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Diss Factsheets

Toxicological information

Acute Toxicity: inhalation

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Administrative data

acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to guideline
OECD Guideline 403 (Acute Inhalation Toxicity)
GLP compliance:
yes (incl. QA statement)
Test type:
standard acute method
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Specific details on test material used for the study:
- Lot/batch No.of test material: 001175MCAO

- Storage condition of test material: at room temperature; avoid temperatures > 40°C

Test animals

Details on test animals or test system and environmental conditions:
- Source: Harlan Netherlands, Horst
- Age at study initiation: Young adult males and females (about 8 - 12 weeks)
- Weight at study initiation: Animals of comparable weight (180 - 300 g) (± 20% of the mean weight)
- Housing: up to 5 animals per cage
- Diet: Kliba-Labordiät (Maus/Ratte Haltung "GLP"), Provimi Kliba SA, Kaiseraugst, Basel, Switzerland, ad libitum
- Water: Tap water ad Iibitum
- Acclimation period: Acclimatization period at least 5 days before the beginning of the experimental phase; during the acclimatization period, the
animals are accustomed to the environmental conditions of the study and to the diet.

- Temperature (°C): 20 - 24
- Humidity (%): 30 - 70
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12 / 12

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
nose/head only
Analytical verification of test atmosphere concentrations:
gravimetric measurements
Duration of exposure:
4 h
0.25, 0.5 and 1 mg/L (target concentrations)
0.257, 0.485 and 1.068 mg/L (analytical concentrations)
No. of animals per sex per dose:
Control animals:
other: control animals for examination of local effect of the test item in satellite group
Details on study design:
- Duration of observation period following administration: 14 days for main groups, 1 day for satellite group including control group
- Frequency of observations and weighing: A check for moribund and dead animals was made twice each workday and once daily at weekends and on public holidays. Detailed clinical observations were recorded for each animal separately several times during exposure and at least once daily on the pre-exposure day and during the observation period. Individual body weight was determined once during the acclimatization period, at the start of exposure period (day 0) and on days 1, 3 and 7, and weekly thereafter or before the sacrifice of the animals at the end of the observation period. The body weights of1 animals that died or were sacrificed in a moribund state were determined as they were discovered from study day 1 onward.
- Necropsy of survivors performed: yes
- Other examinations performed: concentration of monoethanol amine (MEA) and formaldehyde (FA) in the test atmosphere; organ weight of lung and histological examination of respiratory tract in satellite group animals
- Satellite group: To examine the local effect of the test item, a satellite group of 5 male animals was exposed to the test substance together with the animals of the first exposure group (target concentration 1 mg/L). These animals were sacrificed on study day 1 and subjected to histological examination. Two male animals were exposed to air and were sacrificed with the satellite group animals. They served as control for the histological examinations.
The LC50 was calculated by Probit analysis (FINNEY, D.J. (1971): "Probit Analysis" Cambridge University Press) by means of a computer program. The calculation of the particle size distribution was carried out in the inhalation laboratory on the basis of mathematical methods for evaluating particle measurements (DIN 66141: Darstellung von Korngrößenverteilungen, DIN 66161: Partikelgrößenanalyse (Beuth-Vertrieb GmbH, Berlin 30, FRG und Köln 1, FRG)).

Results and discussion

Effect levelsopen allclose all
Key result
Dose descriptor:
Effect level:
0.371 mg/L air (analytical)
Based on:
test mat.
95% CL:
0.229 - 0.529
Exp. duration:
4 h
Dose descriptor:
Effect level:
0.4 mg/L air (analytical)
Based on:
test mat.
95% CL:
0.167 - 0.943
Exp. duration:
4 h
Dose descriptor:
Effect level:
0.338 mg/L air (analytical)
Based on:
test mat.
Exp. duration:
4 h
Two of the five female animals and one of the five male animals died at 0.257 mg/L. Three of the five female animals and three of the five male animals died at 0.485 mg/L. At 1.068 mg/L all of the male and female animals died or were sacrificed in a moribund state. Lethality was observed either during exposure or shortly after exposure (day 0 to 2).
Clinical signs:
other: Clinical signs of toxicity in animals exposed to 0.257 mg/L comprised accelerated respiration, labored respiration, abdominal respiration, gasping, respiration sounds, colorless discharge of the nose, red encrusted nose, distended abdomen, piloerection, y
Body weight:
Test group 1 (0.257 mg/L): The mean body weights of the surviving animals decreased during the first post exposure observation week but increased during the second week.
Test group 2 (0.485 mg/L): The mean body weights of the surviving animals decreased during the first post exposure observation week but increased during the second week.
Test group 3 (1.068 mg/L): The mean body weights of the surviving animals decreased until the death of the animals.
Gross pathology:
Test group 1 (0.257 mg/L): No gross pathological abnormalities were detected in the female animal that died on study day 0. In the two animals that died on study day 2 (1 male + 1 female), dilation with gaseous content of the stomach and small intestine were found. No gross pathological abnormalities were detected during necropsy in the surviving animals at the termination of the post exposure observation period.
Test group 2 (0.485 mg/L): Gross pathological abnormalities were noted neither in animals died on day 0/day 1, nor in surviving animals at the termination of the post exposure observation period.
Test group 3 (1.068 mg/L): During gross necropsy dilation with gaseous content of the stomach and/or small intestine were observed in individual animals. In other animals no gross pathological abnormalities were noted.
Other findings:
Concentration measurements: The following measured concentrations were tested: 0.257, 0.485 and 1.068 mg/L (analytical concentration). Identity of the test substance was confirmed by off-line infra-red spectroscopy. Moreover, very small fractions of formaldehyde (mean concentrations 0.48 to 0.73 ppm) were detected in the test atmospheres. The mean concentration of monoethanol amine in the test atmospheres was around 0.6 mg/m³, corresponding to 0.0006 mg/L air.
Particle size analysis: Cascade impactor measurements resulted in particle size distributions with mass median aerodynamic diameters (MMADs) between 1.6 and 1.9 μm, which are well within the respirable range.

Satellite animals and its concurrent controls were designated for examination of the respiratory tract by light microscopy on study day 1. Due to the high toxicity however, some of these animals were found dead on study day 1, others were sacrificed in moribund state. Nevertheless, histopathological examination of the respiratory tract revealed up to severe findings in the upper and lower part. Especially the upper part of the respiratory tract (nasal cavity and larynx) was severely affected. The findings were characterized by multifocal to coalescing up to diffuse necrosis of the different epithelia in the nasal cavity, with accompanying inflammation in the moribund sacrificed animals. Also the laryngeal epithelium showed a diffuse necrosis in all levels in the treated animals with inflammation in the surrounding tissue in some animals. The trachea and the lung revealed also slight to minimal treatment-related findings (hemorrhage, edema, emphysema, necrosis) in some animals. In addition, the respiratory tract of one representative female animal was also examined by light microscopy. Similar lesions as those in male animals were observed.

Applicant's summary and conclusion

Interpretation of results:
Category 2 based on GHS criteria
HHT caused concentration-related severe clinical symptoms and mortality after 4-hour head/nose aerosol exposure. Histopathology performed at the high concentration revealed severe lesion at the entire respiratory tract. The death of several test animals is probably a direct consequence of severe diffuse necrosis of laryngeal and nasal epithelium. Under the conditions of this study the LC50 for male and female rats after liquid aerosol
inhalation exposure of HHT was determined to be 0.371 mg/L (analytical concentration).