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Description of key information

Key value for chemical safety assessment

Additional information

There is no specific requirement to generate toxicokinetic information in REACH. Therefore, the toxicokinetic profile (i. e. absorption, distribution, metabolism and elimination) of Acetic acid, 2-sulfo-, mono-C12-14 (even numbered) -alkyl esters, sodium salt was derived from the relevant available information. The physical chemical characteristics of the substance, the results obtained from acute and repeated-dose toxicity studies were used to predict the toxicokinetic behaviour oflauryl sulfoacetate. Furthermore, the inorganic salt content of the substance is ~20.5%. The OECD Toolbox v2.3.0 was used to predict the likely metabolites of the two major components of the substance.

Physico chemical properties

The substance is a UVCB, the main component having a molecular weight of 330 g/mol and contains ~20.55 inorganic salts. The substance is highly water soluble (15.31 g/L), and is hydrophilic based on the octanol/water partition coefficient of (log Kow = -0.31) and is not volatile according to its vapour pressure (4.8x10-12Pa at 25°C). The substance is also surface active because it has a surface tension of 32.0 mN/m.

Absorption:

The physical chemical characteristics described above suggest that the substance has a molecular size that is larger than 200, which is considered to be the upper limit for passive diffusion through biological membranes. Being highly water soluble and of hydrophilic, the substance may be expected to be only poorly absorbed across gastrointestinal epithelial barriers particularly as its molecular size is >200, therefore absorption via the gastrointestinal tract is expected to be minimal. This assumption is supported by the observation of few or no signs of systemic toxicity at 660 mg/kg bw in the acute oral gavage toxicity study conducted on the substance. Deaths were observed but these may be presumed to have been due to local irritation and the absorption of surfactants or irritants may be enhanced because of damage to cell membranes. A 90-day repeat dose toxicity study onlauryl sulfoacetateidentified a NOAEL of 750 mg/kg bw/day, again without clear evidence of systemic toxicity. The observation of no clear systemic effects indicates the absence of significant oral bioavailability of the substance and/or its metabolites.

Dermal absorption of the substance is expected to be low because of its high water solubility and hydrophilicity, together with its relatively high molecular weight, which is much greater than the limit of 200, below which absorption is favoured. Enhanced skin penetration may be expected since the substance, whilst not classified as a skin irritant is corrosive to the eye and caused deaths in a dermal toxicity study, primarily because of corrosive effects at the site of prolonged application. The surface tension (32.0 mN/m) is greater than the upper limit of 10 mN/m, below which is considered to enhance dermal absorption because of a surfactant nature. The ~20.5% inorganic salt content is expected to be not absorbed through the skin.

The potential for inhalation toxicity was not evaluated in vivo. However, the vapour pressure of the substance (4.8x10-12Pa at 25°C) indicates the absence of volatility and therefore no exposure by inhalation is anticipated. Thus, at ambient temperature, no respiratory absorption is expected under normal use and handling of the substance

Distribution

Systemic distribution of the substance can be predicted from its physical chemical characteristics. Considering that the substance is hydrophilic (log Kow -0.31) and highly water soluble, it is suggested that, upon systemic absorption, the substance may be transported through the circulatory system in the aqueous phase and transport across cell membranes will be limited. The hydrophilicity of the substance and high water solubility indicate that bioaccumulation of any absorbed substance will be unlikely.

Metabolism and excretion

The substance is biodegradable and ingested material may therefore be biodegraded in the intestine and excreted with the faeces. Any absorbed material will likely be excreted to a small extent by the kidneys but largely in the bile because the MW is >300. Absorbed material is not expected to bioaccumulate, a conclusion that is supported by the observation of no systemic toxicity in a 90-day repeat dose toxicity study. The structures of the two main components of this UVCB substance were subjected to metabolite profiling using the OECD Toolbox v2.3.0 QSAR system and the predicted metabolites were partitioned into chemical categories based on USEPA rules (ECOSAR). The Toolbox predicted a total of 16 potential metabolites from the two main components, which are summarized in the table below:

 

US EPA chemical Categorization

Number

%age

Aldehydes (Acute toxicity)

3

19%

Anionic Surfactants

6

38%

Anionic Surfactants|Esters (Acute toxicity)

1

6%

Anionic Surfactants|Esters (Chronic toxicity)

1

6%

Neutral Organics

3

19%

Not categorized

2

13%

total

16

100%

The main components and their metabolites are predicted by OECD Toolbox v2.3.0 to biodegrade quickly and consequently the likelihood of bioaccumulation should be low.