Methyl (R)-lactate

Endpoint summary

Description of key information

Ethyl-S-lactate is highly irritating to the eye.

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no study available

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Additional information

In a acute dermal irritation study, 3 young adult male SPF bred New Zealand White albino rabbits (weight 2130 -2220 g) were dermally exposed to 0.5 ml of undiluted ethyllactate to an area of 2.5 x 2.5 cm. Test sites were covered with an occlusive dressing for 4 hours. Animals were the observed for 14 days. Irritation was scored by the method of Draize et al.. Only mild skin effects were observed on a very small skin area on the edge of the application area, most probably by pressure of the bandage on the test patch underneath. Since normally these kind of exposure conditions will not occur in humans, the toxicological significance of these skin effects is considered dubious. In this study, ethyl lactate is not a dermal irritant.

In an ex vivo bio assay, the Chicken Enucleated Eye Test (CEET), 0.03 ml of undiluted ethyl lactate was applied to enucleated chicken eyes for 10 seconds, after which the corneal surface was rinsed with 20 ml of isotonic saline. The eyes were then examined up to 4 hours after treatment. Irritation was scored as thickness of the cornea, corneal opacity and fluorecein retention.

After treatment, the thickness of the cornea of the test eyes gradually increased considerably; a maximum mean corneal swelling of 31% was obtained at 240 min after treatment. Moderate or severe corneal opacity and severe fluorescein retention by damaged epithelila cells were observed in the test eyes. In addition, the three test eyes showed wrinkling of the corneal epithelium. On the basis of the results obtained with this in vitro (ex vivo) assay and according to the scheme for (EC-)classification applied, the following was concluded: ethyl lactate is moderately irritating to eyes, but in view of the additional effects observed, it is recommended to classify ethyl lactate as R41: risk of serious damage to eyes.

In a sensory irritation study (see section 7.2.2), the RD50 values of ethyl-(L)-lactate were 772 mg/m³ in mice and 791 mg/m³ in rats. In the same study an RD50 of 760 mg/m³ in mice and 701 mg/m³ in rats was found for n-butyl-L-lactate. The similarity in the results for ethyl-L-lactate and n-butyl-L-lactate support the conclusion that the effects on breathing rate can be attributed to irritating effects from the lactic acid formed at hydrolysis of the substances (see statement in section 7.9.3), which is a rapid process during and after uptake in the organism. The sensory irritating effect is thus a pH effect and not a toxic effect.

Justification for selection of skin irritation / corrosion endpoint:
Skin irritation potential of alkyl lactates is related to alkyl chain length, with shorter alkyl esters being not irritating. As such methyl lactate is expected not to be irritating to skin.

Justification for selection of eye irritation endpoint:
Ethyl lactate is moderately irritating to eyes; ethylhexyl lactate is irritating to eyes; reading across suggests that methyl lactate will be moderately irritating to eyes.

Effects on eye irritation: moderately irritating

Effects on respiratory irritation: irritating

Justification for classification or non-classification

In a sensory irritation study, the RD50 values of ethyl-(L)-lactate were 772 mg/m³ in mice and 791 mg/m³ in rats. In the same study an RD50 of 760 mg/m³ in mice and 701 mg/m³ in rats was found for n-butyl-L-lactate. The similarity in the results for ethyl-L-lactate and n-butyl-L-lactate support the conclusion that the effects on breathing rate can be attributed to irritating effects from the lactic acid formed at hydrolysis of the substances (see statement in section 7.9.3), which is a rapid process during and after uptake in the organism. The sensory irritating effect is thus a pH effect and not a toxic effect.