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Description of key information

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records
Reference
Endpoint:
acute toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
Qualifier:
according to
Guideline:
OECD Guideline 423 (Acute Oral toxicity - Acute Toxic Class Method)
Qualifier:
according to
Guideline:
EU Method B.1 tris (Acute Oral Toxicity - Acute Toxic Class Method)
GLP compliance:
yes
Test type:
acute toxic class method
Limit test:
yes
Species:
rat
Strain:
other: Crl:CD(SD)
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: Between 8 and 12 weeks at the time of the administration
- Weight at study initiation: 203 - 217 g
- Fasting period before study: overnight
- Housing: individually
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: At least 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): Average of 20.43 °C (continuous control and recording)
- Humidity (%): Average of 48.88 % (continuous control and recording)
- Photoperiod (hrs dark / hrs light): 12/12
Route of administration:
oral: gavage
Vehicle:
CMC (carboxymethyl cellulose)
Details on oral exposure:
VEHICLE
A 0.1 % aqueous solution of Na-carboxymethylcellulose ("CMC" high viscosity, item No. C- 5013, Sigma) was used as vehicle for the test substance
MAXIMUM DOSE VOLUME APPLIED:
The dose volume was 10 mL per kg body weight. The individual dose volumes were calculated using lhe body weights determined on the day of the
administration
The dosing was performed sequentially to groups of 3 animals per step using a starting dose of 2000 mg per kg body weight.
The sequence of dosing of the lest substance was:
Step 1: 2000 mg per kg body weight.
Step 2: 2000 mg per kg body weight.
Doses:
2000 mg/kg b.w.
No. of animals per sex per dose:
6
Control animals:
no
Details on study design:
Observations were performed within the periods 0 - 0.5, 0.5 - 1, 1 - 2, 2 - 4 and 4 - 6 hours after administration (p.a.) of the test substance and
then at least once a day for a total of 2 weeks. Observations included but were not limited to changes in skin, fur, eyes, the occurrence of secretions and excretions, autonomic activity, changes in gait, posture and the presence of convulsions.
Body weights were determined: before administration, 7 days p.a., 14 days p.a.
Body weight gain was calculated for each week of the study, i.e. between 0 and 7 days p.a., 7 and 14 days p.a.
Sex:
female
Dose descriptor:
LD50
Effect level:
> 2 000 mg/kg bw
Based on:
test mat.
Mortality:
All animals survived until the scheduled termination of the study
Clinical signs:
All animals did not show any clinical signs during the entire observation period.
Body weight:
All animals gained weight in both weeks p.a.
Gross pathology:
No abnormal findings were made in all animals at the necropsy 14 d p.a.
Interpretation of results:
study cannot be used for classification
Remarks:
Migrated information
Conclusions:
No toxic effects of the test substance were noted by signs in life and post mortem in both steps at a dose of 2000 mg test substance
per kg body weight. No mortality occurred. Therefore the LD50, oral is definitely > 2000 mg/kg body weight.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Acute toxicity: via inhalation route

Link to relevant study records
Reference
Endpoint:
acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
Qualifier:
according to
Guideline:
OECD Guideline 403 (Acute Inhalation Toxicity)
Qualifier:
according to
Guideline:
EU Method B.2 (Acute Toxicity (Inhalation))
GLP compliance:
yes (incl. certificate)
Test type:
acute toxic class method
Limit test:
yes
Species:
rat
Strain:
other: rat/CD/Crl:CD
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: males 45 days, females 56 days
- Weight at study initiation: males 204-228 g, females 194-220 g
- Fasting period before study: 16 hours before exposure
- Housing: caged by sex in groups of 2-3 animals/cage
- Diet: feeding was discontinued approx. 16 hours before exposure
- Water: ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22°C +/- 3°C
- Humidity (%): 55% +/- 15%
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 17.11.2003 To: 02.12.2003
Route of administration:
inhalation
Type of inhalation exposure:
nose only
Vehicle:
clean air
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: dynamic inhalation chamber (Rotameter, ROTA Apparate- und Maschinenbau, 0-79664 Wehr/Baden)
- Exposure chamber volume: 40 L
- Method of holding animals in test chamber: in pyrex tubes at the edge of the chamber in a radial position.
- Flow rate of air: 900 L/h
- Method of conditioning air: air was taken from the surrounding atmosphere of the laboratory room and filtered using an in-li ne disposable
gas filter
- System of generating particulates/aerosols: rotating brush dust generator (RBG 1000, PALAS GmbH Partikel und Lasermesstechnik, 0-76229
Karlsruhe)
- Method of particle size determination: cascade impactor (MAY, K.R. Aerosol impaetion jets, J.Aerosol Sei..§, 403 (1975), RESEARCH ENGINEERS Ltd, London N1 5RO, UK
- Treatment of exhaust air: passage through appropriate filter
- Temperature, humidity, oxygen content in air chamber: temperature 22°C +/- 3°C, humidity based on the guidelines, recordings of humidity in
the chamber are not made where dust examinations are carried out, oxygen content 21%

TEST ATMOSPHERE
- Brief description of analytical method used: Dust sampies were taken once every hour during the exposure. For that purpose, a SARTORIUS filter
(Minisart SM 17598 0.45 µm) was placed in the purpose-made inlet of the inhalation chamber in such a way that the opening of the filter was close
to the animals' noses. By means of a piece of silicon tubing, the filter was connected to an air-flow meter attached to a pump. The filter was
weighed before and after sampling (accuracy: 10 µg)
- Samples taken from breathing zone: yes

VEHICLE
- Composition of vehicle: clean air
- Concentration of test material in vehicle:
- Purity: filtered using an in-line disposable gas filter)

TEST ATMOSPHERE
- MMAD (Mass median aerodynamic diameter): 2.383 µm
- Geometric mean diameter: 3.3575 µm
- GSD (Geometric st. dev.): 3.629 µm

Analytical verification of test atmosphere concentrations:
yes
Duration of exposure:
4 h
Concentrations:
5.15 +/- 0.10 mg/l
No. of animals per sex per dose:
5
Control animals:
not specified
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations for mortality and clinical signs: during and after exposure, daily thereafter
- Frequency of weighing: day 0 (prior to dosing), day 7 and day 14
- Necropsy of survivors performed: yes
- Other examinations performed: gross examination of organs at necropsy, organ weights,
Sex:
male/female
Dose descriptor:
LC0
Effect level:
> 5.15 mg/L air (analytical)
Based on:
test mat.
Exp. duration:
4 h
Sex:
male/female
Dose descriptor:
LC50
Effect level:
> 5.15 mg/L air (analytical)
Based on:
test mat.
Exp. duration:
4 h
Mortality:
no mortality occurred
Clinical signs:
Particular attention was directed to observation of tremor, convulsions, salivation, diarrhoea, lethargy, sleep and coma
Body weight:
Individual weights of animals were determined before the exposure and weekly after exposure. Changes in weight were calculated and recorded when survival exceeds one day.
Gross pathology:
Macroscopic post mortem findings: no pathological findings
Interpretation of results:
study cannot be used for classification
Remarks:
Migrated information
Conclusions:
Under the present test conditions, no signs of toxicity were observed at 5.15 ± 0.1 0 mg L-threonine/L air. No mortality occurred. No abnormalities were detected at necropsy. The animals gained the expected weight throughout the study period.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Additional information

Acute oral toxicity

The key study (2010 -0220 -DGT) is an acute oral toxicity GLP study according to OECD Guideline 423 (Acute Oral toxicity - Acute Toxic Class Method). No toxic effects of the test substance were noted by signs in life and post mortem at a dose of 2000 mg test substance per kg body weight. No mortality occurred. Therefore the LD50, oral is definitely > 2000 mg/kg body weight.

This result was supported in another acute oral toxicity study according to OECD 401 with a resulting LD50 > 2000 mg/kg bw (93 -0580 -FGT).

Similar results were obtained in another acute oral toxicity GLP study according to OECD 401 (93 -0020 -DGT). No signs of toxicity were recorded during the observation period. Deaths did not occur. The resulting oral LD50 is >2150 mg/kg bw.

The low acute oral toxicity was confirmed in another published acute oral toxicity study according to OCED 420 (van de Mortel 2010). All animals suvived and the oral LD50 is >2000 mg/kg bw.

In an older study (71 -0026 -FKT) which was performed prior to GLP the LD50 was determined to be > 16 g/kg bw. The study was well documented and acceptable for assessment.

 

Acute inhalative toxicity

The key study is an in vivo GLP-guideline study (2003 -0594 -DGT) performed according to OECD 403. The aim of the available limit test with L-threonine was to obtain information on the acute inhalative toxicity following a single 4 hour exposure of rats. No signs of toxicity were observed at 5.15 +/-0.1 mg test substance/l.  

This result was supported in another GLP-guideline study (2003 -0840 -FGT) according to OECD 403. The 4 -hour LC50 of an aerosol of L-threonine was > 5.22 g/m3.

Acute dermal toxicity

No data on acute dermal toxicity for L-threonine is available. The substance is of very low systemic toxicity as no systemic effects were observed in the acute oral toxicity studies (2000 mg/kg bw) as well as in repeated dose toxicity studies (1000 mg/kg bw). An older study indicate that the acute oral LD50 is even >16000 mg/kg bw. Due to this very low toxicity and the fact that L-threonine with high water solubility and a log P value well below 0 may be too hydrophilic to cross the lipid rich environment of the stratum corneum it is highly improbable that an acute dermal toxicity study would result in any toxicity. Therefore and for animal welfare reasons no further acute dermal toxicity study is justified and the dermal LD50 is assumed to be > 2000 mg/kg bw.

Justification for classification or non-classification