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Diss Factsheets

Administrative data

acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
10 July 1997 to 30 July 1997
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was performed to GLP and in line with standardised guidelines OECD 403, EU Method B.2 and EPA OTS 798.1150 with no deviations thought to impact on the reliability of the presented results.

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guidelineopen allclose all
according to guideline
OECD Guideline 403 (Acute Inhalation Toxicity)
according to guideline
EU Method B.2 (Acute Toxicity (Inhalation))
according to guideline
EPA OTS 798.1150 (Acute inhalation toxicity)
according to guideline
other: J-MAFF59 NohSan No. 4200
GLP compliance:
yes (incl. QA statement)
Test type:
standard acute method
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
sodium 4,6-dimethoxy-N-({[3-(2,2,2-trifluoroethoxy)pyridin-2-yl]sulfonyl}carbamoyl)pyrimidin-2-aminide
EC Number:
Cas Number:
Molecular formula:
sodium 4,6-dimethoxy-N-({[3-(2,2,2-trifluoroethoxy)pyridin-2-yl]sulfonyl}carbamoyl)pyrimidin-2-aminide
Test material form:
solid: particulate/powder
Details on test material:
- Physical state: solid (powder)
- Stability under test conditions: Stable
- Storage condition of test material: Tightly sealed in original container at room temperature protected from direct sunlight.

Test animals

Details on test animals or test system and environmental conditions:
- Age at study initiation: approximately 8-11 weeks
- Weight at study initiation: 211.8-226.1 g (males); 197.2-215.3 g (females)
- Housing: 5 same sex animals per cage
- Fasting period before study: Rats were fasted overnight prior to dosing
- Diet: commercial pelleted diet available ad libitum except during 4-hour exposure period
- Water: municipal water available ad libitum except during 4-hour exposure period
- Acclimation period: 5 days

- Temperature (°C): 21 ± 1 °C
- Humidity (%): 70 ± 10 % (extrema 56-90 %)
- Air changes: approximately 13-14 air changes per hour
- Photoperiod: 12 hours dark / 12 hours light

IN-LIFE DATES: From 10 July 1997 to 30 July 1997

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
nose only
Details on inhalation exposure:
- Exposure apparatus: The exposure chamber was based upon the fluid dynamic modelling of the test atmosphere flow. It ensured a uniform test article distribution, provided a constant stream of test material to each animal and precluded rebreathing the exhaled air.
- Method of holding animals in test chamber: Restraining tubes positioned radially around the exposure chamber
- Source and rate of air: No diluent air was added to the test article. The total airflow was maintained at 32 L/min.
- System of generating particulates/aerosols: The test atmosphere of test material was produced using an aerosol generator connected to a jet mill. The aerosol generated was discharged into the exposure chamber through a neutraliser with a target mass median aerodynamic diameter of 3 µm or less.
- Method of particle size determination: Particle size distribution was determined twice using a cascade impactor. Representative samples were withdrawn from the test atmosphere at a flow rate of 1.01 L/min and the particles deposited according to their aerodynamic size; size fractions were then weighed.
- Temperature, humidity, oxygen concentration (Vol%): Temperature 22.4 °C ± 0.34; Relative humidity 24.9 % ± 7.2; Oxygen concentration 19.7 % ± 0.62 (measurements were taken from group 1)

- Brief description of analytical method used: Atmosphere samples were collected on filters for gravimetric analysis. After collection, each filter residue was dissolved in bi-distilled water using an ultrasonic bath. Sample solutions were then diluted for analysis by HPLC.
- Samples taken from breathing zone: yes
Analytical verification of test atmosphere concentrations:
total weight of test material used during 4 hour exposure period was divided by the total air-flow volume to give the nominal concentrations. Samples from the test atmosphere were also collected on filter papers for gravimetric concentration measurements.
Duration of exposure:
4 h
5 mg/L (target concentration)
8.13 mg/L (nominal) - this was found to be higher than the target concentration due to accumulation of the test material in the exposure system.
5.03 mg/L ± 0.10 (analytical)
5.04 mg/L ± 0.04 (gravimetric)
No. of animals per sex per dose:
Control animals:
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: mortality was checked once daily during the acclimatisation phase, once before exposure on test day 1, once per hour during exposure and once after exposure on test day 1 and twice daily during the remainder of the observation period. Clinical signs were recorded once per hour during exposure, once after exposure on test day 1 and once daily thereafter. Observations included, but were not limited to: changes in behaviour, somatomotor activity, body position, respiration, alteration of the skin, fur, nose and eyes. Bodyweights were recorded on test days 1 (before exposure), 4, 8 and 15 (day of necropsy).
- Necropsy of survivors performed: yes. Animals were examined macroscopically and all abnormalities were recorded. The lungs, trachea, larynx and the head containing the nasopharyngeal tissues were collected from all animals and fixed in neutral phosphate buffered 4% formaldehyde solution. The brain of male no. 4 was fixed similarly. The lungs were instilled with the fixative at a hydrostatic pressure of 30 cm H2O.

Results and discussion

Effect levels
Dose descriptor:
Effect level:
> 5.03 mg/L air (analytical)
Based on:
test mat.
Exp. duration:
4 h
Remarks on result:
other: no mortality was observed in either sex
No animals died during the course of the study.
Clinical signs:
other: There were no clinical signs during the first half of the exposure period. During the latter half, slight or moderate, and marked salivation was seen in all animals, in addition to deep respiration in one of them. One hour after exposure all animals displ
Body weight:
There was a minimal retardation in bodyweight gain in males and a slight retardation in females from treatment day 1 (prior to exposure) to test day 8 (seven days after exposure). From test day 8 until day 15, all animals gained weight normally.
Gross pathology:
Bilateral dilation was seen in the cerebrum of male no. 4. There were no other macroscopical findings at the scheduled necropsy.

Any other information on results incl. tables

Table 1: Exposure conditions

Group Achieved concentrations (mg/L air) MMAD (µm) and GSD
nominal analytical gravimetric
1 8.13 5.03 ± 0.10   n = 4 5.04 ± 0.04              n = 4

3.58 MMAD

3.23 GSD

The nominal concentration was fairly high compared to the analytical and gravimetric concentrations due to accumulation of some of the test material in the exposure system. It was also noted that the particle size of the generated aerosol was greater than the target, indicating that a proportion of the larger particles would have deposited in the upper respiratory tract. The equivalent atmosphere concentration of the particles with an effective cut-off diameter of less than 3 µm was 2.26 mg/L which corresponded to 44.97% of the total particle mass. The particle size distribution obtained was, however, considered to be appropriate for acute inhalation toxicity testing.

Table 2: Bodyweights (g)

Group / Sex Animal Day 1 Day 4 Day 8 Day 15
Group 1 / Males 1 224.7 235.9 250.9 288.4
2 221.2 238.3 253.3 308.4
3 219.9 231.5 246.3 283.3
4 226.1 236.4 247.3 282.4
5 211.8 225.6 236.0 261.0
Mean  220.7 233.6 246.8 285.1
SD 5.6 5.1 6.7 16.9
Group 1 / Females 6 204.9 211.1 212.7 226.5
7 212.2 212.5 213.5 220.9
8 215.3 209.2 211.7 224.9
9 201.4 200.7 198.8 214.2
10 197.2 212.2 210.5 231.2
Mean  206.2 209.1 209.5 223.5
SD 7.5 4.9 6.0 6.4

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Under the conditions of the study, the acute nose-only inhalation LC50 of the test material in rats was determined to be greater than 5.03 mg/L in air and is therefore not classified under Directive 67/548/EEC or under Regulation 1272/2008. The study is considered to be reliable, relevant and adequate for risk assessment and classification and labelling purposes.
Executive summary:

The acute inhalation toxicity of the test material was determined in accordance with standardised guidelines OECD 403, EU Method B.2 and EPA OTS 798.1150. During the study, groups of five male and five female rats were exposed by nose only, flow-past inhalation to the test material at a mean concentration of 5.03 mg/L air. All animals were observed for clinical signs and mortality during exposure and over the course of the 14 day post treatment observation period. On study day 15, all animals underwent necropsy and all gross macroscopical changes were recorded.

During the exposure period, the ranges of temperature, humidity, oxygen content, particle size and airflow were found to be satisfactory. Under the conditions of the study, no animals died. Clinical observations were confined to salivation during the later half of exposure in addition to deep respiration in one animals. Following exposure, restless behaviour was seen in all animals until test day 5 (i.e. 4 days after exposure); ruffled fur in all animals until test day 2, and in six animals until test day 3; and hunched posture in all animals until test day 2. As from test day 6, until termination of the study, all animals were free from clinical signs.

After a minimal retardation in bodyweight gain in males and a slight retardation in females during the first week following the exposure, all male and female animals gained weight normal until scheduled necropsy. The only macroscopical finding was bilateral dilation in the cerebrum of male no 4. This may have been incidental since this finding occasionally occurs in untreated control rats.

In consideration of the presented results, the LC50 of the test material was estimated to be greater than 5.03 mg/L air.