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Acute Toxicity: inhalation

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Administrative data

Endpoint:
acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
experimental phase (acute & sub-acute study): Jun. 5, 2018 - Apr. 17, 2019
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Cross-reference
Reason / purpose for cross-reference:
reference to same study
Reference
Endpoint:
short-term repeated dose toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
experimental phase (acute & sub-acute study): Jun. 5, 2018 - Apr. 17, 2019
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods with acceptable restrictions
Remarks:
only 5 day-test instead of a 28- or 90 day one (but cf. Landsiedel 2014)
Justification for type of information:
Cf. the endpoint: Literature, Landsiedel, 2014, Statement on 5-day studies. It claims that a 5-day study design can be as expressive as a 90-day study for testing nanoparticles.
Reason / purpose for cross-reference:
other: justification information
Reason / purpose for cross-reference:
reference to same study
Qualifier:
no guideline followed
Principles of method if other than guideline:
subacute inhalation: 4-hour exposure daily for 5 days, 3 dose levels, 13-week observation period
GLP compliance:
yes
Limit test:
no
Specific details on test material used for the study:
Test item identification: Sodasil P95
Description: Amorphous silicate of sodium and aluminum
Formula/Chemical group: Nanosilicates
Chemical Abstract No.: 1344-00-9
EINECS No.: 215-684-8
Aspect: White powder
Storage condition: Room temperature
Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals or test system and environmental conditions:
Age (at treatment start): 10 weeks old
Body-weight range(at treatment start): 206.9 – 277.8 g (females) and 314.7 – 490.9 g (males)
Temperature: 20.0ºC – 24.0ºC (Mean 22.0ºC)
Humidity: 40.0% – 80.0% (Mean 60.0%)
Room air renovation cycles: 30
Photoperiod: 12 hours of light: 12 hours of darkness
Feeding: Irradiated certified laboratory dry diet RM1 (P) QC Reference 831193 (batch number 3077, Dietex SDS) was offered with unlimited supply.
Drinking: Autoclaved mineral water was offered ad libitum.
Route of administration:
inhalation: aerosol
Type of inhalation exposure:
whole body
Vehicle:
other: 0.05% BSA (CAS No. 9048-46-8), 30 μL of absolute alcohol and sterile water
Mass median aerodynamic diameter (MMAD):
392.8 nm
Geometric standard deviation (GSD):
14.3
Remarks on MMAD:
Mass dispersion and size, as well as concentration in the air were assessed in the extraction tube from the inhalation chamber by using an optical particle sizer (ITENE). Sodasil P95 concentration measured allowed the observation of different dispersion grades of nanoparticles below 1 and 6 μm, being the resulting mean + standard deviation diameter value of 392.8 + 14.3 nm. According to these results there is a relative relevant difference with regard to the theoretical dose estimated. In contrast measurements made by using two air samples from the inhalation chamber, once upon achieved the steady-state demonstrated that 94–96% of nanoparticles are also ranged at mean values of 252 to 388 nm. Accordingly, actual doses applied to the animals were slightly lower than theoretical ones (i.e., 0.88, 4.39, 21.97 mg/m³ for the subchronic study). Hence, nanoparticles content in the air allowed to confirm the appropriate dose regime in order to assess the impact of subcacute treatments in the in vivo studies.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
s. above (Remarks on MMAD)
Duration of treatment / exposure:
4 hours per day for 5 days
Frequency of treatment:
daily
Dose / conc.:
21.97 mg/m³ air (analytical)
Remarks:
theoretical (cut-off dose): 28.5 mg/m³
Dose / conc.:
4.39 mg/m³ air (analytical)
Remarks:
theoretical (cut-off dose): 5.7 mg/m³
Dose / conc.:
0.88 mg/m³ air (analytical)
Remarks:
theoretical (cut-off dose): 1.1 mg/m³
No. of animals per sex per dose:
5
Control animals:
yes
Details on study design:
Subchronic systemic toxicity of Sodasil P95 was tested in male and female Wistar rats (n=5/sex/dose). Animals were subject to a daily 4-hour inhalation exposure for 5 days at theoretical dose levels of 1.1, 5.7 and 28.5 mg/m³. Actual doses applied to the animals were slightly lower than theoretical ones, i.e., 0.88, 4.39, 21.97 mg/m³.
The administration methods used were based on the procedures described in the OECD TG 436
Acute Inhalation Toxicity – Acute Toxic Class Method and the study design published by Arts et al. (2007) in Food Chem. Toxicol., 45: 1856-1867 to assess subchronic systemic toxicity following subacute exposure of the test item by using an inhalation Scireq chamber.
The observation period was 13 weeks.
Observations and examinations performed and frequency:
The animals were weighed and observed daily for the assessment of toxic effects for 90-94 days (subchronic systemic toxicity study).
Throughout the study periods, food and water were also weighed regularly to monitor changes in food and water intake.
Clinical findings were checked daily by observing any toxic effects.
Sacrifice and pathology:
Blood samples were drawn from the cava vein at the end of the experiment (Day 95) of all animals under light isoflurane anesthesia. The animals were not fasted before blood sampling but allowed access to water ad libitum. The samples were collected in the working day to reduce biological variation caused by circadian rhythms.
In addition, a bronchoalveolar lavage was performed by intubation of the trachea. A total 6 mL of PBS were perfused slowly for 1 minute and the solution was kept inside for 5 minutes before collection. The collected lavage was centrifuged at 1500 g for 10 minutes and then the pellet was resuspended in 0.5 mL of PBS to allow haematological and biomarker analyses.
Bioavailability were assessed in five tissues (blood, lung, liver, kidney and spleen).

At the end of the observational period: 13 weeks (subchronic) after treatment
initiation, all animals were necropsied and a macroscopic examination was performed. A full necropsy was performed on all main study and recovery animals. The necropsy included the examination of the external surface of the body, all orifices, cranial, thoracic and abdominal cavities and the observation of the organs both in situ and after evisceration.
At necropsy, several organs were subjected to microscopic examination:
Lungs, Spleen, Heart, Liver, Kidneys and Thoracic lymph nodes
Statistics:
For continuous data, a parametric analysis was performed to assess if variables follow a normal distribution and variances are homogeneous. If so, a one-way analysis of variance (ANOVA) followed by Dunnett’s test was performed. On the contrary, the Kruskal-Wallis ANOVA followed by the Mann-Whitney U-test was applied if Kolmogorov-Smirnov normality test was significant.
For organ weight data, parametric statistical comparison was done with absolute organ weights and those rated by the terminal body weight of each animal, unless non-parametric methods are applied when normality and variances homogeneity is not reached.
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, non-treatment-related
Description (incidence and severity):
Repeated administration for 5 days did not induce any change in bodyweight or bodyweight gain in females. The pattern was comparable in males, although those treated at the intermediate and high dose levels showed higher body weight gain as compared to controls. This effect was considered null of relevance from a toxicological point of view.
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
no effects observed
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
Hematological analysis at the end of the observational period, where just occasional statistical differences (p<0.05, one-way ANOVA followed by Dunnett’s test or Kruskal-Wallis followed by Mann-Whitney U-test) could be seen: MCHC and monocytes count in males and, MCHC and MCH in females, both compared to control animals. However, these changes had no relevance since the final values were within the normal range of values for this animal species. Overall, the hematological profile in bronchoalveolar lavage (BAL) was not significant, although monocytes count was significantly lower (p<0.05, one-way ANOVA followed by Dunnett’s test) at the highest dose levels as compared to the control group.
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
Blood chemistry analysis in serum and in BAL were also performed. Overall there were no significant effects on any parameter: creatinine, urea, total bilirubin, GPT/ALT, GOT/AST, alkaline phosphatase (serum) and lactic dehydrogenase, albumin and N-acetyl-glucosamine (NAG) (BAL), but total proteins (p<0.05) and alkaline phosphatase (p=0.001, one-way ANOVA followed by Dunnett’s test) were significantly increased in male animals at the low and intermediate dose levels and at the highest level of Sodasil P95, as compared to control animals. These changes were considered effects not biologically relevant from a toxicological point of view.

Collagen concentration was estimated in dry lungs by means of quantification of the hydroxyproline levels. Mean tissue levels of collagen tended to increase with the dose increase in males (4, 18 and 35-fold) and females (34, 171 and 183-fold) at the three dose levels compared to control animals (mean of 2.1 µg/g tissue and
Urinalysis findings:
not examined
Behaviour (functional findings):
no effects observed
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Description (incidence and severity):
Macroscopic examination and organ weights did not allow the observation of any event or trend in male and female animals related to dose administration.
Gross pathological findings:
no effects observed
Description (incidence and severity):
Macroscopic examination and organ weights did not allow the observation of any event or trend in male and female animals related to dose administration.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
no effects observed
Description (incidence and severity):
Histopathological examination of six relevant tissues (heart, lungs, liver, spleen, kidneys and thoracic lymph nodes) did not allow the registration of any relevant event. All findings recorded were considered to be within the range of normal background lesions that may be seen in rats of this strain and age and under the experimental conditions used in this study.
Histopathological findings: neoplastic:
no effects observed
Other effects:
effects observed, treatment-related
Description (incidence and severity):
Bioavailability was assessed in five tissues (blood, lung, liver, kidney and spleen) by TEM.
Small nanosilicates (< 160 nm) were seen in all tissues with the exception of whole blood,
where no conclusive observations could be made. Nanoparticles were confined, as expected,
inside the reticuloendothelial system in lysosomes into macrophages in lungs, Küpffer cells in
liver, proximal tubular cells (close to the glomerulus) in kidneys and in spleen. No nanosilicates
were seen in the nucleus nor in mitochondria. The lysosomal location is commonly known for
all nanoparticles, most of them devoid of any toxicological relevance, and there is no reason
to expect adverse effects here.
Key result
Dose descriptor:
NOAEL
Effect level:
>= 21.97 mg/m³ air
Sex:
male/female
Basis for effect level:
behaviour (functional findings)
body weight and weight gain
clinical biochemistry
clinical signs
food consumption and compound intake
gross pathology
haematology
histopathology: neoplastic
histopathology: non-neoplastic
Remarks on result:
other: The theoretical cut-off dose was 28.5 mg/m³. The actual dose applied to the animals was slightly lower: 21.97 mg/m³.
Key result
Critical effects observed:
no

There were no clinical signs/behavioral changes registered throughout the study and body weight gain and food and water intake of male and female animals treated with Sodasil P95, at the different dose levels, were similar to that registered in control animals.


Overall, no effects could be observed on hematological, serum biochemistry nor biomarkers measured in the bronchoalveolar lavage (BAL) and lung tissue at the end of the experimental period, although monocytes in whole blood, total proteins and alkaline phosphatase in BAL and content of collagen in lungs tended to increase with dose in a significant manner. All these changes were considered as effects (not adverse events) without biological relevance from a safety point of view, they might have been residual repair mechanisms in front of intensive inhalation. Hence, no adverse events could be established based on the hematological, clinical biochemistry in serum and in BAL at any dose level assayed


As expected, the bioavailability measured in five tissues (blood, lung, liver, kidney and spleen) allowed the observation of remnant nanosilicates inside lysosomes of the reticuloendothelial system from the different tissues (lungs, liver, kidneys and spleen), with the exception of whole blood, following the usual pattern seen for other nanoparticles.


Neither macroscopic changes nor clear significant trends in organ weights from animals treated at the different dose levels with Sodasil P95 could be recorded.


Finally, the histopathology examination of six relevant tissues (heart, lungs, liver, spleen, kidneys, and thoracic lymph nodes) did not allow the registration of any relevant effect.


 

Conclusions:
Sodasil P95 administered by 5-day repeated inhalation (and an observation period of 13 weeks) to the Wistar rat showed a No-Observed-Adverse-Event-Level (NOAEL) of 21.97 mg/m³, expressed as actual dose, according to the subchronical assessment.
Executive summary:

Subchronic systemic toxicity of Sodasil P95 was tested in male and female Wistar rats (n=5/sex/dose). Animals were subject to a daily 4-hour inhalation exposure for 5 days at theoretical dose levels of 1.1, 5.7 and 28.5 mg/m³. Actual doses applied to the animals were slightly lower than theoretical ones, i.e. 0.88, 4.39, 21.97 mg/m³. The observation period lasted 13 weeks. Although some effects were observed, none of these were assessed as adverse.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2021
Report date:
2021

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 436 (Acute Inhalation Toxicity: Acute Toxic Class Method)
Deviations:
not specified
GLP compliance:
yes
Test type:
acute toxic class method
Limit test:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
Silicic acid, aluminum sodium salt
EC Number:
215-684-8
EC Name:
Silicic acid, aluminum sodium salt
Cas Number:
1344-00-9
Molecular formula:
nSiO2*mAl2O3*zNa2O n = 2-4; m = 0.12-3.20; z = 0.11-4.5
IUPAC Name:
aluminium(3+) sodium bis(oxosilanebis(olate))
Test material form:
solid: nanoform, no surface treatment
Remarks:
crystalline-free
Specific details on test material used for the study:
Test item identification: Sodasil P95
Description: Amorphous silicate of sodium and aluminum
Formula/Chemical group: Nanosilicates
Chemical Abstract No.: 1344-00-9
EINECS No.: 215-684-8
Aspect: White powder
Storage condition: Room temperature

Test animals

Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals or test system and environmental conditions:
Age (at treatment start): 10 weeks old
Body-weight range(at treatment start): 206.9 – 277.8 g (females) and 314.7 – 490.9 g (males)
Temperature: 20.0ºC – 24.0ºC (Mean 22.0ºC)
Humidity: 40.0% – 80.0% (Mean 60.0%)
Room air renovation cycles: 30
Photoperiod: 12 hours of light: 12 hours of darkness
Feeding: Irradiated certified laboratory dry diet RM1 (P) QC Reference 831193 (batch number 3077, Dietex SDS) was offered with unlimited supply.
Drinking: Autoclaved mineral water was offered ad libitum.

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
whole body
Vehicle:
other: 0.05% BSA (CAS No. 9048-46-8), 30 μL of absolute alcohol and sterile water
Mass median aerodynamic diameter (MMAD):
ca. 392.8 nm
Geometric standard deviation (GSD):
14.8
Remark on MMAD/GSD:
Mass dispersion and particle sizes, as well as concentration in the inhalatory air were measured by ITENE, by using an optical particle sizer OPS-TSI 3330, at least in one occasion for each study. In parallel, samples of solutions for administration and from the air in the inhalation chamber were also collected and measured by using a nanosizer.
Analytical verification of test atmosphere concentrations:
yes
Duration of exposure:
4 h
Concentrations:
theoretical (cut-off) dose: 85.6 mg/m³
actual dose: 65.9 mg/m³
No. of animals per sex per dose:
3
Control animals:
no
Details on study design:
After the acclimatization period of 5 days, a randomly selected animal was marked with a number at the base of the tail with a permanent marker in order to identify the animal.
The dose was prepared immediately before administration, different batches of 6-mL of a solution integrated by 0.05% BSA, 30 μL of absolute alcohol and sterile water (q.s.) to 6 mL and with Sodasil P95 at concentration of 2.567 mg/mL was used. It was not possible to assess higher concentrations or dose levels without affect dispersion and homogeneity feasible for inhalation. The solution is sonicated for 12 minutes at 31-36 mJ/m³ at 20% amplitude in an ultrasound bath.

The animals were exposed to the inhalation procedure at 0.1 mL/min of test item solution and at 3 L air/min for 4 hours (acute toxicity).
The animals were weighed and observed daily for the assessment of toxic effects for 14 days (acute toxicity). Throughout the study periods, food and water were also weighed regularly to monitor changes in food and water intake.
Clinical findings were checked daily by observing any toxic effects. They were graded and recorded according to a scale based on the basic animal welfare supervision protocol proposed by Morton and Griffiths.
Statistics:
For continuous data, a parametric analysis was performed to assess if variables follow a normal distribution and variances are homogeneous. If so, a one-way analysis of variance (ANOVA) followed by Dunnett’s test was performed. On the contrary, the Kruskal-Wallis ANOVA followed by the Mann-Whitney U-test was applied if Kolmogorov-Smirnov normality test was significant.
For organ weight data, parametric statistical comparison was done with absolute organ weights and those rated by the terminal body weight of each animal, unless non-parametric methods are applied when normality and variances homogeneity is not reached.

Results and discussion

Effect levelsopen allclose all
Sex:
male/female
Dose descriptor:
LC0
Effect level:
>= 65.9 mg/m³ air (analytical)
Exp. duration:
4 h
Remarks on result:
not determinable due to absence of adverse toxic effects
Key result
Sex:
male/female
Dose descriptor:
LC50 cut-off
Effect level:
> 85.6 mg/m³ air
Exp. duration:
4 h
Mortality:
No mortality was observed in animals treated with Sodasil P95 at an actual dose level of 65.9 mg/m³.
Clinical signs:
bodyweight loss
Remarks:
Cf. below on body weight loss. No other clinical signs were observed.
Body weight:
Only a very weak and temporary decrease in female body weight could be seen for 2–3 days after inhalation, but this effect is commonly related to the exposure conditions. No effects could be seen on food and water intake.
Gross pathology:
No macroscopic alterations were observed in animals treated with Sodasil P95.

Any other information on results incl. tables

According to the OECD TG 436, the acute lethal dose for inhalation route could not be determined for Sodasil P95, since no mortality or any toxic event could be registered at a theoretical dose level of 85.6 mg/m³ (LC50 cut-off) and an actual one of 65.9 mg/m³. 

Applicant's summary and conclusion

Conclusions:
According to the OECD TG 436, the acute lethal dose for inhalation route could not be determined for Sodasil P95, since no mortality or any toxic event could be registered at theoretical dose level of 85.6 mg/m³ (LC50 cut-off) and an actual one of 65.9 mg/m³. Therefore, the LC50 cut-off is greater than 85.6 mg/m³ and the LC0 at least 65.9 mg/m³.
Executive summary:

The aim of this study was to assess the acute and subchronic systemic toxicity following acute (4-hour exposure) and subacute inhalation (4-hour exposure daily for 5 days) of Sodasil P95 in Wistar rats. Only the acute experiment is documented here, the subacute one is found in chapter 7.5.2. No mortality was observed in both studies.