Isooctadecyl pivalate

Toxicity to soil microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to soil microorganisms

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Reference 2

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study well documented, meets generally accepted specific principles, acceptable for assessment.

Qualifier:

no guideline followed

Principles of method if other than guideline:

This study investigated the ability of Streptomyces to utilize different chain length fatty acids as sole carbon and energy sources, and to characterize their uptake system biochemically.

GLP compliance:

not specified

Analytical monitoring:

not required

Test organisms (inoculum):

other: Streptomyces coelicolor

Remarks:

Not applicable. In-vitro assay.

Details on test conditions:

EFFECT PARAMETERS MEASURED: In-vivo fatty acid degradation

Reference substance (positive control):

no

Remarks on result:

not measured/tested

The study indicated that S.coelicolor strain M145 can effectively utilize fatty acids of different chain length, from C4 to C18, as sole carbon energy source. The in vivo ß-oxidation studies in cells grown in the presence or absence of fatty acids (Table 1), and in vitro assay of two enzymes of the pathway, acyl-CoA synthetase and acyl-CoA dehrdrogenase (Table 2), clearly indicate that S. coelicolor constitutively expressed the enzymes of the ß-oxidation cycle, without the need for the induction by a fatty acid of any chain length. The ß-oxidation pathway in this microorganism, instead of being repressed by glucose was, at least for long-chain fatty acids, stimulated by this metabolite.

Table 1: Rate of ß-oxidation of 300 µM of labeled fatty acids by S.coelicolor M145 grown in SMM-oleate of SMM-glucose

Carbon source	Rate of ß-oxidation (nmol min^-1mL^-1(mg protein)^-1)
	(^14C) palmitate	(^14C) octanoate
Oleate	2.825	2.050
Glucose	4.500	1.950

Table 2: Acyl-CoA synthetase and acyl-CoA dehydrogenase in crude protein extracts prepared from cells of S.coelicolor M145 grown in SMM-glucose or SMM-oleate

Carbon source	Acyl-CoA synthetase (pmol min^-1mL^-1)	Acyl-CoA dehydrogenase (U (mg protein)^-1)
Oleate	8.3 +/- 0.5	35.0 +/- 0.5
Glucose	95.0 +/- 1.0	40.0 +/- 0.5

 

Reference 3

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study well documented, meets generally accepted specific principles, acceptable for assessment.

Qualifier:

no guideline followed

Principles of method if other than guideline:

The degradation of an oil additive in soil was investigated. Lysimeter was used to follow the migration and progressive biodegradation of the oils by soil microorganisms over time. Also metabolites were identified.

GLP compliance:

not specified

Analytical monitoring:

yes

Details on sampling:

- Sampling method: The lysimeters were cur at various depths into slices of 2.5, 5 or 10 cm thickness. The soil was sieved (mesh size=2 mm) and a 100 g sample was taken according to standard NF X31-100.
- Sample storage conditions before analysis: at -18 °C in a polyethylene bag

Vehicle:

yes

Details on preparation and application of test substrate:

APPLICATION OF TEST SUBSTANCE TO SOIL
- Method: Methyl oleate was applied as an emulsion in water containing 50 g/L R508 (sorbitan ester) as emulsifier.

Test organisms (inoculum):

soil

Total exposure duration:

120 d

Test temperature:

19 - 22 °C (depends on depth of soil)

Nominal and measured concentrations:

Methyl oleate was applied to the soil at its recommended rate of 2 L/ha, equivalent to 5.5 mg/10 mL of water for the surface of the lysimeter.

Remarks on result:

not measured/tested

Degradation of methyl oleate in the soil

Totally degradation had occurred after 60 days. The half-life was determined as 7 days, during this time, it migrated by only 15 cm. The distributions of these metabolites in space and time changed in a more diffuse manner than that of the parent compound. All those found were shorter carbon-chain fatty acids (Table 1).

Table 1: Characterization of the degradation products of methyl oleate

Fatty acid	Log Kow	Maximum depth (cm)
Oleic acid	-	15
Heptadecanoic acid	-	15
Palmitic acid	7.17	25
Pentadecanoic acid	-	25
Myristic acid	6.11	30
Tridecanoic acid	-	30
Lauric acid	4.6	40
Undecanoic acid	-	50
Capic acid	4.09	50
Pelargonic acid	-	60
Caprylic acid	3.05	50
Heptylic acid	1.92	60
Caproic acid	1.87	60
Valeric acid	1.39	60
Butyric acid	0.79	60
Propionic acid	0.33	60

 

None of the metabolites were detected after 60 days, suggesting that methyl oleate was completely degraded at this point. The plant ester did not migrate very deeply in the soil because it was rapidly broken down by microorganisms in the soil and did not have time to migrate. β-oxidation and ω-oxidation led to the appearance of metabolites that migrated to depths of up to 60 cm and were completely degraded within 60 days.

Reference 4

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study well documented, meets generally accepted specific principles, acceptable for assessment.

Qualifier:

no guideline followed

Principles of method if other than guideline:

The degradation of the model molecule (pure tristearin) was investigated in three different soil types, to determine the behavior of fatty wastes.

GLP compliance:

not specified

Analytical monitoring:

yes

Vehicle:

no

Test organisms (inoculum):

soil

Total exposure duration:

8 wk

Test temperature:

20 °C

Nominal and measured concentrations:

0.2% (wt/wt)

Remarks on result:

not measured/tested

Free lipids were extracted from representative samples and of the combined replicates of each control and supplemented soil. The concentration of free lipids extracted after 1 and 4 weeks from each series. After the first week a low diminution of total free lipids was observed (GOV: 2.7%; CHA: 2.6%; SOR: 3.5%). After 4 weeks, the amount of free lipids decreased (CHA: 11%; SOR: 8%; GOV: no variations). Fluctuations of lipid concentrations observed with time in the control were attributed to an increased activity of soil microorganisms due to the incubation. The main result was the great increase during the first week of the acid + polar fractions. This probably indicates the oxidation and hydrolysis process of the added compound. The amounts decreased when the incubation prolonged to 4 weeks. These compounds did not accumulate as they are certainly intermediate compounds in the biodegradation process. The evolution of the concentrations of monoacid and di-, keto- and hydroxy- acid fractions significantly increased during the first week. After 4 weeks a decrease of quantities was followed. The increase obtained during the first week. Monocarboxylic acids were then predominant over di-, keto- and hydroxylacids in the three soils. The results show that, due to the soil supplementation with tristearin, free fatty acids were produced. After soil microflora adaption, these compounds are utilized as they are freed by enzymatic hydrolysis. A part of the of the monocarboxyclic acids is probably oxidized to form di-, keto- and hydroxyl-acids. Contrary the acid fractions evolution, the amounts of the neutral fractions increased between 1 and 4 weeks in the supplemental soils. This is due to the increase of the quantity of alcohols and polar neutral compounds. Bio-oxidation processes seem to be more efficient after 4 weeks. After 1 week also a low decrease, compared to the controls, in the amounts of hydrocarbons consecutive to a low increase of the ester fractions.

Main result of the monoacid fractions analysis was the rapid formation of stearic acid in considerable amounts. This result showed that an intense hydrolysis reaction with specific lipase of tristearin had occurred after the soil supplementation. The investigations of ester fractions showed that new alkanoic acids (methyl stearate, ethyl stearate, and propyl stearate), not determined in the controls, were generated in the supplemented soils. Among other processes the following hypothesis to explain the formation of these compounds were proposed:

1.      Bioesterfication of a part of the free stearic acid, released by an enzymatic hydrolysis reaction

2.      Alcoholysis of the triglyceride to form esters, directly

3.      And/or direct formation of these compounds from tristearin with C-C and C-O bond cleavages

Description of key information

The Chemical Safety Assessment does not indicate the need to further investigate the toxicity to soil microorganisms.

Additional information

No experimental data is available, in which the toxicity of Isooctadecyl pivalate (CAS 58958-60-4) to soil microorganisms was assessed. However, the Chemical Safety Assessment does not indicate the need for further assessment ofterrestrial organisms. According to Regulation (EC) No. 1907/2006, Annex X, Column 2, 9.4 there is no need for further studies on the effects towards terrestrial organisms when direct and indirect exposure of the soil compartment is unlikely. Direct and indirect exposure of the soil compartment is considered unlikely based on the identified uses and substance properties (low water solubility, low vapour pressure, and ready biodegradability), respectively. Thus, only marginal release into the environment is expected and whatever fraction is still released is expected to undergo rapid biodegradation. Thus, the chronic exposure of terrestrial organisms is considered unlikely.

Based on the aquatic toxicity profile of the substance, neither acute nor chronic terrestrial toxicity is expected. In addition, experimental findings showed that Isooctadecyl pivalate is not toxic to aquatic microorganisms up to a concentration of 100 mg/L (OECD 301 F, toxicity control).

Moreover, evidence from literature indicates that soil microorganism communities are capable of degrading fatty acid esters (Hita et al. 1996 and Cecutti et al. 2002) and exploiting these as energy source (Banchio & Gramajo 1997).

The degradation of the model triglyceride tristearin, a glycerin tri-esterified with stearic acid, was investigated in three different soils for 4 weeks (Hita et al. 1996). The amount of stearic acid increased considerably during the experiment showing the hydrolytic activity of lipases breaking the ester bonds. Furthermore, the generation of new alkanoic acids (methyl stearate, ethyl stearate and propyl stearate) was identified which were not present in the controls and disappeared again after 4 weeks, leading to the conclusion that degradation by soil microorganisms had occurred. Similar findings were obtained by Cecutti et al., who demonstrated that the plant oil methyl oleate and its metabolites completely degraded after 60 d incubation in soil samples after a total exposure of 120 d. What is more, there is further evidence that fatty acids are non-toxic and can be used in the catabolism of microorganisms, such as Streptomyces coelicolor, a common gram-positive soil bacterium, which uses fatty acids (C4-C18) as sole carbon end energy source (Banchio and Gramajo, 1997).

Thus, the available literature shows that soil microorganisms are capable of breaking up ester bonds, degrading fatty acids in significant amounts and exploiting these as energy source, thus indicating that fatty acids have non-toxic properties.

Taking all the available information into account in a Weight of Evidence approach in accordance with Annex XI, 1.2, effects on soil microorganisms are thus not expected to be of concern, and consequently, no further testing is required.  

 

References

Banchio, C. and Gramajo, H.C. (1997): Medium- and long-chain fatty acid uptake and utilization by Streptomyces coelicolor A3(2): first characterization of a Gram-positive bacterial system. Microbiology 143, 2439-2447.

Cecutti, C., Agius, D., Caussade, B., Gaset, A. (2002): Fate in the soil of an oil additive of plant origin. Pest Manag Sci 58, 1236-1242.

ECHA (2017) Guidance on information requirements and chemical safety assessment, Chapter R.7c: Endpoint specific guidance

Hita, C., Parlanti, E., Jambu, P., Joffre, H., Ambles, A. (1996): Triglyceride degradation in soil.Org Geochem 25(1/2), 19-28.