Registration Dossier

Administrative data

acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
February 2005-May 2005
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline Study Under GLP

Data source

Reference Type:
study report
Report Date:

Materials and methods

Test guidelineopen allclose all
according to
OECD Guideline 403 (Acute Inhalation Toxicity)
according to
EPA OPPTS 870.1300 (Acute inhalation toxicity)
GLP compliance:
yes (incl. certificate)
Test type:
acute toxic class method
Limit test:

Test material

Test material form:
solid: particulate/powder
migrated information: powder
Details on test material:
Test Substance Identification: Cetylpyridinium Chloride
Lot#: 00217966
Test Substance Description: White powder
Purity: 100.1% by assay
Date received: January 12, 2005
PSL Reference No: 050112-ID
Study Initiation Date: January 12, 2005

Test animals

Details on test animals and environmental conditions:
Housing: The animals were singly housed in suspended stainless steel caging with mesh floors. Litter paper was placed beneath the cage and was changed at least three times per week.
Animal Room Temperature Range: 20-23 Degrees C.
Photoperiod: 12-hour light/dark cycle
Acclimation Period: 21-28 Days
Food: Purina Rodent Chow #5002
Water: Tap water was supplied ad-libitum by an automatic water dispensing system except during exposure.
Contaminants: There were no known contaminants reasonably expected to be found in the food or water at levels which would have interfered with the results of this study.

Administration / exposure

Route of administration:
inhalation: dust
Type of inhalation exposure:
nose only
Details on inhalation exposure:
Nose-Only Exposure Chamber: A nose-only inhalation chamber with an internal volume of approximately 6.7 liters (Mini-Nose Only Inhalation Chamber, ADG Developments LTD) was used for exposure. Animals were individually housed inpolycarbonate holding tubes which seal to the chamber with an "O" ring during exposure. The base unit tenninates the chamber with a 0.5-inch diameter tube for discharged air

Air Supply: Filtered air was supplied by an air compressor (JUN-AIR, Model #6-15) to the dust generator and was measured using a Mass Flowmeter (Omega, Model #FMA 5613). Additional compressed mixing air, supplied using dry filtered air from a compressed air tank (WELCO) was introduced into the chamber to help uniformly distribute the test atmosphere by creating a vortex at the chamber inlet and was measured with a Mass Flowmeter (Omega, Model #FMA 5613). Chamber airflow was monitored throughout the exposure period and recorded periodically.

Ambient Conditions: The temperature and relative humidity within the chamber as well as the room were monitored continuously during each exposure. In-chamber measurements were made with a Humidity-Temperature Indicator (Taylor, Model #5502) and room conditions were measured with a Temperature-Humidity Monitor (Dickson, Model #TH550). Temperature and humidity values were recorded every 15 minutes for the first hour of exposure and every 30 minutes thereafter.

Test Substance Preparation: The test substance was processed in a 1.6-gallon urethane­ lined millingjar (Abbethane, Paul O'Abbe) with porcelain grinding media (0.5'' balls) for 24 hours. After milling, the test substance was sieved through a 3/8 inch polyethylene sieve to separate it from the grinding media and any other large particles that remained. The test substance was then further ground in a coffee mill (Krups, Model 203) and passed through a 600-micron USA standard testing sieve.

Dust Generation: The test substance was aerosolized using a modified Wright Dust Generator driven by a variable speed motor (Dayton, Model 4Z538A). The test substance was packed into the dust container (Wright, Model DF 183 [0.51 mg/L] or Model DF 183A SS [0.054 mg/L]) and compressed to 1,000 lbs/in2 using a lab press (Cmver, Model C). The container was then fitted with a stainless steel cutting head (Model DF 194SS [0.54 mg/L] or Model DF193SS [0.054 mg/L]) and cutting blade (Model DF 191SS [0.51 mg/L] or Model DF 190SS [0.054 mg/L]). Compressed air was supplied to the dust generator at 30 psi. The aerosolized dust was then fed directly into the chamber through the dust outlet assembly.

Chamber Concentration Measurements: Gravimetric samples were withdrawn at 5 (0.054 mg/L) or 6 (0.51 mg/L) intervals from the breathing zone of the animals during each exposure. Samples were collected using 25 mm glass fiber filters (GF/B Whatman) in a filter holder attached by Y,.inch tygon tubing to avacuum pump (Reliance Electric, Model #G557X). 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 Flowmeter (Omega, Model #FMA 5610).

Particle Size Distribution: An eight-stage Andersen cascade impactor was used to assess the particle size distribution of the test atmosphere. Samples were withdrawn from the breathing zone of the animals at two intervals during each exposure. The filter paper collection stages were weighed before and after sampling to determine the mass collected upon each stage. The aerodynamic mass median diameter and geometric standard deviation were determined graphically using two-cycle logarithmic probit axes.

Exposure Period: For each exposure level, the animals were exposed to the targeted chamber concentration for at least 4 hours. At each level, the exposure period was extended beyond 4 hours to allow the chamber to reach equilibrium (T99). At the end of each exposure period, the generation was terminated and the chamber was operated for 15 minutes with clean air. At the end of this period, the animals were removed from the chamber. Prior to being returned to their cages, excess test substance was removed from the fur of each animal.

Analytical verification of test atmosphere concentrations:
0.054 mg/L
Duration of exposure:
4 h
0.05 and 0.5 mg/L
No. of animals per sex per dose:
5 males and 5 females 0.5 mg/L
5 males and 5 females 0.05 mg/L
Gravimetric and nominal chamber concentrations at 0.054 and 0.51 mg/L respectively.
Control animals:
Details on study design:
The procedures and aerosolization equipment used for each exposure were based on the results of pretest data. In each instance, the conditions of generation were modified to achieve the targeted chamber concentration with a desirable particle size distribution.

Results and discussion

Effect levels
Dose descriptor:
Effect level:
>= 0.054 - <= 0.51 mg/L air (analytical)
Based on:
test mat.
Exp. duration:
4 h
9 of 10 animals died at 0.51 mg/L. There was no mortality at the 0.054 mg/L exposure level. All animals (5 females, 5 males) survived the exposure to the test atmosphere and gained body weight

0.51 mg/L Exposure Level
All five males and four females died within three days of exposure to the test atmosphere.
Clinical signs:
Clinical signs at the 0.054 mg/L exposure Level, for four animals, included reduced fecal volume and hypoactivity. The affected animals recovered by Day 3, and along with the other animals, appeared active and healthy for the remainder of the 14-day observation period.

0.51 mg/L Exposure Level
All five males and four females died within the three days of exposure to the test atmosphere. Toxic signs noted prior to death included abnormal respiration, abnormal posture, and hypoactivity. The surviving female exhibited similar clinical signs as well as reduced fecal volume. However, the animal recovered by Day 7 and appeared active and healthy for the remainder of the study.
Body weight:
Males: 303-368 Grams
Females: 200-250 Grams
Gross pathology:
At the 0.054 mg/L exposure level, no gross abnomalities were noted for the animals when necropsied at the conclusion of the 14-day observation period.
At the 0.51 mg/L exposure level, a gross necropsy of the decedants revealed discoloration and edema of the lungs and mucous-filled tracheas. No gross abnormalities were noted for the euthanized animal when necropsied at the conclusion of the 14-day observation period.

Any other information on results incl. tables

For the 0.054 exposure level, the gravimetric and nominal chamber concentrations were 0.054 and 0.14 mg/L, respectively. The mass median aerodynamic diameter was estimated to be 2.8 μm based on the particle size distribution as measured with an Andersen Cascade Impactor.
For the 0.51 mg/l exposure level, the gravimetric and nominal chamber concentrations were 0.51 and 1.24 mg/L, respectively. The mass median aerodynamic diameter was estimated to be 2.9 μm based on the particle size distribution as measured with an Andersen Cascade Impactor.

TargetConcentration (m2/L)



TrialChamberConcentration (mg/L)











Applicant's summary and conclusion

Interpretation of results:
other: LC50 between 0.054 and 0.51 mg/L
Criteria used for interpretation of results: EU
The inhalation LC50 of Cetylpyridinium Chloride is between 0.054 and 0.51 mg/L in male and female rats.