(R)-p-mentha-1,8-diene

Toxicity to microorganisms

Link to relevant study record(s)

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:

D-Limonene is one of the main constituents of dipentene multiconstituent (REACTION MASS OF BETA-PHELLANDRENE AND D-LIMONENE AND L-LIMONENE). Therefore, data on dipentene multiconstituent can be used for extrapolation to d-limonene. See read-across justification document in section 13.

Reason / purpose for cross-reference:

read-across source

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 6.1.7/1: 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 6.1.7/2: 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 multi-constituent 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-hour acute toxicity study, activated sludge were exposed to dipentene multi-constituent 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 Guidline OECD 209.

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

 

Therefore, dipentene multi-constituent is classified as not harmful to microorganisms and this study satisfies with the guidelines requirements for activated sludge toxicity study.

Description of key information

Data available on a structurally related substance, dipentene multiconstituent, show an EC50 of 209 mg/L and an EC10 of 18 mg/L

for toxicity to microorganisms.

Key value for chemical safety assessment

EC50 for microorganisms:

209 mg/L

EC10 or NOEC for microorganisms:

18 mg/L