3-hydroxy-2-methyl-4-pyrone

Endpoint summary

Description of key information

Read-across to Ethyl maltol (CAS No. 4940-11-8) - Skin irritation: Not irritating (OECD 439/GLP)

Read-across to Ethyl maltol (CAS No. 4940-11-8) - Eye irritation: Not irritating (OECD 405)

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Reference 1

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 November 2016 - 13 January 2017

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Read-across data; OECD439/GLP study

Qualifier:

according to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

Version / remarks:

2015

Qualifier:

according to guideline

Guideline:

EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)

Version / remarks:

No 761/2009

Qualifier:

according to guideline

Guideline:

other: UN GHS

Version / remarks:

published 2003, last (6th) revision 2015

GLP compliance:

yes (incl. QA statement)

Remarks:

14 September 2015

Test system:

human skin model

Source species:

human

Cell type:

other: epidermal keratinocytes (NHEK)

Cell source:

other: SkinEthic Laboratories, Lyon, France

Source strain:

other: not applicable

Justification for test system used:

According to testing guideline OECD Guideline 439

Vehicle:

water

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EpiSkin™
- Tissue batch number(s): 17-EKIN-002
- Production date/Shipping date/Delivery date: 10 jan 2017
- Date of initiation of testing: 10 jan 2017 (start tissue exposure experiments)

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure/ post-treatment incubation: 37 °C

REMOVAL OF TEST MATERIAL AND CONTROLS
-Tissues were washed with phosphate buffered saline to remove residual test item.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 0.3 mg/ml in PBS
- Incubation time: 3 hours at 37 °C
- Spectrophotometer: not specified
- Wavelength: 570 nm

NUMBER OF REPLICATE TISSUES: 3

DECISION CRITERIA
- A test substance is considered irritant in the skin irritation test if: The relative mean tissue viability of three individual tissues after 15 minutes of exposure to the test substance and 42 hours of post incubation is ≤ 50% of the mean viability of the negative controls.
- A test substance is considered non-irritant in the in vitro skin irritation test if: The relative mean tissue viability of three individual tissues after 15 minutes of exposure to the test substance and 42 hours of post incubation is > 50% of the mean viability of the negative controls.

Control samples:

yes, concurrent vehicle

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- 5 µL of deionised water was topically applied to the epidermal surface in order to improve further contact between the solid and the epidermis. Each approximately 10 mg of the test item was applied and spread to the wetted triplicate tissues.

Duration of treatment / exposure:

15 minutes

Duration of post-treatment incubation (if applicable):

42 hours

Number of replicates:

3

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Relative mean tissue viability of test item compared to the negative control tissues (100%)

Value:

122.8

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Remarks:

8.1% viability

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

OTHER EFFECTS:
- Direct-MTT reduction: No colour changes observed
- Colour interference with MTT: Not colour changes observed

ACCEPTANCE OF RESULTS:
- The relative mean tissue viability for the positive control treated tissues was 8.1% relative to the negative control treated tissues and the standard deviation value of the viability was 15.9%. The positive control acceptance criteria were therefore satisfied.
- The mean OD570 for the negative control treated tissues was between ≥ 0.6 and ≤ 1.5 and the standard deviation value of the viability was 8.2%. The negative control acceptance criteria were therefore satisfied.
- The standard deviation calculated from individual tissue viabilities of the three identically test item treated tissues was 7.4%. The test item acceptance criterion was therefore satisfied.

Results after treatment with Ethyl Maltol and controls

Test Group	Mean Absorbance of 3 Tissues	Relative Absorbance [%] Tissue 1/ 2/ 3**	Relative Standard Deviation [%]	Rel. Absorbance [% of Negative Control]***
Negative Control	1.053	105.5 / 103.9 / 90.6	8.2	100.0
Positive Control	0.086	7.0 / 7.8 / 9.6	15.9	8.1
Test Item	1.293	112.4 / 129.1 / 126.8	7.4	122.8

** relative absorbance per tissue [rounded values]

*** relative absorbance per treatment group [rounded values]

Interpretation of results:

GHS criteria not met

Remarks:

Not classified according to CLP.

Conclusions:

Ethyl Maltol is not a skin irritant.

Executive summary:

In an in vitro skin irritation assay in the human epidermal model EpiSkin (1801400), reconstructed human keratinocytes (moistened with 5µL water) was exposed to 10 mg of Ethyl Maltol (>99%) for 15 minutes. Deionised water was used for the negative control and 5% SLS was used for the positive control. After removal of the test substance via washing, tissues were post-incubated for 42 hours. Tissues were then incubated with MTT for 3 hours. The OD570 of isopropyl alcohol extracts was measured on a spectrophotometer. Relative cell viability was calculated for each tissue as % of the mean viability of the negative control tissues.

The controls confirmed the validity of the study. The mean OD570 for the negative control treated tissues was between ≥ 0.6 and ≤ 1.5 (1.053). The mean relative tissue viability (% negative control) of the positive control was ≤ 20% (8.1%). Standard deviation of viability of replicate tissues of all dose/negative control/positive control groups was ≤ 18% (7.4%/8.2%/15.9%).

The colour of the test substance did not interfere with the endpoint. The test substance is not directly MTT reducing. The average viability of tissues treated by the test item, Ethyl Maltol, was 122.8 % of the negative control average value i.e. viability was > 50 %. According to these results, the test substance is not irritating.

Reference 2

Endpoint:

skin irritation: 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

Report is attached below.

Reason / purpose for cross-reference:

read-across source

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Relative mean tissue viability of test item compared to the negative control tissues (100%)

Value:

122.8

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Remarks:

8.1% viability

Remarks on result:

no indication of irritation

Interpretation of results:

GHS criteria not met

Remarks:

Not classified according to CLP

Conclusions:

The test substance, Maltol, was considered not a skin irritant, based on the results of the source substance, ethyl maltol.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Reference 1

Endpoint:

eye irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

29 September 1975 - 6 October 1975

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Read-across data; Performed according to an internal method comparable to OECD TG 405, pre-GLP.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 405 (Acute Eye Irritation / Corrosion)

GLP compliance:

no

Remarks:

pre-GLP

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source: P.P.L

Species:

rabbit

Strain:

not specified

Vehicle:

unchanged (no vehicle)

Amount / concentration applied:

0.05 g

Duration of treatment / exposure:

Single instillation in one eye per animal

Observation period (in vivo):

8 days

Number of animals or in vitro replicates:

6 animals

Irritation parameter:

cornea opacity score

Basis:

mean

Remarks:

mean of 6 animals

Time point:

24/48/72 h

Score:

0.5

Max. score:

4

Reversibility:

fully reversible

Remarks on result:

other:

Remarks:

6/6 animals scored < 1

Irritation parameter:

iris score

Basis:

mean

Remarks:

mean of 6 animals

Time point:

24/48/72 h

Score:

0.39

Max. score:

2

Reversibility:

fully reversible

Remarks on result:

other: 6/6 animals scored < 1

Irritation parameter:

conjunctivae score

Basis:

mean

Remarks:

mean of 6 animals

Time point:

24/48/72 h

Score:

0.66

Max. score:

3

Reversibility:

fully reversible

Remarks on result:

other: 6/6 animals scored <=1

Irritation parameter:

chemosis score

Basis:

mean

Remarks:

mean of 6 animals

Time point:

24/48/72 h

Score:

0.22

Max. score:

4

Reversibility:

fully reversible

Remarks on result:

other: 6/6 animals scored < 1

Irritant / corrosive response data:

Five out of six animals had corneal swelling and some opacity, all animals in the test had slight conjunctivitis and there was evidence of small amount of hemorrhaging of the conjunctivae in three of the rabbits. Four rabbits developed irritis.

Interpretation of results:

other: Not an eye irritant

Remarks:

UNSCEGHS Guidance (June 2001)

Conclusions:

Under the conditions of this test, Ethyl Maltol is not an eye irritant.

Executive summary:

In an eye irritation study (Quest, 1975), 50 mg Ethyl Maltol (>99%) was applied to one cornea of 6 rabbits. Prior to instillation, 1 drop of ophtaine was used to anesthetize the cornea. Eyes were not washed after instillation. Animals were observed at 15 minutes, and 1, 2, 3, 4 and up to 8 days after instillation.

Five out of six animals had some corneal swelling and some opacity; the mean score was 0.5 and all individual scores for corneal opacity were < 1.  Four rabbits developed iritis; the mean score was 0.39 and all individual scores were < 1. There was evidence of small amount of hemorrhaging of the conjunctivae in three eyes of the rabbits. All animals in the test group had slight conjunctivitis; the mean score was 0.66, individual scores were all <=1 and 4/6 animals scored < 1. The mean chemosis score was 0.22 and all individual scores were < 1. After eight days all lesions had cleared up in all animals i.e. the effects were fully reversible.

As this study was conducted according to an older test method and six rabbits were used, the CLP regulation does not provide criteria for the evaluation of such studies. In such cases, the current UNSCEGHS Guidance needs to be applied (adopted in June 2011), as indicated in ‘Guidance on the application of the CLP criteria’, version 5.0, November 2017. Therefore, based on these test results, Ethyl Maltol is not an eye irritant.

Reference 2

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

Report is attached below.

Reason / purpose for cross-reference:

read-across source

Irritation parameter:

cornea opacity score

Basis:

mean

Remarks:

of 6 animals

Time point:

24/48/72 h

Score:

0.5

Max. score:

4

Reversibility:

fully reversible

Remarks on result:

other: 6/6 animals scored < 1

Irritation parameter:

iris score

Basis:

mean

Remarks:

of 6 animals

Time point:

24/48/72 h

Score:

0.39

Max. score:

2

Reversibility:

fully reversible

Remarks on result:

other: 6/6 animals scored < 1

Irritation parameter:

conjunctivae score

Basis:

mean

Remarks:

of 6 animals

Time point:

24/48/72 h

Score:

0.66

Max. score:

3

Reversibility:

fully reversible

Remarks on result:

other: 6/6 animals scored <=1

Irritation parameter:

chemosis score

Basis:

mean

Remarks:

of 6 animals

Time point:

24/48/72 h

Score:

0.22

Max. score:

4

Reversibility:

fully reversible

Remarks on result:

other: 6/6 animals scored < 1

Irritant / corrosive response data:

Five out of six animals had corneal swelling and some opacity, all animals in the test had slight conjunctivitis and there was evidence of small amount of hemorrhaging of the conjunctivae in three of the rabbits. Four rabbits developed irritis.

Interpretation of results:

other: Not an eye irritant

Remarks:

UNSCEGHS Guidance (June 2001)

Conclusions:

The test substance, Maltol, was not considered an eye irritant, based on the results of the source substance, Ethyl Maltol.

Reference 3

Endpoint:

eye irritation: in vitro / ex vivo

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

an in vitro eye irritation study does not need to be conducted because adequate data from an in vivo eye irritation study are available

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin irritation/corrosion

There is no in vitro skin irritation test available for Maltol. There is a read-across in vitro skin irritation study from Ethyl maltol available.

 

In an in vitro skin irritation assay in the human epidermal model EpiSkin (OECD 439/GLP), reconstructed human keratinocytes (moistened with 5µL water) was exposed to 10 mg of Ethyl Maltol (>99%) for 15 minutes. Deionised water was used for the negative control and 5% SLS was used for the positive control. After removal of the test substance via washing, tissues were post-incubated for 42 hours. Tissues were then incubated with MTT for 3 hours. The OD570 of isopropyl alcohol extracts was measured on a spectrophotometer. Relative cell viability was calculated for each tissue as % of the mean viability of the negative control tissues. The controls confirmed the validity of the study. The mean OD570 for the negative control treated tissues was between ≥ 0.6 and ≤ 1.5 (1.053). The mean relative tissue viability (% negative control) of the positive control was ≤ 20% (8.1%). Standard deviation of viability of replicate tissues of all dose/negative control/positive control groups was ≤ 18% (7.4%/8.2%/15.9%). The colour of the test substance did not interfere with the endpoint. The test substance is not directly MTT reducing. The average viability of tissues treated by the test item, Ethyl maltol, was 122.8 % of the negative control average value i.e. viability was > 50 %. According to these results, the test substance is not irritating.

Maltol was predicted to be not irritating.

Serious eye damage/eye irritation

In vitro/in vivo eye irritation studies with Maltol were not available. A read-across in vivo eye irritation study in rabbits with Ethyl Maltol was available.

In an eye irritation study (equivalent or similar to OECD 405), 50 mg Ethyl Maltol (>99%) was applied to one cornea of 6 rabbits. Prior to instillation, 1 drop of ophtaine was used to anesthetize the cornea. Eyes were not washed after instillation. Animals were observed at 15 minutes, and 1, 2, 3, 4 and up to 8 days after instillation.  Mean values, based on the results from the 24, 48 and 72 hour readings, were calculated. Five out of six animals had some corneal swelling and some opacity; the mean score was 0.5 and all individual scores for corneal opacity were < 1.  Four rabbits developed iritis; the mean score was 0.39 and all individual scores were < 1. There was evidence of small amount of hemorrhaging of the conjunctivae in three eyes of the rabbits. All animals in the test group had slight conjunctivitis; the mean score was 0.66, individual scores were all <=1 and 4/6 animals scored < 1. The mean chemosis score was 0.22 and all individual scores were < 1. After eight days all lesions had cleared up in all animals i.e. the effects were fully reversible.

As this study was conducted according to an older test method and six rabbits were used, the CLP regulation does not provide criteria for the evaluation of such studies. In such cases, the current UNSCEGHS Guidance needs to be applied (adopted in June 2011), as indicated in ‘Guidance on the application of the CLP criteria’, version 5.0, November 2017:

a. Classification as serious eye damage – Category 1 if:

(i) at least in one animal effects on the cornea, iris or conjunctiva that are not expected to reverse or have not fully reversed within an observation period of normally 21 days; and/or (ii) at least 4 out of 6 rabbits show a mean score of ≥ 3 for the cornea and/or > 1.5 for the iris;

b. Classification as eye irritation – Category 2 if at least 4 out of 6 rabbits show a mean score of:

(i) ≥ 1 for the cornea and/or

(ii) ≥ 1 for the iris and/or

(iii) ≥ 2 conjunctival erythema and/or

(iv) ≥ 2 conjunctival oedema (swelling) (chemosis)

and which fully reverses within an observation period of normally 21 days.

Based on these criteria, Ethyl Maltol, is not irritating. Maltol is also predicted to be not irritating.

Both studies are suitable to use in the human health assessment.

Justification for classification or non-classification

Based on the available information in the dossier, the substance Maltol (CAS No. 118-71-8) is not classified for skin irritation/corrosion based on the results of the read-across study from Ethyl Maltol (CAS No. 4940-11-8), when considering the criteria outlined in Annex I of 1272/2008/EC.

Based on the available information in the dossier, the substance Maltol (CAS No. 118-71-8) is not classified for serious eye damage/irritation based on the results of the read-across study from Ethyl Maltol (CAS No. 4940-11-8), when considering the criteria outlined in the UNSCEGHS Guidance (June 2011),

as indicated in ‘Guidance on the application of the CLP criteria’, version 5.0, November 2017.