Distillation residues of butyraldehyde, 2-ethylhexenal and isobutanal hydrogenation by-products

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

The potential of the test item distillation residues of butyraldehyde, 2-ethylhexenal and isobutanal hydrogenation by-products to induce delayed contact hypersensitivity was evaluated in the murine Local Lymph Node Assay (LLNA) (Gerbeix, 2010d). Evaluation of local irritation was also carried out in parallel. This study was conducted in compliance with the principles of Good Laboratory Practice.

A preliminary test was first performed in order to define the concentrations of test item to be used in the main test.

In the main test, twenty eight female CBA/J mice were allocated to seven groups:

.           five treated groups of four animals receiving the test item 1-Propene hydroformylation products, by products from distillation residues at the concentration of 1, 2.5, 5, 10 or 25% in a mixture acetone/olive oil (4/1; v/v) (vehicle),

.           one negative control group of four animals receiving the vehicle,

.           one positive control group of four animals receiving the reference item,a‑hexylcinnamaldehyde (HCA), a moderate sensitizer, at the concentration of 25% in the vehicle.

During the induction phase, the test item, vehicle or reference item was applied over the ears (25 µL per ear) for 3 consecutive days (days 1, 2

and 3). After 2 days of resting, the proliferation of lymphocytes in the lymph node draining the application site was measured by incorporation of tritiated methyl thymidine (day 6). The obtained values were used to calculate Stimulation Indices (SI).

The irritant potential of the test item was assessed in parallel by measurement of ear thickness on days 1, 2, 3 and 6.

The test item was soluble in the first recommended vehicle, acetone/olive oil (4/1, v/v). A solution was obtained at the maximum tested concentration of 50%. Consequently, the concentrations selected for the preliminary test were 10, 25, 50 and 100%.

Since the test item was irritant in the preliminary test at the concentrations of 50 and 100%, the highest tested concentration retained for the main test was 25%.

Neither mortality nor clinical signs were observed during the study. No cutaneous reactions and no notable increase in ear thickness were observed at any of the tested concentrations. As all acceptance criteria were met, this experiment was therefore considered valid.

The results are presented in the following table:

 

Treatment	Concentration (%)	Irritation level	Stimulation Index (SI)
Test item	1	non-irritant	0.67
Test item	2.5	non-irritant	0.83
Test item	5	non-irritant	0.98
Test item	10	non-irritant	1.05
Test item	25	non-irritant	1.62
HCA	25	-	4.18

No notable lymphoproliferation was noted with the test item at any tested concentration.

Under the experimental conditions of this study, distillation residues of butyraldehyde, 2-ethylhexenal and isobutanal hydrogenation by-products did not induce delayed contact hypersensitivity in the murine Local Lymph Node Assay.

Migrated from Short description of key information:
distillation residues of butyraldehyde, 2-ethylhexenal and isobutanal hydrogenation by-products, did not induce delayed contact hypersensitivity in the murine Local Lymph Node Assay.

Justification for classification or non-classification

According to the classification criteria laid down in Regulation (EC) N° 1272-2008C and Council Directive 67/548/EEC (and subsequent adaptations), 1-Propene hydroformylation products, by products from distillation residues should not be classified as a skin sensitizer.