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Administrative data

Description of key information

As an analogue substance and two structurally closely related substances did not induce skin irritation and only minor eye irritation that does not require classification, the substance is considered to be not skin and not eye irritating.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records
Reference
Endpoint:
skin irritation: in 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

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The two analogue substances (description of identity below) have essentially the same structure: MOPS is the free acid and MOPS sodium salt is a salt of MOPS. The same applies to the supporting analogue substances MES and MES sodium salt. Both MOPS and MES (and their sodium salts) are composed of identical functional groups, i.e. a heterocyclic morpholine group and a sulfonic acid group. MOPS and MES differ by one C in the length of the carbon chain linking the morpholine and the sulfonic acid group. In aqueous environments, an equilibrium between the sodium salts and their respective freeacids is formed, which is quantified by the dissociation constants pKd of approximately 7.28 (MOPS) and 6.16 (MES) at 20°C. The sodium salts form the free acids to a very large extend by accpeting a proton from H2O, thus leaving the remaining OH- and the aqueous Na+, while the free acids dissociate at a very low level into the respective anions and H+ (forming finally H3O+), while As the ions Na+, OH-, and H3O+ are ubiquitous in water and food, only the freea acids are determining the toxic and eco-toxic properties of the substances, whereas MOPS is the common compound for MOPS and MOPS sodium salt and MES is the common compound for MES (hydrate) and MES sodium salt. No other compounds are formed in both cases. With MES and MOPS consisting of identical functional groups, it can be assumed that the biological targets are the same, at least for local irritating effects. In addition, there is no indication for differences in the (bio)transformation between MOPS and MES, but even in case of minor differences, these can be considered as not relevant for local irritant effects.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The source substance is 3-morpholin-4-ylpropane-1-sulfonate (EC no. 428-420-3; CAS no. not available), referred to here as MOPS sodium salt. MOPS sodium salt is an organic mono-constituent substance with a typical purity of > 98% (w/w) (see also the respective REACH dossier). Any potential impurity is unknown, but considered not relevant for classification or labelling.
The target substance is sodium 4-morpholinapropanesulphonic acid (EC no. 214-478-5; CAS no. 1132-61-2), the free acidt of the source substance, refered to as here as MOPS. Also MOPS is an organic mono-constituent substance, which usually >99% pure. Any potential impurity is unknown, but considered not relevant for classification or labelling.
The analogue appraoch is supported by comparison with two similar substances, i.e. MES (hydrate) and MES sodium salt. Further details are presented in the document 'Analogue approach for MOPS sodium salt and MOPS supported by similarity to MES sodium salt and MES (hydrate)'.

3. ANALOGUE APPROACH JUSTIFICATION
Both substances are zwitterionic aminosulfonic acids with very high structural similarity, which is also reflected in very similar physicochemical properties.
MOPS (target) and MOPS sodium salt (source) will behave identically in studies, in which the substances are directly applied in dilution to buffered water, e.g. in studies of aquatic toxicity, such as toxicity to algae. The same applies to MES (hydrate) and MES sodium salt. But also in studies with high local concentrations, such as skin and eye irritation it can be assumed that MOPS and MOPS sodium salt behave identically, as supported by the absence of any irritation potential of the structurally related substances MES (hydrate) and MES sodium salt.

4. DATA MATRIX
The data matrix is included in the document 'Analogue approach for MOPS sodium salt and MOPS supported by similarity to MES sodium salt and MES (hydrate)' (Annex), attached here below under 'Attached justification`
Reason / purpose:
read-across source
Reason / purpose:
read-across: supporting information
Reason / purpose:
read-across: supporting information
Species:
rabbit
Strain:
New Zealand White
Type of coverage:
semiocclusive
Preparation of test site:
not specified
Vehicle:
water
Duration of treatment / exposure:
4h
Number of animals:
3
Irritation parameter:
erythema score
Basis:
mean
Time point:
24/48/72 h
Score:
0
Max. score:
0
Reversibility:
fully reversible within: 24h
Irritation parameter:
edema score
Basis:
mean
Time point:
24/48/72 h
Score:
0
Max. score:
0
Reversibility:
fully reversible within: 24h
Irritant / corrosive response data:
Very slight edema was noted at two treated skin sites at the 1-hour observation.

In a study according to OECD TG 404 under GLP conditions with the source substance MOPS sodium salt, minor skin irritation effects were observed at 1 hour only. Therefore, MOPS sodium salt is considered as not skin irritating. This result is read-across to the target substance MOPS.

Interpretation of results:
GHS criteria not met
Executive summary:

In a study according to OECD TG 404 under GLP conditions, besides some very slight edema after one hour, no skin irritation effects were observed for the source substance MOPS sodium salt. This result is read-across to the target substance MOPS.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records
Reference
Endpoint:
eye irritation: in 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

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The two analogue substances (description of identity below) have essentially the same structure: MOPS is the free acid and MOPS sodium salt is a salt of MOPS. The same applies to the supporting analogue substances MES and MES sodium salt. Both MOPS and MES (and their sodium salts) are composed of identical functional groups, i.e. a heterocyclic morpholine group and a sulfonic acid group. MOPS and MES differ by one C in the length of the carbon chain linking the morpholine and the sulfonic acid group. In aqueous environments, an equilibrium between the sodium salts and their respective freeacids is formed, which is quantified by the dissociation constants pKd of approximately 7.28 (MOPS) and 6.16 (MES) at 20°C. The sodium salts form the free acids to a very large extend by accpeting a proton from H2O, thus leaving the remaining OH- and the aqueous Na+, while the free acids dissociate at a very low level into the respective anions and H+ (forming finally H3O+), while As the ions Na+, OH-, and H3O+ are ubiquitous in water and food, only the freea acids are determining the toxic and eco-toxic properties of the substances, whereas MOPS is the common compound for MOPS and MOPS sodium salt and MES is the common compound for MES (hydrate) and MES sodium salt. No other compounds are formed in both cases. With MES and MOPS consisting of identical functional groups, it can be assumed that the biological targets are the same, at least for local irritating effects. In addition, there is no indication for differences in the (bio)transformation between MOPS and MES, but even in case of minor differences, these can be considered as not relevant for local irritant effects.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The source substance is 3-morpholin-4-ylpropane-1-sulfonate (EC no. 428-420-3; CAS no. not available), referred to here as MOPS sodium salt. MOPS sodium salt is an organic mono-constituent substance with a typical purity of > 98% (w/w) (see also the respective REACH dossier). Any potential impurity is unknown, but considered not relevant for classification or labelling.
The target substance is sodium 4-morpholinapropanesulphonic acid (EC no. 214-478-5; CAS no. 1132-61-2), the free acidt of the source substance, refered to as here as MOPS. Also MOPS is an organic mono-constituent substance, which usually >99% pure. Any potential impurity is unknown, but considered not relevant for classification or labelling.
The analogue appraoch is supported by comparison with two similar substances, i.e. MES (hydrate) and MES sodium salt. Further details are presented in the document 'Analogue approach for MOPS sodium salt and MOPS supported by similarity to MES sodium salt and MES (hydrate)'.

3. ANALOGUE APPROACH JUSTIFICATION
Both substances are zwitterionic aminosulfonic acids with very high structural similarity, which is also reflected in very similar physicochemical properties.
MOPS (target) and MOPS sodium salt (source) will behave identically in studies, in which the substances are directly applied in dilution to buffered water, e.g. in studies of aquatic toxicity, such as toxicity to algae. The same applies to MES (hydrate) and MES sodium salt. But also in studies with high local concentrations, such as skin and eye irritation it can be assumed that MOPS and MOPS sodium salt behave identically, as supported by the absence of any irritation potential of the structurally related substances MES (hydrate) and MES sodium salt.

4. DATA MATRIX
The data matrix is included in the document 'Analogue approach for MOPS sodium salt and MOPS supported by similarity to MES sodium salt and MES (hydrate)' (Annex), attached here below under 'Attached justification`
Reason / purpose:
read-across source
Reason / purpose:
read-across: supporting information
Reason / purpose:
read-across: supporting information
Species:
rabbit
Strain:
New Zealand White
Amount / concentration applied:
approx 81 mg
Number of animals or in vitro replicates:
3
Irritation parameter:
conjunctivae score
Basis:
animal #1
Time point:
24/48/72 h
Score:
0.7
Max. score:
2
Reversibility:
fully reversible within: 72h
Irritation parameter:
conjunctivae score
Basis:
animal #2
Time point:
24/48/72 h
Score:
0.7
Max. score:
2
Reversibility:
fully reversible within: 72h
Irritation parameter:
conjunctivae score
Basis:
animal #3
Time point:
24/48/72 h
Score:
0.7
Max. score:
2
Reversibility:
fully reversible within: 72h
Irritation parameter:
chemosis score
Basis:
animal #1
Time point:
24/48/72 h
Score:
0.3
Max. score:
2
Reversibility:
fully reversible within: 72h
Irritation parameter:
chemosis score
Basis:
animal #2
Time point:
24/48/72 h
Score:
0.3
Max. score:
2
Reversibility:
fully reversible within: 72h
Irritation parameter:
chemosis score
Basis:
animal #3
Time point:
24/48/72 h
Score:
0.3
Max. score:
2
Reversibility:
fully reversible within: 72h
Irritation parameter:
cornea opacity score
Basis:
mean
Time point:
24/48/72 h
Score:
0
Max. score:
0
Irritation parameter:
iris score
Basis:
mean
Time point:
24/48/72 h
Score:
0
Max. score:
0
Other effects:
Moderate conjunctival irritation was noted in all treated eyes at 1 hour. Minimal conjunctival irritation was observed in all treated eyes after 24 and 48h.
Interpretation of results:
GHS criteria not met
Executive summary:

In a GLP-study according to OECD TG 405 with the source substance MOPS sodium salt, the substances induced minor conjunctival effects and chemosis, which were reversible after 72h. Therefore, MOPS sodium salt is considered as not eye irritating. This result is read-across to the target substance MOPS.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Additional information

Justification for classification or non-classification

As an analogue substance and two structurally closely related substances did not induce skin irritation and only minor eye irritation that does not require classification, the substance does not need to be classified for skin and eye irritation according to the CLP regulation.