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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
9th July 1996 to 7th August 1996
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:
- Name of test material: 1-phenylethyl acetate
- Physical state: colourless liquid
- Name of test material (as cited in study report): Gardenol
- Lot/batch No.: 260657
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): fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva, Aïre) was used.- Preparation of inoculum for exposure: the sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.- Concentration of sludge: the dry weight of suspended solids is determined by taking to 50 mL samples of the homogenised sludge, evaporating water on a steam bath, drying in an oven at 105 - 110 ºC for two hours and weighing the residue. Dry weight of suspended solids: 4.346 g/L. To obtain a concentration of 30 mg/L (dry weight) in a 250 mL flask, 1.73 mL of sludge is needed (inoculum).- Water filtered: the water used during this study is deionised water containing less than 10 mg/L dissolved organic carbon.
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:
TEST CONDITIONS- Composition of medium: prepared by mixing 50 mL of solution A and 2000 mL deionised water, adding 5 mL of each of the solutions B, C and D and making up to 5 litres with deionised water.- Test temperature: 22 ºC- pH: 7.4- pH adjusted: yes (with phosphoric acid or potassium hydroxide as necessary)TEST SYSTEM- Culturing apparatus: 250 mL volumetric flasks- Number of culture flasks/concentration: flasks were prepared in duplicate- Measuring equipment: SAPROMAT D 12, made by J. M. VOITH GmbH, D-7920 HeidenheimSTATISTICAL METHODS:Oxygen uptakes as read on the SAPROMAT meters are corrected:- by deducting the basic oxygen uptake of sludge (flasks 2/7 and 2/8)- proportionally to account for the differences between actual and nominal concentrations of test and reference substances. Averages of identical flasks have been used to obtain the graphs of BOD versus time (Figure 1) and percentage of biodegradation versus time (Figure 2).
Reference substance:
aniline
Preliminary study:
No preliminary study was performed.
Test performance:
No unusual observations were noted in the study.
Key result
Parameter:
% degradation (O2 consumption)
Value:
89
Sampling time:
28 d
Remarks on result:
other: Mean % degradation
Parameter:
% degradation (O2 consumption)
Value:
68
Sampling time:
12 d
Remarks on result:
other: Mean % degradation; 10-day window
Details on results:
1-phenylethyl acetate undergoes an average of 89% biodegradation after 28 days in the test conditions (figure 2). Biodegradation starts on day 2 and reaches 68% at the end of the 10-day window (days 2 to 12).The curve (figure 1) obtained with aniline alone and with 1-phenylethyl acetate and aniline show no toxic effect of 1-phenylethyl acetate on the micro-organisms at the test concentration.
Results with reference substance:
Degradation of aniline exceeds 40% after 7 days and 65% after 14 days: the activity of the inoculum is thus verified and the test is considered as valid.

Table 1: Actual concentrations and pH measurements

 Concentrations (mg/L)     pH   
 Flask number  Test substance  Reference substance  initial  final
 2/5  0  100.0  7.42  7.99
 2/6  0  100.0  7.40  7.91
 2/7  0  0  7.37  7.48
 2/8  0  0  7.34  7.40
 1/11  102.1  0  7.45  7.54
 1/12  100.8  0  7.43  7.46
 1/9  100.2  100.0  7.47  8.29
 7/10  99.4  100.0  7.47  8.46

Nominal concentrations

Test substance: 100 mg/L

Reference substance: 100 mg/L

Table 2: Biodegradation of test substance

 Days:    2  7  12  14  21  28
 BOD sludge  1st flask  B1  5.0  10.0  10.0  12.0  23.0  23.0
 (figure 1)  2nd flask  B2  5.0  7.0  7.0  8.0  17.0  17.0
   mean  B  3.5  8.5  8.5  10.0  20.0  20.0
 BOD test substance  1st flask  C1  33.4  105.9  166.6  178.4  197.2  203.1
 (figure 1)  2nd flask  C2  30.8  110.2  170.7  181.6  236.3  253.1
   1st fl. corr.  C1-B  29.9  97.4  158.1  168.4  177.2  183.1
   2nd fl. corr.  C2-B  27.3  101.7  162.2  171.6  216.3  233.1
 % degradation  1st flask  D1  13  42  68  72  76  78
 (figure 2)  2nd flask  D2  12  43  69  73  92  100
   mean  D  12  43  68  73  84  89

B = (B1 + B2)/2

D1 = 100 * (C1 - B) / ThOD * [S]

D2 = 100 * (C2 - B)/ ThOD * [S]

D = (D1 + D2) / 2

[S] = Initial test substance concentration (mg/L)

Table 3: Biodegradation of reference substance

Days:  5  7  10  14  21  28
 BOD sludge  1st flask  B1  9.0  10.  10.  12.0  23.0  23.0
 (figure 1)  2nd flask  B2  6.0  7.0  7.0  8.0  17.0  17.0
   mean  B  7.5  8.5  8.5  10.0  20.0  20.0
 BOD reference substance  1st flask  A1  186.9  198.9  206.9  214.9  227.9  232.9
 (figure 1)  2nd flask  A2  158.9  192.9  202.9  210.9  222.9  226.9
   1st fl. corr.  A1-B  179.4  190.4  198.4  204.9  207.9  212.9
   2nd fl. corr.  A2-B  151.4  184.4  194.4  200.9  202.9  206.9
 % degradation  1st flask  D1  74  79  82  85  86  88
   2nd flask  D2  63  77  81  83  84  86
   mean  D  69  78  82  84  85  87

B = (B1 + B2) / 2

D1 = 100 * (A1 - B) / ThOD * [S]

D2 = 100 * (A2 - B0 / ThOD * [S]

D = (D1 + D2) /2

[S] = initial test substance concentration (mg/L)

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Under the conditions of the test, 1-phenylethyl acetate undergoes an average 89% biodegradation after 28 days and meets the 10-day widow criterion. Thus the substance is considered to be readily biodegradable.
Executive summary:

The ready biodegradability of 1-phenylethyl acetate has been determined by the Manometric Respirometry Test according to the OECD Guidelines for Testing of Chemicals, Method No. 301 F.

1-phenylethyl acetate undergoes on average 89% biodegradation after 28 days in the test conditions. Biodegradation starts on day 2 and reaches 68% at the end of the 10-day window (days 2 to 12).

Thus 1 -phenylethyl acetate should be regarded as readily biodegradable according to this test.

At the concentration used in the test (100 mg/L), 1-phenylethyl acetate is not inhibitory to the micro-organisms.

Description of key information

1-phenylethyl acetate has been tested for ready biodegradability. It achieved >60 % biodegradation after 28 days and passed the 10 day window criterion in two standardised biodegradation tests. Therefore it is regarded as readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

In the key study, the ready biodegradability of 1-phenylethyl acetate was determined by the Manometric Respirometry Test (OECD 301F) and the study determined that 1-phenylethyl acetate undergoes on average 89% biodegradation after 28 days under test conditions. Biodegradation starts on day 2 and reaches 68% at the end of the 10-day window (days 2 to 12). 1-phenylethyl acetate should therefore be regarded as readily biodegradable according to this test. 1-phenylethyl acetate was also determined to be readily biodegradable in the supporting test (>100% after 28 days in sealed CO2 test, 10 day window criterion met).

A biodegradation study for the structurally closely related analogue, benzyl acetate, is also included in the dossier as relevant supporting information to strengthen the rationale for the use of read-across to benzyl acetate (source substance) in order to address short-term toxicity to aquatic invertebrates and toxicity to aquatic algae for 1-phenylethyl acetate (target substance). In an OECD Guideline 301C study, benzyl acetate was determined to be readily biodegradable. The result has been included in the data matrix of the target records for the two read-across endpoints (acute daphnia and algal inhibition).