pymetrozine (ISO); (E)-4,5-dihydro-6-methyl-4-(3-pyridylmethyleneamino)-1,2,4-triazin-3(2H)-one

Endpoint summary

Description of key information

- Oral: LD50 = 5693 mg/kg bw, male rats (Hsd:Sprague Dawley SD), US EPA 81-1, Glaza 1991

- Dermal: LD50 >2000 mg/kg bw, male/female, rats (Hsd:Sprague Dawley SD), US EPA 81-2, Glaza 1991

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:

18 Jul 1991 to 4 Sep 1991

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 81-1 (Acute Oral Toxicity)

Version / remarks:

1985

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method B.1 (Acute Toxicity (Oral))

Deviations:

no

GLP compliance:

yes

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Remarks:

Hsd:Sprague Dawley SD

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 216 to 294 g (for males), 204 to 268 g (for females)
- Fasting period before study: Yes, approximately 17 to 20 hours before test material administration when food, but not water, was withheld.
- Housing: individually housed in screen-bottom, stainless steel cages (heavy gauge).
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: at least 7 days

ENVIRONMENTAL CONDITIONS
Animal husbandry and housing comply with standards outlined in the "Guide for the Care and Use of Laboratory Animals" (NIH publication number No. 86-23, revised 1985). Variations from the prescribed environmental conditions existed and were considered to have had no effect on the study outcome. No contaminants were expected to have been present in the feed or water which would have interfered with or affected the results of the study.

IN-LIFE DATES:
July 18 to September 4, 1991

Route of administration:

oral: gavage

Vehicle:

water

Remarks:

Destilled

Details on oral exposure:

VEHICLE
- Amount of vehicle: 20.00 mL/kg body weight

Doses:

4000, 5000, 6000, 6500, or 7000 mg/kg of body weight based on range-finding study using the following doses: 1000, 2000, 4000 and 5000 mg/kg of body weight performed with one animal/sex/dose.

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 observations and weighing: Body weights were determined before test material administration (Day 0). Additional body weights were determined at Day 7 and at termination of the experimental phase (Day 14) or at death when survival exceeded 1 day.
- Necropsy of survivors performed: yes, All study animals, whether dying during the study or euthanatized, were subjected to a gross necropsy examination and all abnormalities were recorded. After necropsy, the animals were discarded and all tissues with lesions were collected for possible future histological evaluation.
- Other examinations performed: clinical signs, body weight, organ weights, histopathology, other: Clinical signs and mortality checks were conducted at approximately 1, 2.5, and 4 hours after test material administration. Additional clinical signs and twice a day mortality checks (morning and afternoon) were conducted daily thereafter for 14 days.

Statistics:

The LD50 value for males, females, and the sexes combined was determined by a computer program utilizing probit analysis. No other statistical analyses were required by the protocol.

Preliminary study:

No mortality was observed at levels of 1000, 2000, 4000, or 5000 mg/kg. All animals exhibited weight gain with the exception of one male rat which exhibited a weight loss of 8 g during the first week of the study.

Key result

Sex:

male

Dose descriptor:

LD50

Effect level:

5 693 mg/kg bw

Based on:

test mat.

Sex:

female

Dose descriptor:

LD50

Effect level:

5 955 mg/kg bw

Based on:

test mat.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

5 820 mg/kg bw

Based on:

test mat.

Mortality:

At 4000 mg/kg bw there was no mortality. Most deaths at the higher dose levels occurred from day 7 to 13. A data overview can be found in 'Any other information on results incl. tables'.

Clinical signs:

other: The observed signs included hypoactivity, staggered gait, prostration, red-stained face, lacrimation, dyspnea, soft stool, stained urogenital area, redstained urine, tremors, and hypothermia.

Gross pathology:

At necropsy, the most prominent findings were in the DOTs and pertained to the contents and coloration changes in the gastrointestinal tract. The stomach and small intestines contain material of varied consistency and colour that probably represent test material mixed with ingestions. Some of the observations were also attributed to post-mortem change and autolysis or were considered common incidental findings. There were no visible lesions in the animals surviving to the end of the test periods.

 Table 1. Mortality incidence

Dose (mg/kg bw)	Mortality	Onset of death
Males
4000	0/5
5000	1/5	Day 4
6000	3/5	Days 11, 11, 13
6500	4/5	Days 7, 8, 8, 9
7000	5/5	Days 2, 4, 9, 11
Females
4000	0/5
5000	1/5	Day 8
6000	2/5	Days 1, 10
6500	3/5	Days 7, 9, 10
7000	5/5	Days 2, 5, 8, 9, 10

 

Interpretation of results:

GHS criteria not met

Conclusions:

In this study according to EPA 81-1 guideline the following LD50 values were found: 5693 mg/kg for males and 5955 mg/kg for females.

Executive summary:

In this GLP compliant acute oral toxicity study performed according to EPA guideline 81-1, the test material was evaluated for its acute oral toxicity potential in male and female albino rats (Hsd:Sprague Dawley SD) when administered as a single gavage dose at levels of 4000, 5000, 6000, 6500, and 7000 mg/kg of body weight (5 animals/sex/dose). The test material was dissolved in water. After single exposure, rats were observed for 14 days. Mortality increased with increasing dosis: 0/10, 2/10, 5/10, 7/10 and 10/10 animals receiving 4000, 5000, 6000, 6500 and 7000 respectively. Clinical signs of toxicity included hypoactivity, staggered gait, prostration, red-stained face, lacrimation, dyspnea, soft stool, yellow/red/ or darkstained urogenital area, red-stained urine, tremors, hypothermic to touch, and death. There was no meaningful effect on body weight gain in those animals surviving to termination with the exception of two males which exhibited weight losses of 30 g each during the first week of the study. The most prominent findings observed at necropsy were in the animals dying during the study and pertained to the contents and coloration changes in the gastrointestinal tract. The calculated (probit analysis) oral LD50 was determined to be 5693, 5955, and 5820 mg/kg for males, females, and the sexes combined, respectively. 

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

5 693 mg/kg bw

Quality of whole database:

GLP compliant, US EPA 81-1 guideline study

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

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:

23 Jul 1991 to 6 Aug 1991

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 81-2 (Acute Dermal Toxicity)

Deviations:

no

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

Sprague-Dawley

Remarks:

Hsd:Sprague Dawley SD

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 250 to 286 g (for males), 220 to 244 g (for females)
- Housing: individually housed in screen-bottom, stainless steel cages.
- Diet: a measured amount of Rodent Chow® #5001
- Water: ad libitum
- Acclimation period: at least 7 days

ENVIRONMENTAL CONDITIONS
Animal husbandry and housing comply with standards outlined in the "Guide for the Care and Use of Laboratory Animals" (NIH publication number No. 86-23, revised 1985). Variations from the prescribed environmental conditions existed and were considered to have had no effect on the study outcome. No contaminants were expected to have been present in the feed or water which would have interfered with or affected the results of the study.

- Temperature (°C): 19 to 25
- Humidity (%): 52 to 69

IN-LIFE DATES:
23 July 1991 to 6 August 1991

Type of coverage:

occlusive

Vehicle:

physiological saline

Details on dermal exposure:

TEST SITE
- Area of exposure: back of the rat
- % coverage: at least 10%
- Type of wrap if used: The area of application was covered with a 5.0 cm x 5.0 cm gauze patch secured with paper tape, and overwrapped with Saran Wrap and Elastoplast tape.

REMOVAL OF TEST SUBSTANCE
- Washing: washed using tap water and disposable paper towels
- Time after start of exposure: at the end of the 24-hour exposure period

Duration of exposure:

24 hours

Doses:

2.0 g/kg bw

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 observations and weighing: Clinical signs and mortality checks were conducted at approximately 1, 2.5, and 4 hours after test material administration. The animals were observed daily thereafter for 14 days for clinical signs and dermal irritation and twice a day (morning and afternoon) for mortality. Body weights were determined before test material application (Day 0), at Day 7, and at termination of the experimental phase (Day 14).
- Necropsy of survivors performed: yes

Statistics:

No statistical analyses were required by the protocol.

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Remarks on result:

no indication of skin irritation up to the relevant limit dose level

Mortality:

No mortality observed

Clinical signs:

other: All animals appeared clinically normal and exhibited no dermal irritation throughout the study

Gross pathology:

No deviations from normal morphology were found

Interpretation of results:

other: Not classified according to CLP

Conclusions:

In this GLP compliant US EPA 81-2 study in Sprague-Dawley rats, the LD50 was determined to be > 2000 mg/kg body weight for males/females.

Executive summary:

In this GLP compliant US EPA 81-2 study, the acute dermal toxicity of the test substance was evaluated in male and female Sprague-Dawley rats (5 animals per sex). The moistened test substance was administered as a single topical application under occlusive conditions at a level of 2000 mg/kg of body weight. After 24 hours of exposure, the test substance was washed using tap water and disposable paper towels. Clinical signs, body weight and mortality were recorded for 14 days after the end of the treatment. All animals were clinically normal and exhibited no dermal irritation throughout the study. Body weights were unaffected and no deviations from normal morphology were found. No animals died during the study. The estimated dermal LD50 was determined to be greater than 2000 mg/kg bw.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating dose

Value:

2 000 mg/kg bw

Quality of whole database:

GLP compliant, US EPA 81-2 guideline study

Additional information

All available data was assessed and the studies representing the worst-case effects were included as key studies. The other studies are included as supporting information. The key studies are considered to be worst-case and were selected for the CSA.

Acute oral toxicity

In this GLP compliant acute oral toxicity study performed according to EPA guideline 81-1, the test material was evaluated for its acute oral toxicity potential in male and female albino rats (Hsd:Sprague Dawley SD) when administered as a single gavage dose at levels of 4000, 5000, 6000, 6500, and 7000 mg/kg of body weight (5 animals/sex/dose) (Glaza 1991). The test material was dissolved in water. After single exposure, rats were observed for 14 days. Mortality increased with increasing dosis: 0/10, 2/10, 5/10, 7/10 and 10/10 animals receiving 4000, 5000, 6000, 6500 and 7000 respectively. Clinical signs of toxicity included hypoactivity, staggered gait, prostration, red-stained face, lacrimation, dyspnea, soft stool, yellow/red/ or dark stained urogenital area, red-stained urine, tremors, hypothermic to touch, and death. There was no meaningful effect on body weight gain in those animals surviving to termination with the exception of two males which exhibited weight losses of 30 g each during the first week of the study. The most prominent findings observed at necropsy were in the animals dying during the study and pertained to the contents and coloration changes in the gastrointestinal tract. The calculated (probit analysis) oral LD50 was determined to be 5693, 5955, and 5820 mg/kg for males, females, and the sexes combined, respectively. 

Acute inhalation toxicity

In a GLP compliant acute inhalation toxicity study performed according to OECD guideline 403, groups of 5 male and 5 female Tif: RAI f (SPF) rats were exposed to the test material (Hartmann 1991). Because of the high variability of particle size of technical material as such, it was not possible to generate an aerosol of sufficient concentration and respirable particle size. For the inhalation study the test material had to be milled twice using a jet mill adding 1 % Sipernat 50S, a highly disperse amorphic siliciumoxide. 5 male and 5 female rats (Tif:RAIf (SPF)) were exposed to milled test material for 4 hours (nose only exposure) at the maximum attainable concentration of 1800 mg/m3 air. No mortality was recorded during the study. Clinical signs in both sexes included piloerection, hunched posture, and dyspnea, which cleared by day 4. Body weight gain was in the expected range. Gross necropsy revealed no observable abnormalities. There was no mortality. The observed signs included piloerection, hunched posture, and dyspnea. All animals recovered within 4 days. At autopsy, no compound-related deviations from normal morphology were seen.The acute inhalation LC50 in albino rats was determined to be greater than 1800 mg/m³.

Acute dermal toxicity

In this GLP compliant US EPA 81-2 study, the acute dermal toxicity of the test substance was evaluated in male and female Sprague-Dawley rats (5 animals per sex) (Glaza 1991). The moistened test substance was administered as a single topical application under occlusive conditions at a level of 2000 mg/kg of body weight. After 24 hours of exposure, the test substance was washed using tap water and disposable paper towels. Clinical signs, body weight and mortality were recorded for 14 days after the end of the treatment. All animals were clinically normal and exhibited no dermal irritation throughout the study. Body weights were unaffected and no deviations from normal morphology were found. No animals died during the study. The estimated dermal LD50 was determined to be greater than 2000 mg/kg bw.

Justification for classification or non-classification

Based on the available data on acute oral and dermal toxicity, classification is not warranted according to the EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.