(carboxylatomethyl)hexadecyldimethylammonium

Endpoint summary

Description of key information

Daphnia EC50 in the range 2.0 - 10.0 mg/l (on related substance)

Algal inhibition reported EC50 in the range 2.5 - 11.0 mg/l (on related substance)

Fish toxicity ca LC50 2 mg/l (on related substance)

Overall, the toxicity to algae and Daphnia are similar with the Daphnia perhaps being marginally more sensitive, and it is the Daphnia end point data, which is considered as reliable, that will be used to decide on the classification. Evidence shows that fish are more tolerant to the class of substance than algae and further animal testing is not justified. Acute toxicity is predicted to be in the range of 1 - 10 mg/l.

 

Additional information

The members of the alkyl betaines category are amphoteric surfactants containing a quaternary ammonium ion and a carboxylic structure. They are referred to as inner salts due to their zwitterionic character. They are all manufactured from natural materials such as vegetable oils and can vary in chain length from C8 to C18. They are generally marketed as aqueous solutions (20 - 40 %).

Because of the structural and functional similarities and comparable physico-chemical properties these inner salts and sodium salts, a similar ecotoxicological and toxicological profile can be expected.

Cetyl betaine (C16) and Lauryl betaine (C12) are very closely related chemical structures. The parent compound, betaine, is a naturally occurring N-trimethylated amino acid.

The individual betaines differ only in chain length. They are generally UVCB substances being manufactured from naturally occurring plant and animal sources.

 The Cosmetic Ingredient Review Expert Panel reviewed the product use, formulation and safety data of eleven alkyl betaines, as used in cosmetics. (Final report issued 2014-04-04)

The Panel concluded that the common core chemical structure, similar functions and concentrations in cosmetics, and the predicted physicochemical properties enabled grouping these ingredients and reading across the available toxicological data to support the safety assessment of each individual compound in the entire group.

OECD SIDS data exists for a similar group of betaines, this time with an extra amide bond. These are known as alkylamidopropyl betaines. They also have alkyl chain lengths in the same range as the straight alkyl betaines.

Both types of betaine are used extensively in the cosmetics and personal care products as surfactants and selection of the type used is generally based on the end skin feel, foaming nature and viscosity. They are comparative in their expected toxicology.

Data in the SIDS assessment profile (SIAM 23 - Oct 2006) suggests similar values to those quoted in the end point data here.

The following text has been taken from this document;

“For the acute toxicity of cocamidopropyl betaine to aquatic species reliable results from tests with fish, daphnia, algae, and microorganisms are available. The lowest acute LC/EC50 values for the three trophic levels fish, Daphnia, and algae are in each case in the range of 1.3 – 2 mg active substance/l. Furthermore, one long-term test with fish (according to OECD TG 215), and several chronic tests with Daphnia and algae were conducted. The lowest NOECs are 0.16 mg active substance/l for fish (Oncorhynchus mykiss), 0.03 mg active substance/l for Daphnia magna, and 0.09 mg active substance/l for green algae (Desmodesmus subspicatus). These values were

derived with analytical monitoring (photometric) except for the algae test. However, the effect values within the same species (e.g., Desmodesmus subspicatus, Daphnia magna) have shown a high variability. Recent guideline studies performed in accordance with OECD TG 211 and 201 using state-of-the-art analytical monitoring and a quality of cocamidopropyl betaine currently commercialized, resulted in a lower aquatic toxicity. In these studies the lowest NOEC for daphnids was determined to be 0.932 mg active substance/l. the lowest NOEC (72 h, based on growth rate) for algae was determined to be 3.55 mg active substance/l (72 h-ErC50= 9.86 mg active substance/l). This latter NOEC for algae is further supported by the similar NOEC of 3.53 mg active substance/l calculated using the geometric mean of all valid tests with this algae species. Furthermore, for algae a potential

for recovery from the effect up to a concentration of 96 mg active substance/l has been observed”