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Description of key information

The substanceSodium diisobutylnaphthalenesulphonate (ANS DIB; C8-alkyl naphthalene sulfonate)is basically a UVCB involving a sodium salt of naphthalene sulfonic acid showing some variability in short alkyl chain substitution, mainly involving methyl and butyl groups, resulting to an average of 6.2 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 345 g/Mol. Estimated low vp and log Kow are confirmed by read-across to the very similar ANS IP. The log Kow of 0 or lower suggests that ANS substances have 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

Support for read-across within the category of Alkyl Naphthalene Sulfonates (ANS) is attached to chapter 13.

 

Substance:

The substanceSodium diisobutylnaphthalenesulphonate (ANS DIB; C8-alkyl naphthalene sulfonate) is a UVCB. Based on the level of alkyl substation of naphthalene sulfonate, with on average involving 6.2 carbons.

Sodium diisobutylnaphthalenesulphonateis 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

ANS products are relatively fine powders, with particles sizes below 100 µm. The D10 of the products evaluated varies between 3 and 8 µm. The product can be expected to have a high mp. For the comparable product ANS IP no melting point or boiling point was observed up to400 °C.

The anionic properties of the sulfate at all pH contributes to it water solubility of the naphthalene. It has low surface active properties.

Estimated vapour pressures of the ANS substances are very low ranging between 1.06x10-6 Pa for methyl-ANS and 9.76x10-10Pa for Methyl-Nonyl-ANS, and even lower in case of di-sulfonation, as indicated by the increase from 9.93x10- 9 Pa for Methyl-2-iso-propyl ANS to 2.44x10-14 Pa for its disulfonate at 25°C. These values are estimated for the ANS acids, and it can be expected to be even lower in case of sodium salts. The measured data of 0.00017 Pa at 25 °C for ANS IP confirm the low vp. That levels are higher than calculated values is caused by the presence of other structures in these UVCB’s.

More information on profiling and absorption characteristics is presented in the document in support of read-across within the ANS category, attached to ch.13

 

Toxicokinetic properties:

The properties of C6.2-alkyl naphthalene sulfonate (representing average alkyl chain substitution for the ANS DIB product, which is comparabel to ANS IP product) indicate reasonable solubility, not too high LogPow, which are favourable for systemic absorption. Also (modified) Lipinski rules suggest and QSARs indicate thatANS DIB isexpected 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.ANS DIBis 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.