Use of this information is subject to copyright laws and may require the permission of the owner of the information, as described in the ECHA Legal Notice.
EC number: 931-299-4
CAS number: 68390-94-3
Low absorption potential of the parent substance after oral, dermal and
inhalation exposure. Hydrolysis products are expected to be readily
absorbed from gastrointestinal tract. Parent substance expected to be
hydrolysed to ethylenediamine and palmitic and/or stearic acid.
Ethylenediamine probably conjugated in phase II metabolism and excreted
via the kidneys in the urine. Fatty acids fed into citrate cycle and
degraded to CO2 by beta-oxidation. Not absorbed parent substance to be
excreted in the faeces.
There are no studies available in which the toxicokinetic behaviour of
‘amides, C16-C18 (even), N,N'-ethylenebis’ (EC No. 931-299-4) was
investigated. In accordance with Annex VIII, Column 1, Item 8.8.1, of
Regulation (EC) No. 1907/2006 and with ‘Guidance on information
requirements and chemical safety assessment Chapter R.7c: Endpoint
specific guidance’ (ECHA, 2017), an assessment of the toxicokinetic
behaviour of the substance was conducted to the extent that can be
derived from the relevant available information. This comprises a
qualitative assessment of the available substance specific data on
physico-chemical and toxicological properties according to the Chapter
R.7c Guidance document (ECHA, 2017).
Amides, C16-C18 (even), N,N'-ethylenebis is an UVCB substance, with
three major constituents. The constituents differ in the combination of
palmitic acid (C16) and/or stearic acid (C18) attached to the central
ethylenediamine moiety; thus, there is a C18-C18 constituent, a C18-C16
constituent and a C16-C16 constituent.
The substance has a molecular weight range from 593.94 g/mol for the
C18-C18 constituent to 536.93 g/mol for the C16-C16 constituent. It is a
solid at 20 °C and is insoluble in water. The water solubility of the
three major constituents have been calculated to be in the range of
5.4xE-07 - 5.9xE-07 mg/L at 25 °C, using the WATERNT QSAR model (US EPA,
2014). The log Pow values of the constituents were estimated to be 12 -
14, indicating an extreme lipophilic character of amides, C16-C18
(even), N,N'-ethylenebis. The vapour pressure at 20 °C was extrapolated
to be 2.3E-07 hPa, based on the measured vapour pressure of 1.5 x 10E-05
hPa at 63 °C.
Absorption is a function of the potential for a substance to diffuse
across biological membranes. The most useful parameters providing
information on this potential are the molecular weight, the
octanol/water partition coefficient (log Pow) value and the water
solubility. The log Pow value provides information on the relative
solubility of the substance in water and lipids (ECHA, 2017).
In general, molecular weights below 500 g/mol and log Pow values between
-1 and 4 are favourable for absorption via the gastrointestinal (GI)
tract, provided that the substance is sufficiently water soluble (> 1
mg/L). Lipophilic compounds can be taken up by micellar solubilisation
by bile salts, and this mechanism may be of particular importance for
highly lipophilic compounds (log Pow > 4), especially for those that are
poorly soluble in water (≤ 1 mg/L) as these substances would otherwise
be poorly absorbed (ECHA, 2017).
The molecular weight, log Pow and water solubility of amides, C16-C18
(even), N,N'-ethylenebis all suggest the substance will be poorly
absorbed from the GI tract as relevant parameters fall outside the
favourable ranges. However, micellar solubilisation might play a certain
role due to the extreme lipophilicity of the substance. A limited
absorption after oral exposure to amides, C16-C18 (even),
N,N'-ethylenebis is further supported by the lack of systemic toxicity
observed in three acute oral toxicity studies as well as in a subchronic
(90-day) repeated dose toxicity study. No toxicologically relevant
effects have been noted in any of these studies.
The potential of a substance to be absorbed in the GI tract may be
influenced by chemical changes taking place in GI fluids as a result of
metabolism by GI flora, by enzymes released into the GI tract or by
‘chemical’ hydrolysis at the extreme acidic pH of the stomach. These
changes will alter the physico-chemical characteristics of the substance
and hence predictions based upon the physico-chemical characteristics of
the parent substance may no longer apply or apply to a lesser extent
Amides, C16-C18 (even), N,N'-ethylenebis is the diamide of
ethylenediamine with palmitic and/or stearic acid. The amide groups
(-C(=O)-NH-) may be hydrolysed in the GI tract - either enzymatically or
acid catalysed - to form ethylenediamine and the corresponding acid
moieties (palmitic and/or stearic acid). The rate of hydrolysis is not
known. The smaller molecules of ethylenediamine and the acid moieties
may be absorbed faster than the parent molecule.
In conclusion, based on the available information, amides, C16-C18
(even), N,N'-ethylenebis is predicted to undergo enzymatic hydrolysis in
the GI tract and absorption of the hydrolysis products rather than (or
in addition to) the parent substance is likely. The absorption rate of
the hydrolysis products is expected to be high. Due to the limited
information on the hydrolysis products, as a worst-case approach the
oral absorption potential is assumed to be high.
The dermal uptake of liquids and substances in solution is higher than
that of dry particulates, since dry particulates need to dissolve into
the surface moisture of the skin before uptake can begin. Molecular
weights below 100 g/mol favour dermal uptake, while for those above 500
g/mol the molecule may be too large. Dermal uptake is anticipated to be
low if the water solubility is < 1 mg/L, low to moderate if it is
between 1 - 100 mg/L, and moderate to high if it is between 100 - 10000
mg/L. Log Pow values in the range of 1 to 4 (values between 2 and 3 are
optimal) are favourable for dermal absorption, in particular if the
water solubility is high. For substances with a log Pow above 4, the
rate of penetration may be limited by the rate of transfer between the
stratum corneum and the epidermis, but uptake into the stratum corneum
will be high. Log Pow values above 6 reduce the uptake into the stratum
corneum and decrease the rate of transfer from the stratum corneum to
the epidermis, thus limiting dermal absorption (ECHA, 2017).
Amides, C16-C18 (even), N,N'-ethylenebis is almost insoluble in water,
with the highest water solubility value of its major constituents
estimated to be 5.4xE-07 mg/L. This indicates a low dermal absorption.
Furthermore, the log Pow values of the constituents indicate a reduced
uptake into the stratum corneum. The limited dermal absorption is
further supported by the molecular weights of > 500 g/mol.
The dermal permeability coefficient (Kp) can be calculated from log Pow
and molecular weight (MW) applying the following equation described in
US EPA (2014):
log(Kp) = -2.80 + 0.66 log Pow - 0.0056 MW
Depending on the constituent of amides, C16-C18 (even),
N,N'-ethylenebis, the following permeability coefficients and fluxes
through the skin barrier have been calculated. For the latter, the
respective water solubilities were taken into account.
All values determined indicate a very low dermal absorption potential.
If a substance shows skin irritating or corrosive properties, damage to
the skin surface may enhance penetration. The in-vivo skin irritation
tests according or similar to OECD guideline 404 performed with the
substance indicated only minimal irritating properties; only slight
edema (grade 1 according to Draize) was observed on intact skin.
Therefore, no enhanced penetration of amides, C16-C18 (even),
N,N'-ethylenebis due to skin damage is expected. Moreover, the Local
Lymph Node Assay (LLNA) performed with the substance yielded a negative
result. The lack of a sensitising potential may indicate that the
substance is not systemically available. This further supports the
assumption of a very low dermal absorption.
Taking all the available information into account, the dermal absorption
potential of amides, C16-C18 (even), N,N'-ethylenebis is considered to
be very low.
Amides, C16-C18 (even), N,N'-ethylenebis is a solid and its vapour
pressure is very low (2.3E-07 hPa at 20 °C). The substance, therefore,
has very low volatility. Consequently, under normal use and handling
conditions that avoid the formation of dust, inhalation exposure and
availability for respiratory absorption of the substance in the form of
vapour, gases or mists is not significant (ECHA, 2017). However, the
substance may be available for respiratory absorption in the lung after
inhalation of dust particles, if the substance is handled under open
process conditions. In humans, particles with aerodynamic diameters
below 100 µm have the potential to be inhaled. Particles with
aerodynamic diameters below 50 µm may reach the thoracic region and
those below 15 µm the alveolar region of the respiratory tract (ECHA,
2017). The granulometric analysis of the substance showed D10, D50, and
D90 values of 2.1, 8.76, and 22.5 µm, respectively, which clearly
indicate the particles may be inhaled. A large fraction of the particles
will reach the alveolar region.
The log Pow and water solubility indicate that the target substance has
only a low potential to be absorbed across the respiratory tract
epithelium. In addition, the high molecular weight may have a limiting
effect on the absorption rate. In an acute inhalation toxicity study
performed according to OECD guideline 403, laboured breathing and/or
rales, dark material around nose or mouth, decreased activity, urine
stain, and thrashing in the cage were observed. These clinical signs can
be attributed to the concentration, size and shape of the particles
rather than to a systemic effect caused by the chemical structure of the
substance after absorption in the respiratory system. Moreover, the
clinical signs are considered to be due to local effects of the exposure
rather than systemic effects.
In conclusion, the systemic bioavailability of amides, C16-C18 (even),
N,N'-ethylenebis in humans is considered to be very limited, e.g. after
inhalation of aerosols with an aerodynamic diameter below 15 µm.
However, due to the solid particles that might be deposited in the
deepest regions of the respiratory system, effects originating from the
particulate nature of the substance (local effects as a consequence of
the particle deposition, effects driven by the concentration, size and
shape of the particles) cannot be excluded. In applying a worst-case
scenario, the absorption potential via the inhalation route of exposure
is assumed to be the same as via the oral route of exposure.
Distribution and accumulation
Distribution of a substance within the body depends on the
physico-chemical properties of the substance; especially the molecular
weight, the lipophilic character and the water solubility. In general,
the smaller the molecule, the wider is the distribution. If the molecule
is lipophilic, it is likely to distribute into cells and the
intracellular concentration may be higher than its extracellular
concentration, particularly in fatty tissues (ECHA, 2017).
No toxicologically relevant systemic effects were observed in any of the
studies with amides, C16-C18 (even), N,N'-ethylenebis. The macroscopic
examination during necropsy did not show any target organ for acute
toxicity with the exception of pale lungs and multifocal dark red foci
on the lungs in the acute inhalation study which are attributed to the
concentration and size of the particles of the test substance.
Furthermore, no lasting effects were seen for any parameters in the
subchronic (90-day) study. Therefore, it is not possible to determine
from the experimental data available if the substance will be
distributed to tissues and organs in the body.
As discussed under oral absorption, amides, C16-C18 (even),
N,N'-ethylenebis is expected to undergo enzymatic and/or acid-catalysed
hydrolysis in the GI tract to some extent prior to absorption. After
being absorbed, the hydrolysis products ethylenediamine, palmitic and
stearic acid are expected to be widely distributed, due to the size of
the respective molecules and the functional groups that significantly
increase their water solubility. The substances absorbed from the GI
tract will be transported via the portal vein to the liver, where
further metabolism can take place. Substances that are absorbed through
the pulmonary alveolar membrane or through the skin (which is considered
unlikely for amides, C16-C18 (even), N,N'-ethylenebis) enter the
systemic circulation directly before they are transported to the liver
where metabolism will take place. The substances are not expected to
accumulate in adipose tissue due to the lack of lipophilic groups.
Amides, C16-C18 (even), N,N'-ethylenebis has functional groups that are
suitable for phase I metabolism reactions. The amide groups may be
enzymatically hydrolysed by amidases, which are expressed in most
tissues and play an important role in most organisms (Gossauer, 2006).
The hydrolysis product ethylenediamine may be conjugated (e.g. by
glucuronidation) to form a polar molecule suitable for excretion.
Palmitic and stearic acid are expected to be further metabolised by the
process of β-oxidation for energy generation in the citrate cycle or are
esterified with glycerol to form triacylglycerides that can be stored in
adipose tissue (Lehninger, 1993).
The potential metabolites following enzymatic metabolism of the three
major constituents of the test substance were predicted using the OECD
QSAR Toolbox v4.3.1 (OECD, 2019). This QSAR tool predicts which
metabolites of the test substance may result from enzymatic activity in
the liver and in the skin, and by intestinal bacteria in the GI tract.
Essentially, the hepatic metabolic conversions consist of either
hydrolysis of one or both amide group(s) or addition of a hydroxyl group
to a fatty acid moiety. Hydroxyl groups tend to be introduced toward the
end of the lipophilic carbon-chain and are subsequently subject to
oxidation reactions, resulting in the formation of aldehydes or ketones.
Aldehydes might be further oxidised to carboxylic acids. Depending on
the combination of the fatty acid moieties in the parent compound, up to
77 hepatic metabolites are predicted. In contrast to the hepatic
metabolism, no hydrolysis reactions are predicted to occur in the skin.
Only the introduction of hydroxyl groups is simulated in the skin
metabolism prediction. In general, the hydroxyl groups make the
substances more water-soluble and susceptible to metabolism by phase
II-enzymes. The smaller molecules resulting from hydrolysis of the
parent compounds are also expected to have higher water solubility. The
metabolites formed in the skin are relatively few, compared with the
liver, due to the lower level of enzymes in the skin. The skin
metabolites and any absorbed parent substance will enter the blood
circulation and have the same fate as the hepatic metabolites. A
multitude of up to 114 metabolites were predicted to result from
microbiological metabolism. The high number includes many minor
variations in the carbon-chain length and number of carbonyl- and
hydroxyl groups; reflecting the many microbial enzymes identified. Not
all of these reactions are expected to take place in the human GI tract.
The results of the OECD Toolbox prediction substantiate the information
on metabolism known from the general literature (Lehninger, 1993).
There is no indication that amides, C16-C18 (even), N,N'-ethylenebis is
metabolised to mutagenic intermediates under the relevant test
conditions. All three experimental studies performed on genotoxicity
(Ames test, chromosome aberration test and mouse lymphoma assay) were
negative, with and without metabolic activation. In addition, the
substance did not show skin sensitising properties in the Local Lymph
Node Assay (LLNA), indicating that it is either not taken up through the
skin or not metabolised to reactive compounds that would lead to skin
Ethylenediamine formed as an hydrolysis product of amides, C16-C18
(even), N,N'-ethylenebis will most likely be conjugated with e.g.
glutathione to form more water-soluble compounds and may then be
excreted via the urine. The fatty acids palmitic and stearic acid can be
utilised for energy generation by entering the citrate cycle. Thus, they
are expected to be ultimately degraded to CO2, which will be exhaled.
The fraction of the parent substance that is not absorbed in the GI
tract will be excreted via the faeces. If microbial metabolism occurs,
the smaller metabolites may be absorbed, entering the systemic
circulation. The metabolites are expected to be conjugated as described
above and excreted via the urine.
ECHA (2017). Guidance on information requirements and chemical safety
assessment, Chapter R.7c: Endpoint specific guidance. Version 3.0.
Gossauer, Albert (2006). Struktur und Reaktivität der Biomoleküle,
Verlag Helvetica Chimica Acta, Zürich, 2006
Lehninger, A.L., Nelson, D.L. and Cox, M.M. (1993). Principles of
Biochemistry. Second Edition. Worth Publishers, Inc., New York, USA.
OECD (2019). (Q)SAR Toolbox v4.3.1, https://qsartoolbox.org/, simulation
performed 19 November 2019
US EPA (2014).Estimation Programs Interface Suite™ for Microsoft®
Windows, v 4.11. United States Environmental Protection Agency,
Washington, DC, USA.Downloaded from:
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.
Welcome to the ECHA website. This site is not fully supported in Internet Explorer 7 (and earlier versions). Please upgrade your Internet Explorer to a newer version.
Do not show this message again