Results with reference substance:
87% degradation within 28 days

Mean oxygen depletion and percentage biodegradation values

Culture medium

Day 5

Day 15

Day 28

(a) Dilution water without inoculum

    02depletion (mgO2/I)

 

0.175

 

0.275

 

0.250

(b) Dilution water with inoculum

    02depletion (mgO2/I)

 

0.100

 

0.300

 

0.375

(c) Test substance (3 mg/l)

    02depletion (mgO2/I)

    % degradation

 

3.050

61

 

3.000

60

 

4.325

86

(d) . Standard substance (3 mg/l)

    02depletion (mgO2/I)

    % degradation

 

3.275

65

 

3.450

69

 

4.375

87

t1/2: 10.3 days

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
In a Closed Bottle test (OECD TG 301D) guideline study, the substance was considered readily biodegradable (86% degradation within 28 days, 10 day window passed).
Executive summary:

In a Closed Bottle test according to OECD 301 D methacrylic acid attained 86 % biodegradation within 28 days. The"pass" level of 60 % was reached within 10 days of exceeding 10 % level. Therefore methacrylic acid can be termed as readily biodegradable.

NOTE: Any of data in this dataset are disseminated by the European Union on a right-to-know basis and this is not a publication in the same sense as a book or an article in a journal. The right of ownership in any part of this information is reserved by the data owner(s). The use of this information for any other, e.g. commercial purpose is strictly reserved to the data owners and those persons or legal entities having paid the respective access fee for the intended purpose.

Description of key information

Fragarone is readily biodegradable based on read across from Methacrylic acid (CAS# 79 -41 -1).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

First a short summary of the biodegradation study of the analogue of Fragarone: Methyl acrylic acid is presented and thereafter the read across rationale.

Methacryl acid biodegradation

In a Closed Bottle test according to OECD 301 D Methacrylic acid attained 86 % biodegradation within 28 days. The"pass" level of 60 % was reached within 10 days of exceeding 10 % level. Therefore Methacrylic acid is readily biodegradable.

Read across rationale

Biodegradation of Fragarone (CAS# 16957-70-3) based on read across from data available for Methacrylic acid (CAS# 79-41-4).

 

Introduction and hypothesis for the analogue approach

Fragarone is a 2-pentenoic acid which is methylated at the 2 position. For this substance there are no experimental biodegradation data available. Biodegradation information may be generated by other means, i.e. applying alternative methods such as QSARs, grouping and read-across. For assessing the ready biodegradability of Fragarone, the analogue approach is selected because for a closely related analogue, Methacrylic acid, ready biodegradation information is available which can be used for read across.

Hypothesis: Fragarone has the same biodegradation potential as Methacrylic acid.

Available information: Read-across is performed from Methacrylic acid, for which a ready biodegradation study was performed according to OECD TG 301D (Closed Bottle Test, Rel. 1). In this study, 3 mg/L test substance was inoculated with activated sludge from a sewage treatment plant treating predominantly domestic waste. After 28 days inoculation biodegradation reached 86% based on ThOD. The 10-day pass level of 60% was fulfilled and therefore Methacrylic acid is readily biodegradable.

Target chemical and source chemical(s)

Chemical structures of the target chemical and the source chemical are shown in the data matrix, including physico-chemical properties.

Purity / Impurities

Both Fragarone and Methacrylic acid are mono-constituent substances with purities close to 100%. Neither Fragarone nor Methacrylic acid contain any impurities that are considered to impact the assessment of biodegradation from read across.

Analogue approach justification

According to Annex XI 1.5 read across can be used to replace testing when the similarity can be based on a common backbone and a common functional group. When using read across the result derived should be applicable for C&L and/or risk assessment and it should be presented with adequate and reliable documentation.

Analogue selection: For Fragarone Methacrylic acid was selected as an analogue for read-across because it shares the same backbone and the same functional group and information on ready biodegradability is available.

Structural similarities and differences: Fragarone and Methacrylic acid have the same methylated alkene backbone and both are acids. The only difference between the two substances is that Fragarone has a two C longer hydrocarbon backbone (2-pentene vs. 2-propene).

Bioavailability: Fragarone and Methyl acrylic are very water soluble, have low log Kow and a similar pKa. This means that both are bioavailable for micro-organism and will be dissociated at environmental pH.

Biodegradable structural features:BIOWIN (v4.10) is run to show the biodegradable fragments. Only the BIOWIN modules 5 (‘MITI-linear’) and 6 (‘MITI-non-linear’) are used because these two models are based on ready biodegradability tests, which is the endpoint to be predicted. In the table below the fragments are shown and it can be seen that the fragments are very similar. The number of the type of fragment can differ between the two.

 

Table: summary of BIOWIN predicted data for Fragarone and Methacrylic acid:

Common name

 

Fragarone

 

 

Methacrylic acid

 

Fragment

#

BIOWIN 5

BIOWIN 6

#

BIOWIN 5

BIOWIN 6

Aliphatic acid [-C(=O)-OH]

1

0.1812

1.1346

1

0.1812

1.1346

Methyl [-CH3]

2

0.0008

0.0389

1

0.0004

0.0194

-C=CH [alkenyl hydrogen]

1

0.0062

0.0285

2

0.0124

0.0570

-CH2- [linear]

1

0.0494

0.4295

-

-

-

MW parameter

-

-0.3396

-3.2952

-

-0.2561

-2.4853

Equation constant

-

0.7121

-

-

0.7121

-

Overall score

 

0.6101

0.7031

 

0.6500

0.7775

 

Uncertainty of the prediction: To further support the ready biodegradability, both Fragarone and Methacrylic acid are readily biodegradable according to BIOWIN 5 and 6.There are no remaining uncertainties other than those already addressed in the previous sections.

Conclusions for environmental fate

For Fragarone no biodegradation information is available. Methacrylic acid is used as an analogue.When using read across the result derived should be applicable for C&L and/or risk assessment and be presented with adequate and reliable documentation. This documentation is presented in the current document. Methacrylic acid is considered readily biodegradable and therefore also Fragarone is readily biodegradable.

Final conclusion: Fragarone is readily biodegradable.

 

Data matrix presenting the information relevant for read across of Fragarone from Methacrylic acid

Common name

Fragarone

Methacrylic acid

 

Target

Source

Chemical name

(E)-2-methylpent-2-en-1-oic acid

2-methylprop-2-enoic acid

Chemical structures

CAS #

16957-70-3

79-41-4

EC #

241-026-4

201-204-4

Empirical formula

C6H10O2

C4H6O2

SMILES

O=C(C(=CCC)C)O

CC(=C)C(O)=O

Physico-chemical data

 

 

Molecular weight

114

86

Physical state

Liquid

Liquid

Vp (Pa)

1.63

97

Ws (mg/L)

7858

98000

Log Kow

1.9

0.93

pKa

4.34

4.66

Fate and behaviour

 

 

Biodegradation

Based on read-across:

Readily biodegradable

 

Readily biodegradable (OECD TG 301D)