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EC number: 254-052-6
CAS number: 38640-62-9
Biodegradation in water: screening
Results on biodegradation of DIPN are
ambiguous. In the study rated as key study, no ultimate biodegradation
was demonstrated in a test for ready biodegradability (OECD TG 310)
(LAUS 2011a). Approximately 20 - 25% primary biodegradation was observed
in this test by analysing DIPN concentrations in test medium (LAUS
2011b). An inherent test (OECD 302D with adaptation) resulted in
biodegradation of 37 % within 56 d.
In a MITI II test using a
concentration of 30 mg/L (far above water solubility of DIPN), no
biodegradation was observed (CERI 1977/CITI1992). In contrast, in an
OECD 301 B ready biodegradability test, using concentrations between 0.4
mg/L and 10 mg/L, biodegradation decreased from ca. 84% for a
concentration of 0.4 mg/L (result readily biodegradable) to ca. 20% for
the 10 mg/L concentration (Yoshida and Kojima 1978). As this study
cannot be reliably assessed
and methodological deficiencies cannot be excluded, the study is not
considered being reliable (RL3). DIPN is considered as not biodegradable.
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 (Eurofins, 2020), 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. 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
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. 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 isomer 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.
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