Reaction mass of Disodium (sulphonatothio)acetate and sodium chloride

Endpoint summary

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

The reaction mass of Disodium (sulphonatothio)acetate and sodium chloride is a solid (white powder) but it is sold in solution. Disodium (sulphonatothio)acetate and sodium chloride have a molecular weight of 216.133 g/mol and 58,4 g/mol respectively. The reaction mass has a log Pow of <‑5 at 20°C and ‑1,73 at 25°C, a calculated vapor pressure of <0,0001 Pa at 25°C, and a water solubility of 557 g/l. The reaction mass decomposes (190°C) before melting.

Absorption

Oral absorption

Absorption is a property of a substance to diffuse across biological membranes. Generally, oral absorption is favored for molecular weights below 500 g/mol and log Pow values between -1 and 4. In the gastrointestinal tract absorption of small water-soluble molecules (molecular weight up to around 200 g/mol) occurs through aqueous pores or carriage of such molecules across membranes with the bulk passage of water. The reaction mass assessed in this report is a salt and is therefore completely dissociated in water yielding sodium-, chloride- and (sulphonatothio)acetate-ions. The molecular weight below 200 g/mol of each ion and the high water solubility of 557 g/l makes the reaction mass favorable for absorption through aqueous pores or carriage across membranes with the bulk passage of water. In animal studies after oral dosing adverse effects like mortality, an impaired general state and piloerection have occurred [1,2], thus there is definite proof for a gastrointestinal absorption of the reaction mass after oral uptake.

Dermal absorption

Liquids and substances in solution are taken up more readily than dry particulates via dermal absorption. If the reaction mass is applied as powder, it would have to dissolve into the surface moisture of the skin before an uptake could begin. The reaction mass is however marketed in solution. In general, dermal absorption is favored by small molecular weights and high water solubility of the substance. Log Pow values between 1 and 4 favor dermal absorption, particularly if water solubility is high. However, if water solubility is above 10 g/L and the log P value is below 0, the substance may be too hydrophilic to cross the lipid rich stratum corneum and dermal uptake will be low. The water solubility of 557 g/l of the respective reaction mass is conferred with a high dermal uptake, but together with a log Pow -5, it is too hydrophilic to cross the lipid rich environment of stratum corneum. Also in animal studies no skin irritation and no signs of systemic toxicity after dermal application occurred [3] indicating that dermal absorption will be low.

Based on the user manual for the internet version of the danish (Q)SAR database (version 1 may 2005), dermal penetration/absorption can be calculated with DERMWIN. According to this manual, with an Kp-value below 0.001 the dermal penetration of the test substance is considered to be very low (Kp-value calculated for disodium(sulphonatothio) acetate: 5*10 -8). Thus, based on this calculation dermal absorption compared to oral absorption is considered to be 10% as a worst case estimate. This is supported by acute toxicity data. In an acute dermal toxicity study at a dose of 2000 mg/kg bw no clinical signs and no mortality were seen [3], whereas in an acute oral toxicity study at a dose of 300 mg/kg bw all animals were found dead within one day [2]. Therefore, dermal uptake is considered negligible.

Respiratory absorption

Absorption via the respiratory route also depends on physico-chemical properties like vapor pressure, log Pow and water solubility. The reaction mass has a low calculated vapor pressure of <0,0001 Pa at 25°C. Therefore, inhalation of vapor of the respective reaction mass is very unlikely to occur. Theoretically, if inhalation of particles occurred during handling the reaction mass might be dissolved in the mucus of the respiratory tract due to the high water solubility (557 g/l). Due to the log Pow of <- 5 and molecular weights of each single ion below 200, absorption through aqueous pores or carriage across membranes with the bulk passage of water may occur. Absorption directly across the respiratory tract epithelium by passive diffusion is also possible but due to its hydrophilic character less likely to happen. Thus, absorption in the respiratory tract will be limited based on the low vapor pressure and the physico-chemical properties of the reaction mass.

Distribution

In general, the smaller the molecule the broader is its distribution. The dissolved sodium-, chloride and (sulphonatothio)acetate-ions are relatively small molecules, indicating a wide distribution. Also, the reaction mass is highly water soluble and has a log Pow < -5 and therefore its extracellular concentration will be higher than its intracellular concentration.

Metabolism

The (sulphonatothio)acetate-ion is highly water soluble and therefore not favorable to undergo biotransformation by phase I enzymes which is confirmed by predicted metabolism with the OECD QSAR Toolbox. Based on the structure, theoretically conjugation of the acid group with glucuronide can occur in phase II metabolism.

Excretion

In general, urinary excretion in favored by low molecular weight (below 300 g/mol in the rat) and good water solubility. Therefore, the reaction mass is expected to be excreted mostly via urine.

Accumulation

The reaction mass is highly water soluble and the log P is <0 therefore it is unlikely that the reaction mass is going to accumulate in tissues. Furthermore, the reaction mass is excreted via the urine.

 

 

References

[1] BASF Study on acute oral toxicity in rats 10A0318/14X508, 2016

[2] BASF Study on repeated oral toxicity in rats 88R0543/17S094, 2019

[3] BASF Study on acute dermal toxicity in rats 11A0318/14X655, 2017