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

Endpoint summary

Description of key information

Oral:

Two studies on rats and mice are available.

LD50 in female rat was in the range of 500-1000 mg/kg bw and in male was 1000-2000 mg/kg bw (Stadnicki, 1988).

LD50 in female and male mice were greater than 2000 mg/kg bw (Stadnicki, 1988).

 

Dermal:

One study on rats is available.

LD50 in male and female albino rats was greater than 2000 mg/kg (Weinberg, 2015).

 

Inhalation:

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.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 29 Oct to 12 Nov 1987

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study run to a method comparable with current guidelines and to GLP

Qualifier:

according to guideline

Guideline:

other: Acute toxicology Standard Procedure

Deviations:

no

GLP compliance:

yes

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories Inc., Wilmington MA
- Age at study initiation: Six-week old
- Weight at study initiation: 164.7 to 173.0 grams for male rats, 141.1 to 150.5 grams for female rats
- Fasting period before study: overnight (i.e. for approximately 17 to 18 hours )
- Housing: Polycarbonate shoe box-type cages, males or females given the same dose were housed together (three per cage). The cage floor was covered with hardwood chip bedding (Ab-sob-dri, Lab products). All test animals were transferred into a clean cage each day.
- Diet (e.g. ad libitum): Prolab RMH-3000 pelleted rodent diet (Agway) ad libitum
- Water (e.g. ad libitum): Drinking water was obtained from a municipal water source subject to regulation by the U.S. Environmental Protection Agency. Water was suplied ad libitum from bottles that were changed two times a week.

ENVIRONMENTAL CONDITIONS
- Temperature (°F): 70±2
- Humidity (%): 50±5
- Air changes (per hr): approximately 18 times per hour with air filtered through 80-90% efficiency filters and finally through HEPA filters.
- Photoperiod (hrs dark / hrs light): illuminated by fluorescent lighting 12 hours a day (7:00 am-7:00pm).

IN-LIFE DATES: From 29 Oct to 12 Nov 1987

Route of administration:

oral: unspecified

Vehicle:

other: 0.1% (w/v) aqueous methylcellulose solution

Details on oral exposure:

VEHICLE
- Concentration in vehicle: 10%
- Amount of vehicle (if gavage):
- Justification for choice of vehicle:
- Lot/batch no. (if required): R74386-0376
- Purity:

MAXIMUM DOSE VOLUME APPLIED:

DOSAGE PREPARATION (if unusual):

CLASS METHOD (if applicable)
- Rationale for the selection of the starting dose

Doses:

500, 1000 and 2000 mg/kg

No. of animals per sex per dose:

3

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: All rats were observed for clinical signs and mortality for 14 days after dosing. The individual body weights of the animals was obtained at least six times during the study, i.e. on the day of dosing (day 0) and on the day 1, 4, 7, 10, and prior to the sacrifice on day 14.
- Necropsy of survivors performed: Animals that died during the study and those that survived to sacrifice were necropsied for gross pathological changes.
- Other examinations performed: Changes were apparent on the gastric mucosa of one male rat given the low oral dose of 500 mg/kg. Therefore, the stomach of this animal was submitted to Pathology for microscopic evaluation. Following fixation in 10% neutral buffered formalin, the tissue was trimmed, embedded in paraffin, cut at 5 to 6 microns, and stained with hematoxylin and eosin.

Statistics:

None stated

Sex:

female

Dose descriptor:

approximate LD50

Effect level:

500 - 1 000 mg/kg bw

Based on:

test mat.

Sex:

male

Dose descriptor:

approximate LD50

Effect level:

1 000 - 2 000 mg/kg bw

Based on:

test mat.

Mortality:

No mortality was produced by an oral dose of 500 mg/kg in animals of either sex or by a dose of 1000 mg/kg in males. Two of three females given 1000 mg/kg and all rats given the high dose of 2000 mg/kg died.

Clinical signs:

other: In animals given the low dose of 500 mg/kg, no clinical signs were noted on the day of dosing (day 0), and one rat of either sex was asymptomatic throught the 14-day observation period. Within about 5 to 7 hours of dosing, the activity of animals given 10

Gross pathology:

In the animals found dead on day 2 or day 3, the liver was dark, a yellowish material was apparent on the mucosa of the stomach near the pylorus, and portions of the small intestine were rendened and contained a yellow material. In the rats found dead on day 4 or 6, the lungs were reddened and mottled, the liver was dark, and the pancreas appeared white. The stomach contained a considerable amount of food, but the intestines were essentially empty. The kidneys were dark in situ and reddened throughout when cross-sectioned, the spleen was small, and a lack of body fat was noted.
At sacrifice on day 14, no gross pathological changes were apperent in any of the surviving rats with the exception of one low dose male which had been asyptomatic throught the study period. In this animal, white focal areas, measuring 1 to 2 mm in diameter, were visible on the aglandular portion the stomach when viewed in situ. When the stomach was excised and oppened, six raised areas, ranging in size from 1 to 8 mm in diameter, were apperent on the aglandular mucosa. At the three larger areas, there was a very narrow band of whitish, thichened, and rounded tissue at the perimeter of the rained edge. The center of these areas was depressed and often contained a small amount oof white material that was firmly adhered to the underlying mucosa. No gross changes were noted on the glandular portion of the stomach, and all other internal organs of this animal appeared essentially normal.

Other findings:

Microscopically, the raised white areas that were seen grossly on the mucosa of the aglandular stomach are keratinaceous cysts with associated mucosal dysplasia. These structures appear to be developmental defects rather than treatment-related lesions. The mucosal projections consist of submucosal, keratin-filled cysts opening to the interior of the stomach via small pores surrounded by narrow rims of glandular mucosa consisting of many pits lined by simple cilumnar epithelium and scattered goblet cells. These are overlain by mucus, keratin, and cell debris and in turn are surrounded by rims of thickly keratinized, stratified squamous epithelium that becomes less keratinized where it extends down onto the stalk of each projection.

Interpretation of results:

Toxicity Category IV

Remarks:

Criteria used for interpretation of results: EU

Conclusions:

The approximate acute oral median lethal dose (LD50) of the test item in the female rat was estimated to be in the range of 500 - 1000 mg/kg body weight, and the approximate LD50 for males was between 1000 and 2000 mg/kg bw.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

500 mg/kg bw

Quality of whole database:

1 (reliable without restriction)

Acute toxicity: via inhalation route

Link to relevant study records

Reference

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

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

Specific details on test material used for the study:

Lot no. DOA1401027
Purity: 97.4%

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

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.

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.

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.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LC50

Value:

0.54 mg/L air

Physical form:

inhalation: aerosol

Quality of whole database:

1 (reliable without restriction)

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 08 to 23 Apr 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study run to a method comparable with current guidelines and to GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Deviations:

no

GLP compliance:

yes

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc., Raleigh, NC
- Age at study initiation: The animals were approximately 8 weeks old at the time of dose administration
- Weight at study initiation: body weight values ranged from 258 g to 279 g for males and 185 g to 200 g for females, ± 20% of the mean for each sex.
- Fasting period before study:
- Housing: all animals were housed individually in clean, stainless steel, wire-mesh cages suspended above cage board.
- 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): 21.3°C to 21.4°C
- Humidity (%): ranged from 39.1% to 58.4%
- Air changes (per hr): a minimum of 10 fresh air changes per hour
- Photoperiod (hrs dark / hrs light): a 12-hour light (0600 hours to 1800 hours)/12-hour dark photoperiod

Type of coverage:

semiocclusive

Details on dermal exposure:

TEST SITE
- Area of exposure: at least 10% of the total body surface
- Type of wrap if used: Each dose was applied to the unabraded skin and overwrapped with gauze binders (<8-ply) that were secured with nonirritating tape.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): Upon completion of exposure, the bandages were removed and the sites were wiped with disposable paper towels moistened with tepid tap water.
- Time after start of exposure: 24 hours

Duration of exposure:

24 hours

Doses:

2000 mg/kg

No. of animals per sex per dose:

one group of 5 male and 5 female rats

Control animals:

not required

Details on study design:

- Duration of observation period following administration: 14 days

MORTALITY
The rats were observed for mortality and moribundity at approximately 1, 2, and 4 hours post-application on study day 0 and twice daily, once in the morning and once in the afternoon, thereafter for 14 days.

CLINICAL OBSERVATIONS
The rats were observed at approximately 1, 2, and 4 hours post-application on study day 0 and once daily thereafter for 14 days. Observations included, but were not limited to, evaluation for changes in appearance of skin and fur, eyes, mucous membranes, respiratory and circulatory systems, autonomic effects, and central nervous system effects.

DERMAL OBSERVATIONS
The application sites were observed for erythema, edema, and other dermal findings approximately 30-60 minutes after bandage removal and daily thereafter through study day 14.

BODY WEIGHTS
Body weights were obtained and recorded on study days 0 (initiation), 7, and 14 (termination).

NECROPSY
Upon termination, all rats were euthanized by carbon dioxide inhalation. The major organ systems of the cranial, thoracic, and abdominal cavities and the eyes, skin, and application site were examined for all animals. Tissues were discarded.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

There were no deaths during the study.

Clinical signs:

other: Clinical observations were limited to colored material (red, yellow, and/or brown) on various body surfaces (around nose and mouth and/or on anogenital area) for 2 males and 1 female, dermal atonia for 1 male, and soft feces for 1 male on 1 or 2 occasions

Gross pathology:

There were no gross necropsy findings for any examined tissues.

Other findings:

There were no dermal findings noted during the study.

Interpretation of results:

not classified

Remarks:

Criteria used for interpretation of results: EU

Conclusions:

Based on the results of this study, the LD50 of the test substance was greater than 2000 mg/kg when administered once dermally for 24 hours to the clipped, unabraded skin of male and female albino rats.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Quality of whole database:

1 (reliable without restriction)

Additional information

Oral:

Two studies on rats and mice are available.

The approximate acute oral median lethal dose (LD50) of the test item in the female rat was estimated to be in the range of 500 -1000 mg/kg body weight, and the approximate LD50 for males was between 1000 and 2000 mg/kg bw (Stadnicki, 1988). Key study.

The approximate acute oral median lethal dose (LD50) of the test item in the female and male mice were estimated to be greater than 2000 mg/kg body weight (Stadnicki, 1988).

Acute intraperitoneal LD50 were also estimated in these two studies, as greater than 300 mg/kg for rats and 700 -1000 mg/kg for mice.

 

Dermal:

One study is available which was conducted according to OECD Guideline 402 under GLP (Weinberg, 2015).

The LD50 of the test substance was greater than 2000 mg/kg when administered once dermally for 24 hours to the clipped, unabraded skin of male and female albino rats. Key study.

 

Inhalation:

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 in an OECD 403 study under GLP. Key study.

Justification for classification or non-classification

Oral: 300 < Oral LD50 <= 2000 mg/kg bw (actual value: F 500 -1000 mg/kg bw, M 1000 -2000 mg/kg bw); no significant toxic effects observed.

Dermal: rat LD50 > 2000 mg/kg bw (actual value > 2000 mg/kg bw); no significant toxic effects observed.

Inhalation: 0.5 <rat LC50 <=1.0 mg/L dust (actual value 0.54 mg/L dust); no significant toxic effects observed.

 

Therefore in accordance with Regulation (EC) No. 1272/2008(as amended by Regulation (EC) No. 286/2011) Table 3.1.1, this substance should be classified as Category 4 for acute oral toxicity, Category 3 for acute inhalation toxicity and should not be classified for acute dermal toxicity endpoint.

In accordance with Regulation (EC) No. 1272/2008 Table 3.8.1, this substance should not be classified for STOT SE endpoint.