Registration Dossier

Administrative data

Endpoint:
acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
12-Apr-2010 - 26-Apr-2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study performed in accordance with GLP and internationally accepted guideline

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2010
Report date:
2010

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 403 (Acute Inhalation Toxicity)
GLP compliance:
yes (incl. QA statement)
Test type:
fixed concentration procedure

Test material

Constituent 1
Chemical structure
Reference substance name:
Kieselguhr, soda ash flux-calcined
EC Number:
272-489-0
EC Name:
Kieselguhr, soda ash flux-calcined
Cas Number:
68855-54-9
Molecular formula:
SiO2
IUPAC Name:
dioxosilane
Details on test material:
Identification: Soda-ash flux-calcined kieselguhr
Description: White powder
Batch Number: 211184
Purity: 100%
Expiry Date (Retest Date): 31-Dec-2013
Storage Conditions: At room temperature (20 ± 5°C), protected from direct sunlight.

Test animals

Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Harlan Laboratories B.V. Kreuzelweg 53 5961 NM Horst / Netherlands
- Age at study initiation: Males: 8 weeks; Females: 9 weeks
- Weight at study initiation: Males: 263.9 to 284.3 g ;Females: 182.6 to 198.0 g
- Fasting period before study:
- Housing: Animals were housed in groups of 5 of the same sex in Makrolon® type-IV cages with wire mesh tops and standard softwood bedding
- Diet: Animals had ad libitum access to a pelleted standard Harlan Teklad 2914C rat maintenance diet ( except during the period when the animalsand) batch no. were restrained in exposure tubes.
- Water: Community tap water from Füllinsdorf ad libitum in water bottles, except during the period when they were restrained in exposure tubes
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature : 22 ± 3 °C,
- Humidity: 30 - 70%
- Air changes: 10 - 15 air changes per hour
- Photoperiod 12 hour fluorescent light / 12 hour dark cycle:


Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
nose only
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Inhalation exposure was performed using a flow-past, nose-only exposure system.
- Method of holding animals in test chamber: The animals were confined separately in restraint tubes which were positioned radially around the exposure chamber.
- Source and rate of air: The exposure system ensured a uniform distribution and provided a constant flow of test material to each exposure tube. The flow of air at each tube was 1.0 L/min.
- System of generating particulates/aerosols: A dust aerosol was generated from the test item using a CR 3020 rotating brush aerosol generator connected to a micronizing jet mill. The aerosol generated was then discharged into the exposure chamber through a 63Ni charge neutralizer
- Method of particle size determination: The particle size distribution of the test aerosol was determined three times during exposure using a 7 stage Mercer cascade Impactor (Model 02-130, In-Tox. Products Inc., Albuquerque, New Mexico, U.S.A.). The particle size distribution was measured by gravimetrically analyzing the test item deposited on each stage of the cascade impactor. Mass Median Aerodynamic Diameters (MMAD) and Geometric Standard Deviations (GSD) were calculated on the basis of the results from the impactor, using Microsoft Excel Software . The target range was 1 to 4 μm for the MMAD and between 1.5 and 3 for the GSD.
- Temperature, humidity, pressure in air chamber: The temperature and relative humidity of the test atmosphere was measured continuously during
exposure using a calibrated device. The results were recorded manually and are reported at 30 minute intervals from the start of exposure and additionally at the end of exposure The actual airflow rate through the exposure chamber was recorded at approximately 30 minute intervals from the start of the inhalation exposure.




TEST ATMOSPHERE
- Particle size distribution: Particle size distribution data are presented in table 4
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): MMAD and GSD data are presented in tables 2 and3

Duration of exposure:
4 h
Concentrations:
The mean gravimetric aerosol concentration determined was 2.7 mg/L air
The nominal aerosol concentration was 20.4 mg/L air.

No. of animals per sex per dose:
5 males and 5 females
Control animals:
no
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Observations for viability were recorded once before exposure on the day of exposure (test day
1), three times during exposure, immediately and 1 h after exposure on test day 1 and twice daily during the observation period. Observations for clinical signs was examined three times during exposure, immediately and 1 h after exposure on test day 1 and once daily during the observation period.The body weight of each animal was recorded on test days 1 (before exposure), 2, 4, 8 and 15 (before necropsy).
- Necropsy of survivors performed: yes
Statistics:
No statistical analysis was performed as only one group was allocated to the study

Results and discussion

Effect levels
Sex:
male/female
Dose descriptor:
LC50
Effect level:
> 2.6 mg/L air
Based on:
test mat.
Exp. duration:
4 h
Mortality:
All animals survived the scheduled observation period
Clinical signs:
other: Moderately ruffled fur was noted in all animals on test day 1 after the end of the exposure and persisted with a reduced severity degree until test day 2. In addition, a slightly scabbed nose was recorded in all animals on test day 1 after the end of the
Body weight:
From test day 1 to test day 2, marginal to slight body weight loss was noted in five males and four females. Thereafter normal body weight development was recorded in these animals. Marginal body weight loss or stagnation of the body weight gain is not unusual in inhalation studies. Therefore, effects on the body weight were considered to be mainly due to the restraining of the animals in the tubes during the nose-only exposure procedure and not related to treatment with the test item. However, a contribution of a test-item related effect cannot be excluded completely.




Gross pathology:
No macroscopic findings were present at necropsy

Any other information on results incl. tables

Test atmosphere conditions:

Temperature, relative humidity and oxygen concentration during exposure were considered to be satisfactory for this type of study. Data on temperature, relative humidity and oxygen concentration are presented in table 1.

Table 1: Temperature, relative humidity and oxygen concentration

Recording time[hours:min]

O2 concentration [Vol %]

Temperature [°C]

Relative humidity [% RH]

06:30

20.6

22.2

9.2

07:00

20.6

22.3

5.6

07:30

20.7

22.4

5.4

08:00

20.6

22.3

5.7

08:30

20.7

22.3

5.5

09:00

20.6

22.3

5.5

09:30

20.6

22.4

7.2

10:00

20.6

22.3

5.0

10:30

20.7

22.3

5.2

10:39

20.6

22.3

5.1

Mean

St. Dev

N

20.6

0.0

10

22.3

0.1

10

5.9

1.3

10

Gravimetric determination of aerosol concentrations:

The mean gravimetric aerosol concentration determined was 2.7 mg/L air. The aerosol concentration was in general stable during the exposure period. Data on gravimetric aerosol concentrations are presented in table 2.

Table 2: Gravimetric determination of aerosol concentrations

Sampling time [hours:min]

Sampling volume [L]

Amount of test item on the filter [mg]

Gravimetric aerosol concentration [mg/L air]

06:40 – 06:45

4.9

9.592

2.0

06:50 – 06:55

4.9

14.728

3.0

07:40 – 07:45

4.9

14.220

2.9

08:40 – 08:45

4.9

13.151

2.7

09:43 – 09:48

4.9

14.605

3.0

Mean

St. Dev

N

 

2.7

0.4

5

Chemical determination of aerosol concentrations:

The chemically determined aerosol concentration was in general stable during the exposure period. Only one single value at the beginning of the aerosol generation was lower. The remainder of the values were close to the technical limit of approximately 3 mg/L as targeted. The chemical aerosol concentration compared favourably to the gravimetrically determined concentration. This was in accordance with the high purity of the test item. Details on chemically determined aerosol concentrations are presented in table 3.

Table 3: Chemical determination of aerosol concentrations

Sampling time [hours:min]

Sampling volume [L]

Amount of test item on the filter [mg]

Gravimetric aerosol concentration [mg/L air]

06:40 – 06:45

4.9

9.135

1.9

06:50 – 06:55

4.9

13.93

2.9

07:40 – 07:45

4.9

13.60

2.8

08:40 – 08:45

4.9

12.70

2.6

09:43 – 09:48

4.9

14.13

2.9

Mean

St. Dev

N

 

2.6

0.4

5

 

Particle size distribution:

The Mass Median Aerodynamic Diameters (MMAD) obtained from tree gravimetric measurements of particle size distribution during the exposure were similar (MMAD between 2.39 and 2.95 μm). This led to the conclusion that the particle size of the generated aerosol was fairly stable during the whole exposure period. The MMADs were well within the target range of 1 to 4 μm, thus deposition of the particles can be assumed to have occurred in both the upper and the lower respiratory tract. In addition, the Geometric Standard Deviations (GSD) were within the target range of 1.5 to 3. Hence, the particle size distributions obtained were considered to be appropriate for acute inhalation toxicity testing. Data on particle size distribution are presented in table 4.

Table 4: Particle size distribution

Time

Total amount collected [µg]

 

MMAD [µm]

GSD

Corr.Coeff (R )

% < 4 µm

1

--

2

4.6

3

3.0

4

2.13

5

1.6

6

1.06

7

0.715

8

0.325

06:58

1487

19.4

30.3

16.6

13.4

9.8

7.5

0.8

2.2

2.75

2.32

0.964

67.2

07:42

1919

23.4

27.6

16.1

16.3

7.7

4.7

1.4

2.9

2.95

2.47

0.957

63.2

08:42

828

13.9

32.7

16.5

11.6

6.6

12.6

3.7

2.3

2.39

2.35

0.973

72.8

Applicant's summary and conclusion

Interpretation of results:
not classified
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
In conclusion, the LC50 of Soda-ash flux-calcined kieselguhr obtained in this study was estimated to be greater than 2.6 mg/L air (chemically determined mean aerosol concentration). As the study was conducted up to the maximum attainable concentration and in accordance with Regulation (EC) No. 1272/2008 (EU CLP) the substance is not considered to be classified.

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