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Environmental fate & pathways

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Additional information

The Sarcosine category contains N-acyl derivatives of N-methylglycine that function as hair-conditioning agents and surfactant-cleansing agents in cosmetic formulations. Other uses in non-cosmetic areas are known and some sarcosines are used in the metal finishing and processing industries as anti-rust agents. Their salts are known generally as N-acyl sarcosinates, fatty acid sarcosinates, or sarcosinates.

Structural similarities of the category substances are reflected in similar physico-chemical properties and mode of action. They have a common structural formula (see attachment), where R may be either hydrogen or sodium; the N-acyl part is a fatty acid chain ranging in length between 12 to 18 carbon atoms (R’ = C11 to C17) and having up to three unsaturations.

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 human toxicity, environmental fate and eco-toxicity, 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)”. Therefore, the available experimental data were collected and evaluated according to Annex XI in regard to:

-      Test duration (only tests which cover the expected exposure duration were regarded as suitable)

-      Key parameters of the test (only tests that cover the key parameter were accepted as suitable)

-      Comparability of the test systems

-      The adequacy of the results for C&L

-      The documentation of the test procedures (only in case of good documentation data)

Only data that were judged to cover the requirements specified above were used as adequate data suitable for the category and its members. In this particular case the similarity of the Sarcosine category members is justified, in accordance with the specifications listed in Regulation (EC) No. 1907/2006 Annex XI, 1.5 Grouping of substances and read across, on basis of scope of variability and overlapping of composition, representative molecular structure, physico-chemical properties, toxicological, ecotoxicological profiles and supported by various QSAR methods. There is no convincing evidence that any one of these respective chemicals might lie out of the overall profile of this category. The key points that the members share are:

(i) Common origin: produced from condensation of fatty acids and N-methyl glycine. Typically the fatty acid needs to be activated in the form of chloride.

(ii) Similar structural features: long hydrophobic chain connected to a polar head through an amide bond

(iii) Similar physico-chemical properties: recognizable trends in melting point, boiling point, water solubility and partition coefficient. Similar surface tension activity.

(iv) Common properties for environmental fate & eco-toxicological profile: readily biodegradable, no potential for bioaccumulation, low to moderate adsorption potential, clear trend of increasing toxicity in aquatic organisms correlating with increasing carbon chain length, being the C18 compounds the most toxic substances.

(v) Similar metabolic pathways: the substances within the Sarcosine category have similar toxicokinetic behaviour that consists in no hydrolysis before absorption and absorption of the intact substance followed by a rapid excretion.

(vi) Common levels and mode of human health related effects: the available data on toxicological properties show that the substances of the Sarcosine category have similar toxicokinetic behaviour, no hydrolysis of the ester bond before absorption, absorption of the intact substance followed by a rapid excretion. The substances within the category showed acute toxicity via the inhalation route due to their irritant properties (reflected by their self-warning characteristics), skin irritating effects and severe damaging effects on the eye. Despite these corrosive/irritating effects, the constant pattern in toxicological properties within all substances considered herein consists in a lack of change of potency of properties.Thus, the category members showed no acute oral or dermal toxicity, no skin sensitisation properties, are of low systemic toxicity after repeated oral exposure, are not mutagenic or clastogenic, have shown no indication for reproduction toxicity and have no effect on intrauterine development.

 

Similar environmental fate and pathway

Table. Environmental fate and pathway (*)

ID No.

Substance

CAS No.

Chain length

Biodegradability: screening tests

Bioaccumulation (BCF/ BAF [L/kg])

Adsorption/Desorption [log Koc]

Hydrolysis

# 1

N-lauroylsarcosine

97-78-9

C12 acid

RA from CAS 137-16-6

(Q)SAR: 150.7/150.7 (Arnot-Gobas)

(Q)SAR: 2.43 – 3.91 (Franco and Trapp)

Data waiving (readily biodegradable)

# 2

Sodium N-lauroylsarcosinate

137-16-6

C12 salt

Experimental result:

readily biodegradable

(Q)SAR: 0.966/0.966 (Arnot-Gobas)

(Q)SAR: 1.84 – 2.32 (Franco and Trapp)

Data waiving (readily biodegradable)

# 3

N-(1-oxotetradecyl) sarcosine

52558-73-3

C14 acid

RA from CAS 30364-52-1

(Q)SAR: 306.9/308 (Arnot-Gobas)

(Q)SAR: 2.45 – 4.58 (Franco and Trapp)

Data waiving (readily biodegradable)

# 4

Sodium N-methyl-N-(1-oxotetradecyl)aminoacetate

30364-52-1

C14 salt

Experimental result:

readily biodegradable

(Q)SAR: 1.835/1.835 (Arnot-Gobas)

(Q)SAR: 2.2 – 2.52 (Franco and Trapp)

Data waiving (readily biodegradable)

# 5

(Z)-N-methyl-N-(1-oxo-9-octadecenyl)glycine

110-25-8

C18 acid

Experimental result:

readily biodegradable

Q)SAR: 562.8/2344 (Arnot-Gobas)

(Q)SAR: 2.47 – 5.06 (Franco and Trapp)

Data waiving (readily biodegradable)

# 6

Reaction products of oleoyl sarcosine with sodium hydroxide

--

C18 salt

RA from CAS 110-25-8

(Q)SAR: 211.7-1509/309.1-13420 (Arnot-Gobas)

(Q)SAR: 2.69 – 3.15 (Franco and Trapp)

Data waiving (readily biodegradable)

(*) substances marked in bold are registered under REACH Regulation EC 1907/2006 in 2013, the remaining substances were registered in 2010 or will be registered later.

The substances of the Sarcosine category are all readily biodegradable according to OECD criteria, hence they will not be persistent in the environment. Abiotic hydrolysis is not relevant, since all members of the category are readily biodegradable and thus expected to be rapidly eliminated through biodegradation in natural waters.

Corresponding to the trend observed for the octanol-water partition coefficient (log Pow), a trend can be noticed for adsorption and bioaccumulation potential. The salts show lower adsorption and bioaccumulation potential than the respective acids. Furthermore, the potential for adsorption and bioaccumulation increases with increasing fatty acid chain length from C12 and C14 to C18 for the salts and the acids. For both salts (C12, Sodium N-lauroylsarcosinate, CAS 137-16-6, and C14, Sodium N-methyl-N-(1-oxotetradecyl) aminoacetate, CAS 30364-51-3) with lower chain length a low adsorption potential is assumed as the log Pow and the log Koc values are below 3. Due to this low partition coefficient values (log Pow < 3) for both salts, bioaccumulation potential can be excluded as well. For the salt with the highest fatty acid chain length (Reaction products of oleoyl sarcosine with sodium hydroxide) and the three acids in the category (N-lauroylsarcosine (CAS 97-78-9), N-(1-oxotetradecyl)sarcosine (CAS 52558-73-3) and (Z)-N-methyl-N-(1-oxo-9-octadecenyl) glycine (CAS 110-25-8)) log Koc values above 3 were calculated (Franco and Trapp, 2008). Nevertheless, bioavailability to aquatic organisms is assumed to be low for these four substances as due to their readily biodegradable nature and adsorption potential, the substances will be extensively biodegraded in conventional STPs, and a significant degree of adsorption to sewage sludge is expected. Therefore, discharged concentrations into the environment are expected to be low. In addition, extensive and rapid excretion is observed for these substances in mammals, and calculated BCF values are well below the value of 2000 L/kg considered as criterion to define a substance as Bioaccumulative (B) according to Annex XIII of Regulation (EC) No. 1907/2006. Based on all the available information, low bioaccumulation potential of all category members is expected.

Considering the water solubility values (400 and 360 g/L), the low volatilization potential (0.0000749 and 0.00104 Pa) and the low adsorption potential (log Kow < 3) for the two salts with the lowest fatty acid chain length (Sodium N-lauroylsarcosinate (C12), CAS 137-16-6, and Sodium N-methyl-N-(1-oxotetradecyl) aminoacetate (C14), CAS 30364-51-3), if released into the environment, both category members will tend to be mainly distributed in the aquatic compartment. Nevertheless, due to their ready biodegradability, persistence of the substances in water is not expected. On the other hand, in view of the water solubility values (0.5 – 400 g/L), the low volatilization potential (9.25E-08 – 39.9 Pa) and the low to moderate adsorption potential (log Koc = 2.43 – 5.06) of the remaining four category members (the salt with the highest fatty acid chain length (C18) and the three acids (C12, C14 and C18)), these substances are expected to be mainly distributed in the soil and sediment compartments, if released into the environment. Nevertheless, persistency in these compartments is not anticipated either, due to readily biodegradable nature of the substances.

Abiotic degradation

Abiotic degradation of all category members is not a relevant pathway for degradation in water as the substances are readily biodegradable and are expected to be rapidly eliminated by biodegradation from the aquatic environment. Additional data on phototransformation of the substances in air are not available. However, this is not expected to be a relevant degradation pathway since the substances are not expected to enter the atmospheric compartment in significant amounts based on the estimated or measured vapour pressure values under ambient conditions (9.25E-08 – 39.9 Pa).

Biodegradation

Ready biodegradability studies are available for three category members, for the salt with the lowest fatty acid chain length (C12, Sodium N-lauroylsarcosinate, CAS 137-16-6), for the salt with the C14 fatty acid chain length (Sodium N-methyl-N-(1-oxotetradecyl) aminoacetate, CAS 30364-51-3) and for the acid with the longest fatty acid chain length (C18, (Z)-N-methyl-N-(1-oxo-9-octadecenyl) glycine, CAS 110-25-8). Thus, a biodegradability test is available for each fatty acid chain length of the category and read across was done between the corresponding salts and acids. Since dissociation of the sodium salt under environmental conditions yields the same ionic species as dissociation of the acidic form of the substance, this read across can be considered as justified. This read-across is in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5. The best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substance was used for the assessment. Nevertheless, as it can be seen in the data matrix below, all reliable data in the category support the hazard assessment of each category member by showing a consistent pattern of results. Therefore, biodegradation data from Sodium N-lauroylsarcosinate (CAS 137-16-6,C12 salt) are used as read across for the corresponding acid (N-lauroylsarcosine, CAS 97-78-9). Based on the results obtained for the read-across substance Sodium N-lauroylsarcosinate (CAS 137-16-6) (82% after 28 d), both substances can be classified as readily biodegradable according to the strict OECD criteria.

Biodegradation data from the C14 salt (Sodium N-methyl-N-(1-oxotetradecyl) aminoacetate, CAS 30364-51-3) are used as read across for the corresponding acid (N-(1-oxotetradecyl) sarcosine, CAS 52558-73-3). Since dissociation of the sodium salt under environmental conditions yields the same ionic species as dissociation of the acidic form of the substance, this read across can be considered as justified. Results from two biodegradation tests for the C14 salt show between 71 and 83% biodegradation after 28 days, but the 10-day window was not achieved. However, experience has shown that a 10 day window is commonly not achieved with these protocols as the carbon dioxide produced at any time point will take time to be sparged into the sodium hydroxide traps. Therefore, data from a similar Sarcosine category member, (Z)-N-methyl-N-(1-oxo-9-octadecenyl) glycine (CAS 110-25-8), representing an acid with a longer carbon chain length (C18), is used as read across. Except for different cations (hydrogen vs. sodium) and different carbon chain length (longer chain length (C18) vs. shorter chain length (C14)), the source and the target substance have similar chemical structures. This read across is considered a worst case approach since the chain length is the determining factor for biodegradation. Based on CO2 evolution, the substance attained 85.2% degradation after 28 days, fulfilling the 10-day window criterion, and can thus be classified as readily biodegradable according to the strict OECD criteria. This read-across is in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5. In this case of read-across, the worst case (higher carbon chain length) read-across substance was used for the assessment. Nevertheless, as it can be seen in the data matrix below, all reliable data in the category support the hazard assessment of each category member by showing a consistent pattern of results. Based on the results from structurally similar read-across substances (including a worst-case substance) and the stringency of the ready biodegradability tests (including the experience that a 10 day window is commonly not achieved with the study protocol used), it can be concluded that N-(1-oxotetradecyl) sarcosine (CAS 52558-73-3) and Sodium N-methyl-N-(1-oxotetradecyl) aminoacetate (CAS 30364-51-3) can be considered as readily biodegradable.

Biodegradation data from the C18 acid ((Z)-N-methyl-N-(1-oxo-9-octadecenyl) glycine, CAS 110-15-8) are used as read across for the corresponding salt (Reaction products of oleoyl sarcosine with sodium hydroxide). Except for different cations (hydrogen vs. sodium) the anions of both the source and target substance have identical chemical structures. Since dissociation of the sodium salt under environmental conditions (pH 4 - 9) yields the same ionic species as dissociation of the acidic form of the substance, this read across can be considered as justified. Based on CO2 evolution, (Z)-N-methyl-N-(1-oxo-9-octadecenyl) glycine (CAS 110-25-8) attained 85.2% degradation after 28 days, fulfilling the 10-day window and can thus be considered as readily biodegradable according to the strict OECD criteria. Based on these results from the structurally related read-across substance (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5.) it can be concluded that Reaction products of oleoyl sarcosine with sodium hydroxide is readily biodegradable according to the OECD criteria as well.

Since all category members are concluded to be readily biodegradable, all substances are expected to be rapidly biodegraded by microorganisms both in the aquatic and the terrestrial environments; therefore, in accordance with Regulation (EC) No 1907/2006, Annex IX, Column 2, 9.2.1.2. – 9.2.1.4., further simulation testing for biodegradation in water and sediment or soil is not required.

Bioaccumulation

Experimental bioaccumulation data are not available for the members of the Sarcosine category. However, BCF values were calculated (BCFBAF v3.01) for each category member indicating a low bioaccumulation potential.

The potential for bioaccumulation follows a trend within the category, being lower for the salts than for the acids. Furthermore, the potential for bioaccumulation (BCFBAF v3.01) increases with increasing fatty acid chain length from C12 and C14 to C18 for the salts (BCF = 0.966, 1.835 and 211.7– 1509 L/kg, respectively) and the acids (150.7, 306.9 and 562.8 L/kg, for C12, C14 and C18, respectively). For the salts with the shortest chain lengths (Sodium N-lauroylsarcosinate (C12), CAS 137-16-6, and Sodium N-methyl-N-(1-oxotetradecyl) aminoacetate (C14), CAS 30364-51-3) bioaccumulation potential can be excluded as well due to the partition coefficient values (log Pow), which are below 3. For the salt with the highest fatty acid chain length (C18) (Reaction products of oleoyl sarcosine with sodium hydroxide) and the three acids in the category (N-lauroylsarcosine (CAS 97-78-9), N-(1-oxotetradecyl) sarcosine (CAS 52558-73-3) and (Z)-N-methyl-N-(1-oxo-9-octadecenyl) glycine (CAS 110-25-8)), all with log Pow values above 3, the bioavailability to aquatic organisms is expected to be low. Due to their readily biodegradable nature, the substances will be extensively biodegraded in conventional STPs and due to their considerable adsorption potential, a significant degree of adsorption to sewage sludge is expected, leading to low discharged concentrations in water. Available data on the metabolism and excretion of sarcosinates in mammals clearly indicate extensive and rapid excretion of these substances, leading to low bioaccumulation potential (see section 7.1). Additionally, all QSAR estimations using the BCFBAF v3.01 program support this conclusion, with BCF values well below the value of 2000 L/kg considered as criterion to define a substance as Bioaccumulative (B) according to Annex XIII of Regulation (EC) No 1907/2006. Based on all the available information, low bioaccumulation potential of all category members is expected.

Adsorption (Log Koc)

Koc values were calculated (Franco and Trapp, 2008) for all category members.

Corresponding to the trend observed for the octanol-water partition coefficient (log Pow), a trend can be noticed regarding adsorption. The salts show lower adsorption potential than the respective acids. In addition, the adsorption potential increases with increasing fatty acid chain length from C12 to C18 for the salts (log Koc = 1.84 – 3.15) and the acids (log Koc = 2.43 – 5.06). For the salts (C12, Sodium N-lauroylsarcosinate, CAS 137-16-6, and C14, Sodium N-methyl-N-(1-oxotetradecyl) aminoacetate, CAS 30364-51-3) with lower chain length a low adsorption potential is assumed as the log Pow and the log Koc values are below 3. For the salt with the highest fatty acid chain length (C18, Reaction products of oleoyl sarcosine with sodium hydroxide) and the three acids in the category (N-lauroylsarcosine (CAS 97-78-9), N-(1-oxotetradecyl) sarcosine (CAS 52558-73-3) and (Z)-N-methyl-N-(1-oxo-9-octadecenyl) glycine (110-25-8)) log Koc values ranging from 2.43 – 3.91, 2.45 – 4.58 and 2.47 – 5.06, respectively, were calculated (Franco and Trapp, 2008) indicating a low to moderate adsorption potential.

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