Nonanoic acid

Endpoint summary

Description of key information

Pelargonic acid exerted no skin sensitising potential in a valid OECD TG 406 Buehler test using Guinea pigs (KS, RL1). Positive observations made in a murine local lymph node assay with nonanoic acid are concluded to be not indicative for skin sensitising properties, due to the known fact that strong irritants may yield false positive results in this assay. This interpretation as false positive result is supported by mechanistic studies.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1981

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

no

Principles of method if other than guideline:

delayed contact hypersensitivity in the guinea pig

GLP compliance:

no

Type of study:

Buehler test

Justification for non-LLNA method:

there is no justification why in the past (1981) the study was performed using Buehler test.

Species:

guinea pig

Strain:

Hartley

Sex:

male/female

Details on test animals and environmental conditions:

TEST ANIMALS
- Weight at study initiation: males 302 to 396 grams; females 303 to 367 grams
- Housing: singly in suspended stainless steel cages
- Diet: Charles River Vitamin-C fortified Guinea pig diet, ad libitum
- Water: automatic watering system, ad libitum
- Acclimation period: 16 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 65-75°F
- Photoperiod (hrs dark / hrs light): 12/12 hours

Route:

epicutaneous, occlusive

Vehicle:

other: 80 % Ethanol and Acetone (induction); acetone (challenge)

Concentration / amount:

Induction: 100%
Challenge: 10%;
Re-challenge: 25%

Route:

epicutaneous, occlusive

Vehicle:

other: 80 % Ethanol and Acetone (induction); acetone (challenge)

Concentration / amount:

Induction: 100%
Challenge: 10%;
Re-challenge: 25%

No. of animals per dose:

20 (10 male, 10 females) in the definitive experiment received the test substance

Details on study design:

RANGE FINDING TESTS:
- No. of animals: 16
- Vehicle: acetone
- Concentrations: 5, 10, 25, 50, 75, and 100%
- Application of test material: each animal was dosed with two to four different concentrations, at different sites of the clipped dorsal skin.
- Application of test material: 0.2 mL of test material mixture was applied beneath a surgical gauze square, placed directly to the test site. The gauze was covered with plastic sheeting and held in place with an elastic adhesive bandage.
- Evaluation of skin reactions: observation for signs of skin irritation were made approx. 24 and 48 hours after dosing. Evaluation was made according to OECD TG 406, paragraph 23.


MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 9 expoures in total; 3 exposures per week
- Exposure period: 3 weeks
- Test groups: 20 animals (10 m, 10 f)
- Control group:
-- Positive control; DCNB; 12 animals (6 m, 6 f)
-- Irritation control (challenge only): pelargonic acid 8 animals; DCNB 8 animals (4m, 4f each)
- Site: dorsal skin, right side of the midline
- Frequency of applications: 3 exposures per week
- Duration: 6 hours each
- Concentrations:
-- pelargonic acid: 100% inductions 1-5; 75% from the 6th induction onwards, due to severe skin irritation
-- DCNB: 0.5 and 0.75% during inductions 1 through 8; ninth induction was omitted due to severe skin irritation


B. CHALLENGE EXPOSURE
- No. of exposures: 2
- Day(s) of challenge: 1
- Exposure period: 6 hours
- Test groups: as above
- Control group: as described above
- Site: dorsal skin, sites left of the midline
- Concentrations:
--pelargonic acid: 10% (challenge); 25% (re-challenge, 7 days after first challenge))
-- DCNB: 0.1% at challenge and at re-challenge
- Evaluation (hr after challenge): 24 and 48 after challenge dosing (and after re-challnge dosing)


OTHER: Re-challenge was made 7 days after the challenge treatment

Challenge controls:

yes

Positive control substance(s):

yes

Remarks:

2,4-dinitrochlorbenzene

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Remarks on result:

not measured/tested

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

other: irritation controls, DCNB (or pelargonic acid) only

No. with + reactions:

0

Total no. in group:

16

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: other: irritation controls, DCNB (or pelargonic acid) only. No with. + reactions: 0.0. Total no. in groups: 16.0.

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

other: irritation controls, DCNB (or pelargonic acid) only

No. with + reactions:

0

Total no. in group:

16

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: other: irritation controls, DCNB (or pelargonic acid) only. No with. + reactions: 0.0. Total no. in groups: 16.0.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

10%

No. with + reactions:

0

Total no. in group:

20

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 10%. No with. + reactions: 0.0. Total no. in groups: 20.0.

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

10%

No. with + reactions:

0

Total no. in group:

20

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 10%. No with. + reactions: 0.0. Total no. in groups: 20.0.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

other: test group, re-challenge

Dose level:

25%

No. with + reactions:

3

Total no. in group:

20

Clinical observations:

barely perceptible erythema

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: other: test group, re-challenge. Dose level: 25%. No with. + reactions: 3.0. Total no. in groups: 20.0. Clinical observations: barely perceptible erythema.

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

other: test group, re-challenge

Dose level:

25%

No. with + reactions:

1

Total no. in group:

20

Clinical observations:

barely perceptible erythema

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: other: test group, re-challenge. Dose level: 25%. No with. + reactions: 1.0. Total no. in groups: 20.0. Clinical observations: barely perceptible erythema.

Reading:

1st reading

Hours after challenge:

24

Group:

positive control

Dose level:

0.1%

No. with + reactions:

10

Total no. in group:

20

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: positive control. Dose level: 0.1%. No with. + reactions: 10.0. Total no. in groups: 20.0.

Reading:

2nd reading

Hours after challenge:

48

Group:

positive control

Dose level:

0.1%

No. with + reactions:

10

Total no. in group:

20

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: positive control. Dose level: 0.1%. No with. + reactions: 10.0. Total no. in groups: 20.0.

 

Pelargonic acid:

0/20 test animals challenged with 10-% test substance exhibited any dermal response, 3/20 showed barely perceptible erythema (+/-) after challenge with 25% test substance at 24 h, and 1/20 at 48 h. No irritation responses were noted in the corresponding controls with the 10- and 25-% solutions. Scores of +/- are considered equivocal.

Positive control, DCNB:
9/12 animals challenged with the positive control, 0.1% 2,4-dinitrochlorobenzene, had a score of 1 and greater. No responses for the irritation controls for this treatment were observed. This means 9/12 animals showed positive results (because of a dermal score of 1 or greater, in the absence of a dermal response in irritation control animals).

 

 

 

Materials	Hr	Erythema evaluation scores					Total No. of animals
		0	+/-	1	2	3
DCNB, 0.1%	24	2	1	3	6	0	12
	48	2	2	4	4	0
Irritation control	24	8	0	0	0	0	8
	48	8	0	0	0	0
Pelargonicacid10%	24	20	0	0	0	0	20
	48	20	0	0	0	0
Re-challenge, 25%	24	17	3	0	0	0	20
	48	19	1	0	0	0
Irritation control	24	8	0	0	0	0	8
	48	8	0	0	0	0
Re-challenge irritationcontrol	24	7	1	0	0	0	7
	48	7	1	0	0	0

 

 

Interpretation of results:

GHS criteria not met

Conclusions:

The test substance exhibited no potential to produce dermal sensitization in a Buehler test using guinea pigs.

Executive summary:

A dermal sensitisation study was performed according to OECD TG 406 (Buehler) using Hartley guinea pigs. During induction, pelargonoic acid was applied at a concentration of 100% ( at 75% beginning with the 6th treatment due to severe dermal irritation) to a surgical gauze which was directly placed onto the dorsal skin under occlusive conditions for 6 hours. 9 induction treatments were performed within 3 weeks. No dermal sensitisation reaction was seen at 24 and 48 hours after a challenge (patch technique; 14 days after the last induction insult; concentration 10%). Following a re-challenge (patch technique; 7 days after the first challenge; concentration 25%), 3 out of 20 animals exhibited barely perceptible erythema after 24 and 48 h, which were stated to be ambiguous concerning the sensitisation potential of the test substance. Hence the test item elicited no skin sensitisation potential.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

A dermal sensitisation study was performed according to OECD TG 406 (Buehler) using Hartley guinea pigs. During induction, nonanoic acid (NA) was applied at a concentration of 100% (at 75% beginning with the 6th treatment due to severe dermal irritation) to a surgical gauze which was directly placed onto the dorsal skin under occlusive conditions for 6 hours. 9 induction treatments were performed within 3 weeks. No dermal sensitisation reaction was seen at 24 and 48 hours after a challenge (patch technique; 14 days after the last induction insult; concentration 10%). Following a re-challenge (patch technique; 7 days after the first challenge; concentration 25%), 3 out of 20 animals exhibited barely perceptible erythema after 24 and 48 h, which were stated to be ambiguous concerning the sensitisation potential of the test substance. Hence the test item elicited no skin sensitisation potential. This study is considered to be reliable as it was conducted and reported in accordance with the current test guideline OECD TG 406 (Celanese/Bio/dynamics, 1981), and, therefore, selected as the key study.

A murine Local Lymph Node Assay (conducted according to OECD TG 429, positive controls are missing) was performed in a reliable manner (RL 2) to test the sensitisation potential of the test item (purity: not mentioned; applied concentrations: 12.5, 25, 50 and 100% (w/v); used vehicle: non or dimethylformamide).The authors report a stimulation index of 3.3 respectively 5.4 at concentrations of 50 respectively 100% nonanoic acid, thus indicating a positive result. According to the authors it is generally believed that "the LLNA does not have the capacity to discriminate between non-specific proliferation and weak sensitizing ability of strong irritants. It is hypothesized that minimal lymph node proliferation may occur following irritant exposure due to non-specific Langerhans cell migration to draining lymph nodes" (Woolhiser et al., 1998). Thus the presented SIs, can be interpreted as a false positive result and the study is considered as disregarded. Thus the strong irritant nonanoic acid is stated to be non sensitising by Montelius et al. (1998). 

The same findings in the classical murine LLNA are reported by other authors (publications with low reliability - RL 3; Woolhiser et al., 1998; Gerberick et al. 2007). These authors drew also the conclusion that due to the strong irritation potential of NA it can be regarded to be not sensitising, thus supporting Montelius et al. (1998).

Due to the known fact that certain non-sensitizing irritants may yield false positive results in the LLNA, as in the case of nonanoic acid, reasearch is done to elucidate additional more conclusive endpoints. A variety of such mechanistic publications also sustain the conclusion made in the previously described studies. Ku et al. (2008a; RL 3) made use of gene expression microarrays and RT-PCR quantification method. They found, the transcripts for Ifng, Ifi27, Il12rb1, and Zbp1 were upregulated compared with vehicle control in all sensitizers (positive control), but downregulated or not significantly affected at all by any dose of the irritant NA. All of these genes are associated with T-cell proliferation in a positive manner. Another publication of these authors (Ku et al., 2008b; RL 3) stated that sensitizers, but not the irritant, NA, evoke pronounced IL-2, IL-3 and IFN-gamma protein and mRNA responses.

This proves also true for mRNA levels of Granzyme B (GzmB, which is produced by cytotoxic T-cells). Thus, the mentioned cytokines as well as GzmB are good markers for discriminating between sensitizers and irritants.

Other publications whith investigations made in other species than mouse support the negative conclusion for nonanoic acid. An in vitro study on human ex vivo skin biopsy cultures (Pistoor et al., 1996; RL 3) as well as an in vivo study (human maximisation test; Opdyke, 1978; RL 4) identify NA as a non-sensitiser.

In the publication by Kolle et al. (2019) NA showed negative results in two of three different in vitro tests for single events of sensitisation on a cellular level. The KeratinoSens and DPRA assays wshowed nagative results, the h-CLAT (CD86) a positive result. By applying the 2 out of 3 approach, the test substance would be classified as a non-sensitizer based on the negative DPRA and KeratinoSens result.

Overall, pelargonic acid lacks a skin sensitsing potential.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

With respect to the negative conclusions in the key study on skin sensitisation no classification according to Regulation (EC) No 1272/2008 is required.