Reaction mass of sodium octane-1-sulfonate and disodium octane-1,2-disulfonate

Endpoint summary

Description of key information

Read-across: OECD 431, GLP, EpiDerm Reconstructed Human Epidermis (RHE) Model GLP, skin corrosive

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
Please refer to the Read-across statement attached under section 13.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
This Read-Across is based on the hypothesis that the target and the source substances have similar environmental fate and (eco)toxicological properties, because both substances have the same common compound octyl sulfonate while another main constituent of the target substance octyl disulfonate is considered to have similar level of toxicity as octyl sulfonate. Other non-common compounds represented by impurities are considered not to influence the read-across validity because they are either structurally identical in the target and in the source substances or, if different, do not contribute to the toxicity effects because they are also anionic sulfonates with the same functional groups and their content is very low.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Please refer to the Read-across statement attached under section 13.

3. ANALOGUE APPROACH JUSTIFICATION
All ANS category members are corrosive or higly irritating to skin and eyes. Since PASs are reported to be structurally between the two other sub-groups - alkyl sulfates and the α-olefin sulfonates - as they share the saturated alkyl chain with the sulfonic acid group, they are assumed to have the same reactivity to skin and eyes (SIDS, 2007).
Since the main constituents and most of the impurities of the target substance are also anionic surfactants with the same functional groups and the same length of hydrophobic carbon octyl chain, the same mode of toxicological action is expected for the target and the source substances. The constituents of the target substance do not possess functional groups associated with other modes of action or toxicity effects. Toxicokinetic behavior of the constituents of the target substance is expected to be essentially the same as that of the source substance. The second main constituent octyl disulfonate is a more hydrophilic chemical than the common compound octyl sulfonate, so that its absorption through the skin may be even lower than the absorption of octyl sulfonate. Moreover, octyl disolfonate is more polar and possesses higher hydrophilicity, because of the presence the secondary sulfonic group, so that a damage of cell mebranes may be even less pronounced by this constituent than by the octyl sulfonate. Thus, an enhancement of irritation properties is not likely. The impurities are also structurally similar to the main constituents with octyl rest and sulfonate groups at different positions. The minor amounts of other impurities (hexadecyl sulfonate, octyl sulfinosulfonate, benzoic acid and tert-butyl alcohol) are not expected to impact irritation properties of the target substance to a significant extent, if they were tested in irritation studies, because they do not contain functional groups associated with irritation properties and their amounts are very low. Therefore, it is predicted that the target substance would possess the same irritation potential to skin and eyes as the source substance.

4. DATA MATRIX
Please refer to the Read-across statement attached under section 13.

Reason / purpose for cross-reference:

read-across source

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

3 min exposure

Value:

87.9

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Remarks:

predicted result from the source substance

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

60 min exposure

Value:

4.2

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

positive indication of irritation

Remarks:

predicted result from the source substance

Other effects / acceptance of results:

- OTHER EFFECTS:
- Visible damage on test system: No
- Direct-MTT reduction: No
- Colour interference with MTT: No

DEMONSTRATION OF TECHNICAL PROFICIENCY: Yes

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: Yes
- Acceptance criteria met for positive control: Yes
- Acceptance criteria met for variability between replicate measurements: Yes
- Range of historical values if different from the ones specified in the test guideline: N/A

Table 2:       Mean OD₅₇₀Values and Viabilities for the Negative Control Item, Positive Control Item and Test Item

Tissue	Exposure Period	MeanOD570of individual tissues	Mean OD570of duplicate tissues	Standard Deviation	Coefficient of Variation (%)***	Relative Mean Viability (%)
Negative Control	3 Minutes	1.646	1.663*	0.025	1.5	100
		1.681
	60 Minutes	1.680	1.695*	0.020	1.2
		1.709
Positive Control	3 Minutes	0.144	0.148	0.005	3.1	8.9
		0.151
	60 Minutes	0.075	0.097	0.032	32.8	5.7**
		0.120
Test Item	3 Minutes	1.482	1.462	0.029	2.0	87.9
		1.442
	60 Minutes	0.077	0.071	0.020	1.2	4.2
		0.066

* mean OD₅₇₀0.7 – 2.8

** mean relative tissue viability of the 60 min positive control < 15 %

*** COV (in the range of 20 – 100 % viability) between two tissues treated identically is ≤ 30 %

Interpretation of results:

other: A combination of optional Sub-categories 1B-and-1C

Conclusions:

In this study under the given conditions the source substance sodium octae-1-sulfonate showed corrosive effects. The mean relative tissue viability (% negative control) was reduced below 15% after 60 min treatment but not below 50% after 3 min treatment. Sodium Octane-1-sulphonate is therefore classified as “corrosive“ in accordance with UN GHS sub-category 1B. The same result is predicted for the target substance.

Executive summary:

OECD 431 (2017) - The skin corrosivity potential of the source substance sodium octane-1-sulphonate was assessed using an EpiDerm Reconstructed Human Epidermis (RHE) Model Kit in accordance with OECD guidance 431 and GLP.

Duplicate tissues were treated with the test item for exposure periods of 3 and 60 mins. At the end of the exposure period the test item was rinsed from each tissue before being loaded with MTT. After MTT loading each tissue was placed in 2 mL isopropanol for MTT extraction. After extraction, each tissue was pierced and the extraction solution aliquoted for absorbance measurements. Absorbency at 570 nm of each well was measured using a spectrophotometer.

Mean viability of tissues exposed to the test substance after 3 and 60 minutes were 87.9 % and 4.2 %, respectively. The quality criteria required for acceptance of the results was met.

Under the conditions of this study the test substance is considered to be corrosive to the skin in accordance with a combination of optional UN GHS sub-categories 1B and 1C; however for the purposes of conservative classification the substances is designated as corrossive: sub-category 1B.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (corrosive)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

OECD 431 (2017) - The skin corrosivity potential of sodium octane-1-sulphonate was assessed using an EpiDerm Reconstructed Human Epidermis (RHE) Model Kit in accordance with OECD guidance 431 and GLP.

Duplicate tissues were treated with the test item for exposure periods of 3 and 60 mins. At the end of the exposure period the test item was rinsed from each tissue before being loaded with MTT. After MTT loading each tissue was placed in 2 mL isopropanol for MTT extraction. After extraction, each tissue was pierced and the extraction solution aliquoted for absorbance measurements. Absorbency at 570 nm of each well was measured using a spectrophotometer.

Mean viability of tissues exposed to the test substance after 3 and 60 minutes were 87.9 % and 4.2 %, respectively. The quality criteria required for acceptance of the results was met.

Under the conditions of this study the test substance is considered to be corrosive to the skin in accordance with a combination of optional UN GHS sub-categories 1B and 1C; however for the purposes of conservative classification the substances is designated as corrossive: sub-category 1B.

Justification for classification or non-classification

Based on the available data on the source substance, the registered substance is classified as skin corrosive Cat. 1B (H314) and eye damaging Cat. 1 (H318) according to Regulation (EC) no 1272/2008.