Malic acid

Endpoint summary

Description of key information

Read across has been made to malic acid from fumaric acid which was a slight or mild skin irritant and a moderate eye irritant. .

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vivo

Type of information:

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

Adequacy of study:

key study

Study period:

25 April 1984 to 9 May 1984

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline-compliant, proprietary study. For read-across justification see Section 13.

Qualifier:

according to guideline

Guideline:

OECD Guideline 404 (Acute Dermal Irritation / Corrosion)

Principles of method if other than guideline:

Study was conducted in accordance with OECD Method 404

GLP compliance:

yes

Species:

rabbit

Strain:

other: small white Russian

Details on test animals or test system and environmental conditions:

Male and female rabbits between 1.9 and 2.8 kg were housed in individual stainless steel cages and acclimated for 14 days. Rabbits received K4 single diet for rabbits (Ssniff Special Feed GmbH) and water ad libitum. Room temperature was 20C with 60% relative humidity. Air was exchanged 15 times per hour and a 12 hr light-dark cycle was employed.

Type of coverage:

occlusive

Preparation of test site:

shaved

Vehicle:

other: paraffin oil

Controls:

not required

Amount / concentration applied:

0.5 g test material wetted with paraffin oil

Duration of treatment / exposure:

4 hrs

Observation period:

1, 24, 48 and 72 hours as well as 5, 7, 8, 12 and 14 days

Number of animals:

3 males and 3 females

Details on study design:

TEST SITE
- Area of exposure: 6 cm2 patch of skin
- Type of wrap if used: linen cloth (2.5 x 2.5 cm) covered with a polyethylene foil (6 x 6 cm). The application site was secured with an elastic band.


REMOVAL OF TEST SUBSTANCE
- Washing (if done): distilled water

SCORING SYSTEM:

Erythema and Eschar Formation:
No erythema...0
Very slight erythema (barely perceptible)...1
Well-defined erythema...2
Moderate to severe erythema...3
Severe erythema to slight eschar formation...4

Oedema Formation:
No oedema...0
Very slight oedema...1
Slight oedema...2
Moderate oedema...3
Severe oedema...4

Reaction values for redness and swelling were calculated for 1, 24, 48 and 72 hours after patch removal. These absolute values were added together and divided by the number of assessment times (4) to determine irritation index:

0 - 0.5 Not irritating
0.6 - 3.0 Mildly irritating
3.1 -5.0 Moderately irritating
5.0 - 8.0 Highly irritating

Irritation parameter:

overall irritation score

Basis:

mean

Time point:

other: 72 hrs

Score:

0.63

Reversibility:

fully reversible within: 14 days

Irritant / corrosive response data:

The mean score over 24-72 hours for redness was calculated to be 0.72
The mean score over 24-72 hours for swelling was calculated to be 0.11
Neither scores warrant classification for skin irritation

Individual and average redness (R) and swelling (S) values

Animal number	1 hr		24 hr		48 hr		72 hr
	R	S	R	S	R	S	R	S
1	0	0	0	0	0	0	0	0
2	0	0	1	0	1	0	1	0
3	0	0	*2	0	*1	1	*2	0
4	0	0	0	0	1	0	1	0
5	0	0	0	0	0	0	0	0
6	0	0	0	0	1	0	2	1
Total	0		0.5		0.83		1.17
Average	2.50 / 4 = 0.63
*Redness directly on the application surface

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

This study supports the conclusion that fumaric acid is a mild skin irritant that does not require classification for dermal irritation according to EU and GHS systems. It is proposed to classify malic acid the same way.

Executive summary:

Dermal application of 0.5 g fumaric acid was mildly irritating to the skin of male and female rabbits. Fumaric acid did not elicit dermal reactions that would exceed the threshold for classification in accordance with EU criteria.

Read across to fumaric acid is considered valid and malic acid is considered to exhibit similar properties. Classification is not required

The rational for read across is that fumaric acid will metabolise in biological systems to malic acid.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vivo

Type of information:

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

Adequacy of study:

key study

Study period:

25 April 1984 to 16 May 1984

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline-compliant, proprietary study. For read-across justification see Section 13.

Qualifier:

according to guideline

Guideline:

OECD Guideline 405 (Acute Eye Irritation / Corrosion)

GLP compliance:

yes

Species:

rabbit

Strain:

other: small white Russian

Details on test animals or tissues and environmental conditions:

Male and female rabbits between 1.9 and 2.1 kg were housed in individual stainless steel cages and acclimated for 14 days. Rabbits received K4 single diet for rabbits (Ssniff Special Feed GmbH) and water ad libitum. Room temperature was 20C with 60% relative humidity. Air was exchanged 15 times per hour and a 12 hr light-dark cycle was employed.

Vehicle:

unchanged (no vehicle)

Controls:

other: left eyelid of each animal

Amount / concentration applied:

0.1 g fumaric acid

Duration of treatment / exposure:

The test material was not washed out.

Observation period (in vivo):

1, 24, 48 and 72 hours and 5, 7, 9, 12, 15, 19 and 21 days.

Number of animals or in vitro replicates:

3 males and 3 females

Details on study design:

Test material was applied to the lower conjunctival sac of the right eye by pulling away the lower eyelid. The left eye was treated in one animal.
The contralateral eye served as a concurrent, inherent control

Irritation parameter:

overall irritation score

Basis:

mean

Time point:

other: 72 hrs

Score:

42.8

Reversibility:

not fully reversible within: 21 days

Irritant / corrosive response data:

The mean values over the 24, 48 and 72 hour post-instillation observations were:

corneal opacity = 2.0
Iris = 0.28
Conjunctival redness = 2.83
conjunctival chemosis = 1.72

Table 1. Cornea Evaluation: Degree of Opacity (A) x Extent of Opacity (B) x 5

Animal number	1 hr				24 hr			48 hr				72 hr
	A		B	AxBx5		A	B	AxBx5		A	B	AxBx5	A	B	AxBx5
1	1		4*	20		1	4	20		1	4	20	1	4	20
2	1		4	20		1	4	20		1	4	20	2	4	40
3	2		4	20		2	4+	40		2	4+	40	3	2-	30
4	2		4	20		3	2	30		4	2-	40	4	2-	40
5	2		4	20		1	4+	20		4	2-	40	3	2-	30
6	1		4	20		1	4	20		1	4	20	1	4	20
Mean				30				25				30			30
*Circular streak (0-4 mm) on the pupil; +Spot on the cornea with opacity up to white coloration; - Remaining surface: reduction in normal clarity

Table 2. Iris Evaluation: A = Change

Animal number	1 hr		24 hrs		48 + 72 hrs
	A	A x 5	A	A x 5	A	A x 5
1	0	0	0	0	0	0
2	0	0	0	0	0	0
3	0	0	0	0	1*	5
4	0	0	0	0	0	0
5	0	0	1*	5	1*	5
6	0	0	0	0	0	0
Mean		0		0.83		1.67
*Circumcorneal injection

Table 3. Conjunctive Evaluation: Redness (A) + Swelling (B) + Exudation (C)

Animal number	1 hr				24 hrs				48 hrs				72 hrs
	A	B	C	(A+B+C) 2	A	B	C	(A+B+C) 2	A	B	C	(A+B+C) 2	A	B	C	(A+B+C) 2
1	2	2	2	12	3	2	2	14	3	1	2	12	3	1	1	10
2	2	3	2	14	3	2	2	14	2	2	2	12	3-	2	1	12
3	2*	3	2	14	2	2	2	12	3-	2	2	14	3-	2	1	12
4	2	3	2	14	3+	2	3	16	3	2	3	16	3-	2	2	14
5	2*	2	2	12	2	2	2	12	3	1	2	12	3-	1	2	12
6	2	2	2	12	3	2	2	14	3	2	2	14	3	1	2	12
Mean				13				13.67				13.33				12.0
*Necrotic spots on mucous membrane; +Skin-like mucous on the cornea; -White layer is exuded from the mucous membrane

Interpretation of results:

moderately irritating

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

This study supports the conclusion that fumaric acid and malic are moderate eye irritants requiring classification.

Executive summary:

Application of 0.1 g fumaric acid to the eyes of male and female rabbits was considered moderately irritating to the eye and ocular mucous membrane. Fumaric acid is classified as an eye irritant. It is assigned the symbol Xi and the risk-phrase R36 - irritating to the eyes according to Directive 67/548/EEC. It is assigned the pictogram GHS07 with the signal word warning and the hazard statement H319 "causes serious eye irritation".

Read across to fumaric acid is considered valid and malic acid is considerd to exhibit similar properties and require classification as iritating to eyes. It is not considered valid to perform further animal tests on malic acid.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

In the absence of detailed data on malic acid, data are presented for fumaric acid. Malic acid and fumaric acid have similar dissociation constants and are considered moderately strong organic acids. Local irritation is expected, but dilution will quickly reduce effects.

The data on fumaric acid are in agreement with summary data reported in Patty’s industrial hygiene and toxicology, 3rd ed., 4937, 4941– 4942 (1981–2) New York. Wiley and Sons.

Effects on skin irritation/corrosion: slightly irritating

Effects on eye irritation: moderately irritating

Justification for classification or non-classification

Fumaric acid is listed on Annex I of Directive 67/548/EEC as an irritant to eyes (Xi; R36).

The mild skin irritation observed was insufficient to justify classification of fumaric acid. Moderate, reversible eye irritation shows that fumaric acid should remain classified for ocular irritation according to current EU and GHS criteria.

It is proposed to classify malic acid the same.