Naphthalenesulfonic acid, bis(1-methylethyl)-, Me derivs., sodium salts

Endpoint summary

Description of key information

The substanceNaphthalenesulfonic acid, bis(1-methylethyl)-,methyl derivs., sodium salt(C7-alkyl naphthalene sulphonate)is basically a UVCB involving a sodium salt of naphthalene sulphonic acid showing some variability in short alkyl chain substitution, mainly involving methyl and isopropyl groups, resulting to an average of 7-carbons.No metabolism or toxicokinetic data was generated on any of the constituents involved with this dataset. The information in this chapter has been derived based on the physicochemical properties of the substance, information from QSAR models, i.e. QSAR Toolbox (v.4.2) and EpiSuite (v. 4.1) and information on bioaccumulation potential from the chapter on environmental fate and pathways. The substance has an average molecular weight of 346 g/Mol and a measured low vapour pressure of1.7 × 10^-4Paat 25°C. The log Kow of 0 suggests that the substance has a low bioaccumulation potential. The QSAR Toolbox (version 4.2) was used to estimate the human intestinal absorption. The absorption is considered to be 100% by all routes.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

100

Absorption rate - dermal (%):

100

Absorption rate - inhalation (%):

100

Additional information

Substance:

The substance “Naphthalenesulfonic acid, bis(1-methylethyl)-,methyl derivs., sodium salt”, further referred to asC7-alkyl naphthalene sulphonate, is a UVCB of which the most representative structure is given in the properties table below.C7-alkyl naphthalene sulphonateis anionic at all physiological pH.Based on its anionic and (limited) surfactant properties, the structure is not expected to easily pass membrane structures, but cytotoxicity through disruption of cell membrane is expected. This is supported by study results: All available data indicates that the NOAEL is driven by local effects of the substance on skin and gastro-intestinal tract, and generally low systemic toxicity.

 

No metabolism or toxicokinetic data was generated on any of the constituents involved with this dataset. The information in this chapter has been derived based on Profiling, the physicochemical properties of the substance, information from QSAR models, i.e. QSAR Toolbox (v.4.2) and EpiSuite (v. 4.1) and information on bioaccumulation potential from the chapter on environmental fate and pathways.

 

Physical-chemical properties:

The pure substance is a solid, without melting point or boiling point observed up to400 °C.

The anionic properties of the sulphate at all pH contributes to it water solubility of the naphthalene as is demonstrated by the measured value of 10 g/L. It has low surface active properties i.e.>33 mN/m at 25ºC) as shown by measured surface tension of50 mN/m.

The measured vapour pressure is with1.7 × 10^-4Paat 25°C low, although higher than expected from calculations. This is probably due to the impurities in this UVCB substance.

Profiling structure: Acid and sodium salt: See attached document

Toxicokinetic properties:

The properties ofC7-alkyl naphthalene sulphonateindicate reasonable solubility, not too high LogPow, which are favourable for systemic absorption. Also (modified) Lipinski rules suggest and QSARs indicate thatC7-alkyl naphthalene sulphonateis expected to be well absorbed.

 

Oral absorption:

Ingestion is not a likely route of exposure and the irritating effects would characterise accidental oral exposure. Due to lack of actual test data on the substance, a worst case approach is taken and the default 100% is used in the risk assessment.

 

Dermal absorption:

No experimental data are available on dermal absorption.C7-alkyl naphthalene sulphonateis not expected to easily pass the skin in view of its ionised form at physiological conditions..

Due to the irritating nature of the substance, the required risk management measures to handle it should minimize the potential for contact with the skin. However due to the irritating properties which would possibly compromise the barrier properties of the skin, possible exposure to the test substance would have to be assumed to result in 100% absorption. The low octanol water partition coefficient of 0 would reduce its potential for being absorbed through the skin, but the estimation of dermal absorption performed using EpiSuite (v.4.1) indicates some uptake.

Lacking adequate quantitative evaluation, 100% dermal absorption is considered as worst case assumption.

 

Respiratory absorption:

As a worst case, absorption via the inhalational route is also considered to be complete, although exposure to the substance via inhalation is low based on the physical appearance of the substance. In view of thevery low vapour pressure is exposure via inhalation in principle only possible via dust (substance is powder with a D₁₀of 3 µm) or aerosol. In both cases most is expected to be deposited in the nose, throat and upper airways and will be subsequently swallowed following mucociliary transportation to pharynx. This would result to no principal difference in absorption compared oral route. Asworst case approach also 100% absorption is considered via inhalation route.

 

The substance is not considered to have a potential for bioaccumulation, based on its water solubility properties and the low Kow value, and lack of increased toxicity observed in repeated dose studies of different duration.