Malonic acid

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Justification for type of information:

Succinic acid may be used as an analogue for malonic acid, based on the following considerations. Firstly, dicarboxylic acids are naturally occurring metabolic products of fatty acid oxidation, and are rapidly beta-oxidised. A category approach for short-medium chain dicarboxylic acids, including malonic acid and succinic acid, has been validated and used by various bodies including the Cosmetics Ingredient Review Panel and the European Food Safety Authority.The study was carried out to provide a comparison between the LLNA and GPMT tests, rather than to investigate the properties of the test materials, nevertheless it follows standard OECD guidelines and was carried out in accordance with GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

GLP compliance:

not specified

Remarks:

GLP claimed, but validation not seen

Type of study:

mouse local lymph node assay (LLNA)

Specific details on test material used for the study:

Succinic acid (Aldrich No. 398055), purity 99%, was obtained from Sigma-Aldrich (Munich, Germany)

Species:

mouse

Strain:

other: SPF-CBA/Ca01aHsd

Sex:

female

Details on test animals and environmental conditions:

Female SPF-CBA/Ca01aHsd mice (6–12 weeks) were purchased from Harlan Winkelmann (Borchen, Germany). The mice were housed in groups in Macrolon cages on Altromin saw fiber bedding. The animals were barrier-maintained (semi-barrier) in an air conditioned room (temperature 22 ± 3 °C, relative humidity 55 ± 10%) with a 12-h light/dark cycle and air change rate of at least 10/h. The acclimatization period was at least five days. Food (Altromin 1324 maintenance diet for rats and mice, totally-pathogen-free and tap water were provided ad libitum.

Vehicle:

dimethyl sulphoxide

Concentration:

5%, 10%, 25%

No. of animals per dose:

5

Details on study design:

A preliminary experiment was performed with three animals to detect the highest tolerable exposure concentration. Three different concentrations of the test compound were applied daily to the ears of the animals, which were observed for systemic effects and local skin irritation. Local irritant effects expressed as ear swelling were assessed by measuring the ear thickness on day 1 and day 4.In the main test, groups of 5 mice were treated by topical applications of 25 ll test or control solution to the entire dorsal surface of each ear. Topical applications were performed once daily over three consecutive days. A negative control group was treated with the vehicle alone. The positive control group received p-phenylenediamine at 1% in the respective vehicle. On day 6, all mice were dosed with 20 lCi 3H-methyl thymidine by intravenous injection into the tail vein. Approximately 5 h after 3H-methyl thymidine injection, all mice were sacrificed. The draining auricular lymph nodes were excised, weighed (the left and right lymph nodes were weighed and the mean calculated for each mouse), individually pooled for each animal (two lymph nodes per animal) and collected in PBS.Cell suspensions were prepared and tritated thymidine was measured using a scintillation counter and expressed as disintegrations per minute.The proliferative response of the lymph node cells was expressed as number of disintegrations per node (DPM/node) adjusted for background values. The Stimulation Index was calculated as the ratio of the arithmetic mean of DPM/node values for the test and control groups.In addition to the requirements of the OECD guideline, a lymph node weight index (LNWI) was calculated as the ratio of the arithmetic mean lymph node weight values of the test group and the negative control group.

Positive control substance(s):

other: p-phenylenediamine at 1%

Parameter:

SI

Value:

1.3

Test group / Remarks:

25% concentration

Parameter:

SI

Value:

1.2

Test group / Remarks:

10% concentration

Parameter:

SI

Value:

1.2

Test group / Remarks:

5% concentration

Succinic acid gave clearly negative results, i.e. SI values were below 3 for all tested concentrations. As the lymph node weight reaction was weak and lacked a dose–response relationship, the SI result was given precedence. Therefore, succinic acid was considered to show no skin sensitizing potential in the LLNA.

Stimulation indices (SI) ± SD and lymph node weight indices (LNWI) ± SD obtained in the LLNA

Test substance	Vehicle Parameter	Index ± SD at test concentration
		25%	10%	5%
Succinic acid	DMSO SI	1.3 ± 0.7	1.2 ± 0.3	1.2 ± 0.4
	LNWI	1.1 ± 0.1	1.1 ± 0.1	1.12 ± 0.03

Interpretation of results:

GHS criteria not met

Conclusions:

Succinic acid gave clearly negative results in the mouse LLNA test, i.e. SI values were below 3 for all tested concentrations. As the lymph node weight reaction was weak and lacked a dose–response relationship, the SI result was given precedence. Therefore, succinic acid was considered to show no skin sensitizing potential in the LLNA.

Executive summary:

The skin sensitization potential of eight unsaturated and one saturated lipid (bio)chemicals was tested in both the LLNA and the GPMT to address the hypothesis that chemicals with unsaturated carbon–carbon double bonds may result in a higher number of unspecific (false positive) results in the LLNA compared to the GPMT. In this test series, succinic acid gave clearly negative results (SI <3) and was not considered sensitising.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)