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EC number: 254-052-6
CAS number: 38640-62-9
Due to its chemical structure,
diisopropylnaphthalene (DIPN) cannot be hydrolyzed. The structure of the
molecule does not contain hydrolysable groups.
Phototransformation in air
No data available (not required for
Phototransformation in water
Photolytic half-life of 2,6-DIPN (used
as supporting substance) in distilled water was 16 h using a high
pressure mercury lamp as irradiation source. For 2,7-DIPN, a half-life
of 6.4 h was determined. In salt water, phototransformation was
accelerated (half-life of 2,6 DIPN in 0.5 M NaCl < 4 h).
Phototransformation in soil
No data available (not required for
Biodegradation in water: screening
Results on biodegradation of DIPN are
ambiguous. In concentrations below solubility in water, DIPN seems to be
readily biodegradable (Yoshida 1978_301 B, dissolved substrate). At
higher concentrations, inherent biodegradability has been demonstrated
(Yoshida 1978_301 B, not dissolved substrate). In a MITI II test, no
biodegradation was observed (CERI 1977/CITI1992). In a sealed vessel CO2
head space test (OECD TG 310) using 14C ring labelled
diisopropylnaphthalene, no significant ultimate biodegradation could be
demonstrated (LAUS 2010a). Analysing DIPN content by GC in the test
medium, primary biodegradation of approx. 20 - 30 % and total
degradation of approx. 50 % was observed after 56 days (LAUS 2010b).
Biodegradation in surface water, sediment and
soil: simulation tests
Tests on aerobic mineralisation in surface water
according to OECD 309 were performed for the isomers 1,3-DIPN and
1,4-DIPN, which were shown on screening test level to be less
degradable. Since only a negligible amount of CO2 (0 – 0.1% AR) was
formed and no metabolites occurred both isomers can be considered as
stable under the OECD 309 test condition (Eurofins, 2020). However,
based on volatility the dissipation time from water phase was very
short. The determined DisT50 values were below 2 days indicating a rapid
evaporation from the water phase, which means that the results of the
OECD 309 studies are not sufficient for a final persistence assessment. Therefore,
QSAR estimates for the degradation in the compartments sediment and soil
were considered additionally in a weight of evidence approach. For
degradation in sediment the QSAR prediction is persistent (P) and/or
very persistent (vP). For the soil compartment the QSAR prediction leads
to a “borderline result” with a DT50 close to the P threshold of 120
days. Both QSARs can be considered as reliable since the substance is in
the applicability domain of the model. Based on study results and QSAR
estimates, it can be assumed that bis(isopropyl)naphthalene (CAS
38640-62-9) contains persistent and/or very persistent isomers. Therefore,
the isomeric mixture bis(isopropyl)naphthalene (CAS 38640-62-9) needs to
be assessed as potentially persistent (P) and/or very persistent (vP).
No substantial new findings can be expected from further simulation
tests with DIPN isomers. Therefore, further testing is not intended.
Mode of degradation in actual use
Bioaccumulation: aquatic / sediment
Bis(isopropyl)naphthalene (DIPN) is an isomeric
mixture, which consist of seven isomers (1,3-, 1,4-, 1,5-, 1,6-, 2,6-
and 2,7-DIPN). Bioaccumulation potential differs between the isomers.
According to OECD 305 the lipid normalized BCF values were determined to
range between 810 -2500 (low dose group; 0.47 µg/L)
and 2200-7800 (high dose group; 4.85 µg/L), respectively. Hence, some
isomers of bis(isopropy)naphthalene fulfil the criterion of being
bioaccumualtive (BCF > 200). Although the
environmental relevance of the results from the high exposure concentration
is questionable (see expert statement ETC, 2017) the highest measured
BCF value of 7800 was used as an worst case assumption for the
bioaccumulation assessment. Therefore, the isomer mixture
bis(isopropyl)naphthalene (CAS 38640-62-9) was assessed as
bioaccumulative (B) and potentially very bioaccumulative (vB) under
Transport and distribution
Based on Koc values of 33,108 or
188,973 (log Koc 4.5576 or 5.2764) calculated using two different
methods, DIPN is expected to have a low mobility and high accumulation
potential in soil (MWC, 2009).
Henry’s Law constant
Using the method of bond contribution
and group contribution, Henry's Law constants of 202 and 197 Pa*m³/mol
were determined, indicating quite rapid volatilization of DIPN from
water into air.
In Japan, bis(isopropyl)naphthalene
DIPN was detected in environmental samples from two locations. In sea
mud from the mouth of a river (Osaka Bay), 0.019 to 0.16 ppm (n = 5) of
DIPN were analyzed and in sea fish (Yokkaichi Bay), levels of ca. 0.003
ppm (n = 7) were found (Sumino 1977).
Close to a paper recycling plant, DIPN
concentrations in river sediment were found to be 0.3 - 23.0 µg/g (Sato
1980). At the wastewater discharge of another plant, 2200 µg/g were
analyzed but 100 m downstream, only concentrations of 8.5 µg/g were
detected (Haga et al.1984).
Surveys of the Environmental Agency of
Japan published environmental monitoring data in surface water, sediment
and fish of the years 1975, 1977, 1980 and 2005/2006/2007 (see Summary
in the table below):
was detectable in 10 out of 400 water samples with a maximum of 0.0044
was positive in 35 out of 358 sediment samples (10 %) with a maximum
(2005) of 7500 µg/kg dry weight
was positive in 41 out of 349 fish samples (12 %) with a maximum (1975)
of 48 µg/kg wet weight.
of monitoring data 1975 - 2005/2007 (follow-up 2009 and 2010, see below
addendum Suzuki et al. 2012)
[Chemical Risk Information Platform (CHRIP) 2010 / (Environment Agency,
Number of detection A/B
[µg/L (water), µg/g dwt (sediment), µg/g wwt (fish)]
Range of detection
Limit of detection
70 - 5,000*
0.01 – 10
0.01 - 20
0.00071 – 0.0015
0.061 - 0.19
0.03 - 0.25
0.0019 - 0.1
0.00074 - 0.6
0.049 - 0.064
0.01 - 1.0
0.0037 – 7.5
0.025 - 0.25
0.00052 - 0.0017
0.0002 - 0.5
0.006 - 0.025
0.002 – 2.5
0.00019 – 0.027
2009 and 2010 (Suzuki et al. 2012), sampling was continued in the
Southern Hyogo prefecture, which embraced 41 sampling points in the
Osaka bay and the Seto Inland Sea:
Seawater: <1.9 - 9.8 ng/L DIPN was found.
Sediment: <1.1 - 100 μg/kg dw (30 points in 2009), the highest solitary
contamination of 4400 μg/kg dw was detected in a river sediment of a
river without a relevant industrial source.
Fish tissue (Japanese sea perches: Lateolabrax japonicus): 1.2 - 3.4
μg/kg ww (five samples). There was no difference in the levels of DIPN
in males and females; however, the isomers 1,3- and 1,4 -DIPN were more
pronounced in female perch.
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