L-lysine, compound with S-(carboxymethyl)-L-cysteine (1:1)

Endpoint summary

Description of key information

Not skin and eye irritant.

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

The potential of target substance to cause skin and eye irritation was assessed in vitro.

Skin irritation was assessed according to OECD guideline 439, using human epidermal model.

In main experiment, tissues were exposed to test substance for 42 minutes using 3 replicates for test substance and positive and negative controls.

After treatment, the substance was removed and tissues were incubated for approximately 42 hours. At the end of incubation, tissues were incubated for 3 hours with MTT solution at 37 °C; then, tissues were incubated in isopropanol for 2 hours at room temperature under shaking. Optical density (OD550) of extracts was measured on a spectrophotometer. Relative cell viability, calculated as % of mean viability of negative control tissues, was 108.9 ± 8.5 %, i.e. viability was > 50 %.

Eye irritation was assessed using a 3D human cornea epithelium reconstituted (SkinEthic HCE). The test method is comparable to that described in the OECD guideline 492 (2017).

Three replicates were used for test substance as well as positive control with 0.5 % SLS and negative control with phosphate buffer.

Test item was applied as such for 1 hour at room temperature. After treatment, the substance was removed and tissues were incubated for 16 hours. At the end of incubation, tissues were incubated for 3 hours with MTT solution at 37 °C; then, tissues were incubated in isopropanol for 2 hours at room temperature under shaking. Optical density (OD570) of extracts was measured on a spectrophotometer. Relative cell viability, calculated as % of mean viability of negative control tissues, was 100.7 ± 1.2 %, i.e. viability was > 50 %

Justification for classification or non-classification

In vitro alternatives, validated and accepted, may be used in classification decisions in categories set by CLP Regulation (EC 1272/2008). The ECHA guidance 'Chapter R.7a' (v. 6.0, July 2017) provides a description about information for classification that may be derived from in vitro studies depending on the testing guideline followed.

As for skin irritation, the relative cell viability is calculated for each tissue as % of mean of negative control tissues viability, which is set at 100 %.  Prediction of irritation is based on tissue viability after treatment and post-treatment incubation. In particular, according to OECD guideline 439:  

- tissue viability ≤ to 50 % identifies the substance as requiring a classification, but further testing is needed to decide on classification in cat. 1 or 2.

 - tissue viability > 50 % identifies the substance as not classified.  

A single test run composed of 3 replicate tissues should be sufficient for a test chemical when the classification is unequivocal. However, in cases of borderline results, such as non-concordant replicate measurements and/or mean percent viability equal to 50 ± 5 %, a second run should be considered, as well as a third one in case of discordant results between the first two runs.  

As for eye irritation, the mean percent tissue viability is normalised to the negative control, which is set at 100 %.

According to OECD guideline 492, the percentage tissue viability cut-off value for identifying test chemicals not requiring classification for eye irritation or serious eye damage is as follows:  

- tissue viability > 50 % identifies the substance as not classified.  

- tissue viability ≤ 50 %  identifies the substance as requiring a classification, but further testing is needed to decide on classification in cat. 1 or 2.

Based on experimental findings, test substance was not classified for skin and eye irritation within the CLP Regulation (EC 1272/2008).