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Toxicological information

Dermal absorption

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Administrative data

Endpoint:
dermal absorption
Type of information:
other: assessement of dermal absorption potential based on physico-chemical properties and toxicological data
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: An assessment of dermal absorption potential was performed, taking into account the chemical structure, the available physico-chemical-data and the available toxicological data.

Data source

Reference
Reference Type:
other: Expert statement
Title:
Unnamed
Year:
2016
Report date:
2016

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: Technical guidance document, Part I, 2003; ECHA guidance R7C., 2014
Deviations:
no
GLP compliance:
no
Remarks:
not applicable

Test material

Constituent 1
Chemical structure
Reference substance name:
Benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs., para-, sodium salts
EC Number:
946-212-5
Molecular formula:
Too complex
IUPAC Name:
Benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs., para-, sodium salts

Results and discussion

Percutaneous absorption
Parameter:
percentage
Absorption:
10 %
Remarks on result:
other: The target substance sodium sulfonate is expected to be poorly absorbed following dermal exposure into the stratum corneum, due to its LogPow of 7.99 and low water solubility (0.255 mg/L)

Any other information on results incl. tables

In order to cross the skin, a compound must first penetrate into the stratum corneum and may subsequently reach the epidermis, the dermis and the vascular network. The stratum corneum provides its greatest barrier function against hydrophilic compounds, whereas the epidermis is most resistant to penetration by highly lipophilic compounds. Substances with a molecular weight above 500 are normally not able to penetrate the skin. The substance must be sufficiently soluble in water to partition from the stratum corneum into the epidermis. Therefore if the water solubility is below 1 mg/L, dermal uptake is likely to be low. Additionally LogPow values between 1 and 4 favour dermal absorption (values between 2 and 3 are optimal; TGD, Part I, Appendix IV; ECHA guidance R7.C, 2014). Above 4, the rate of penetration may be limited by the rate of transfer between the stratum corneum and the epidermis, but uptake into the stratum corneum will be high. Above 6, the rate of transfer between the stratum corneum and the epidermis will be slow and will limit absorption across the skin. Uptake into the stratum corneum itself may be slow. Vapours of substances with vapour pressures below 100 Pa are likely to have enough contact time to be absorbed and the amount absorbed dermally is most likely more than 10% and less than 100 % of the amount that would be absorbed by inhalation. If the substance is a skin irritant or corrosive, damage to the skin surface may enhance penetration. During the whole absorption process into the skin, the compound can be subject to biotransformation.

In the case of sodium sulfonate the molecular weight of around 500 g/mol (432.64 - 516.79), indicates already a marginal potential to penetrate the skin. This is accompanied by a low hydrophilicity of the substance (logPow of 7.99) and low water solubility (0.255 mg/L). Even though the stratum corneum is open for lipophilic substances, the epidermis is very resistant against penetration by highly lipophilic substances (logPow >4). However, the amount of sodium sulfonate,which is absorbed following dermal exposure into the stratum corneum is unlikely to be transferred into the epidermis. Although the substance shows characteristics of a surfactant, it is not irritating to skin, and therefore an enhancement of dermal absorption can be ruled out.

In support of this hypothesis (the low dermal absorption), the systemic toxicity ofthe calcium sulfonate read across substance CAS 70024-69-0 and of CAS 115733-09-0via the skin is low (acute dermal toxicity, LD50 value of > 2000 and > 5000 mg/kg bw for rats, respectively).

In conclusion, the evaluation of all the available indicators and the results of toxicity studies allow the allocation of the chemical in question into the group of chemicals with a low dermal absorption. In detail, due to it’s molecular weight, logPow of 7.99, low water solubility (0.255 mg/L) and the results for the dermal acute toxicity, the use of a factor of 10 % for the estimation of dermal uptake for sodium sulfonate is justified(Schuhmacher –Wolz et al.,2003; TGD, Part I, 2003; ECHA guidance R.7C, 2014).

Applicant's summary and conclusion

Conclusions:
No significant dermal absorption is expected for the target substance sodium sulfonate.
Executive summary:

Sodium sulfonate has the molecular weight of around 500 g/mol (432.64 - 516.79), which indicates already a marginal potential to penetrate the skin. This is accompanied by a low hydrophilicity of the substance (logPow of 7.99) and low water solubility (0.255 mg/L). Even though the stratum corneum is open for lipophilic substances, the epidermis is very resistant against penetration by highly lipophilic substances (logPow >4). However, the amount of sodium sulfonate,which is absorbed following dermal exposure into the stratum corneum is unlikely to be transferred into the epidermis. Although the substance shows characteristics of a surfactant, it is not irritating to skin, and therefore an enhancement of dermal absorption can be ruled out.

In support of this hypothesis (the low dermal absorption), the systemic toxicity of the calcium sulfonate read across substance CAS 70024-69-0 and of CAS 115733-09-0 via the skin is low (acute dermal toxicity, LD50 value of > 2000 and > 5000 mg/kg bw for rats, respectively).

In conclusion, the evaluation of all the available indicators and the results of toxicity studies allow the allocation of the chemical in question into the group of chemicals with a low dermal absorption. In detail, due to it’s molecular weight, logPow of 7.99, low water solubility (0.255 mg/L) and the results for the dermal acute toxicity, the use of a factor of 10 % for the estimation of dermal uptake for sodium sulfonate is justified (Schuhmacher –Wolz et al.,2003; TGD, Part I, 2003; ECHA guidance R.7C, 2014).