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EC number: 218-485-4
CAS number: 2162-73-4
The phototransformation in air of
2,4,6-triisopropyl-m-phenylene diisocyanate was predicted with the help
of the computer program AOPWIN v1.92 (EPIWIN software) by US-EPA ,
resulting in an atmospheric half-life of 0.280 days (around 3.40 hours)
(Chemservice S.A., 2011).
Regarding hydrolysis, one experimental
result as well as one QSAR prediction is available for the test
substance. Based on the results of the experimental study, the test
substance is hydrolytically unstable and undergoes rapid hydrolysis.
Abiotic degradation > 90% was observed within 3 min at 20 °C in
demineralized water with a half life time of about 37 seconds (Neuland,
2020). This result is supported by the prediction of HYDROWIN v2.00
(EPIWIN software) by US-EPA, which detected ISOCYANATES as hydrolysable
substance class (Chemservice S.A., 2012). Accordingly, the
hydrolysis half-life will be less than 10 minutes at 25 °C and even at
Regarding biodegradation in water, one
experimental result as well as one QSAR prediction is available for the
test substance. Based on the results of the experimental study, no
degradation had been occurred after 28 days of test duration and the
substance was not found to be bacteriotoxic (Müller, 1997). This result
is supported by the prediction of BIOWIN v4.10 (EPIWIN software), which
concludes that the substance is not readily biodegradable (Chemservice
S.A., 2011). TheSTART
plug-in in Toxtree (v.2.1.0) assigns the chemical as "class III -
unknown" (Chemservice S.A., 2011).
Regarding biodegradation in soil, sediment
and surface water no information is provided, since direct as well as
indirect exposure to the environment is unlikely, which is proven by the
conducted exposure assessment. For further information please
refer to Section 9 and 10 of the CSR. Hence, these endpoints are
waived based on exposure considerations.
Due to the very fast hydrolysis (DT50=
37s) hydrolysis and the resulting instability of the test substance, it
was considered most meaningful to cover the information on the
bioaccumulative potential by the consideration of the degradation
products. Based on the results of the hydrolysis study conducted at
CURRENTA GmbH according to OECD 111, 2,4,6-triisopropyl-m-phenylene
diamine (TRIDA, CAS 6318-09-08) was expected as major hydrolysis and
polymeric ureas as potential minor hydrolysis products (Neuland, 2020).
Accordingly, the bioaccumulative potential
was analysed for the main hydrolysis product2,4,6-triisopropyl-m-phenylene
diamine (TRIDA, CAS 6318-09-08).The study was running under GLP
according to OECD TG 305-I using aqueous exosure. Based on the mean
measured concentration of the test material in the test water, the
bioconcentration factor was determined for steady state (BCFSS),
including a normalisation to 5% lipid content (BCFSSL) and
was 1.44-1.88 L/kg and 4.5-6.1 L/kg, respectively, indicating a low
potential for bioaccumulation. As a worst-case assumption the upper
value of 6.1 L/kg is taken as key value for further risk assessment.
Polymeric ureas are considered as polymers
under REACH. Therefore they do not have to be registered and evaluated
according to Chapter 1; Article 2, Paragraph 9 Regulation No. 1907/2006.
Regardless of the evaluation of available data, the determination of the
bioaccumulative potential of the polymeric ureas as minor hydrolysis
product is waived accordingly.
As supporting information a WoE approach
using QSAR prediction (BCFBAF v3.01) is presented for the test substance
itself, indicating a low potential for bioaccumulation in fish. Using
the regression-based estimate (traditional method) a BCF of 7065 L/kg
wet-wt was calculated. Using the Arnot-Gobas method, which is based on
the mechanistic first principles, the BCF results in a value of 5970
L/kg wet-wt. The whole body primary biotransformation rate estimate for
fish gives a half-life of 3.214 days, whereby the rate constant (kM) for
10 g fish is designated as 0.2157/day. This is taken into account to
predict the apparent metabolism half-life in fish for the substance. For
the lower trophic level a BCF of 232.2 L/kg wet-wt is calculated,
whereas for the mid trophic level the BCF will result in 210.5 L/kg
wet-wt and the higher trophic level gives a value of 152.8 L/kg wet-wt.
A terrestrial bioaccumulation study is not
triggered for a registration of a tonnage band of 100 - 1000 tons/year
according to REACH Regulation (EC) 1907/2006.
Transport and distribution
Regarding the soil adsorption potential for
2,4,6-triisopropyl-m-phenylene diisocyanate only a QSAR prediction is
reported which was performed by the computer program KOCWIN v2.00
(Chemservice S.A., 2011). A Koc value of 539300 L/kg (5.393 E+005 L/kg)
was estimated by the Salbjic molecular connectivity (MCI) method, which
is taken more seriously into account, due to the fact that it includes
improved correction factors. The traditional method gives a value of
3639000 L/kg (3.639 E+006 L/kg).
Henry´s law states that the solubility of a
gas in a liquid solution at a constant temperature will be proportional
to the partial pressure of the gas which is above the solution (Henry,
1803). This information is not mandatory for a registration under REACH
Regulation (EC) 1907/2006 in a tonnage band of 100 - 1000 tons/year.
However, the Henry´s Law Constant can be predicted with the help of
HENRYWIN v3.20 (Chemservice S.A., 2011). A constant of 7.49 Pa*m³/mol
was predicted at 25 °C for the substance 2,4,6-triisopropyl-m-phenylene
Monitoring data are only available for the
read across substance toluene diisocyanate. Atmospheric emissions are
low, typical emission losses for TDI are 25 g/t (Tury, 2004). Laboratory
studies show that the substance does not react with water in the gas
phase at a significant rate. The primary degradation reaction of these
aromatic diisocyanates in the atmosphere is expected to be oxidized by
OH radicals with an estimated half-life of one day. Laboratory studies
also show that this reaction is not expected to result in increased
ground-level ozone accumulation. It is indicated that degradation by
photolytically generated radicals, rather than by direct photolysis will
occur. In a vapour phase no hydrolysis was detected. The reaction rate
of TDI with OH radicals, measured relative to that of toluene, was
estimated as >= 7.4 x 10E12 cm³/molecule/ sec. Both isomers of TDI were
found to inhibit ozone formation and radical levels in all experiments.
This atmospheric degradation of TDI by OH radicals raises concerns that
the process might lead to ozone or smog formation. Smog chamber studies
have shown that this is not the case. Furthermore, TDI should not be
considered an ozone precursor. Overall, it can be concluded that no
significant long-term or wide-ranging environmental effects would be
expected from current emissions of TDI to air.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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