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EC number: 250-178-0
CAS number: 30399-84-9
NOEC ≥ 1000 mg/kg soil dw (OECD 222; Eisenia fetida); based on read-across
Since no studies are available on the toxicity of Isodecanoic acid
(CAS No. 30399 -84 -9) to soil macroorganisms, the assessment was based
on a study conducted with the sub-category 1 member Fatty acids, C16 -18
and C18 -unsatd., branched and linear (CAS No. 68955 -98 -6).
The study conducted with Fatty acids, C16-18 and C18-unsaturated,
branched and linear, “Monomer acid” (CAS No. 68955-98-6) was performed
according to OECD guideline 222 and GLP (Winkelmann, 2014). The test
organism Eisenia fetida was exposed to the test substance at
concentrations of 62.5, 125, 250, 500 and 1000 mg /kg soil dry weight
for 8 weeks. As no statistically significant effects were observed, the
NOEC was determined to be ≥ 1000 mg/kg soil dw.
In accordance with Article 13 (1) of Regulation (EC) No 1907/2006,
"information on intrinsic properties of substances may be generated by
means other than tests, provided that the conditions set out in Annex XI
are met. In particular for ecotoxicity, information shall be generated
whenever possible by means other than vertebrate animal tests", which
includes the use of information from structurally related substances
(grouping or read-across).
Having regard to the general rules for grouping of substances and
read-across approach laid down in Annex XI, Item 1.5, of Regulation (EC)
No 1907/2006, whereby substances may be considered as a category
provided that their physicochemical, toxicological and ecotoxicological
properties are likely to be similar or follow a regular pattern as a
result of structural similarity. The long term toxicity on soil
macroorganisms in accordance to Regulation (EC) No 1907/2006, Annex IX
9.4 Effects on terrestrial organisms was tested on the read across
substance, Fatty acids, C16-18 and C18-unsaturated, branched and linear,
“Monomer acid” (CAS No. 68955-98-6). As UVCB substances derived from
natural sources, both Fatty acids, C16-18 and C18-unsaturated, branched
and linear, “Monomer acid” and Octadecanoic acid, branched and linear,
“Hydrogenated monomer acid”, as all members of this category are
chemically similar, as they are all essentially a complex mixture of C16
- C18 or C18 unsaturated and saturated, branched and linear fatty acids
with varying structural geometric isomers C16 -C18 unsaturated fatty
acids as Octadecanoic acid branched and Linear.
The key points that the members share are:
Please refer to IUCLID Chapter 6.3 for more details on the
The selection of Fatty acids, C16-18 and C18-unsatd., branched and
linear (CAS No. 68955-98-6) as representative test substance for the
sub-category “monomers” was an iterative process of combination of
The water solubility of Fatty Acids, C16-18 and C-18, Unsaturated,
Branched and Linear, measured as the sum solubility of all the
components of the test material was estimated to be 15.0 mg/L at 20°C.
However, the water solubility based on its two major constituents is 0.6
mg/L at 20°C. Media preparation trials, conducted for the chronic
daphnia study, demonstrated that solubility was below 5 mg/L. The actual
solubility of the UVCB substance is therefore assumed to be below 15
mg/L. As the substance however has the highest solubility within the
subcategory, it represents a worst case scenario in terms of
The only difference between this member of the sub-category and
all other members is the degree of saturation or hydrogenation,
respectively. In fact, all substances are closely similar. Based on an
evaluation conducted using the OECD Toolbox, the degree of saturation is
estimated to not have any effect on the toxicity profile of C18 fatty
acids. The profiles for C18 fatty acids containing 0, 1 or 2 double
bonds are the same in terms of lack of structural alerts, toxic hazard
classification by Cramer, aquatic toxicity mode of action by OASIS,
aquatic toxicity classification by ECOSAR, etc. For the unsaturated
fatty acids additional organic functional groups are indicated (allyl,
alkene), but these are not coupled to any structural alerts for protein
binding. Experimental data on the long-term toxicity of 16/18C fatty
acids to daphnia seem to indicate that unsaturated fatty acids even have
slightly higher toxic potential compared to the corresponding saturated
fatty acids (MOE, 2008; MOE 2003, entered under IUCLID section 5.1.4).
This observation could possibly be explained by the fact that additional
steps are required for the β-oxidation process, when double bonds are
present, and more energy is thus needed for the metabolism of
unsaturated fatty acids (Berg, Tymoczko and Stryer, 2002). Based on this
information, Fatty Acids, C16-18 and C-18, Unsaturated, Branched and
Linear can be considered as a worst case read-across
substance. Additionally, the production volume of the unsaturated form
is much higher than the other members. Therefore, one can assume that
the risk of any exposure would be highest here due to large production
volumes. Whereas, Octadecanoic acid branched and linear, is more or less
to be considered as an intermediate for the production of
Isooctadecanoic acid, therefore one would expect a more limited exposure
to the aquatic environment. Isooctadecanoic acid also has a lower
expected production volume.
Based on all aspects discussed above, it was decided to test Fatty
Acids, C16-18 and C-18, Unsaturated, Branched and Linear as
representative member of the sub-category 1 “predominantly monomers”.
Based on this result, and due to the structural and profile
similarities of the two substances, as are explained within the overall
endpoint summary it can be concluded that no toxicological effects on
soil macroorganisms are expected for Isooctadecanoic acid.
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