1,3-diisopropylbenzene

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
In this justification, the read-across (bridging) concept is applied. Please refer to a full version of Read-across statement attached in the section 13 "Assessment reports".

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The underlying hypothesis for the read-across is that the target and the source substance have similar toxicological properties (including the same target organs) due to their structural similarity, resemblance to their chemical reactivity, and therefore a similar mode of action.
The source substance ‘Mixture of 1,3-diisopropylbenzene and 1,4-diisopropylbenzene' is a mixture of structural isomers, 1,3- diisopropylbenzene(target substance) and 1,4-diisopropylbenzene. The physico-chemical properties are highly equivalent based on the high structural similarity. As a conclusion, it is scientifically justified to address the endpoint Bioaccumulation: aquatic / sediment with data on this mixture of isomers.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source substance: Mixture of 1,3-diisopropylbenzene and 1,4-diisopropylbenzene (Diisopropylbenzene), CAS no. 25321-09-9
structural formula: C12H18
Smiles: CC(C)C1=CC=CC=C1C(C)C
Molecular weight: 162 g/mol
CAS 25321-09-9
EC No 246-835-6
purity: not specified

target substance: 1.3-diisopropylbenzene (or m-DIPB)
structural formula: C12H18
Smiles: CC(C)c1cccc(c1)C(C)C
Molecular weight: 162 g/mol
CAS 99-62-7
EC No 202-773-1
purity: not specified

No additional information is available on purity of the source and the target substances. Both substances are normally of high purity, containing only minor amounts of impurities that do not influence the read-across validity.

3. ANALOGUE APPROACH JUSTIFICATION
Please refer to the full version of the read-across statement attached in the section 13 "Assessment reports".


4. DATA MATRIX
Please refer to the full version of the read-across statement attached in the section 13 "Assessment reports".

Reason / purpose for cross-reference:

read-across source

Lipid content:

ca. 5.052 %

Time point:

other: Mean lipid content over the depuration phase (i.e. the midpoint of the depuration phase calculated from the mean lipid values at the end of the uptake phase/start of depuration and the end of the depuration phase).

Key result

Conc. / dose:

ca. 10 µg/L

Type:

BCF

Value:

1 628.2 L/kg

Basis:

normalised lipid fraction

Calculation basis:

kinetic

Key result

Conc. / dose:

ca. 100 µg/L

Type:

BCF

Value:

1 708.9 L/kg

Basis:

normalised lipid fraction

Calculation basis:

kinetic

Key result

Conc. / dose:

ca. 10 µg/L

Type:

BCF

Value:

1 726 L/kg

Basis:

normalised lipid fraction

Calculation basis:

steady state

Key result

Conc. / dose:

ca. 100 µg/L

Type:

BCF

Value:

1 892 L/kg

Basis:

normalised lipid fraction

Calculation basis:

steady state

Details on results:

- Mortality of test organisms: There were no observed mortalities in all conditions during the tests.

- Behavioural abnormalities: All fish appeared normal and healthy throughout the test.

- Measurement of test substance in water: Analytical measurements of both isomers 1,3 DIPB and 1,4 DIPB were made in water for the DIPB10 treatment. Due to technical problems (e.g. syringe leaking, power shutdown) some of the sampling points were out of the range of the expected value during the uptake phase (day 1-3). Until the rest of the uptake phase the concentration of the test item remained stable. As the concentrations of the test item were not maintained within ± 20 % of the mean of the measured concentrations values during the uptake phase (see deviation) and as a flow-through exposure system was used, a time-weighted arithmetic mean (TWAM) of the exposure concentration was calculated. This TWAM was calculated according to the procedure described OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures. Similarly to the DIPB10 treatment, at the highest concentration treatment (DIPB100) some of the sampling points were out of the range of the expected value during the uptake phase. This could be explained as well by some technical limit but also by the solubility of the test item in this condition. Indeed, the concentration of the test item in water tend to increase during the exposition. In this way, as the concentrations of the test item were not maintained within ± 20 % of the mean of the measured concentrations values during the uptake phase (see deviation) and as a flow-through exposure system was used, a time-weighted arithmetic mean (TWAM) of the exposure concentration was calculated for both isomers and the mixture.

- Steady state fish tissue measurements: Analytical measurement of both isomers 1,3 DIPB and 1,4 DIPB were made in fish tissues. While the concentrations of the test item in water were not maintained within ± 20 % during all the test for the DIPB10 treatment, this occurred only between day 1 and day 3 and remained stable after. A steady state is then reached for the last three sampling points (from day 9 to 14) of the uptake phase (three successive analysis made on samples at intervals of at least 2 days are within ± 20 % of each other). Also in the DIPB100 treatment, the concentrations of the test item in water were not maintained within ± 20 % during all the test probably due to its low solubility in water and the fact that this concentration tend to increase during the exposure. As in the DIPB10 condition the steady state was reached from days 9 to 14, the steady state in the DIPB100 condition is therefore empirically considered to be reached for the last four sampling points of the uptake phase (days 7,9,11,14). It was performed, in order to smooth the oscillation of the test item concentration in fish that occurred.

- Growth measurements (length and total wet weight) for individual fish collected during uptake and depuration in each condition. A linear least squares correlation was calculated for the ln(fish weight) vs. day for each condition for the whole study, uptake and depuration phases. An analysis of the covariance was performed and highlighted that there was no significative difference (p<0.05) of the overall fish growth between phase (uptake/depuration) and between all conditions. In this context, fish weight from all conditions were pooled and overall growth rate constant (kg) was calculated by performing a linear least squares correlation on the individual data of the control, solvent control, DIPB10 and DIPB 100 conditions.

-In order to calculate a kinetic BCF for each isomer and the mixture, estimation of the parameters k1 and k2 were performed by using mathematical models and statistical methods made available as an R-package named “bcmfR” (latest version 0.4-18). This package is distributed via OECD website. The choice of the best fit model was based on the normality of the residues (Q-Q plot and Shapiro-Wilk test). For each of the isomers and the mixture for both exposure concentrations, the Box-Cox transformed data was the best fit model.

Physicochemical Measurement of Water During the Test

Treatment	Sampling Date	Dissolved oxygen (%)	pH	Conductivity (μS.cm-1)	Hardness (°dH)	Alkalinity (mg.CaCO3-1)	Temperature (°C)
Control	9/12/2019	91.5	7.7	349.1	11.6	207.06	21.08
	16/12/2019	96.3	7.5	351.5
	23/12/2019	88.5	7.6	341.8	10.6	189.21	21.3
	30/12/2019	79.2	7.5	344.1	11.8	210.63	21.4
	6/1/2020	87.7	7.8	347.1	21.3
	7/1/2020	83.2	7.5	333.8	9.94	177.429	21.4
Solvent control	9/12/2019	90.4	7.8	343.1	10.3	183.855	21.1
	16/12/2019	88.5	7.5	337.5	21.3
	23/12/2019	85.4	7.6	339.1	11.7	208.845	21.4
	30/12/2019	78.3	7.7	342.5	11.3	201.705	21.5
	6/1/2020	85.5	7.6	332.1	21.5
	7/1/2020	81.9	7.6	334.9	9.99	178.3215	21.4
DIPB10	9/12/2019	90.2	7.8	331	11.1	198.135	21.15
	16/12/2019	87.2	7.5	336.9	21.3
	23/12/2019	82.2	7.6	337	10.9	194.565	21.5
	30/12/2019	81.4	7.8	342.3	11.9	212.415	21.4
	6/1/2020	84.2	7.7	332	21.4
	7/1/2020	80.7	7.7	329.6	9.22	164.577	21.5
DIPB100	9/12/2019	89.9	7.7	331.1	10.9	194.565	21.11
	16/12/2019	88.3	7.4	338.3	21.1
	23/12/2019	86.3	7.5	340	10.9	194.565	21.5
	30/12/2019	80.5	7.9	340.4	11.8	210.63	21.5
	6/1/2020	91.9	7.6	340	21.5
	7/1/2020	84.2	7.7	328.6	10.6	189.21	21.4

 

Water Concentration of Both Isomers in Each Treatment (ug/L)
Sampling date	Time	Phase	DIPB10		DIPB100		Control*		Solvent control*
			1,3-DIPB	1,4-DIPB	1,3-DIPB	1,4-DIPB	1,3-DIPB	1,4-DIPB	1,3-DIPB	1,4-DIPB
9/12/2019	10:00	Uptake	2.163	2.74	8.231	10.645	<0.478	<0.582	<0.478	<0.582
9/12/2019	10:00	Uptake	2.268	2.91	8.437	10.986	<0.478	<0.582	<0.478	<0.582
9/12/2019	10:00	Uptake	2.214	2.877	7.719	10.02	<0.478	<0.582	<0.478	<0.582
9/12/2019	15:30	Uptake	1.634	2.068	7.542	9.535	NA	NA	NA	NA
9/12/2019	15:30	Uptake	1.551	1.959	7.435	9.382	NA	NA	NA	NA
9/12/2019	15:30	Uptake	1.477	1.857	7.438	9.338	NA	NA	NA	NA
10/12/2019	10:00	Uptake	1.718	1.976	9.9419	11.093	NA	NA	NA	NA
10/12/2019	10:00	Uptake	1.64	1.995	9.544	11.948	NA	NA	NA	NA
10/12/2019	10:00	Uptake	1.735	2.112	8.865	10.92	NA	NA	NA	NA
10/12/2019	15:30	Uptake	4.78	5.845	7.778	9.566	<0.478	<0.582	<0.478	<0.582
10/12/2019	15:30	Uptake	4.59	5.834	7.279	8.949	<0.478	<0.582	<0.478	<0.582
10/12/2019	15:30	Uptake	4.835	5.932	7.88	9.662	<0.478	<0.582	<0.478	<0.582
11/12/2019	9:38	Uptake	<0.478**	<0.582**	8.4622	10.36	<0.478	<0.582	<0.478	<0.582
11/12/2019	9:38	Uptake	<0.478**	<0.582**	8.4717	10.294	<0.478	<0.582	<0.478	<0.582
11/12/2019	9:38	Uptake	<0.478**	<0.582**	8.4484	10.232	<0.478	<0.582	<0.478	<0.582
11/12/2019	15:54	Uptake	<0.478**	<0.582**	8.9575	11.022	NA	NA	NA	NA
11/12/2019	15:54	Uptake	<0.478**	<0.582**	8.4918	10.435	NA	NA	NA	NA
11/12/2019	15:54	Uptake	<0.478**	<0.582**	8.714	10.717	NA	NA	NA	NA
12/12/2019	10:50	Uptake	8.577	10.671	10.128	12.499	<0.478	<0.582	<0.478	<0.582
12/12/2019	15:22	Uptake	3.547	4.278	8.8	10.968
13/12/19	9:30	Uptake	2.349	2.809	8.521	10.421	<0.478	<0.582	<0.478	<0.582
13/12/19	15:03	Uptake	1.618	1.971	9.062	11.281	NA	NA	NA	NA
16/12/19	9:23	Uptake	2.055	2.47	10.522	12.804	<0.478	<0.582	<0.478	<0.582
16/12/19	15:34	Uptake	1.624	1.974	8.261	10.015
17/12/19	10:18	Uptake	2.019	2.463	10.948	13.459	<0.478	<0.582	<0.478	<0.582
17/12/19	15:12	Uptake	2.044	2.489	10.467	13.854	NA	NA	NA	NA
18/12/19	9:42	Uptake	1.755	2.19	11.264	14.355	<0.478	<0.582	<0.478	<0.582
18/12/19	15:32	Uptake	1.705	2.036	9.231	11.624
19/12/19	9:04	Uptake	1.981	2.335	11.882	14.717	<0.478	<0.582	<0.478	<0.582
19/12/19	15:30	Uptake	1.958	2.338	10.245	12.799	NA	NA	NA	NA
20/12/19	11:51	Uptake	1.874	2.169	11.97	14.68	<0.478	<0.582	<0.478	<0.582
20/12/19	15:13	Uptake	1.832	2.137	13.011	16.09	NA	NA	NA	NA
23/12/19	9:22	Uptake	1.793	2.07	8.799	10.5	<0.478	<0.582	<0.478	<0.582
23/12/19	14:03	Depuration	<0.478	<0.582	0.639	0.759	NA	NA	NA	NA
24/12/19	9:07	Depuration	<0.478	<0.582	0.69	0.796	<0.478	<0.582	<0.478	<0.582
3/1/2020	10:00	Depuration	<0.478	<0.582	<0.478	<0.582	<0.478	<0.582	<0.478	<0.582
7/1/2020	10:20	Depuration	<0.478	<0.582	<0.478	<0.582	<0.478	<0.582	<0.478	<0.582
7/1/2020	10:20	Depuration	<0.478	<0.582	<0.478	<0.582	<0.478	<0.582	<0.478	<0.582
7/1/2020	10:20	Depuration	<0.478	<0.582	<0.478	<0.582	NA	NA	NA	NA
*not determined when blank
** In order to calculate an mean exposure concentration when the test chemical is detected but not quantified we used a value of half of the LOQ (OCDE (2019), Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures, OECD Series on Testing and Assessment, Éditions OECD, Paris, https://doi.org/10.1787/0ed2f88e-en )

 

Time-weighted average (TWA) concentrations (Cw (μg.L-1 )) during the uptake phase
Component	DIPB10			DIPB100
	Mean	-20%	+20%	Mean	-20%	+20%
1,3 DIPB	2.203	1.763	2.644	9.922	7.938	11.906
1,4 DIPB	2.663	2.130	3.196	12.253	9.802	14.704
Mixture	5.166	4.133	6.199	23.540	18.832	28.248

 

 

DIPB10 Steady State Fish Tissue Concentration (Cf)
Uptake Phase Day	1,3 DIPB (μg.g-1)	1,4 DIPB (μg.g-1)	Mixture DIPB (μg.g-1)
Day 9	4.413	6.791	11.894
Day 9	4.257	5.850	10.729
Day 9	2.444	3.629	6.447
Day 9	4.409	5.075	10.068
Day 9 Mean	3.881	5.336	9.785
Day 11	3.127	4.479	8.074
Day 11	2.638	3.922	6.964
Day 11	6.113	6.358	13.239
Day 11	2.746	3.830	6.981
Day 11 Mean	3.656	4.647	8.814
Day 14	3.712	4.747	8.980
Day 14	5.638	6.547	12.935
Day 14	3.800	4.840	9.172
Day 14	2.815	3.414	6.613
Day 14 Mean	3.991	4.887	9.425
Day 9-14 Mean	3.843	4.957	9.341
Day 9-14 Mean - 20 %	3.074	3.965	7.473
Day 9-14 Mean + 20 %	4.611	5.948	11.210
DIPB100 Steady State Fish Tissue Concentration (Cf)
Uptake Phase Day	1,3 DIPB# (μg.g-1)	1,4 DIPB (μg.g-1)	Mixture DIPB (μg.g-1)
Day 7	19.864	26.936	49.682
Day 7	9.332	10.904	21.482
Day 7	16.276	23.335	42.05
Day 7	20.957	22.646	46.288
Day 7 Mean	16.607	20.955	39.875
Day 9	20.126	29.194	52.357
Day 9	8.073	11.629	20.915
Day 9	9.644	14.596	25.732
Day 9	16.053	21.784	40.167
Day 9 Mean	13.474	19.301	34.793
Day 11	31.809	36.840	72.876
Day 11	29.360	40.091	73.727
Day 11	31.000	44.386	80.028
Day 11	9.552	15.907	27.027
Day 11 Mean	25.430	34.306	63.414
Day 14	19.901	28.694	51.587
Day 14	17.218	23.425	43.145
Day 14	26.275	36.415	66.550
Day 14	18.083	29.942	45.674
Day 14 Mean	20.369	28.369	51.739
Day 7-14 Mean	18.970	25.733	47.455
Day 7-14 Mean - 20 %	15.176	20.586	37.964
Day 7-14 Mean + 20 %	22.764	30.879	56.946

 

 

Lipid Content (%) Wet Weight
Time	Control	Solvent Control	DIPB10	DIPB100
Day 0	1.975
	2.602
	1.288
	1.49
Day 14 (end of uptake phase)	3.957	3.924	5.095	3.357
	2.075	5.445	5.475	3.019
	3.474	3.178	2.605	3.49
Day 29 (end of depuration phase)	5.084	6.441	6.441	5.13
	4.893	5.475	6.163	6.196
	6.341	6.104	6.104	5.433
	6.547	6.275	5.542	6.396
	---	---	5.054	6.859
According to the Guidance Document on Aspects of OECD TG 305 on Fish Bioaccumulation Series on Testing & Assessment No. 264 [ENV/JM/MONO(2017)16]. Fish lipid content is usually measured at three time points during a study. However, these time points can vary, as can the durations of the uptake and depuration phase of studies. This means that an arithmetic mean of the available measurements would not necessarily represent the true, time-weighted average, lipid content. Analysis by Brooke and Crookes (51) showed that there was little difference between several different ways of deriving average lipid content. For simplicity, it is suggested to use the mean lipid content over the depuration phase (i.e. the midpoint of the depuration phase calculated from the mean lipid values at the end of the uptake phase/start of depuration and the end of the depuration phase). In this context, based on fish at the end of the uptake phase and fish at the end of the depuration phase, the fish lipid mean content is 5.052 %.

 

Study Results for Individual Isomers and Mixture

	1,3 DIPB isomer		1,4 DIPB isomer		Mixed DIPB
	DIPB 10 µg/L	DIPB 100 µg/L	DIPB 10 µg/L	DIPB 100 µg/L	DIPB 10 µg/L	DIPB 100 µg/L
Kinetic BCF
kg ( day^-1)	0.0206	0.0206	0.0206	0.0206	0.0206	0.0206
Ln (%)	5.052	5.052	5.052	5.052	5.052	5.052
k1 (L.kg^-1.day^-1)	575.3	662.25	597.29	685.31	582.17	672.62
k2 (day^-1)	0.3703	0.4041	0.3313	0.374	0.3434	0.3846
k2g (day^-1)	0.3497	0.3835	0.3107	0.3534	0.3228	0.364
BCFK (L.kg^-1)	1553.6	1638.6	1802.7	1832.6	1695.5	1718.7
BCFKg (L.kg^-1)	1645.1	1726.7	1922.2	1939.4	1803.7	1847.7
BCFKL (L.kg^-1)	1537.6	1621.7	1784.1	1813.7	1678	1701
BCFKgL (L.kg^-1)	1628.2	1708.9	1902.4	1919.4	1785.1	1828.7
(CI 95%)	(1416.4 -1839.9)	(1483.3 -1934.4)	(1678.8 -2126)	(1673.4 -2165.5)	(1569.9 -2000.3)	(1593.9 -2063.5)
t1/2g (days)	1.9821	1.8072	2.2307	1.9616	2.1475	1.9041
Steady-state BCF
Cf (mg.kg^-1)	3.843	18.97	4.957	25.73	9.341	47.45
Cw (mg.L^-1 )	2.203	9.222	4.957	25.73	9.341	47.45
BCFSS (L.kg^-1)	1744	1912*	1861	2100*	1790	2016*
BCFSSL (L.kg^-1)	1726	1892*	1842	2078*	1808	1995*
*These data have to be taken with care because the steady state was empirically considered to be reached for the last four sampling points of the uptake phase

Validity criteria fulfilled:

yes

Conclusions:

The BCFKgL(L.kg-1) obtained in this study for the test item (mixture of isomers DIPB) was between 1785.1 and 1828.7. The BCFKgL(L.kg-1) for the 1,3-DIPB isomer was between 1628.2 and 1708.9, and the BCFKgL(L.kg-1) for the 1,4-DIPB isomer was between 1902.4 and 1919.4. These results suggest that the individual isomers as well as the mixture of isomers do not meet the Bioaccumulation (B) threshold of 2000 under a PBT/vPvB assessment. These results suggest that the individual isomers as well as the mixture of isomers do not meet the Bioaccumulation (B) threshold of 2000 under a PBT/vPvB assessment.

Executive summary:

The aim of this study was to obtain laboratory data to determine the bioconcentration factor (BCF) of the test item at two different concentrations in the bluegill (Lepomis macrochirus), through aqueous exposure based on the OECD TG 305 (2012). The test item was a mixture of isomers 1,3-diisopropylbenzene (1,3-DIPB) and 1,4-diisopropylbenzene (1,4-DIPB). Since the test item was poorly soluble under the test condition, stock solutions were prepared in Dimethylformamide, considered as an appropriate solvent. Four different conditions were used during the test: (i) Control, (ii) Solvent Control, (iii) DIPB mixture at 10 μg.L^-1(nominal concentration) (DIPB10) and (iv) DIPB mixture at 100 μg.L^-1(nominal concentration) (DIPB100). The test solutions were prepared by dilution of the stock solutions with housing water in a mixing chamber and with vigorous stirring to aid dispersion. The test was divided into two phases, the uptake phase which lasted 14 days followed by a depuration phase. The total duration of the test lasted 29 days. No toxic effect of the test item and/or the solvent control were observed.

 

According to the Guidance on Information Requirements and Chemical Safety Assessment (Chapter R.11: PBT/vPvB Assessment, ECHA; Version 3.0 – June 2017), the resulting BCF that is preferred for a comparison with the bioaccumulation criteria is the kinetic growth corrected and lipid normalised (to 5 % lipids) BCF value (BCF_KgL). Moreover, it has to be compared to the BCF_SSL. In this study the BCF_KgLbased on first order kinetics is in the same order of magnitude than the BCF_SSL, indicating clearly that a steady-state has been attained in the uptake phase.

 

By comparing BCF_KgLbetween conditions (DIPB10 and DIPB100) for both isomers (and consequently for the mixture), it is important to note as well that the difference is not clearly marked with 5 % and 1 % of difference, respectively. This calculation was made according to the guidance document on aspects of OECD TG 305 on fish bioaccumulation (2017;§2.5.1). This lack of clear difference between BCF_KgLobtained in each condition confirmed as well the low impact of the noted deviation of the study plan. This deviation regarded that the concentration of the test substance in the test chambers was not maintained within +/- 20 % of the mean of the measured values during the uptake phase.

By consequence, the BCF_KgL(L.kg^-1) obtained in this study for the test item (mixture of isomers DIPB) was between 1785.1 and 1828.7. The BCF_KgL(L.kg^-1) for the 1,3-DIPB isomer was between 1628.2 and 1708.9, and the BCF_KgL(L.kg^-1) for the 1,4-DIPB isomer was between 1902.4 and 1919.4. These results suggest that the individual isomers as well as the mixture of isomers do not meet the Bioaccumulation (B) threshold of 2000 under a PBT/vPvB assessment.

Reference 2

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

other information

Study period:

November 2019 to march 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Reference 3

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
In this justification, the read-across (bridging) concept is applied. Please refer to a full version of Read-across statement attached in the section 13 "Assessment reports".

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The underlying hypothesis for the read-across is that the target and the source substance have similar toxicological properties (including the same target organs) due to their structural similarity, resemblance to their chemical reactivity, and therefore a similar mode of action.
The source substance ‘Mixture of 1,3-diisopropylbenzene and 1,4-diisopropylbenzene' is a mixture of structural isomers, 1,3- diisopropylbenzene(target substance) and 1,4-diisopropylbenzene. The physico-chemical properties are highly equivalent based on the high structural similarity. As a conclusion, it is scientifically justified to address the endpoint Bioaccumulation: aquatic / sediment with data on this mixture of isomers.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source substance: Mixture of 1,3-diisopropylbenzene and 1,4-diisopropylbenzene (Diisopropylbenzene), CAS no. 25321-09-9
structural formula: C12H18
Smiles: CC(C)C1=CC=CC=C1C(C)C
Molecular weight: 162 g/mol
CAS 25321-09-9
EC No 246-835-6
purity: not specified

target substance: 1.3-diisopropylbenzene (or m-DIPB)
structural formula: C12H18
Smiles: CC(C)c1cccc(c1)C(C)C
Molecular weight: 162 g/mol
CAS 99-62-7
EC No 202-773-1
purity: not specified

No additional information is available on purity of the source and the target substances. Both substances are normally of high purity, containing only minor amounts of impurities that do not influence the read-across validity.

3. ANALOGUE APPROACH JUSTIFICATION
Please refer to the full version of the read-across statement attached in the section 13 "Assessment reports".

4. DATA MATRIX
Please refer to the full version of the read-across statement attached in the section 13 "Assessment reports".

Reason / purpose for cross-reference:

read-across source

Route of exposure:

aqueous

Temp.:

ca. 25 °C

Type:

BCF

Value:

>= 503 - <= 1 680

Remarks on result:

other: m-diisopropylbenzene

Remarks:

Conc.in environment / dose:20 ug/L

Temp.:

ca. 25 °C

Type:

BCF

Value:

>= 546 - <= 3 210

Remarks on result:

other: m-diisopropylbenzene

Remarks:

Conc.in environment / dose:2 ug/L

Elimination:

no

Details on results:

Visual observation: normal

The elute showed two peaks on the GC-MS chart.
This is due to the fact that the test substance is an isomeric mixture.
A comparison of the retention times with the pure isomers showed that the peak before the isomeric pure product showed a higher retention time than the peak after the isomeric pure product. The later peak was found to be the P rest.
The GC (FlD detector) analysis showed that the peak containing m-unity was 61.7% and that containing P- rest was 35.5 %.
In this test, the concentrations are expressed as the total amount of the test substance for convenience.
In this test, the concentration is expressed as the amount of the whole sample for convenience.
The actual amount of each component is determined by multiplying this value by the number of skewers contained.

Fish body - Trial fish test
If the concentration in the fish is significantly higher than at the time of the recovery test Dilute the final volume solution accordingly.
Recoveries from the above operation (with 60 females of the substance to be tested)
　　　　　　m-form: 97.7 %
　　　　　　p-form: 98.4 %.

Test water:
recoveries from the procedure:
first concentration zone:
m-form: 88.7 %
p-form 89.4 %

second concentration zone:
m-form: 90.3 %
p-form 89.4 %

Measured value

Table 1-1 Concentration in water tank (weighted average)                          (Unit: ppb (W/V))

	1 W	2 W	4 W	6 W	8 W
First concentration zone	9.48	10.4	11.5	11.7	12.0
Second concentration zone	0.811	0.914	1.02	1.05	1.11

 

Table 1-2 Tank concentration (for each peak)                    (Unit: ppb (W/V))

		1 W	2 W	4 W	6 W	8 W
First concentration zone	m-form	9.80	10.8	11.9	12.1	12.3
	p-form	8.92	9.81	10.8	11.0	11.5
Second concentration zone	m-form	0.851	0.961	1.08	1.11	1.16
	p-form	0.742	0.833	0.919	0.955	1.02

 

Concentration test results

Table 2-1 Enrichment factor for reagents (weighted average)

	1 W	2 W	4 W	6 W	8 W
First concentration zone	1030	1610	743	1710	900
	1210	760	1240	513	1910
					1590
Second concentration zone	1050	1550	1140	1510	3120
	1040	534	817	1300	1140
					972

 

Table 2-2 Concentration factor of the substance to be tested (m-form)

	1 W	2 W	4 W	6 W	8 W
First concentration zone	1110	1660	756	1500	857
	1280	771	1370	503	1680
					1400
Second concentration zone	858	1400	1200	1600	3210
	1160	546	840	1180	1250
					1050

Table 2-3 Concentration factor of the substance to be tested (p-form)

	1 W	2 W	4 W	6 W	8 W
First concentration zone	894	1510	721	2070	975
	1110	742	1020	530	2300
					1930
Second concentration zone	1380	1820	1030	1360	2960
	826	512	776	1520	954
					837

Method of calculating the weighted average

The weighted average of the water coffin concentration and concentration factor is calculated by the following formula:

weighted mean value = (∑ X I Ci)/(∑Xi)

where X i : the content of each component

　　　C i : concentration or concentration factor for each

 

The content test of each component was determined from the peak area of the gas chromatograph (detector FID) as follows

　　m-form: 61.7 % of the total

　　p-form:  35.5 % of the total

Validity criteria fulfilled:

yes

Conclusions:

For m-diisopropylbenzene BCF values were ranging from 503 to 1680 at 20 µg/L and 546 to 3210 at 2 µg/L. The bioconcentration potential is moderately high.

Executive summary:

In a study conducted similiar to OECD Guideline 305 Cyprinus carpio were exposed to m-/p-diisopropylbenzene concentrations of 2 and 20 µg/L for 56 d (8 weeks). For p-diisopropylbenzene BCF values ranging from 530 to 2300 at 20 µg/L and 512 to 2960 at 2 µg/L were determined and for m-diisopropylbenzene BCF values ranging from 503 to 1680 at 20 µg/L and 546 to 3210 at 2 µg/L. The bioconcentration potential is moderately high.

Description of key information

BCF studies, OECD 305 guideline study, BCF values of 1628.2 L/Kg and 1708.9 L/Kg at two exposure concentrations of 10 and 100 µg/L, respectively.

Key value for chemical safety assessment

BCF (aquatic species):

1 708.9 L/kg ww

Additional information

The bioconcentration factor (BCF) of a mixture of isomers 1,3-diisopropylbenzene (1,3-DIPB) and 1,4-diisopropylbenzene (1,4-DIPB) was tested in the first Key study (Lejon, 2020) at two different concentrations in the bluegill (Lepomis macrochirus), through aqueous exposure based on the OECD TG 305 (2012). Four different conditions were used during the test: (i) Control, (ii) Solvent Control, (iii) DIPB mixture at 10 μg.L-1(nominal concentration) (DIPB10) and (iv) DIPB mixture at 100 μg.L-1(nominal concentration) (DIPB100). The test was divided into two phases, the uptake phase which lasted 14 days followed by a depuration phase. The total duration of the test lasted 29 days. No toxic effect of the test item and/or the solvent control were observed. In this study the BCFKgL based on first order kinetics was in the same order of magnitude than the BCF_SSL, indicating clearly that a steady-state has been attained in the uptake phase.

By comparing BCF_KgL between conditions (DIPB10 and DIPB100) for both isomers (and consequently for the mixture), it is important to note as well that the difference is not clearly marked with 5 % and 1 % of difference, respectively.  This lack of clear difference between BCF_KgL obtained in each condition confirmed as well as the low impact of the noted deviation of the study plan. This deviation regarded that the concentration of the test substance in the test chambers was not maintained within +/- 20 % of the mean of the measured values during the uptake phase.

By consequence, the BCF_KgL(L.kg-1) obtained in this study for the test item (mixture of isomers DIPB) was between 1785.1 and 1828.7.

The BCF_KgL(L.kg-1) for the 1,3-DIPB isomer was between 1628.2 and 1708.9, and the BCF_KgL(L.kg-1) for the 1,4-DIPB isomer was between 1902.4 and 1919.4.

These results suggest that the individual isomers as well as the mixture of isomers do not meet the Bioaccumulation (B) threshold of 2000 under a PBT/vPvB assessment.

 

The second Key BCF study conducted according to OECD Guideline 305 E (Bioaccumulation: Flow-through Fish Test) Cyprinus carpio were exposed to the mixed isomers m-/p-diisopropylbenzene concentrations of 2 and 20 µg/L for 56 d.

BCF values were measured for each isomer independently. For p-diisopropylbenzene BCF values ranging from 530 to 2300 at 20 µg/L and 512 to 2960 at 2 µg/L were determined and for m-diisopropylbenzene BCF values ranging from 503 to 1680 at 20 µg/L and 546 to 3210 at 2 µg/L. 

 

In conclusion, the test item does not meet the classification criteria for B or vB.