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Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Justification for type of information:
The main constituents of dipentene multiconstituent present at concentration above 10% are d-limonène, l-limonène and beta-phellandrene. It has the same main constituents as REACTION MASS OF BETA-PHELLANDRENE AND D-LIMONENE AND L-LIMONENE. Therefore, data on dipentene multiconstituent can be used for extrapolation to REACTION MASS OF BETA-PHELLANDRENE AND D-LIMONENE AND L-LIMONENE. See read-across justification document in section 13.
Reason / purpose:
read-across source
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
209 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
18 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
other: EC20
Effect conc.:
41 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
other: EC80
Effect conc.:
1 062 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
The calculated respiration rates and inhibition percentages of dipentene are presented in Table II and the results of the graphical probit analysis are shown in Figure 2
Results with reference substance (positive control):
The EC50 of the reference compound was 7 mg/L which is within the prescribed range of 5 to 30 mg/L (Table I and Figure 1)

Table 1: Respiration rates of the activated sludge, inhibition percentages, and pH at various concentrations of 3,5-dichlorophenol after 3 hours contact time. 

Concentration

mg/L

Activity

mg O2/g.min

Inhibition%

pH

start

test

pH

end

test

Temperature

end test

(°C)

Control

0.282

--

6.8

7.0

20.6

Control

0.253

--

6.8

7.0

20.3

Control*

0.276

--

6.8

7.1

20.9

Control*

0.259

--

6.8

7.1

21.1

1.5*

0.235

12

6.8

6.9

21.0

3.0

0.165

38

6.9

7.2

20.4

5.9

0.135

49

6.9

7.2

20.7

11.8

0.106

60

6.9

7.2

20.4

23.6

0.053

80

6.9

7.2

20.8

47.2

0.035

87

6.9

7.1

7.1

* = Inhibition percentages at concentrations indicated by the asterisk are calculated with the controls indicated by the asterisk

Table 2: Respiration rates of the activated sludge, inhibition percentages and pH at various concentrations of dipentene after 3 hours contact time

Concentration

mg/L

Activity

mg O2/g.min

Inhibition%

pH

end

test

Temperature

end test

(°C)

Control

0.296

--

7.1

20.5

Control

0.290

--

7.2

20.5

Control*

0.313

--

7.2

20.8

Control*

0.290

--

7.2

21.0

8.45*

0.284

6

7.2

21.0

16.9*

0.307

-2

7.1

20.9

33.8

0.238

19

7.2

20.4

67.6

0.174

41

7.3

20.3

135.2

0.133

54

7.4

20.3

270.4

0.122

58

7.4

20.5

540.8

0.133

54

7.4

20.5

* = Inhibition percentages at concentrations indicated by the asterisk are calculated with the controls indicated by the asterisk.

Validity criteria fulfilled:
yes
Remarks:
The control respiration rates were within 15% of each other; the EC50 of the reference compound was 7 mg/L
Conclusions:
The EC50 of dipentene multiconstituent for activated sludge after 3 hours contact time is 209 mg/L.
The EC10, EC20 and EC80 are 18, 41 and 1062 mg/L, respectively
Executive summary:

In a 3 hours acute toxicity study, activated sludge were exposed to dipentene multiconstituent at nominal concentrations of 0 (control), 8.45, 16.9, 33.8, 67.6, 135.2, 270.4, 540.8 mg/L under static conditions in accordance with guideline OECD 209.

The EC50  and EC10 values based on inhibition of respiration rate were 209 and 18 mg/L, respectively.

Therefore, the test item is classified as not harmful to activated sludge.

 

This toxicity study satisfies the guidelines requirements for activated sludge toxicity study.

Description of key information

In a 3 hour acute toxicity study, activated sludge were exposed to dipentene multiconstituent, a structurally related substance, at nominal concentrations of 0 (control), 8.45, 16.9, 33.8, 67.6, 135.2, 270.4, 540.8 mg/L under static conditions in accordance with guideline OECD 209.
The EC50 and EC10 values based on inhibition of respiration rate were 209 and 18 mg/L, respectively.

Key value for chemical safety assessment

EC50 for microorganisms:
209 mg/L
EC10 or NOEC for microorganisms:
18 mg/L

Additional information

The study was conducted with a structurally related substance and is in line with the guidelines requirements for activated sludge toxicity study. The test item is considered as not harmful.

For further information on read-across justification, see section 13 "justification of read-across".