Methyl stearate

Toxicity to aquatic algae and cyanobacteria

Description of key information

In the SCAE-Me category a trend for the toxicity of algae can be observed. The highest toxicity was determined for methyl laurate (CAS 111-82-0, fatty acid chain length C12). The toxicity decreases with shorter and longer chain length of the fatty acids.
Of the substances to be registered, the following SCAE-Me show toxicity to algae and aquatic invertebrates leading to a classification R50 according to 67/548/EWG and Aquatic Acute 1 according to Regulation (EC) No 1272/2008:  
¿ Methyl laurate (CAS 111-82-0) 
¿ Fatty acids, C12-18 and C18 -unsatd., methyl esters (CAS 1234694 -02 -0) 
¿ Fatty acids, C8-18 and C18-unsatd., Me esters (CAS 67762-37-2) 
¿ Fatty acids, C12-14 (even numbered), methyl esters (CAS 308065-15-8) 
This SCAE-Me show also toxicity to algae, but do not lead to a classification:
¿ Methyl octanoate (CAS 111-11-5) 
¿ Methyl decanoate (CAS 110-42-9) 
¿ Fatty acids, C8-10, Me esters (CAS 85566-26-3) 
All other SCAE-Me of this category are not toxic to aquatic organisms. This are: 
¿ Methyl myristate (CAS 124-10-7) 
¿ Methyl palmitate (CAS 112-39-0) 
¿ Methyl stearate (CAS 112-61-8) 
¿ Fatty acids, C16-18, Me esters (CAS 85586-21-6)

Additional information

Three studies, investigating the toxicity to freshwater algae of SCAE-Me, are available for the SCAE-Me category. In addition, two QSAR-calculations for SCAE-Me were performed.

Table1: Experimental results, QSAR-calculations and Read across of the key studies, which were used for the single substances of the SCAE-Me for the algae toxicity

CAS-No.	111-11-5	110-42-9	111-82-0	124-10-7	112-39-0	112-61-8
Algae toxicity	QSAR, EC50 (96h) = 4.76 mg/L	QSAR, EC50 (96h) = 1.35 mg/L	Experimental result,P. subcapitata, EC50 (72h) = 0.324 mg/L (meas. initial)	Experimental result,P. subcapitata, EC50 (72h) > 0.023 mg/L (meas. TWA), EL50 (72h) > 100 mg/L (nominal)	RA from 124-10-7: Experimental result,P. subcapitata, EC50 (72h) > 0.023 mg/L (meas. TWA), EL50 (72h) > 100 mg/L (nominal)	RA from 124-10-7: Experimental result,P. subcapitata, EC50 (72h) > 0.023 mg/L (meas. TWA), EL50 (72h) > 100 mg/L (nominal)

 

Table2: Read across, this was used for the UVCB substances of the SCAE-Me.

CAS-No.	85566-26-3	1234694-02-0	67762-37-2	308065-15-8	85586-21-6
Algae toxicity	RA from 111-11-5: QSAR, EC50 (96h) = 1.35 mg/L	RA from 111-82-0:Experimental result,P. subcapitata, EC50 (72h) = 0.324 mg/L (meas. initial)	RA from 111-82-0:Experimental result,P. subcapitata, EC50 (72h) = 0.324 mg/L (meas. initial)	RA from 111-82-0:Experimental result,P. subcapitata, EC50 (72h) = 0.324 mg/L (meas. initial)	RA from 124-10-7: Experimental result,P. subcapitata, EC50 (72h) > 0.023 mg/L (meas. TWA), EL50 (72h) > 100 mg/L (nominal)

 

In the category, there can be observed a trend for the toxicity of freshwater algae. This is related to the toxicity mode of action (narcosis). Thus, a linear dependence on log Kow is expected. The highest toxicity was determined for methyl laurate (CAS 111-82-0, fatty acid chain length C12). In the GLP-study (Ministry of the Environment of Japan, 2006) according to OECD 201 the EC50 (72h) for growth rate was determined as 0.324 mg/L for Pseudokirchnerella subcapitata. A supporting study (Guhl, 1993) according to DIN 38412, part 9 support the high toxicity for algae. In this study an EC50 (96h) of 1.45 mg/L was determined for Desmodesmus subspicatus. The toxicity decreases with shorter and longer chain length of the fatty acids. For methyl decanoate (CAS 110-42-9, fatty acid chain length C10) a lower toxicity for Pseudokirchnerella subcapitata was estimated. One QSAR-calculation for methyl decanoate yielded an EC50 of 1.35 mg/L (ECOSAR, 2008). In addition, in one GLP-study (Bouwman, 2010) according to OECD 201 an EC50 of > 0.055 mg/L (arithm. mean) and > 3.93 mg/L (initial) was determined for methyl decanoate. As the measured test concentration (arithm. mean) did not reach the water solubility of methyl decanoate (10.62 mg/L), the QSAR-calculation was used as key study. One other QSAR-calculation for methyl octanoate (CAS 111-11-5, fatty acid chain length C8) yielded EC50 of 4.76 mg/L (ECOSAR, 2008). Both QSAR estimations were confirmed by a good performance of the model for C12, and thus can be considered as validated. The algae toxicity for methyl octanoate is as expected lower than the toxicity for methyl decanoate. Methyl myristate (CAS 124-10 -7, fatty acid chain length C14) showed no toxicity to Pseudokirchnerella subcapitata. One GLP-study (Migchielsen, 2010) according to OECD 201 generated an ErL50 (72h) > 100 mg/L and NOELR ¿ 100 mg/L. The measured concentration at the start of the test from the WSF prepared at 100 mg/L was 0.42 mg/L. The concentration decreased below the Limit Of Detection (LOD) after 24 hours of exposure (< 0.014 mg/L). As the Water soluble Fraction (WSF) method achieve the maximum dissolved concentration, it can be assumed, that no toxicity of methyl myristate (CAS-No. 124-10-7) is expected in the range of the water solubility. Therefore and due to the low water solubility of methyl palmitate (CAS 112-39-0) and methyl stearate (CAS 112-61-8), which have a chain length of C16 respectively C18 fatty acid, no toxicity for freshwater algae can be expected in the range of water solubility for methyl palmitate (0.004003 mg/L) and methyl stearate (0.0003 mg/L).

The UVCB substances could be derived from the single substances. The single substances with the highest percentage in the UVCB are decisive. Therefore, methyl decanoate (CAS 110-42-9) and methyl octanoate (CAS 111-11-5) were used as read across for Fatty acids, C8-10, Me esters (CAS 85566-26-3), as these both substances are the main components of Fatty acids, C8-10, Me esters. Due to the more sensitive estimated result for algae for methyl decanoate (CAS 110-42-9), this QSAR-calculation was used as key-study. Further, as Fatty acids, C12-18 and C18 -unsatd., methyl esters (CAS 1234694 -02 -0), Fatty acids, C8-18 and C18-unsatd., Me esters (CAS 67762-37-2) and Fatty acids, C12-14 (even numbered), methyl esters (CAS 308065-15-8) have a great percentage of C12 Fatty acid (> 30%), methyl laurate (CAS 111-82-0) was used as read across for these UVCB substances. The UVCB Fatty acids, C16-18, Me esters (CAS 85586-21-6) with a great percentage of C16 and C18 Fatty acids could be deviated from methyl palmitate (CAS 112-39-0) and methyl stearate (CAS 112-61-8), which were based on methyl myristate (CAS 124-10-7).

Of the substances to be registered, the following SCAE-Me show toxicity to algae leading to a classification R50 according to 67/548/EWG and Aquatic Acute 1 according to Regulation (EC) No 1272/2008: 

·       Methyl laurate (CAS 111-82-0)

·       Fatty acids, C12-18 and C18 -unsatd., methyl esters (CAS 1234694 -02 -0)

·       Fatty acids, C8-18 and C18-unsatd., Me esters (CAS 67762-37-2)

·       Fatty acids, C12-14 (even numbered), methyl esters (CAS 308065-15-8)

 

This SCAE-Me show also toxicity to algae, but do not lead to a classification:

·       Methyl octanoate (CAS 111-11-5)

·       Methyl decanoate (CAS 110-42-9)

·       Fatty acids, C8-10, Me esters (CAS 85566-26-3)

 

All other SCAE-Me of this category are not toxic to aquatic organisms. This are:

·       Methyl myristate (CAS 124-10-7)

·       Methyl palmitate (CAS 112-39-0)

·       Methyl stearate (CAS 112-61-8)

·       Fatty acids, C16-18, Me esters (CAS 85586-21-6)