Methyl (S)-(-)-lactate

Endpoint summary

Description of key information

No studies with the target substance methyl (S)-lactate itself are available for the assessment of repeated dose toxicity. However, an oral and an inhalation repeated dose toxicity study were conducted with suitable read-across partners which are thus used to assess the specific target organ toxicity of the target substance.

Three sub-acute inhalation toxicity studies with ethyl (S)-lactate and butyl (S)-lactate revealed clear respiratory local effects, described as histopathological changes in the olfactory and respiratory epithelia. No clear systemic toxic effects were detected.

Oral sub-chronic toxicity is addressed by a study conducted with a suitable read-across partner, calcium lactate pentahydrate. No adverse effects were reported after oral administration of calcium lactate pentahydrate via drinking water. The NOAEL in this study is 4500 mg/kg bw/day for both sexes (calculated from 50,000 mg/L by applying a conversion factor of 0.09 for rats as recommended in the EFSA guidance document [EFSA Journal 2012 (10(3): 2579]). Therefore, lactic acid/free lactate is of no systemic toxicological concern.

In addition, in a sub-chronic repeated dose toxicity study, methanol was administered daily to 30 Sprague-Dawley rats/sex/dose via oral gavage at dose levels of 0, 100, 500 and 2500 mg/kg bw/day for total of 90 days. Elevated levels (p≤ 0.05 in males) of serum alanine transaminase (ALT) and serum alkaline phosphatase (SAP), and increased (but not statistically significant) liver weights in both male and female rats suggest possible treatment-related effects in rats bolus dosed with 2500 mg methanol/kg bw/day despite the absence of supportive histopathologic lesions in the liver. Brain weights of high-dose group (2500 mg/kg bw/day) males and females were significantly less than those of the control group at terminal sacrifice. Based on these findings, 500 mg/kg bw/day methanol is considered as the NOAEL from this rat study (corresponding to 1625 mg/kg bw/day Methyl (S)-lactate). This dose is much higher as the limit dose of 1000 mg/kg bw/day mentioned in the OECD TG 408.

In a sub-acute repeated dose toxicity study, methanol was administered to 5 male/female Wistar rats/dose by inhalation in whole body exposure chambers at concentrations of 0, 500, 2000 and 5000 ppm as vapour, for 6 hours per day, 5 days/week for a total of 20 days.

No treatment-related effects on mortality, clinical signs, body / organ weights, gross/histopathologic or ophthalmoscopic examinations were noted. The only treatment and dose-related effect noted was that of mucoid nasal discharge in rats, which was considered reflective of upper respiratory tract irritation.

Based on the results, the NOAEC can be considered to be 5000 ppm, which equals 6.552 mg/L. In summary, no classification for repeated specific target organ toxicity is warranted for the target substance as no adverse systemic effects were observed up to the limit doses of the respective OECD test guidelines.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

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:

body weight and weight gain

Critical effects observed:

no

Conclusions:

In conclusion, 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.

Reference 2

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 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:

not specified

Mortality:

not specified

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not specified

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Endocrine findings:

not specified

Urinalysis findings:

not specified

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

not examined

Other effects:

not specified

Details on results:

There were no differences between dosed animals and controls in body weight gain, food consumption, or upon gross or microscopic evaluations. Elevated levels (p≤ 0.05 in males) of serum alanine transaminase (ALT) and serum alkaline phosphatase (SAP), and increased (but not statistically significant) liver weights in both male and female rats suggest possible treatment-related effects in rats bolus dosed with 2500 mg methanol/kg bw/day despite the absence of supportive histopathologic lesions in the liver. Brain weights of high-dose group (2500 mg/kg bw/day) males and females were significantly less than those of the control group at terminal sacrifice. The only histopathology noted was a higher incidence of colloid in the hypophyseal cleft of the pituitary gland in the high-dose versus control group males (13/20 versus 0/20) and females (9/20 versus 3/20). Based on these findings, 500 mg/kg bw/day of methanol is considered as the NOAEL from this rat study.

Key result

Dose descriptor:

NOAEL

Effect level:

500 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: increased liver enzyme levels and reduced brain weights

Critical effects observed:

not specified

Conclusions:

In conclusion, in a sub-chronic repeated-dose toxicity study, methanol was administered to rats for 90 days via oral gavage. Based on the results, the NOAEL was established to be 500 mg/kg bw/day.

Executive summary:

In a sub-chronic repeated dose toxicity study, methanol was administered daily to 30 Sprague-Dawley rats/sex/dose via oral gavage at dose levels of 0, 100, 500 and 2500 mg/kg bw/day for total of 90 days.

There were no differences between dosed animals and controls in body weight gain, food consumption, or upon gross or microscopic evaluations. Elevated levels (p≤ 0.05 in males) of serum alanine transaminase (ALT) and serum alkaline phosphatase (SAP), and increased (but not statistically significant) liver weights in both male and female rats suggest possible treatment-related effects in rats bolus dosed with 2500 mg methanol/kg bw/day despite the absence of supportive histopathologic lesions in the liver. Brain weights of high-dose group (2500 mg/kg bw/day) males and females were significantly less than those of the control group at terminal sacrifice. The only histopathology finding noted was a higher incidence of colloid in the hypophyseal cleft of the pituitary gland in the high-dose versus control group males (13/20 versus 0/20) and females (9/20 versus 3/20). Based on these findings, 500 mg/kg bw/day of methanol is considered as the NOAEL from this rat study (corresponding to 1625 mg/kg bw/day Methyl (S)-lactate)

This dose is much higher as the limit dose of 1000 mg/kg bw/day mentioned in the OECD TG 408.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

For 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):

Increased instances of discharges about the eyes and nose-lacrimation, mucoid nasal discharge, red nasal discharge, and dried red nasal discharge - were observed. The frequencies of these findings were increased in the treated groups, but only the incidence of mucoid nasal discharge appeared to be dose-related.

Mortality:

no mortality observed

Description (incidence):

All animals survived the duration of the study.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Body weights for treated rats were comparable to their respective controls.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

no effects observed

Description (incidence and severity):

Results of terminal ophthalmoscopic examinations on high-dose rats revealed no ocular abnormalities that could be attributed to methanol exposure.

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Endocrine findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

Comparisons of organ weights for male rats revealed no statistically significant intergroup differences. Female rats of the mid-dose group had significantly (p≤ 0.05) higher relative spleen weights. These differences by themselves are not of any apparent biological significance.

Gross pathological findings:

no effects observed

Description (incidence and severity):

Gross pathological examination of control and high-dose rats revealed no effects from exposure to methanol.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Description (incidence and severity):

Histopathological examination of control and high-dose rats revealed no effects from exposure to methanol.

Other effects:

not specified

Key result

Dose descriptor:

NOAEC

Effect level:

5 000 ppm (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no adverse effects observed

Critical effects observed:

no

Chamber concentrations:

Based on infrared analysis of chamber atmospheres, animals in groups I, II, III, and IV received exposure to mean concentrations of 0, 520, 1980, and 5010 ppm, respectively. Mean nominal concentrations were 550 (group II), 2330 (group III), and 5330 (group IV) ppm. Occasional discrepancies between nominal and analytical values were within the limits of expected experimental error (± 10%)

Conclusions:

In conclusion, in a sub-chronic repeated-dose toxicity study, methanol was administered to rats for 13 weeks via inhalation. The repeated daily exposure to methanol vapors (up to 5000 ppm) does not result in adverse effects on body / organ weights, gross and histopathologic or ophthalmoscopic examinations in rats. Based on the results, the NOAEC was established to be 5000 ppm for methanol.

Executive summary:

In a sub-acute repeated dose toxicity study, methanol (purity 99.85%) was administered to 5 male/female Wistar rats/dose by inhalation in whole body exposure chambers at concentrations of 0, 500, 2000 and 5000 ppm as vapour, for 6 hours per day, 5 days/week for a total of 20 days.

No treatment-related effects on mortality, clinical signs, body / organ weights, gross/histopathologic or ophthalmoscopic examinations were noted. The only treatment and dose-related effect noted was that of mucoid nasal discharge in rats, which was considered reflective of upper respiratory tract irritation.

Based on the results, the NOAEC can be considered to be 5000 ppm, which equals 6.552 mg/L. Thus, in accordance with CLP Regualtion 1272/2008 no classifcation for STOT RE is warranted.

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

Reference 2

Endpoint:

short-term repeated dose toxicity: inhalation

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 report attached in section 13 of IUCLID.

Reason / purpose for cross-reference:

read-across source

Clinical signs:

no effects observed

Description (incidence and severity):

see box "Details on results"

Mortality:

no mortality observed

Description (incidence):

see box "Details on results"

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

see box "Details on results"

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

see box "Details on results"

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

see box "Details on results"

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

see box "Details on results"

Endocrine findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

see box "Details on results"

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

see box "Details on results"

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY
Exposure to ethyl lactate did not result in changes in condition, health or mortality. One male exposed to 600 and 2 females exposed to 2500 mg/m³ showed transient trembling.

BODY WEIGHT AND WEIGHT GAIN
All animals gained weight during the exposure period, but the rats of the 2500 mg/m³ group considerably less than the other rats. The differences with controls was statistically significant at all stages. Mean weight gain of the other test groups was comparable with that of the controls both in males and in females.

FOOD CONSUMPTION
Food consumption was depressed in rats exposed to 2500 mg/m³ throughout the study. In males the differences with the controls were statistically significant during all weeks, and in females during the first two weeks and during the last week. Food intake was statistically significantly lower in males exposed to 150 mg/m³ than in controls during the last week. During the first three weeks food consumption tended to be even higher than in controls. In addition, males of the 600 mg/m³ group showed a completely comparable food consumption pattern as the controls. Therefore, the decreased food consumption value in the low-concentration group is considered an isolated finding unrelated to the exposure.

HAEMATOLOGY
The haematological variables examined did not show differences amongst the groups attributable to treatment. The values showed the common variation between the individual animals and between the groups.

CLINICAL CHEMISTRY
Urea values were lower in rats exposed to 2500 mg/m³ than in controls, reaching a statistically significant extent in females only. Glucose values were statistically significantly higher in males of the highest-concentration group when compared with those of the controls. The other biochemical parameters examined did not show differences which could be related to the exposure to ethyl lactate. One rat exposed to 150 mg ethyl lactate/m³ air had very high levels of aspartate aminotransferase and alanine aminotransferase in plasma. These were considered isolated findings unrelated to treatment.

ORGAN WEIGHTS
Absolute liver weights were statistically significantly decreased in males and females exposed to 2500 mg/m³ in comparison with liver weights of the controls. However, when the liver weights were expressed relative to body weight, they did not differ statistically significantly from that of the controls. Relative weights of testes and adrenals were statistically significantly higher in male rats exposed to the highest concentration, whereas the absolute weights of these organs were completey comparable with those of the controls.

GROSS PATHOLOGY
Gross examination at autopsy revealed one control male with small testis and one male of the low dose group with two small testes. These gross changes are common findings in rats. They are, therefore, considered not to be related to treatment. No other gross findings were observed.

HISTOPATHOLOGY: NON-NEOPLASTIC
Treatment related changes were observed in the nose, both in the respiratory and the olfactory epithelium. Minimal changes occurred in the low dose group; incidence and severity increased with the concentration levels.
- Respiratory epithelium:
The changes consisted of hyperplasia and hypertrophy of goblet cells, mainly in epithelium of the nasal septum and ventrolateral parts of the nasal cavity and, in more severe cases, also of the nasoturbinates. Frequently, these changes were accompanied by nest-like infolds of goblet cells. The effect on the respiratory epithelium was found in all treatment groups and the severity was distinctly concentration-related. All animals of the 600 mg/m³ group and most animals of the 2500 mg/m³ group showed hyperplasia of the ciliated epithelium covering the nasal turbinates and the lateral walls. Two males and two females of the 600 mg/m³ group showed a few small cysts in the hyperplastic respiratory epithelium of the nasoturbinates.
- Olfactory epithelium:
The changes mainly occurred in the dorsal part of the nose and consisted of moderate to very severe atrophy with epithelial disarrangement, ingrowth in the lamina propria and replacement of olfactory epithelium by respiratory epithelium with nest-like infolds. The olfactory epithelial atrophy was characterized (in order of increasing severity) by: disarrangement, disappearing of the cellular apices, and flattening of the cells and thinning of the olfactory layer as a whole. In several animals exposed to 2500 mg/m³ locally there was hardly any epithelium recognizable.
In most animals of the 2500 mg/m³ group loss of nerve bundels and Bowman's glands was observed in the lamina properia of the dorsal part of the nasal cavity. The loss was most obvious in the caudal parts. Inflammatory changes occurred only in a few animals of the high dose group.
Apart from slight hypertrophy and hyperplasia of goblet cells in two males none of the control animals showed histopathological nasal changes.

The histopathological changes observed in the other organs examined are common findings in the strain of rats used. These lesions were about equally distributed amongst control and test groups, or occurred only in a single animal. Therefore, they are not considered to be related to the exposure to the test substance.

Key result

Dose descriptor:

NOAEC

Remarks:

local effects

Effect level:

< 150 mg/m³ air (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: see 'Remarks'

Key result

Dose descriptor:

NOAEC

Remarks:

systemic effects

Effect level:

2 500 mg/m³ air (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no indications of clear systemic effects associated with the treatment.

Critical effects observed:

not specified

Analytical results:

Mean daily actual concentrations turned out to be 145 (± 2), 603 (± 2) and 2451 (± 21) mg/m³. Between brackets the standard error of the mean (SEM) is given. The nominal concentrations were 138, 569, and 2092 mg/m³, which is slightly lower than the actual concentrations. The nominal concentration is calculated from the use of test material during exposure and the volume of air passed through the inhalation chamber. The determination of the volume of air through the chambers, however, is not very exact. This might be an explanation for the differences between the nominal and actual concentrations. Occasionally, the nebulizers did not work well during a short period, resulting in low mean daily concentrations with a high SEM.

Conclusions:

In a sub-acute inhalation toxicity study, Ethyl (S)-lactate (99.8% purity) showed no effects on condition, health and behaviour. The most prominent finding consisted of histopathological changes to the lining epithelium of the nasal cavity of rats. Based on the results, the NOAEC (local) for rats is considered to be < 150 mg/m³ and as no clear systemic effects were noted, the NOAEC (systemic) for rats is considered to be 2500 mg/m³.

Executive summary:

In a sub-acute inhalation toxicity study ethyl lactate was administered to 5 male and 5 female Wistar derived rats/concentration by whole body exposure at concentrations of 0, 1.5, 0.6 and 2.5 mg/L (0, 150, 600 and 2500 mg/m³) for 6 hours per day, 5 days/week for a total of 28 days.

The exposure to ethyl lactate resulted in concentration-related adverse effects in the nose of all test groups and in growth retardation and decreased food consumption in rats exposed to 2500 mg ethyl lactate/ m³ air. Growth retardation might be explained by the impaired ability to smell and taste as a result of severe damage to the olfactory epithelium. The increased blood glucose value in males exposed to 2500 mg/m³ is considered an isolated finding unrelated to treatment. Further all observed effects can be explained from the reduced food intake and subsequent growth retardation. It was concluded that the NOEC (local) was lower than 150 mg/m³ and the NOEC (systemic) is considered to be 2500 mg/m³.

This sub-acute toxicity study in the rat is acceptable and satisfies the guideline requirement (OECD 412) for a sub-acute inhalation study in the rat.

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

Reference 3

Endpoint:

short-term repeated dose toxicity: inhalation

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 report attached in section 13 of IUCLID.

Reason / purpose for cross-reference:

read-across source

Clinical signs:

no effects observed

Description (incidence and severity):

see box "Details on results"

Mortality:

no mortality observed

Description (incidence):

see box "Details on results"

Body weight and weight changes:

no effects observed

Description (incidence and severity):

see box "Details on results"

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Endocrine findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Description (incidence and severity):

see box "Details on results"

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

see box "Details on results"

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Details on results:

CLINICAL SIGNS AND SURVIVAL
No clinical symptoms or signs of systemic toxicity were observed during the study. All study animals survived to the scheduled sacrifice.

BODY WEIGHTS
There were no statistically significant differences in mean body weights between the test groups and the controls.

GROSS PATHOLOGY
Gross examination of animals of the main groups at autopsy revealed a slightly oedematous and red discoloured thymus in one male of the control
group and in one male of the mid-concentration group. The kidneys of one male of the control group were slightly enlarged and soft. These gross changes are common findings in rats and they are not considered to have any toxicological relevance. One female rat of the mid-concentration group showed a subcutaneous haemorrhage between the eyes, which was most probably caused
by trauma and was not regarded to have any clinical significance. Gross examination of rats of the recovery groups did not reveal any abnormalities.

HISTOPATHOLOGY: NON-NEOPLASTIC
In a few rats of either sex of both the main and the recovery groups (controls included), the respiratory epithelium of the nasal cavity showed minimal changes, seen as nest-like infolds and slight hypertrophy/hyperplasia. The changes were about equally distributed amongst the various groups or occurred in a single animal only. Therefore, the changes were not ascribed to inhalation of ethyl lactate.

Key result

Dose descriptor:

NOAEC

Remarks:

local effects

Effect level:

200 mg/m³ air (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: see 'Remarks'

Key result

Dose descriptor:

NOAEC

Remarks:

systemic

Effect level:

200 mg/m³ air (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse systemic effects observed at the high concentration of 200 mg/m³

Critical effects observed:

not specified

Analytical results:

The mean daily concentrations of ethyl lactate in the test atmospheres during exposure were 24 (+/- 1) mg/m³, 73 (+/- 5) mg/m³ and 202 (+/- 3) mg/m³. The actual concentrations were generally close to the intended concentrations.

Conclusions:

In a sub-acute inhalation toxicity study in rats, Ethyl (S)-lactate showed no adverse effects. There were no compound related effects in mortality, clinical signs, body weight or gross and histological pathology. Microscopic examination revealed minimal changes (nest-like infolds, slight hypertrophy, and slight hyperplasia) in the nasal respiratory epithelium of animals in all groups, the control group included. Type and incidence of the changes were similar in the various groups, or the changes occurred in a single animal only. These changes were not ascribed to treatment. Based on the results, the NOEC is considered to be 200 mg/m³.

Executive summary:

In a sub-acute inhalation toxicity study, Ethyl (S)-lactate was administered to 5 male and 5 female Wistar rats/concentration by whole body exposure at concentrations of 0, 0.025, 0.075 and 0.2 mg/L (0, 25, 75 and 200 mg/m³) for 6 hours per day, 5 days/week for a total of 28 days. Two additional (recovery) groups of 5 male and 5 female Wistar rats exposed to 0 or 0.2 mg/ were kept untreated for 28 post-exposure days. Clinical observations, growth, macroscopical observations at autopsy and microscopical examinations of the nose were used as criteria for disclosing possible harmful effects. There were no compound related effects in mortality, clinical signs, body weight or gross and histological pathology. Microscopic examination revealed minimal changes (nest-like infolds, slight hypertrophy, and slight hyperplasia) in the nasal respiratory epithelium of animals in all groups, the control group included. Type and incidence of the changes were similar in the various groups, or the changes occurred in a single animal only. These changes were not ascribed to treatment. Based on the results, the NOAEC is considered to be 200 mg/m³.

In contrast to a previously conducted study (TNO report V90.322, 1995), in which rats were exposed to 150, 600 or 2500 mg ethyl (S)-lactate per m³ for 28 days, the results of the present study show that rats exposed to 25, 75 or 200 mg ethyl (S)-lactate per m³ for the same period did not develop compound-related histopathological changes in the nose. The histopathological changes observed at an exposure concentration of 150 mg/m³ (TNO report V 90.322), viz. replacement of olfactory epithelium by respiratory epithelium, goblet cell hypertrophy and moderate goblet cell hyperplasia, were considered to be in line with the changes observed at concentration-response relationship including the response seen at the 150 mg/m³ exposure concentration. The minimal changes observed in the present study consisting of nest-like infolds and slight hypertrophy and hyperplasia are fully comparable to the minimal changes observed at the 150 mg/m³ level of the previous study. However, since in the present study these minimal changes were observed in all groups, controls included, and their incidences in treatment groups were not different from those in the control group, or the changes occurred in a single animal only, these minimal alterations were not ascribed to treatment. Therefore, it is concluded that the no-adverse-effect concentration, as regards to local effects, in the present study is 200 mg/m³, indicating that the level of 150 mg/m³ used in the previous study (TNO report V 90.322, 1995), should be considered a no-adverse-effect concentration as well.

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

Reference 4

Endpoint:

short-term repeated dose toxicity: inhalation

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 report attached in section 13 of IUCLID.

Reason / purpose for cross-reference:

read-across source

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

General condition and behaviour were not adversely affected by exposure to the test material. Clinical signs included a visually slightly increased superficial breathing pattern in animals exposed to the highest concentration during exposure and areas of sparsely haired skin in one control rat.

Mortality:

no mortality observed

Description (incidence):

No mortality was observed until the scheduled autopsy.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

There were no statistically significant differences in mean body weights and mean body weight gain between the treatment groups and the controls although body weight gain in animals exposed to the high concentration vapour test atmosphere appeared slightly lower than those in the other groups.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

There were no statistically significant difference in the mean absolute and relative organ weights between the treatment groups and the controls.

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

Gross examination at autopsy revealed findings in the epididymides, kidneys, mediastinal lymph nodes, skin/subcutis and testes in one or two animals only. Moreover, the findings are common for rats of this strain and age. Most animals exhibited gross findings in the lungs. However, the incidences of these findings were about equally distributed between the groups, including the control group. Therefore, the changes were considered not to be related to the treatment.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Microscopic examination of the nasal tissues showed very slight to slight transitional epithelium hyperplasia at level 2 in 5 of 6 animals exposed to 600 mg/m³. Slight focal transitional epithelium hyperplasia was also observed in one animal exposed to 600 mg/m³ (nasal level 1) and in one control animal (nasal level 2). One animal exposed to 600 mg/m³ additionally showed very slight focal squamous epithelial hyperplasia (nasal level 1). Very slight focal goblet cell hyperplasia (nasal level 3) was seen in two animals exposed to 600 mg/m³. No nasal tissue changes were observed in animals exposed to 75 or 200 mg/m³.

Histopathological findings: neoplastic:

not examined

Key result

Dose descriptor:

NOAEC

Remarks:

systemic

Effect level:

600 mg/m³ air

Based on:

test mat.

Sex:

male

Basis for effect level:

other: no adverse systemic effects observed in any test group

Key result

Dose descriptor:

NOAEC

Remarks:

local

Effect level:

200 mg/m³ air

Based on:

test mat.

Sex:

male

Basis for effect level:

histopathology: non-neoplastic

Remarks on result:

other: Very slight to slight transitional epithelium hyperplasia of the nasal passages.

Critical effects observed:

yes

Lowest effective dose / conc.:

600 mg/L air (nominal)

System:

respiratory system: upper respiratory tract

Organ:

nasal cavity

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

yes

Analytical results on actual concentration:

The overall mean daily concentrations of the test item vapour in the test atmospheres were 73 ± 7, 199 ± 11 and 591 ± 16 mg/m³ for the low, mid and high concentration test atmosphere, respectively.

Airflow:

Mean airflow through the control unit was 33.2 L/min, mean airflow through the low concentration unit was 28.5 L/min. The total airflow through the mid and high concentration unit could not be established, but was minimally 20.5 and 28.5 L/min, respectively.

Nominal concentration:

Nominal concentrations of the mid and high concentration test atmosphere could not be calculated. The mean nominal concentration of the low BL vapour test atmosphere was 112 ± 29 mg/m³, which was of the same order of magnitude as the actual concentration.

Temperature and relative humidity:

The daily mean temperatures in the test atmospheres were between 20.8 and 21.2 °C, the daily mean relative humidities were between 38 and 43%.

Conclusions:

In a sub-acute inhalation toxicity study, Butyl (S)-lactate (purity 98.9%) showed no effects on survival, body weight, organ weights and gross pathology. The most prominent finding consisted of histopathological changes in the nasal cavity of rats exposed to 600 mg/m³. Therefore, the NOAEC (local) for male rats is considered to be 200 mg/m³ and as no systemic effects were noted, the NOAEC (systemic) for male rats is considered to exceed 600 mg/m³.

Executive summary:

In a sub-acute inhalation toxicity study, toxicity of the test item (purity 98.9 %) was examined in male Wistar rats. Groups of 6 male rats were exposed nose-only to target vapour concentrations of 0, 75, 200 or 600 mg/m³ test item for 6 hours a day, 5 days a week during a period of 4 weeks (a total of 20 exposure days). No adverse effects were observed on survival, body and organ weights, and gross pathology. The most prominent finding consisted of histopathological changes in the nasal tissues, which showed transitional epithelium hyperplasia in almost all animals exposed to 600 mg/m³ test item but not in animals exposed to lower concentrations. These nasal changes are related to treatment and point to an irritating effect of Butyl-(S)-lactate on the nasal epithelium. Therefore, the local NOAEC is considered to be 200 mg/m³. The systemic NOAEC is considered to exceed 600 mg/m³ as no systemic effects were observed. This sub-acute toxicity study in the rat is acceptable and satisfies the guideline requirement according to OECD 412 for a sub-acute inhalation study in the rat.

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

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Species:

rat

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

150 mg/m³

Study duration:

subacute

Species:

rat

Quality of whole database:

GLP guideline studies

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

In a sub-acute inhalation toxicity study on a suitable read-across partner, ethyl (S)-lactate was administered to 5 male and 5 female Wistar rats/concentration by whole body exposure at concentrations of 0, 0.025, 0.075 and 0.2 mg/L (0, 25, 75 and 200 mg/m³) for 6 hours per day, 5 days/week for a total of 28 days. Two additional (recovery) groups of 5 male and 5 female Wistar rats exposed to 0 or 0.2 mg/L were kept untreated for 28 post-exposure days (TNO report V91.416). Clinical observations, growth, macroscopical observations at autopsy and microscopical examinations of the nose were used as criteria for disclosing possible harmful effects.

There were no compound-related effects on mortality, clinical signs, body weight or gross and histological pathology. Microscopic examination revealed minimal changes (nest-like infolds, slight hypertrophy, and slight hyperplasia) in the nasal respiratory epithelium of animals in all groups, the control group included. Type and incidence of the changes were similar in the various groups, or the changes occurred in a single animal only. These changes were not ascribed to treatment. The NOAEC was considered to be 200 mg/m³.

In contrast to a second study (TNO report V 90.322), in which rats were exposed to 150, 600 or 2500 mg ethyl (S)-lactate per m³ for 28 days, the results of the above-mentioned study (TNO report V91.416) shows that rats exposed to 25, 75 or 200 mg ethyl lactate per m³ for the same period did not develop compound-related histopathological changes in the nose.The minimal changes observed in this study consisting of nest-like infolds and slight hypertrophy and hyperplasia are fully comparable to the minimal changes observed at the 150 mg/m³ level of the second study. However, since these minimal changes were observed in all groups, controls included, and their incidences in treatment groups were not different from those in the control group, or the changes occurred in a single animal only, these minimal alterations were not ascribed to treatment and the NOEC is considered to be 200 mg/m³. By combining the results of the two studies, it can be concluded that the concentration of 150 mg/m³ used in the second study (TNO report V 90.322), should be considered a no-adverse-effect level as well.

In this second study, the exposure to ethyl (S)-lactate at levels up to 2500 mg/m³ resulted in concentration-related adverse effects in the nose of all test groups and in growth retardation and decreased food consumption in rats exposed to 2500 mg ethyl lactate/m³ air. Growth retardation might be explained by the impaired ability to smell and taste because of severe damage to the olfactory epithelium. The increased blood glucose value in males exposed to 2500 mg/m³ is considered an isolated finding unrelated to treatment. Furthermore, all observed effects can be explained by the reduced food intake and subsequent growth retardation.

These results were confirmed in a third sub-acute inhalation toxicity study, in which the toxicity of butyl (S)-lactate was examined in male Wistar rats. Groups of 6 male rats were exposed nose-only to target concentrations of 0, 75, 200 or 600 mg/m³ test item for 6 hours a day, 5 days a week during a period of 4 weeks (a total of 20 exposure days). No adverse effects were observed on survival, body and organ weights, and gross pathology. The most prominent finding consisted of histopathological changes in the nasal tissues, which showed transitional epithelium hyperplasia in almost all animals exposed to 600 mg/m³ test item but not in animals exposed to lower concentrations. These nasal changes are related to treatment and point to an irritating effect of butyl (S)-lactate on the nasal epithelium. Therefore, the local NOAEC is considered to be 200 mg/m³. The systemic NOAEC is considered to exceed 600 mg/m³ as no systemic effects were observed.

In a sub-chronic repeated dose toxicity with read-across partner calcium lactate pentahydrate, no adverse effects were reported after oral administration via drinking water. The NOAEL in this study is considered to be 4500 mg/kg bw/day for both sexes (calculated from 50,000 mg/L by applying a conversion factor of 0.09 for rats as recommended in the EFSA guidance document[EFSA Journal 2012 (10(3): 2579]).). Therefore, lactic acid/free lactate is of no systemic toxicological concern.

In addition, in a sub-chronic repeated dose toxicity study, methanol was administered daily to 30 Sprague-Dawley rats/sex/dose via oral gavage at dose levels of 0, 100, 500 and 2500 mg/kg bw/day for total of 90 days. Elevated levels (p≤ 0.05 in males) of serum alanine transaminase (ALT) and serum alkaline phosphatase (SAP), and increased (but not statistically significant) liver weights in both male and female rats suggest possible treatment-related effects in rats bolus dosed with 2500 mg methanol/kg bw/day despite the absence of supportive histopathologic lesions in the liver. Brain weights of high-dose group (2500 mg/kg bw/day) males and females were significantly less than those of the control group at terminal sacrifice. Based on these findings, 500 mg/kg bw/day methanol is considered as the NOAEL from this rat study (corresponding to 1625 mg/kg bw/day Methyl (S)-lactate). This dose is much higher as the limit dose of 1000 mg/kg bw/day mentioned in the OECD TG 408.

In a sub-acute repeated dose toxicity study, methanol was administered to 5 male/female Wistar rats/dose by inhalation in whole body exposure chambers at concentrations of 0, 500, 2000 and 5000 ppm as vapour, for 6 hours per day, 5 days/week for a total of 20 days. No treatment-related effects on mortality, clinical signs, body / organ weights, gross/histopathologic or ophthalmoscopic examinations were noted. The only treatment and dose-related effect noted was that of mucoid nasal discharge in rats, which was considered reflective of upper respiratory tract irritation

Altogether, given the existing data and taking a weight-of-evidence approach, there is no systemic toxicity concern for methyl (S)-lactate and no classification is warranted. For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Justification for classification or non-classification

Based on the available data, the target substance methyl (S)-lactate does not warrant classification for repeated specific target organ toxicity in accordance with CLP Regulation 1272/2008. Classification as H335, STOT SE 3 is warranted due to the local inhalation effect in the nose caused by hydrolysis of the lactate ester and subsequent acidification.