Benzoic acid, 2-[4-(diethylamino)-2-hydroxybenzoyl]-, hexyl ester

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:

2017

Report date:

2017

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

GLP compliance:

yes (incl. QA statement)

Remarks:

Product Safety Labs; 2394 US Highway 130; Dayton, NJ 08810; USA

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

443-860-6

EC Name:

-

Cas Number:

302776-68-7

Molecular formula:

C24 H31 N O4

IUPAC Name:

hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate

Test animals

Species:

rat

Strain:

Wistar

Remarks:

Charles River Wistar Hannover, albino (SPF).

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Received from Charles River Laboratories, Raleigh, NC on May 11, 2017.
- Age at study initiation: Young adult (9 weeks)
- Weight at study initiation: 252-267 g (males) and 190-202 g (females) at experimental start. The weight variation of animals was within 20% of the mean weight for each sex.
- Housing: group housed
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19-23
- Humidity (%): 42-69
- Air changes (per hr): 13
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: To:

Administration / exposure

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose only

Vehicle:

air

Mass median aerodynamic diameter (MMAD):

2.52 µm

Geometric standard deviation (GSD):

2.34

Details on inhalation exposure:

Nose-Only Exposure Chamber:
Animals were individually housed in polycarbonate holding tubes which seal to the chamber with an “O” ring during exposure. The base unit terminates the chamber with a 0.5-inch diameter tube for discharged air.

Air Supply:
Filtered generator air was supplied to the spray atomization nozzle by an air compressor, and measured with a Mass Flow Controller. Additional filtered mixing air from the same air compressor, measured with a Mass Flow Controller, was introduced into the chamber to help uniformly distribute the test atmosphere by creating a vortex at the chamber inlet. Chamber airflow was monitored throughout the exposure period and recorded periodically. The exposure was conducted under slight negative pressure.

Ambient Conditions:
Temperature and relative humidity values were recorded every 15 minutes for the first hour of exposure and approximately every 15 or 30 minutes thereafter.

Atmosphere Generation:
The test substance was aerosolized using a Jet-Mill. The test substance was delivered from the hopper using a variable speed motor and a 3/8-inch, closed pitch helix into the Jet-Mill. Compressed generator and mixing air were both supplied. The aerosolized dust was then fed directly into the chamber through the dust outlet assembly.

Chamber Concentration Measurements:
Gravimetric samples were withdrawn at 6 intervals from the breathing zone of the animals. Samples were collected using 37 mm glass fiber filters in a filter holder attached by ¼ inch Tygon® tubing to a vacuum pump. Filter papers were weighed before and after collection to determine the mass collected. This value was divided by the total volume of air sampled to determine the chamber concentration. Sample airflows were measured using a Mass Flow Controller.

Particle Size Distribution:
An eight-stage 1 ACFM Andersen Ambient Particle Sizing Sampler was used to assess the particle size distribution of the test atmosphere. Samples were withdrawn from the breathing zone of the animals at three intervals. The filter paper collection stages were weighed before and after sampling to determine the mass collected upon each stage. The mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) were calculated using two-cycle logarithmic probit axes.

Exposure Period:
The animals were exposed to the targeted chamber concentration for at least 4 hours. The exposure period was extended beyond 4 hours to allow the chamber to reach equilibrium (T99). At the end of the exposure period, the generation was terminated and the chamber was operated for at least 15 minutes further with clean air to allow the test atmosphere to fully dissipate. At the end of this period the animals were removed from the exposure tubes. Prior to being returned to their cages, excess test substance was removed from the fur of each animal by rinsing with tap water and wiping with clean paper towels.


Exposure condition values:
Compressed Generator Air (Lpm): 60.0
Compressed Mixing Air (Lpm): 10.0
Total Air (Lpm)*: 70.0
Compressed Generator/Mixing Air (psi): 50/10
Time for 90% equilibration of the chamber atmosphere - T90 (min): 2.05
Time for 99% equilibration of the chamber atmosphere - T99 (min): 4.09
Exposure Chamber Temp. Range (ºC): 20-23
Exposure Chamber Relative Humidity Range (%): 60-65
Ambient Room Temp. Range (ºC): 21-22
Ambient Room Relative Humidity Range (%): 57-60
Total Time of Exposure (min): 245
Number of Air Changes Per Hour: 67

*Total air = compressed generator air + compressed mixing air

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Remarks on duration:

Total Time of Exposure (min): 245

Concentrations:

5.22 mg/L

No. of animals per sex per dose:

5

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of weighing: Individual body weights of the animals were recorded prior to test substance exposure (initial) and again on Days 1, 3, 7, and 14 (terminal).
- Frequency of observations: All animals were observed for mortality during the exposure period. The animals were examined for signs of gross toxicity, and behavioral changes upon removal from the exposure tube and at least once daily thereafter for 14 days. Observations included gross evaluation of skin and fur, eyes and mucous membranes, respiratory, circulatory, autonomic and central nervous systems, somatomotor activity and behavior pattern. Particular attention was directed to observation of tremors, convulsions, salivation, diarrhea, and coma.
- Necropsy of survivors performed: yes
All rats were euthanized via CO2 inhalation at the end of the 14-day observation period. Gross necropsies were performed on all animals. Tissues and organs of the thoracic and abdominal cavities were examined.

Statistics:

Statistical analysis was limited to the calculation of the mean and standard deviation.

Results and discussion

Preliminary study:

Pre-Test Trials
Prior to initiation of the full inhalation study, pre-test trials were conducted to establish generation procedures to achieve, to the extent possible, the desired chamber concentration (5.0 mg/L) and desired particle size distribution (mass median aerodynamic diameter between 1 and 4 μm). In these trials, the following adjustments were made in an attempt to achieve these objectives:
- Air Pressure: constant
- Compressed Generator Airflow: constant
- Compressed Mixing Airflow: constant
- Total Airflow: constant
- Motor Setting: varied
- Dust Generating System: constant
- Helix Size: constant
- Material Preparation: constant
- Vacuum Pump: constant
- Concentration Sampling Time: constant
The procedures and aerosolization equipment used in the full test were based on the results of pre-test trial number 4 which provided a gravimetric chamber concentration of 5.25 mg/L and a mass median aerodynamic diameter of 2.48 μm.

Effect levels

Sex:

male/female

Dose descriptor:

LC0

Effect level:

5.22 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Mortality:

All animals survived exposure to the test atmosphere.

Clinical signs:

other: Following exposure, all rats exhibited irregular respiration. However, all animals recovered by Day 2 and appeared active and healthy for the remainder of the 14-day observation period.

Body weight:

All animals gained body weight during the study.

Gross pathology:

No gross abnormalities were noted for any of the animals when necropsied at the end of the 14-day observation period.