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The most important structural feature of C8-18AS Mg & TEA is the presence of a predominantly linear aliphatic hydrocarbon chain with a polar sulfate group, neutralized with a counter ion (i.e., Na+, K+, NH4+, or an alkanolamine cation). The hydrophobic hydrocarbon chain (with a length between C8 and C18) and the polar sulfate group confer surfactant properties and enable the commercial use as an anionic surfactant. The counter ion will not influence chemical reactivity and classification for the purpose of this assessment is not expected to be affected by the difference in counter ion (ref. OECD SIDS 2007, HERA Report 2002, Koennecker et al. 2011).


In aqueous environments the salts will dissociate, so that the counter ions will not fundamentally alter pathways of tissue disposition, metabolism, excretion, or target organs of toxicity. Accordingly no major differences were found in most of the endpoints between the compounds with different counter ions (ref. OECD SIDS 2007, HERA Report 2002, Koennecker et al. 2011). Moreover, several of the counter-ions have also been assessed in the OECD HPV Program and/or according to REACH Regulation (EC) No 1907/2006: triethanolamine (CAS 102-71-6), the ammonia category (CAS 7664-41-7; 1336-21-6; 7783-18-8; 12593-60-1) and ammonium salts, like ammonium sulfate (CAS 7783-20-2), chloride (CAS 12125-02-9) and bicarbonate (CAS 1066-33-7).


 


Physico-chemical properties relevant for environmental toxicity of alkyl sulfates:


The most important parameter influencing PC-properties is the varying length of the alkyl chain.


- Vapour pressure - as ionic substances, alkyl sulfates are characterized by low vapour pressures.


- Partition coefficient - as surfactants concentrate at hydrophilic/hydrophobic boundaries and do not equilibrate between phases, Pow is not a good descriptor of surfactant hydrophobicity and only of a limited predictive value for the partitioning of these compounds in the environment. Nevertheless, experimental Pow values have been obtained, usually as quotients of solubilities in octanol and in water. Partition coefficients are low (mostly negative values of log Pow) and they increase with the alkyl chain range.


- Water solubility - the solubility in water is high, in the range of 100-1000 g/L. Particular values decrease with the alkyl chain range.


 


Environmental fate and pathways of alkyl sulfates:


- C8-18AS Mg & TEA is readily biodegradable. Abiotic degradation (e.g. hydrolysis) is not a relevant for environmental pathway due to the chemical structure of the substance.


- C8-18AS Mg & TEA is non-volatile, which implies that atmospheric photodegradation is irrelevant.


- As the log Pow-value is below 3, a potential for bioaccumulation can be excluded.


- Due to the low to moderate log Koc-value, it can be predicted that the sorption to sludge, sediments and soils will be relatively low. Alkyl sulfates are unlikely to persist in the aquatic environment.


 


Aquatic toxicity of alkyl sulfates:


The results of toxicity tests on three different trophic levels demonstrate that fish are the most sensitive trophic level, followed by invertebrates and algae in regard to short-term toxicity.


Short-term toxicity to fish was determined in one study in accordance with guideline OECD 203 and showed a moderate acute toxicity (BASF SE, 2020).


The same can be said for short-term toxicity to aquatic invertebrates which was evaluated in one study according to guideline OECD 202.


Available information on the long-term toxic effects of alkyl sulfates to Ceriodaphnia dubia includes the substances with a carbon chain length from C10 to C18. A clear response curve was observed - toxicity increase with chain length from C12 to C14 and then decreased up to C18. Since C18-AS is insoluble in calcium-containing water (i.e., Ceriodaphnia test waters), the effects are due to physical interactions, not the classic uptake into the organism and then elicit toxicity. Chronic toxicity testing with Daphnia magna using the technical product C14 -15 proved that these are the most toxic chain lengths for aquatic invertebrates (OECD SIDS, 2007).


Several reliable experimental studies with algae are available for alkyl sulfates. It seems that algae react less sensitive to alkyl sulfate exposure than fish and invertebrates. The results do not allow the clear prediction of a chain length dependency of algal toxicity because most of the studies were conducted with technical products. Nevertheless, it seems that the most toxic chain lengths are C10 and also C14 - C15 (OECD SIDS, 2007).


Activated sludge respiration inhibition tests and Pseudomonas putida tests are available for the alkyl sulfates of chain lengths from C12 to C18. In Pseudomonas putida testing a tendency of increasing toxic effects with increasing carbon chain length could be observed (OECD SIDS, 2007).


 


Acute toxicity key values of C8-18AS Mg & TEA (CAS 85586-38-5):


- For fish: 96h LC50 (mortality) = 2.91 mg/L


- For invertebrates: 48h EC50 (Daphnia magna, immobilization) = 3.84 mg/L


- For algae: 72h EC50 (Desmodesmus subcapitatus, growth rate) = 11 mg/L (nominal concentration, EU Method C.3, read-across from CAS 90583-18-9)


 


Chronic toxicity key values of C8-18AS Mg & TEA (CAS 85586-38-5):


- For fish: 42d NOEC (Pimephales promelas; mortality and growth) >= 1.357 mg/L (read-across from CAS 151-21-3)


- For invertebrates: 21d NOEC (Daphnia magna, reproduction) = 0.22 mg/L (read-across from CAS 142-87-0 and CAS 151-21-3, CAS 1191-50-1, CAS 1120-01-0)


- For algae: 72h NOEC (Desmodesmus subcapitatus, growth rate) = 0.6 mg/L (nominal concentration, EU Method C.3, read-across from CAS 85586-07-8)


- For microorganisms: 3h EC50 (activated sludge respiration inhibition) = 135 mg/L (nominal concentration, EU method C.11, read-across from CAS 151-21-3)


 


 


 


 

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