Avermectin A1a, 25-cyclohexyl-5-O-demethyl-25-de(1-methylpropyl)-

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From Feb 22 to Apr 05, 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test type:

acute toxic class method

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

(1'R,2S,4'S,5S,6R,8'R,10'E,12'S,13'S,14'E,16'E,20'R,21'R,24'S)-6-cyclohexyl-21',24'-dihydroxy-12'-{[(2R,4S,5S,6S)-5-{[(2S,4S,5S,6S)-5-hydroxy-4-methoxy-6-methyloxan-2-yl]oxy}-4-methoxy-6-methyloxan-2-yl]oxy}-5,11',13',22'-tetramethyl-5,6-dihydro-3',7',19'-trioxaspiro[pyran-2,6'-tetracyclo[15.6.1.1⁴,⁸.0²⁰,²⁴]pentacosane]-10',14',16',22'-tetraen-2'-one

EC Number:

601-490-4

Cas Number:

117704-25-3

Molecular formula:

C50H74O14

IUPAC Name:

(1'R,2S,4'S,5S,6R,8'R,10'E,12'S,13'S,14'E,16'E,20'R,21'R,24'S)-6-cyclohexyl-21',24'-dihydroxy-12'-{[(2R,4S,5S,6S)-5-{[(2S,4S,5S,6S)-5-hydroxy-4-methoxy-6-methyloxan-2-yl]oxy}-4-methoxy-6-methyloxan-2-yl]oxy}-5,11',13',22'-tetramethyl-5,6-dihydro-3',7',19'-trioxaspiro[pyran-2,6'-tetracyclo[15.6.1.1⁴,⁸.0²⁰,²⁴]pentacosane]-10',14',16',22'-tetraen-2'-one

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

Details on test material:

Batch No.: 20418-3-1
Purity: 99.9%

Specific details on test material used for the study:

Lot no. DOA1401027
Purity: 97.4%

Test animals

Species:

rat

Strain:

Sprague-Dawley

Remarks:

Crl:CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Rationale for alternative/additional species to rat (if applicable)
- Source: Charles River Laboratories (Raleigh, NC)
- Females (if applicable) nulliparous and non-pregnant: [yes/no]
- Rationale for use of males (if applicable)
- Age at study initiation: 8 to 9 weeks old
- Weight at study initiation: 241 g to 325 g for males and from 194 g to 240 g for females
- Fasting period before study: yes
- Housing: all animals were housed individually in suspended wire-mesh cages.
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: a minimum of 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22°C ± 3°C
- Humidity (%): 50% ± 20% relative humidity
- Air changes (per hr): 10 fresh air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours light/12 hours dark

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

air

Mass median aerodynamic diameter (MMAD):

1.8 - 2.2 µm

Geometric standard deviation (GSD):

2.89 - 4.91

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 7.9-L stainless steel conventional nose-only exposure system
with rubber grommets in exposure ports to engage the animal holding tubes.
- Method of holding animals in test chamber: Animals were restrained in nose-only exposure holding tubes during exposure.
- Source and rate of air (airflow): Airflow to the exposure system was provided using a dry, breathing quality, in-house, compressed air source.
- System of generating particulates/aerosols: The test substance was delivered using an auger-type feeder which fed test substance at a constant rate to a jet mill air micronizer operating as a particle size reduction and dispersion device. The Accurate feeder was equipped with a 1/2-inch solid core auger. Using a regulator, dry, compressed air was supplied to the micronizing and inlet ports of the jet mill. The resulting aerosol from the jet mill was delivered to the nose-only exposure system through 22-mm corrugated respiratory tubing. A “T” fitting was placed in-line prior to the nose-only exposure system to provide humidified dilution air in an attempt to achieve the protocol-specified humidity range and further dilute the atmosphere as necessary.
- Method of particle size determination: Three aerosol particle size measurements were conducted during each exposure using a 7-stage stainless-steel cascade impactor. Pre-weighed,
stainless steel discs coated with a toluene and Apiezion grease solution were used as the collection substrates. A pre-weighed, 25-mm glass-fiber filter was used as the collection substrate for the final stage. Samples were collected at approximately 2 L/minute for 4, 1, and 0.5 minutes for the 0.083, 0.70, and 4.5 mg/L groups, respectively. The filters were re-weighed and the particle size was calculated based on the impactor stage cut-offs. The aerosol size was expressed as the MMAD and the GSD.
- Temperature, humidity, pressure in air chamber: Exposure atmosphere environmental conditions were recorded at approximately 60-minute intervals during the exposure. A temperature and relative humidity transmitter probe was used with a display unit to monitor temperature and percent relative humidity within the exposure system.

TEST ATMOSPHERE
- Brief description of analytical method and equipment used: Actual exposure concentrations were determined every 5 to 42 minutes using standard gravimetric methods.
- Samples taken from breathing zone: yes, Samples were collected on pre-weighed, 25-mm glass-fiber filters held in an open-faced filter holder positioned in the animal exposure port (i.e., in the breathing zone of the animal) of the nose-only exposure system. A measured volume of the exposure atmosphere was pulled through the filter to quantitatively collect aerosol particles. Following sample collection, the filters were re-weighed and the concentration calculated as the filter weight difference divided by the sample volume.
Samples were collected at approximately 0.8 to 1.7 L/minute for 3, 3, and 1 minute(s) for the 0.083, 0.70, and 4.5 mg/L groups, respectively.

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

Nominal concentrations: 5, 0.6, 0.1 mg/L; Actual concentrations: 4.5, 0.7, 0.083 mg/L

No. of animals per sex per dose:

5 males and 5 females

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing:
Each animal was observed for mortality at the approximate midpoint of exposure and twice daily thereafter for 14 days (once in the morning and once in the afternoon, except on the day of scheduled necropsy).
Each animal was observed immediately following exposure on study day 0, once approximately
1 to 2 hours following exposure, and once daily thereafter for 14 days for clinical signs of toxicity. Observations were recorded at approximately the same time each day and included, but were not limited to: changes in the skin and fur, eyes and mucous membranes, and also changes to the respiratory, circulatory, autonomic and central nervous systems, somatomotor activity, and behavior pattern.
Body weights were obtained prior to exposure on study day 0 and on post-exposure days 1, 3, 7, and 14. A final body weight was collected for all animals that died on study.

- Necropsy of survivors performed:
Animals in extremis or at the scheduled necropsy were euthanized by isoflurane anesthesia
followed by exsanguination and subject to necropsy. The major organ systems of the cranial,
thoracic, and abdominal cavities were examined for all animals. No tissue or organs were
retained and the carcasses were discarded after necropsy.

Results and discussion

Effect levels

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

0.54 mg/L air (analytical)

Based on:

test mat.

95% CL:

0.25 - 0.82

Exp. duration:

4 h

Mortality:

One female in the 0.70 mg/L group and 3 males and 5 females in the 4.5 mg/L group were found
dead on study day 1. In addition, 2 males and 4 females in the 0.70 mg/L group and 2 males in
the 4.5 mg/L group were euthanized in extremis by study day 1 due to clinical observations
including hypoactivity, hyper-reactivity to touch, rales, labored respiration, decreased
respiration, prostration, body cool to touch, and/or extremities cool to touch. Total mortality was
0/10, 7/10, and 10/10 animals for the 0.083, 0.70, and 4.5 mg/L groups, respectively.

Clinical signs:

irregular respiration

Remarks:

Hyper-Reactivity to Touch, Prostration, Labored Respiration, Partial Closure eyes

Body weight:

From study day 0 to 1, all surviving animals in the 4.5 mg/L group lost 23 to 35 grams; all
surviving animals in the 0.70 mg/L group lost 27 to 45 grams; and 4 males and 4 females in the
0.083 mg/L group lost 6 to 18 grams. One male in the 0.70 mg/L group lost 17 grams from
study day 1 to 3. All surviving animals surpassed their initial (study day 0) body weight by
study day 14.

Gross pathology:

Macroscopic findings noted for animals that died in the 4.5 mg/L group were pale lungs for
one animal and distended urinary bladder and yellow matting of the skin for one animal. There were no other macroscopic findings for animals that died. There were no macroscopic findings for animals at the scheduled necropsy.

Applicant's summary and conclusion

Conclusions:

The LC50 of the test substance was 0.54 mg/L when male and female Crl:CD(SD) rats were exposed to a dust aerosol of the test substance as a single, 4-hour, nose-only exposure.