Cysteine hydrochloride

Endpoint summary

Key value for chemical safety assessment

Toxic effect type:

dose-dependent

Effects on fertility

Description of key information

In a combined study with Norwegian rats over 6 generations possible effects on fertility and developmental toxicity of L-Cysteine hydrochloride monohydrate were tested. The substance was added to flour in concentrations of 0, 35, 350 and 3500 ppm. With this flour bread was baked. After the baking a powder was produced and was mixed to a diet. This resulted in an estimated daily intake of L-cysteine hydrochloride monohydrate of 0, 2.7, 27 and 270 mg/kg bw..
No adverse effects on fertility occurred in the rats during the experiment even at the high level of Lcysteine hydrochloride monohydrate treatment.

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

270 mg/kg bw/day

Study duration:

chronic

Species:

rat

Quality of whole database:

Klimisch 2: reliable with restrictions

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

L-Cysteine hydrochloride monohydrate was added to flour in concentrations of 0, 35, 350 and 3500 ppm. With this flour bread was baked. After the baking the bred was sliced, freeze-dried, crushed and milled. This powder was mixed to a diet. The diets contained about 77% of bread crumbs on dry weight.
An animal weight of 100 g and a daily feed intake of 10 g diet per animal and day is estimated. 77% of milled bread was added to this diet. This resulted in an estimated daily intake of L-cysteine hydrochloride monohydrate of 0, 2.7, 27 and 270 mg/kg bw.. All in all 7 generations were studied.
Recorded are number born, litter weight at birth, numbers weaned and litter weight at weaning, carcass, liver and kidney weights of all slaughtered aninmals, post mortem examination for gross lesions. In the 0 and 3500 ppm groups the principal characteristics of the response to the treatment were measured:
rate of change per generation in litter size and weight at birth and at weaning, and the rate of change in the size of the cracasses, livers and kidneys of both adults and weaning rats.
Breeding rats of the fifth generation at about 150 days of age and receiving the diet with the highest treatment (3500 ppm) were examined histopathologically. They showed no lesions atypical in normal rats of that age.
No obvious adverse effects on fertility occurred in the rats during the experiment even at the high level of L-cysteine hydrochloride monohydrate treatment.

Effects on developmental toxicity

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

L-Cysteine is essential in the body and human exposure through food has at least the same order of magnitude as the doses used in the prenatal developmental toxicity study (OECD 414). Human cells handle large quantities of L-Cysteine and that this amino acid is an essential component of normal cellular function. Overall, from all available data it can be excluded that Cysteine-HCl has toxic effects on the developing organism. Further testing of Cysteine-HCl in a prenatal developmental toxicity study (OECD 414) in mammals is not justified and makes no sense for animal welfare reasons.

Justification for classification or non-classification

From the detailed evaluation of the available reliable data in comparison with the criteria set out in the CLP-regulation, it is concluded that L-cysteine hydrochloride monohydrate as well as the anhydrous form does not need to be classified with regard to reproduction toxicity.