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EC number: 230-896-0
CAS number: 7360-38-5
For detailed information on the results please refer to the attached
The catalytic activity of
the carboxylesterase family leads to a rapid
biotransformation/metabolism of xenobiotics which reduces the
bioaccumulation or bioconcentration potential. Several in-vivo
and in-vitro experiments showed the biotransformation of xenobiotics in
fish. The biotransformation reactions have been shown
to occur in fish at rates which have siginificant effects on toxicity
and residue dynamics of selected chemicals. Inhibition of these
reactions can lead to increased toxicity and bioaccumulation factors.
Thus, it was shown that the carboxylesterase activity has an influence
on the bioaccumulation of xenobiotics.
The metabolic efficiency of the liver in the
enzymatic hydrolysis of exogenous substrates is dependent on both the
substrate type and the fish species. Indeed, the fish studied metabolise
much more readily phenyl acetate, the typical substrate of A-esterases,
and the phosphate monoester, than the B-esterase substrates. The
inter-species differences in activities (referred to unit body weight)
vary within a factor of 7 – 17 for esterases (with p-nitrophenyl
phosphate, phenyl acetate or ethyl-butyrate as substrate), while
reaching a factor of variation of even 60 for acetanilide amidase.
In line with previous evidence on hepatic
mono-oxygenase and glutathione S-transferases, guppy is the most active
fish species, also with reference to non-specific hydrolases. At
variance with results on the other enzyme families, carp also is endowed
with the highest levels of hydrolases.
Propane-1,2,3-triyl 2-ethylhexanoate (CAS No. 7360-38-5) exhibits a low potential for bioaccumulation, based on QSAR calculations and rapid metabolisation as expected for this substance.
No experimental data evaluating the bioaccumulation potential of
Propane-1,2,3-triyl 2-ethylhexanoate (CAS No. 7360-38-5) is available.
The substance exhibits a high log Kow (log Kow = 8.98), suggesting
potential to bioaccumulate in biota. However, the information gathered
on environmental behaviour and metabolism in combination with
QSAR-estimated values provide enough evidence (in accordance to the
REACh Regulation (EC) No 1907/2006, Annex XI General rules for
adaptation of the standard testing regime set out in Annexes VII to X,
1.2, to cover the data requirements of Regulation (EC) No. 1907/2006,
Annex IX) to state that this substance is likely to show no
Intrinsic properties and fate
Propane-1,2,3-triyl 2-ethylhexanoate (CAS No. 7360-38-5) is readily
biodegradable.According to the Guidance on information
requirements and chemical safety assessment, Chapter R.7b, readily
biodegradable substances can be expected to undergo rapid and ultimate
degradation in most environments, including biological Sewage Treatment
Plants (STPs) (ECHA, 2017b).Therefore, after passing through
conventional STPs, only low concentrations of these substances are
likely to be (if at all) released into the environment.
Propane-1,2,3-triyl 2-ethylhexanoate (CAS No. 7360-38-5) exhibits
a high log Kow (log Kow = 8.98) and a water solubility < 0.05 mg/L. The
Guidance on information requirements and chemical safety assessment,
Chapter R7.B (ECHA, 2017b) states that once insoluble chemicals enter a
standard STP, they will be extensively removed in the primary settling
tank and fat trap and thus, only limited amounts will get in contact
with activated sludge organisms. Nevertheless, once this contact takes
place, these substances are expected to be removed from the water column
to a significant degree by adsorption to sewage sludge (Guidance on
information requirements and chemical safety assessment, Chapter R.7a,
ECHA, 2017a) and the rest will be extensively biodegraded (due to ready
biodegradability).Thus, discharged concentrations of these
substances into the aqueous compartment are likely to be very low.Should
the substances be released into the water phase, due to their
hydrophobicity and expected high adsorption potential, they will tend to
bind to sediment and other particulate organic matter, and therefore,
the actual dissolved fraction available to fish via water will be
reduced. Thus, the main route of exposure for aquatic organisms such as
fish will be via food ingestion or contact with suspended solids.
Additional information on the bioaccumulation Propane-1,2,3-triyl
2-ethylhexanoate (CAS No. 7360-38-5) in fish species is available.
Estimated bioconcentration (BCF) and bioaccumulation (BAF) values were
calculated for this substance using the BCFBAF v3.01 program (Estimation
Programs Interface Suite™ for Microsoft® Windows v 4.11., US EPA),
including biotransformation rates (Arnot-Gobas method). Even though the
substance is outside the applicability domain of the used model (model
training set is constituted of substances with log Kow values in the
range of 0.31 to 8.70), the calculations (especially the low BCF values
calculated using the Arnot-Gobas method) reflect the rapid
biotransformation assumed for Propane-1,2,3-triyl 2-ethylhexanoate (CAS
No. 7360-38-5). The calculated BCF and BAF values are 360 L/kg (BCF,
regression based estimate) and 1.05 (Arnot-Gobas method, BCF and BAF,
respectively). BCF calculations reflect the bioaccumulation potential
after uptake via water, whereas the BAF gives an indication of the
bioaccumulation when all exposure routes (water, food, etc.) are taken
The obtained results indicate that Propane-1,2,3-triyl
2-ethylhexanoate is likely to show no bioaccumulation potential.According
to Regulation (EC) No. 1907/2006, Annex XIII, 1.1.2, a substance only
fulfills the bioaccumulation criterion (B) when BCF values are > 2000.
Even though this condition is preferred to be confirmed with
experimental data, in this case the estimated QSAR-based BCFs provide
sufficient reliable evidence which suggests that the substance will not
Metabolism of Propane-1,2,3-triyl 2-ethylhexanoate
If Propane-1,2,3-triyl 2-ethylhexanoate is uptaken by living organisms,
aliphatic esters such as the substance will be initially metabolized via
enzymatic hydrolysis to the respective fatty acid and alcohol components
as would other dietary fats (e.g., Linfield, 1984). The hydrolysis is
catalyzed by carboxylesterases and esterases, with B-esterases located
in hepatocytes of mammals being the most important (Heymann, 1980;
Anders, 1989). However, carboxylesterase activity has also been reported
from a wide variety of tissues in invertebrates and fishes (e.g.,
Leinweber, 1987; Suldano et al., 1992; Barron et al., 1999; Wheelock et
al., 2008). In fish, the high catalytic activity, low substrate
specificity and wide distribution of the enzymes in conjunction with a
high tissue content lead to a rapid biotransformation of aliphatic
esters, which significantly reduces its bioaccumulation potential (Lech
& Melancon, 1980; Lech & Bend, 1980).
Glycerol and 2-ethylhexanoic acid are the expected hydrolysis products
from the enzymatic reaction catalyzed by carboxylesterase. The
metabolism of fatty alcohols has been intensively reviewed in the
literature (e.g., see Rizzo et al., 1987; Hargrove et al., 2004). The
free alcohols can either be esterified to form wax esters (which are
similar to triglycerides) or they can be transformed to fatty acids in a
two-step enzymatic process catalyzed by alcohol dehydrogenase (ADH) and
aldehyde dehydrogenase (ALDH). The responsible enzymes ADH and ALDH are
present in a large number of animals including plants, microorganisms
and fish (e.g., Sund & Theorell, 1963; Nilson, 1990; Yoshida et al.,
1997; Reimers et al., 2004; Lassen et al., 2005).
The metabolism of alcohols in fish was intensively studied by
Reimers et al. (2004).They isolated and characterized two cDNAs
from the zebra fish, Danio rerio, encoding ADHs, which showed specific
metabolic activity in in-vitro assays with various alcohol components
ranging from C4 to C8. The emerging aldehydes were shown to be further
oxidized to the corresponding fatty acid by ALDH enzymes. The most
effective ALDH2, which is mainly located in the mitochondria of liver
cells showed a similarity of 75% to mammalian ALDH2 enzymes and a
similar catalytic activity (also see Nilsson, 1988). The same metabolic
pathway was shown for longer chain alcohols, such as stearyl and oleyl
alcohol in the intestines of rats (Sieber et al., 1974).
The further metabolism of the fatty acids in general is also well
investigated in various organisms, such as plants (e.g., Harwood 1988),
fish (e.g., Henderson, 1996; Turchini, 2006) or algae (e.g., Nichols,
1968).The free fatty acids can either be stored as triglycerides
or be oxidized via mitochondrial ß-oxidation removing C2-units, in order
to store usable energy in form of ATP (Masoro, 1977). Acetyl-CoA, the
final product of the ß-oxidation process, can further be mineralized in
the tricarboxylic acid cycle via different enzymatically catalyzed
processes to carbon dioxide.
Both hydrolysis products, 2-ethylhexanoic acid and glycerol, were
assessed as safe by authorities regarding their bioaccumulation
potential (Environment Canada, 2011; OECD, 2002).This is also
underlined by their low log Kow values (-1.65 and 2.96, for Glycerol and
2-ethylhexanoic acid, respectively; values calculated using KOWWIN
Summarizing, Propane-1,2,3-triyl 2-ethylhexanoate is expected to
be rapidly hydrolyzed to 2-ethylhexanoic acid and glycerol.Both
hydrolysis products are supposed to be satisfactory metabolized in
aquatic organisms and are not bioaccumulative. Therefore, for
Propane-1,2,3-triyl 2-ethylhexanoate no potential for bioaccumulation is
to be expected.
Propane-1,2,3-triyl 2-ethylhexanoate is not expected to be
bioaccumulative. Due to it´s readily biodegradable nature, extensive
degradation of this substances in conventional STPs will take place and
only low concentrations are expected to be released (if at all) into the
environment. Once present in the aquatic compartment, further
biodegradation will occur and, due the high log Kow will be bioavailable
to aquatic organisms such as fish mainly via feed and contact with
suspended organic particles. After uptake by fish species, extensive and
fast biotransformation of the substance into Glycerol and
2-ethylhexanoic acid is expected. The supporting BCF/BAF values
estimated with the BCFBAF v3.01 program also indicate that this
substance will not be bioaccumulative (all well below 2000 L/kg).
The information above provides strong evidence supporting the
statement that rapid metabolism and low bioaccumulation potential can be
expected for this substance.
A detailed reference list is provided in the technical dossier (see
IUCLID, section 13) and within the CSR.
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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