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Description of key information

Lactide (18:1 mixture of L-lactide and m-lactide) was tested in dogs in a 2 week dose range finding study and a subsequent 90-day full study conducted similar to OECD TG 408. The primary toxic effect was irritation of the gastrointestinal tract at 100 mg/kg bw/day in the 90-day study. Lactide is a suitable read across partner as dilactide is a mixture of D- and L-lactide isomers. In addition, an oral subchronic repeated dose toxicity study conducted with a suitable read-across partner, calcium lactate was used to assess the specific target organ toxicity of the target substance. Based on the results, no classification for specific target organ toxicity is warranted for dilactide.  
    
    
    
    
    

In addition,in an oral subchronic repeated dose toxicity study conducted with a suitable read-across partner, calcium lactate was used to assess the specific target organ toxicity of the target substance. Based on the results, no classification for specific target organ toxicity is warranted for D-lactide.

Key value for chemical safety assessment

Toxic effect type:
dose-dependent

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Referenceopen allclose all

Endpoint:
short-term repeated dose toxicity: oral
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Clinical signs:
effects observed, treatment-related
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY
Emesis occured in the two highest dose groups of both sexes. Diarrhoea was also observed, occuring in one male dog in the 100 mg/kg group and in both female dogs in the 2500 mg/kg group. One female dog that experienced a high incidence of emesis was also observed to be hypoactive on days 4-14 of the study.

BODY WEIGHT AND WEIGHT GAIN
Male dogs in the 1000 mg/kg group and dogs of both sexes in the 2500 mg/kg group showed a net loss between day 1 and terminal sacrifice

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
Food consumption was slightly depressed for male dogs in the 1000 mg/kg group during the second week and for male dogs in the 2500 mg/kg group during both weeks of the study

HAEMATOLOGY
no effect

CLINICAL CHEMISTRY
no effect

URINALYSIS
no effect

ORGAN WEIGHTS
A decrease in absolute and relative thymus weight (> 60% reduction) was observed in one male dog in the 1000 and in all dogs of the both sexes in the 2500 mg/kg dose group. A decrease in absolute and relative spleen weights were observed in one male dog in the 1000 and in both male dogs in the 2500 mg/kg day dose group.

GROSS PATHOLOGY
Gross lesions indicative of irritation were present in one female and both male dogs in the 400 mg/kg group and in all four dogs in the 2500 mg/kg group, but were abesent in the 1000 mg/kg group.These lesions included dark discoloration of the stomach and focal stomach lesions.

HISTOPATHOLOGY: NON-NEOPLASTIC
Lesions in the stomach, oesophagus and kidneys of dogs of both sexes were observed. Minimal or mild haemorrhage involving the mucosa or submucosa of the stomach was observed in one dog of each sex in the 400 mg/kg group and in one female and both male dogs in the 2500 mg/kg group. Stomach ulceration was seen in one male and both females dogs in the 2500 mg/kg group. Oesophageal mild ulceration was present in one 1000 mg/kg female dog and oesophagal erosion was present in one 2500 mg/kg female dog. Mild to moderate renal tubular regeneration was present in both male and both female dogs from the high dose group. Atrophy of the spleen and thymus was evident in male dogs from the 1000 mg/kg group and in dogs of both sexes from the 2500 mg/kg group.
Dose descriptor:
LOAEL
Remarks:
(systemic)
Effect level:
2 500 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: renal toxicity (Mild to moderate renal tubular regeneration)
Dose descriptor:
NOAEL
Remarks:
(systemic)
Effect level:
1 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: renal toxicity (Mild to moderate renal tubular regeneration)
Dose descriptor:
LOAEL
Remarks:
(local)
Effect level:
400 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: irritation of the alimentary tract
Dose descriptor:
NOAEL
Remarks:
(local)
Effect level:
100 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: irritation of the alimentary tract
Critical effects observed:
not specified

Table 1: Overview of effects

    dose in mg/kg/d (2 wk)
    0 10 100 400 1000 2500
Clinical signs emesis* - - - - 4/4 4/4
Body weights Reductions in body weight gain* - - - - 2/4 4/4
Organ weights Reductions in absolute and relative thymus weights* - - - - 1m/4 4/4
  reductions in absolute and relative spleen weights* - - - - 1m/4 2m/4
Gross and microscopic lesions Minimal or mild haemorrhage involving the mucosa and/or submucosa of the stomach* - - - 1f1m/4 - 1f2m/4
  Stomach erosion of minimal severity* - - - - - 1m/4
  Stomach ulceration* - - - - - 1m2f/4
  Mild oesophageal ulceration/oesophageal erosion* - - - - 1f/4 1f/4
  Congestion of the small intestinal mucosa* - - - 1m/4 - 4/4
  Mild to moderaterenaltubularregeneration - - - - - 4/4
Clinical pathology Blood:
total leucocyte count, erythrocyte count, haemoglobin, haematocrit, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, platelet count, and dierential leucocyte count.		 - - - - - -
Clinical chemistry Blood:
blood urea; nitrogen, creatinine, serum glucose, serum aspartate ;aminotransferase, serum alanine aminotransferase, alkaline phosphatase, g-glutamyl transferase, sodium, potassium, chloride, calcium, inorganic phosphate, total protein, albumin, albumin/total protein ratio, total bilirubin and cholesterol. Prothrombin time and activated partial prothrombin time		 - - - - - -
  Urine:
specifc gravity; urine microscopic sediment; pH, ketones, protein, glucose, bilirubin, and occult blood		 - - - - - -
*) effects considered to be related to irritation of the alimentary tract; m: male; f: female
Conclusions:
The primary toxic effect of lactide in dogs under the experimental conditions employed was irritation of the alimentary tract starting at 400 mg/kg bw/day. In addition, lactide appeared to exhibit renal toxicity. Regeneration of the renal tubular epithelium, frequently seen as a reparative or adaptive change following tubular epithelial necrosis, was observed in dogs of both sexes at 2500 mg/kg bw/day.
Executive summary:

In a subacute oral toxicity (dose range finding) study, lactide (18:1 mixture of L-lactide and m-lactide) was administered to 2 beagle dogs/sex/dose by capsule at dose levels of 10, 100, 400, 1000 and 2500 mg/kg bw/day for 2 weeks. The primary toxic effect of lactide in dogs was irritation of the alimentary tract. As irritating effects occurred down to a daily dose of 400 mg/kg bw/day a (local) LOAEL can be determined with 400 mg/kg bw/day. At a daily dose of 100 mg/kg bw/day no lesions were noted by gross and histopathology. Thus, the (local) NOAEL can be determined with 100 mg/kg bw/day.

At 1000 and 2500 mg/kg/d effects on body weight, and absolute and relative organ weights were reported in thymus and spleen. These effects were considered to be related to the irritation of the alimentary tract. In contrast, a mild to moderate renal tubular regeneration was reported in all animals of the 2500 mg/kg bw/day dose group. Regeneration of the renal tububar epithelium is frequently seen as a reparative or adaptive change following tubular epithelial necrosis, and is suggestive of prior damage to this tissue. Although the mechanism of this effect is unknown, it cannot be excluded it is based on lactide toxicity. Based on the possible renal toxicity the (systemic) LOAEL is 2500 mg/kg bw/day. The (systemic) NOAEL for orally administered lactide to dogs under the conditions of this study is 1000 mg/kg bw/day.

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Endpoint:
sub-chronic toxicity: oral
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
Emesis once in each of two female dogs (one in the 0 mg/kg and one in the 100 mg/kg group during week 9). Bloody diarrhoea was seen once during week 6 in one female dog of the 100 mg/kg group
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Description (incidence and severity):
Administration of lactide had no signicant effect (p < 0.01) on body weights of dogs of either sex.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
Administration of lactide had no significant effect (p < 0.01) on food consumption for dogs of either sex.
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
no effects observed
Description (incidence and severity):
Lactide produced no biologically significant alterations in any of the haematology parameters
Clinical biochemistry findings:
no effects observed
Description (incidence and severity):
Lactide produced no biologically significant alterations in any of the clinical biochemistry parameters
Endocrine findings:
not examined
Urinalysis findings:
no effects observed
Description (incidence and severity):
Lactide produced no biologically significant alterations in any of the urinalysis parameters
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
Stomach foci in one male/female from the 100 mg/kg, and one female from the 4 mg/kg dose group
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Moderately severe ulceration of the stomach mucosa seen in one female dog of the high dose group. All other histopathologic
lesions in this dog and all histopathologic lesions in other dogs were considered to be unrelated to lactide administration.
Histopathological findings: neoplastic:
no effects observed
Dose descriptor:
NOAEL
Remarks:
(systemic)
Effect level:
100 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: no adverse effects observed at the highest tested dose
Dose descriptor:
LOAEL
Remarks:
(local)
Effect level:
100 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: gastrointestinal irritation
Dose descriptor:
NOAEL
Remarks:
(local)
Effect level:
20 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: gastrointestinal irritation
Critical effects observed:
not specified

Table 1: Incidence of gross lesions in dogs treated for 13 weeks with oral doses of lactide
             
Dose group 0 mg/kg 4 mg/kg 20 mg/kg 100 mg/kg
Males
Stomach focus 0 0 0 1
 
Females
Stomach focus 0 1 0 1

Incidence= number of dogs in a given dose group with a given lesion. n=4 for all dose groups

Conclusions:
Lactide acts primarily, if not only, as an irritant after oral administration. 13-week NOAEL is 100 mg/kg bw/day.
Executive summary:

In a subchronic toxicity study lactide (18:1 mixture of l-lactide and m-lactide) was administered to 4 beagle dogs/sex/dose by capsule at dose levels of 4, 20, 100 mg/kg bw/day for 13 weeks.

The only apparent toxic effect at 100 mg/kg bw/day was gastrointestinal irritation. Therefore, the local LOAEL is 100 mg/kg bw/day. No systemic effects were reported at 100 mg/kg bw/day. Thus, the systemic NOAEL for orally administered lactide under the conditions of this study was considered to be 100 mg/kg bw/day.

This subchronic study in dog is acceptable and satisfies the principle requirement for a subchronic oral study similar to OECD 409 in dog.

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Endpoint:
sub-chronic toxicity: oral
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Details on results:
All observed effects could be attributed to calcium overload/imbalance. No lactate toxicity was observed.
Dose descriptor:
NOAEL
Effect level:
50 000 mg/L drinking water
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: no lactate toxicity observed
Critical effects observed:
no

Lactate is a normal metabolic species in all vertebrates; tolerance for lactate is high. Adverse effects observed were due to calcium overload.

Conclusions:
5% calcium lactate in drinking water or diet does not result in adverse effects attributable to lactate.
Executive summary:

In a subchronic toxicity study (similar to OECD 408), Calcium lactate was administered to Fischer 344/DuCrj rats.

In Experiment I, Calcium lactate was mixed at 5, 2.5, 1.25, 0.6, and 0.3% in the drinking water and the rats were given this solution ad libitum for 13 weeks. As a result, the inhibition of body weight gain in the 5% group fell within 10% of that in the control group. Some examination values showed variations in the hematological and hematobiochemical studies, but no controversial findings were obtained in the pathohistological search. Since the highest solubility of Calcium lactate is 5%, experiments II and III were carried out by giving blended diet in order to study the toxicity at higher doses. In experiment II, Calcium lactate was mixed at concentrations of 30, 20, 10, and 5% in the B-blend powder diet and then the rats were given this diet ad libitum for 20 weeks. In experiment III, the rats were given the CRF-1 or the B-blend powder diet ad libitum for 8 weeks. As a result, in experiment II, nephrocalcinosis was observed in all the groups including the control group. The degree of the lesion was in reverse correlation with the administered concentrations of calcium and the lesion was seen more intensely in female rats. In experiment III, nephrocalcinosis resulting from the administration of the B-blend diet was already observed in the 4th week. Nephrocalcinosis as observed in experiments II and III was attributable to the small Ca/P value in the B-blend diet.

From the above results, the optimal dose for a long-term toxicity/carcinogenicity study has been determined to be 5 and 2.5% based on the values obtained from experiment I.

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
100 mg/kg bw/day
Study duration:
subchronic
Species:
dog
Quality of whole database:
comparable to guideline study

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Lactide is rapidly hydrolysed to lactic acid in water and in vivo (gastric acid). Lactic acid is a ubiquitous and essential molecule of life. Lactate is non-toxic, any (local) effects are due to pH effects only.

In addition, in an oral toxicity (dose range finding) study, lactide was administered to beagle dogs by capsule at dose levels of 10, 100, 400, 1000 and 2500 mg/kg bw/day for 2 weeks, and 0, 4, 20 and 100 mg/kg bw/day for 13 weeks. The primary toxic effect of lactide in dogs was irritation of the alimentary tract. As irritating effects occurred down to a daily dose of 400 mg/kg bw (for 2 wks), the sub-chronic study was run with a maximum dose of 100 mg/kg bw/day.

At 1000 and 2500 mg/kg bw/day effects on body weight, and absolute and relative organ weights were reported in the 14-day dose range finding study for thymus and spleen. These effects were considered secondary to the irritation of the alimentary tract. In addition, a mild to moderate renal tubular regeneration was reported in all animals of the 2500 mg/kg bw/day dose group. Regeneration of the renal tubular epithelium is frequently seen as a reparative or adaptive change following tubular epithelial necrosis, and is suggestive of prior damage to this tissue. Although the mechanism of this effect is unknown, lactide toxicity cannot be excluded. Based on the possible renal toxicity the (systemic) LOAEL is 2500 mg/kg bw/day. That's well above the limit dose of 1000 mg/kg bw/day for a sub-acute toxicity study.

No systemic adverse effects were reported at the highest dose tested in the 90d study (100 mg/kg bw/day). Therefore, the (systemic) NOAEL for orally administered lactide in a 90d study in dog is considered to be 100 mg/kg bw/day. The primary toxic effect after oral dosing was irritation of the gastrointestinal tract at 100 mg/kg bw/day.

In addition, an oral subchronic repeated dose toxicity study conducted with a suitable read-across partner, calcium lactate was used to assess the specific target organ toxicity of the target substance. High levels of exposure to calcium lactate in the diet (up to 30% in feed) did not lead to any lactate-associated effects after sub-chronic exposure; all effects observed were due to the excessive intake of calcium. It could be concluded that any deleterious effects of lactic acid are caused by the effect of lactic acid on local pH, not on any biological effect of lactate.

In addition, lactic acid is a natural metabolite found in humans and animals as it is endogenously produced from metabolic pathways such as glycogen breakdown, glycolysis and amino acid metabolism. Normal human blood contains 8–17 mg lactic acid/100 mL plasma, and the concentration of lactate in normal human skin is three times or more than in the blood due to glycolytic enzymes, which actively convert glucose to lactic acid in the epidermis. Lactic acid has been detected in blood but also in several other body fluids and tissues. Concentrations of lactic acid increase significantly during intense exercise. At rest, blood concentrations of 1–1.5 mmol/L (90.1–135.12 mg/L) have been reported, which can increase up to 10 mmol/L (900.8 mg/L) during exercise. External human exposure to lactic acid can occur via its natural presence in food, for example in fruit, vegetables, sour milk products, and fermented products such as sauerkraut, yoghurt, and beer. Based on the available information on concentrations of lactic acid in some of these products, an estimate of the daily consumption of lactic acid due to its natural presence in food was made using the ‘FAO/WHO standard European diet’. A (minimum) daily intake of 1.175 g/person/day was calculated using the available information. Another source of external exposure is its use as food additive; as such it is authorized in Europe (E270) and the United States (generally recognized as safe = GRAS). A daily intake of 1.65–2.76 g/person/day was estimated using the “Per Capita times 10” method, based on the amount of lactic acid placed on the market (EU and USA) as a food additive by the registrant (please refer to IUCLID section 7.1.1, Sterenborg 2007 for detailed information and references). Due to its role as a common and natural food ingredient, and ubiquitous metabolic product/substrate in mammals with proven low toxicity, it can safely be concluded that lactic acid does not contribute to any systemic effects. Lactic acid is a major and essential species in mammalian primary metabolism, and a ubiquitous ingredient in all kinds of food. There is no way of lowering exposure below minimum required levels or normal (or even abnormal) internal levels. Furthermore, lactobacilli, which produce lactic acid as their major fermentation product, are abundantly found in humans, including breast milk and vaginal cavity, and are considered as probiotic bacteria. Infants can be exposed to lactobacilli during breastfeeding. Lactobacilli are known to be beneficial in preserving healthy vaginal functions such as maintenance of acidic vaginal pH and the prevention of infections. These observations are common textbook knowledge hence can be considered as adequately and reliably documented, fulfilling the criteria of REACH Annex XI, section 1.1.

The results obtained from sub-chronic toxicity studies (IUCLID section 7.5.1) and from a chronic toxicity study (IUCLID section 7.7) showed that there is no lactic acid specific adverse systemic effect after repeated exposure.

Altogether, given the existing data and taking a weight-of-evidence approach, there is no systemic toxicity concern of lactic acid/lactide and no classification is warranted.


Justification for classification or non-classification

Dilactide is to be considered non-toxic; the only effect are due to local irritation in the gastrointestinal tract as a consequence of the formation of lacate derivates including lactoyl lactic acid and monomeric lactic acid. Therefore, based on the available data from suitable read across partners and in accordance with the CLP Regulation 1272/2008, dilactide does not warrant classification for repeated dose toxicity.