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Justification for grouping of substances and read-across
The polyol esters category comprises of 49 aliphatic esters of
polyfunctional alcohols containing two to six reactive hydroxyl groups
and one to six fatty acid chains. The category contains mono
constituent, multi-constituent and UVCB substances with fatty acid
carbon chain lengths ranging from C5 - C28, which are mainly saturated
but also mono unsaturated C16 and C18, polyunsaturated C18, branched C5
and C9,branched C14 – C22 building mono-, di-, tri-, and tetra
esterswith an alcohol (i.e. polyol).
The available data allows for an accurate hazard and risk assessment of
the category and the category concept is applied for the assessment of
environmental fate and environmental and human health hazards. Thus,
where applicable, environmental and human health effects are predicted
from adequate and reliable data for source substance(s) within the group
by interpolation to the target substances in the group (read-across
approach) applying the group concept in accordance with Annex XI, Item
1.5, of Regulation (EC) No 1907/2006. In particular, for each specific
endpoint the source substance(s) structurally closest to the target
substance is/are chosen for read-across, with due regard to the
requirements of adequacy and reliability of the available data.
Structural similarities and similarities in properties and/or activities
of the source and target substance are the basis of read-across.
A detailed justification for the grouping of chemicals and read-across
is provided in the technical dossier (see IUCLID Sections 5, 6.1 and 13)
and within Chapter 7.1 of the CSR.
All poylol esters have a similar profile having the same environmental
fate properties; low water solubility, low mobility in soil, ready
biodegradability, low persistence and low bioaccumulation potential.
Additionally all polyol esters do not show toxicological effects up to
the water solubility limit. Nevertheless for an easier overview the
category was organized into three groups, which are characterized
according to their major alcohol moiety (NPG, TMP or PE).
The following table illustrates the read across approach taken within
the PE ester group of the polyol esters category. For practicality
reasons, only the ecotoxicological parameters for the terrestric
compartment of the relevant substances used as part of a read across
approach for the PE esters of the category have been listed in the table
below. The complete data matrix of all polyol esters for terrestrial
toxicity is however detailed within the category justification attached
in IUCLID section 13 of this dossier.
Toxicity to soil macroorganisms except arthropods
Toxicity to terrestrial arthropods
Toxicity to terrestrial plants
Toxicity to soil microorganisms
NOEC (56 d) ≥ 1000 mg/kg dw soil
Waiving based on CSA
RA: CAS 25151-96-6
EC50 (28 d) > 1000 mg/kg dw soil
RA: CAS 71010-76-9
RA: CAS 68604-44-4
NOEC (14 d) ≥ 1000 mg/kg dw
a) Category members subject to the REACh Phase-in registration deadline
of 31 May 2013 are indicated in bold font
b) Substances that are either already registered under REACh or
not subject to the REACh Phase-in registration deadline of 31 May 2013,
are indicated in normal font
c) Substance of the TMP group used as read across substance (aquatic
toxicity) for the PE esters group.
Lack of data for a given endpoint is indicated by “--“.
NOTE: Not all of polyol esters within the category are discussed in this
endpoint summary i.e. only polyol esters of the PE group relevant for
this discussion, in particular PE polyol esters which have terrestrial
toxicity data available. For further information on the complete polyol
ester category please refer to category justification (IUCLID Section
Testing of the toxicity on earthworm evaluates the exposure to the test
substance via soil pore water, surface contact as well as by ingestion
of soil particles. A long-term test is considered not be relevant as the
results of the chemical safety assessment according to Annex I of
Regulation (EC) No 1907/2006 did not indicate the need to investigate
further effects of the substance on terrestrial organisms. All category
members have been shown to be readily biodegradable and therefore do not
have a potential for persistence and thus no indirect chronic exposure
of the soil. Additionally, no toxicity was observed in the standard
acute toxicity tests to aquatic organisms on the three trophic levels
(fish, daphnia, algae). Since indirect exposure is ruled out due to the
ready biodegradability of the substance, only direct exposure could pose
a risk. A higher solubility would imply that if exposure were to occur
this substance would not only be adsorbed to soil particles (log Koc >5)
but also concentrations may exist within the soil pore water also. The
smaller fatty acid chain length increases the water solubility and
therefore the bioavailability in the pore water. Water solubility is
negatively correlated with the C-chain length of the fatty alcohol and
fatty acid (Lide, 2005). Therefore, a substance with shorter fatty acid
chains with higher water solubility can be seen as a worst case for
absorption via pore water since it has an increased bioavailability in
the pore water (ECHA, 2012). The substances with longer fatty acid
chains with higher adsorption potential represent a worst case for the
uptake via ingestion of soil bounded particles.
For the assessment of terrestrial toxicity five studies (according to
OECD 222, 207 and 216) are available for four PE group members. Chronic
toxicity studies conducted under GLP according to OECD 222 with
earthworms exposed to the group members fatty acids, C16-18 and
C18-unsaturated, esters with pentaerythritol (CAS 85711-45-1),
2,2-bis(hydroxymethyl)-1,3-propanediyl dioleate (CAS 25151-96-6) and
fatty acids, C16-18 and C18-unsatd., tetraesters with pentaerythritol
(CAS 68604-44-4) resulted in no effects on mortality and reproduction up
to a concentration of 1000 mg/kg dw soil in all three chronic toxicity
studies. Additionally, in an acute test according to OECD 207 with
decanoic acid, mixed esters with heptanoic acid, octanoic acid,
pentaerythritol and valeric acid (CAS No. 71010-76-9) no mortality
occurred in both the control and treatment group resulting in a NOEC (14
d) ≥ 1000 mg/kg dw soil. These four substances represent both ends of
the group and the results are used to cover other polyol esters by
interpolation. The category member decanoic acid, mixed esters with
heptanoic acid, octanoic acid, pentaerythritol and valeric acid (CAS
71010-76-9) belongs to the lower end of the category (C5-C10 fatty acid
chain length) and is assumed to represent worst case in terms of
absorption via pore water as explained above. The long-term studies with
fatty acids, C16-18 and C18-unsaturated, esters with pentaerythritol
(CAS 85711-45-1), 2,2-bis(hydroxymethyl)-1,3-propanediyl dioleate (CAS
25151-96-6) and fatty acids, C16-18 and C18-unsatd., tetraesters with
pentaerythritol (CAS 68604-44-4) strengthen the read-across approach for
esters with fatty alcohol chain lengths of C16-18 and C18 unsaturated.
The toxicity to soil micro-organisms with
2,2-bis(hydroxymethyl)-1,3-propanediyl dioleate (CAS 25151-96-6) was
tested in a GLP study according to OECD 216. The EC50 for the nitrogen
transformation was calculated to be > 1000 mg/kg dw soil (the highest
concentration tested). Available data for toxicity to aquatic
microorganisms for the PE ester group members confirms the determination
of a lack of toxicity to soil microorganisms. No inhibition of
respiration rate of aquatic microorganisms was observed in any of the
available studies for the PE esters group members. This is supported by
further evidence from literature data. This data showed that soil
microorganism communities are well capable of degrading fatty acid
esters (Hita et al., 1996 and Cecutti et al., 2002) and use them as
energy source (Banchio & Gramajo, 1997). Based on the available
information, effects on soil microorganisms are not expected to be of
Based on the currently available data it can be concluded that the
terrestrial toxicity of the members of the PE esters is low. All
substances within the group are characterized by similar
physico/chemical parameters like low water solubility (< 0.3 mg/L) and
high log Koc (> 3), indicating a similar behaviour in the environment.
The log Kow values of the PE esters are also high (> 5). The TMP ester
decanoic acid, ester with 2-ethyl-2-(hydroxymethyl)-1,3-propanediol
octanoate (CAS 11138-60-6) which is also considered in the PE esters
group has an experimentally determined log Kow (> 2.7) supported by
calculated values according to KOWWIN programme v1.67 (log Kow =
10.64-13.59). The group members are predominately esters of
pentaerythritol with varying fatty acid chain lengths (C5-C28 as well as
C16 unsaturated and C18 unsaturated) and thus, a similar metabolic
pathway is expected. Consequently, bioaccumulation is not expected due
to rapid metabolisation.
All members of the group are readily biodegradable (> 60% biodegradation
in 28 days). The Guidance on information requirements and chemical
safety assessment, Chapter R7.b (ECHA, 2012) 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, 2012)) and the rest will be extensively biodegraded
(due to ready biodegradability). Thus in conclusion, due to its readily
biodegradable nature, extensive degradation of this substance in
conventional STPs will take place, thus, discharged concentrations of
these substances into the aqueous compartment are likely to be very low.
If direct/indirect application of the substances occurs (indirect via
sludge application) will occur, the substance will again be rapidly
degraded until ultimate biodegradation.
After absorption, the group members are expected to be enzymatically
hydrolyzed by carboxylesterases yielding the corresponding alcohol and
fatty acid. The test substances have a log Kow of > 4 indicating a
potential for bioaccumulation. But due to the low water solubility,
rapid environmental biodegradation and metabolisation via enzymatic
hydrolysis, a relevant uptake and bioaccumulation in aquatic organisms
is not expected. Enzymatic breakdown will initially lead to the free
fatty acid and the free alcohol (e. g. pentaerythritol). From literature
it is well known, that these hydrolysis products will be metabolized and
excreted in fish effectively (Heymann, 1980; Lech & Bend, 1980; Lech &
Melancon, 1980; Murphy & Lutenske, 1990). This is supported by low
calculated BCF values of 0.89 – 24.7 L/kg ww (BCFBAF v3.01, Arnot-Gobas,
including biotransformation, upper trophic). Since the hydrolysis
products are supposed to be satisfactory metabolized in organisms, no
potential for bioaccumulation is to be expected. For more information on
the metabolism of enzymatic hydrolysis products please refer to IUCLID
section 5.3 or Chapter 4.3 Bioaccumulation.
In conclusion, the members of the PE esters are unlikely to pose a risk
for terrestrial organisms based on a) the lack of exposure and b) the
low toxicity as expected for this substance for terrestrial organisms
based on the available experimental data, metabolism considerations and
the lack of adverse effects in aquatic ecotoxicity tests.
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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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