2-aminoethanol hydrobromide

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 436 (Acute Inhalation Toxicity: Acute Toxic Class Method)

Deviations:

yes

Remarks:

These deviations were considered to have not affected the integrity or validity of the study.

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.52 (Acute Inhalation Toxicity - Acute Toxic Class Method)

Deviations:

yes

Remarks:

These deviations were considered to have not affected the integrity or validity of the study.

GLP compliance:

yes (incl. QA statement)

Test type:

acute toxic class method

Limit test:

no

Test material

Reference

Name:

Unnamed

Type:

Constituent

Test animals

Species:

rat

Strain:

other: RccHan™ : WIST

Sex:

male/female

Details on test animals or test system and environmental conditions:

Male and female RccHan™ : WIST strain rats have an acclimatization period of at least 5 days. At the start of the study the animals were approximately 8 to 12 weeks old and within the weight range of 200 g to 350 g. The females were nulliparous and non-pregnant.
The animals were housed in groups of up to three by sex in solid-floor polypropylene cages with stainless steel lids, furnished with softwood flakes. With the exception of the exposure period, free access to mains drinking water and food was allowed throughout the study. The temperature and relative humidity were set to achieve limits of 19 to 25°C and 30 to 70% respectively. The rate of air exchange was at least fifteen changes per hour and the lighting was controlled by a time switch to give 12 hours continuous light and 12 hours darkness. The animals were retained in this accommodation at all times except during the exposure period.

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

other: Formulations were prepared with sterile water (2-aminoethanol hydrobromide: water, 60:40 w/w) to improve the aerosolisation properties of the test item.

Mass median aerodynamic diameter (MMAD):

ca. 2.54 µm

Geometric standard deviation (GSD):

ca. 2.59

Details on inhalation exposure:

Atmosphere generation:
The test item formulation was aerosolized using a metal concentric jet nebulizer located at the top of the exposure chamber. The nebulizer was connected to a plastic syringe attached to an infusion pump, which provided a continuous supply of test item formulation under pressure, and to a metered compressed air supply. Compressed air was supplied by means of an oil free compressor and passed through a water trap and respiratory quality filters before it was introduced to the nebulizer.
The cylindrical exposure chamber had a volume of approximately 30 liters (dimensions: 28 cm diameter x 50 cm high). The concentration within the chamber was controlled by adjusting rate of the infusion pump.
The extract from the exposure chamber passed through a ‘scrubber’ trap and was connected with a high efficiency filter to a metered exhaust system. The chamber was maintained under negative pressure.
Homogeneity of the test atmosphere within the chamber was not specifically determined during this study. Chambers of the same design have been fully validated and shown to produce evenly distributed atmospheres in the animals’ breathing zone with a wide variety of test items. Prior to the start of the study, test item atmospheres were generated within the exposure chamber. During this characterization period test item input rates, air flow settings, generation methods and formulation details were varied in an attempt to achieve the required atmospheric conditions.

Sighting exposure:
During the characterization phase of the study, a group of two rats (one male and one female) were exposed to an atmosphere of the test item at a target concentration of 5.0 mg/L for four hours.

Exposure Procedure:
During the exposure period, each rat was individually held in a tapered, polycarbonate restraining tube fitted onto a single tier of the exposure chamber and sealed by means of a rubber ‘O’ ring. Only the nose of each animal was exposed to the test atmosphere. Following an appropriate equilibration period a group of six rats (three males and three females), was exposed to an atmosphere formulation of the test item (2-aminoethanol hydrobromide: water, 60:40 w/w) for a period of 4 hours. Based on the results of the sighting test, a target concentration of 1 mg/L was used for the exposure. As the mean achieved concentration was 128 % of target and no deaths occurred, it was considered that no further levels were required as the results of the sighting study showed that a significant number of deaths would be likely at a concentration of 5 mg/L.

Exposure Chamber Temperature and Relative Humidity:
The temperature and relative humidity inside the exposure chamber were measured by an electronic thermometer/humidity meter located in a vacant port in the animals’ breathing zone of the chamber and recorded every 30 minutes throughout the 4-Hour exposure period.

Exposure Chamber Oxygen Concentration:
Oxygen levels within the exposure chamber were measured by an electronic oxygen analyzer located in a port in the animals breathing zone during the 4 Hour exposure period. The test atmosphere was generated to contain at least 19% oxygen.

Exposure Chamber Atmosphere Concentration:
As the test item in its original state was a solid it was considered that the non-volatile component of the batch used during the formal exposure was 100 %. The test atmosphere was sampled at regular intervals during the exposure period. A weighed glass fiber filter was placed in a filter holder and temporarily sealed in a vacant port of the exposure chamber in the animals’ breathing zone. A known quantity of the exposure chamber atmosphere was drawn through the filter using a vacuum pump.
After sampling, the filter was dried in a desiccator at room temperature for approximately 24 hours and then weighed again. The difference in the pre and post sampling weights, divided by the volume of atmosphere sampled, was the chamber concentration in terms of non-volatile component. Additional sterile water added to improve aerosolization was considered not to affect the gravimetric calculation as all of the filters were dried thoroughly (for 24 hours) prior to weighing.
Based on the consideration that the test item was 100 % non-volatile, these figures were adjusted to obtain a true figure for the test item concentration in the chamber.
The nominal chamber concentration was calculated by dividing the mass of test item disseminated into the chamber by the total volume of air that flowed through the chamber during the exposure.
The nominal concentration was 352% of the actual mean achieved atmosphere concentration and shows that keeping the aerosol airborne was relatively straightforward when the test item was formulated in water.

Analytical verification of test atmosphere concentrations:

no

Remarks:

Due to the short-term nature of the study, no analysis was carried out to determine the homogeneity, concentration or stability of the test item formulation. This exception is considered not to affect the integrity or validity of the study.

Duration of exposure:

ca. 4 h

Concentrations:

5 mg/L in the sighting study (mean achieved atmosphere concentration: 5.06 mg/L)
1 mg/L in the main test (mean achieved atmosphere concentration: 1.28 mg/L)

No. of animals per sex per dose:

3 rats/sex

Control animals:

no

Details on study design:

Clinical Signs:
All animals were observed for clinical signs at hourly intervals during exposure, immediately on removal from the restraining tubes at the end of exposure, 1 hour after termination of exposure and subsequently once daily for 14 days. Any evidence of overt toxicity was recorded at each observation.

Body Weight:
Individual body weights were recorded on arrival, prior to treatment on the day of exposure (Day 0) and on Days 1, 3, 7 and 14.

Necropsy:
At the end of the 14 observation period all animals were killed by intravenous overdose of sodium pentobarbitone. All animals were subjected to a full external and internal examination and any macroscopic abnormalities were recorded. The respiratory tract was subjected to a detailed macroscopic examination for signs of irritancy or local toxicity.

Data Evaluation:
Data evaluations included the relationship, if any, between the animals’ exposure to the test item and the incidence and severity of all abnormalities including behavioral and clinical observations, necropsy findings, body weight changes, mortality and any other toxicological effects. Using the mortality data obtained, an estimate of the acute inhalation median lethal concentration (LC50) of the test item was made.

Results and discussion

Preliminary study:

Sighting:
During exposure both animals exhibited decreased respiratory rate and wet fur and areas of red/brown staining around the eyes was noted in the male. Both animals were found dead after 3 hours exposure.
As both animals died during exposure no significant body weight data was obtained. The following macroscopic abnormalities were detected at necropsy:
-Lungs – Pale, dark patches.
-Stomach – gaseous distension.

Effect levels

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 1 - <= 5 mg/L air

Based on:

test mat.

Exp. duration:

4 h

Mortality:

There were no deaths noted among the 6 animals treated (3 females and 3 males).

Clinical signs:

other: Signs of hunched posture and pilo-erection are commonly seen in animals for short periods on removal from the chamber following 4-hour inhalation studies. Wet fur and fur stained by the test item are commonly recorded both during and for a short period af

Body weight:

With the exception of one female that showed body weight loss on Day 1 post-exposure, and one female that showed body weight loss from Day 3 to Day 7, all animals showed expected gains in body weight during the recovery period.

Gross pathology:

The following macroscopic abnormalities were detected at necropsy:
-Lungs – Abnormally red, dark patches.
No abnormalities were noted in one male and one female at necropsy.

Applicant's summary and conclusion

Interpretation of results:

Category 4 based on GHS criteria

Conclusions:

None of the animals died in a group of six rats exposed to mean achieved atmosphere concentration of 1.28 mg/L, however as both animals died during the sighting test at a mean achieved atmosphere concentration of 5.06 mg/L, it was considered that proceeding to the next higher concentration (5 mg/L) would result in the deaths of a large number of test animals and would not result in a change of classification. It was therefore considered appropriate to halt the study after one exposure and conclude that the acute inhalation median lethal concentration (4 hour LC50) of the test item in the Wistar strain rat was >1 to 5 mg/L.