thiamethoxam (ISO); 3-(2-chloro-thiazol-5-ylmethyl)-5-methyl[1,3,5]oxadiazinan-4-ylidene-N-nitroamine

Endpoint summary

Description of key information

- Oral: LD50 = 1536 mg/kg bw (95% 1267 - 1905 mg/kg bw), male/female, rat; equivalent to OECD 401, Oda 1996

- Inhalation: LC50 (4h) ≥3.72 mg/L, male/female, rat, OECD 403, Shutoh 1996

- Dermal: LD50 > 2000 mg/kg bw; male/female, rat, OECD 402, Oda 1996

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:

not specified

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

other: 59 NohSan No. 4200

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

Crj: CD(SD)

Remarks:

SPF rats

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Females (if applicable) nulliparous and non-pregnant: not specified
- Age at study initiation: 7 weeks old
- Weight at study initiation: 189 to 211 g in males and 132 to 154 g in females
- Fasting period before study: overnight prior to administration. Animals were fed once again 2 hours after administration.
- Housing: The animals were housed in groups of 2 to 3 in stainless steel wire mash cages
- Diet: A pellet diet ad libitum
- Water: Tap water ad libitum
- Acclimation period: Approximately 1 week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23 ± 3
- Humidity (%): 50 ± 20
- Air changes: 11 to 13 minutes per hour
- Photoperiod (hrs dark / hrs light): 12 /12

IN-LIFE DATES: From: To: Start: 6 Oct., 1995; End: 23 May 1996

Route of administration:

oral: gavage

Vehicle:

methylcellulose

Remarks:

0.5%

Details on oral exposure:

PRELIMINARY TOXICITY STUDY
In a preliminary acute oral toxicity study, three groups were used. Each consisted of three male and three female 7 week old CD(SD) rats. These groups had the test article administered at dose levels of 800, 2000 and 5000 mg/kg bw. 1 animal of each sex in the 2000 mg/kg bw group and 2 animals of each sex in the 5000 mg/kg bw group died. Consequently 5 dose levels, 900, 1500, 2300, 3800 and 6000 mg/kg bw were selected for both sexes in the main study.

VEHICLE:
- Amount of vehicle (if gavage): 20 mL/ kg bw

MAXIMUM DOSE VOLUME APPLIED: 6000 mg/kg bw

Doses:

900, 1500, 2300, 3800 and 6000 mg/kg bw

No. of animals per sex per dose:

5

Control animals:

yes

Remarks:

vehicle (0.5% methylcellulose solution)

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: The animals were examined frequently for the first six hours after dosing and twice daily in the morning and afternoon thereafter for 14 days for mortality and clinical abnormalities during the study. Body weights were recorded immediately prior to administration and the dose volume for each animal was calculated based on the weights. Body weights were also recorded on days 1, 2, 3, 7, 10 and 14 after administration at a set time.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight,organ weights, macroscopic examinations

Statistics:

The oral LD50 and the 95% confidence limits were calculated using the Probit method from the cumulative mortality rate 14 days after administration. For body weights, group mean values with standard deviation were calculated.

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

1 563 mg/kg bw

Based on:

test mat.

95% CL:

> 1 086 - < 2 174

Mortality:

3 animals of each sex treated at a dose level of 1500 mg/kg bw were found dead 2 to 6 hours after dosing. The same results was also seen at 2300 mg/kg bw. At the test doses of 3800 and 6000 mg/kg bw all test animals in the groups were killed after dosing.

Clinical signs:

other: Decrease in spontaneous movement, tonic convulsions and ptosis were observed, beginning from 1 hour after dosing in each sex in the 1500 mg/kg bw and above groups. The surviving animals returned to normal on the day following dosing.

Gross pathology:

There were no macroscopic abnormalities observed.

Interpretation of results:

Category 4 based on GHS criteria

Conclusions:

The LD50 values were 1563 mg/kg bw (95% CI 1086 – 2174 mg/kg bw) in both sexes and 1563 mg/kg bw (95% CI 1267 – 1905 mg/kg bw) in both sexes combined.

Executive summary:

In an acute oral toxicity study, 6 groups of 7 week old Crj:CD (SD) strain rats (each group consisting of 5 animals of each sex), were given a single oral dose of the test substance (98.60%.) in methylcelluloseat doses of 900, 1500, 2300, 3800 or 6000 mg/kg bw and observed for 14 days. A control group consisting of 5 male and 5 female rats were treated with 0.5% methylcellulose solution alone and were also observed. The animals were examined frequently for the first six hours after dosing and twice daily in the morning and afternoon thereafter for 14 days for mortality and clinical abnormalities during the study. Body weights were recorded throughout the study. In the males and females in each group, ptosis was observed beginning from one hour after dosing. In each sex in the 1500mg/kg bw and above groups, decrease in spontaneous movement and tonic convulsion were also observed. Initial deaths were seen at the 1500 mg/kg bw group with 3 animals of each sex, this was also seen with 4 animals of each sex in the 2300 mg/kg bw group and all animals in the 3800 and 6000 mg/kg bw group. The oral LD50 for males and for females is 1563 mg/kg bw (95% CI 1086 – 2174 mg/kg bw). The combined (males and females) oral LD50 1563 mg/kg bw (95% CI 1267 – 1905 mg/kg).

 

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

1 563 mg/kg bw

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:

not specified

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Version / remarks:

1981

Qualifier:

according to guideline

Guideline:

EU Method B.2 (Acute Toxicity (Inhalation))

Version / remarks:

1992

Qualifier:

according to guideline

Guideline:

EPA OPP 81-3 (Acute inhalation toxicity)

Version / remarks:

1984

Qualifier:

according to guideline

Guideline:

other: Japan MAFF Guideline, 59 NohSan No 4200

Version / remarks:

1985

GLP compliance:

yes

Test type:

traditional method

Limit test:

no

Species:

rat

Strain:

Crj: CD(SD)

Remarks:

SPF

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: 8 weeks old
- Weight at study initiation: 279-300 g (males); 184-211 g (females)
- Housing: 5 animals per stainless steel wire cage, sexes separately
- Diet: A certified pelleted diet MF ad libitum except during exposure.
- Water: Well water ad libitum except during exposure.
- Acclimation period: 1 week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 55 ± 15
- Air changes: At least 10 changes / hour
- Photoperiod (hrs dark / hrs light): 12 / 12

IN-LIFE DATES: Start: 9 Apr., 1996 End: 2 May 1996

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose only

Vehicle:

air

Mass median aerodynamic diameter (MMAD):

>= 5.1 - <= 5.6 µm

Geometric standard deviation (GSD):

>= 1.8 - <= 2.1

Remark on MMAD/GSD:

The mean values of MMAD and standard deviations of the test substance were 5.1 µm and 2.1 in group 1, and 5.6 µm and 1.8 in group 2.

Details on inhalation exposure:

EXPOSURE CONDITIONS: Two inhalation exposures of the test substance were conducted. The air flow rate in the chamber was very stable at 20 L/min during the exposure period. The mean actual atmospheric concentrations of the test substance were 1.02 mg/L (group 1) and 3.72 mg/L (group 2). The ratios of the mean actual atmospheric concentrations of the test article to the nominal concentration were 9.4% (group 1) and 6.6% (group 2).

GENERATION OF THE TEST ATMOSPHERE / CHAMBER DESCRIPTION: The test atmosphere was generated using a turn-table type dust feeder with compressed air from an air compressor. The air flow rate in the chamber was regulated by a flow controller at 20 L/minute. The air change was 37.5 times/hour, ensuring an oxygen content of at least 19%. The air in the chamber was filtered with an exhaust filter system consisting of a bag filter, a HEPA filter and an activated charcoal filter, and was emitted to the atmosphere using a vacuum pump. Animals were exposed nose-only to the atmosphere. They were held individually in animal holders attached to the inhalation chamber and were exposed to the test substance for 4 hours.

TEST ATMOSPHERE CONCENTRATION: The particulate concentration of the test atmosphere, close to the animals’ breathing zone, was measured gravimetrically with a balance (Mettler AE 163, Mettler Instrumente AG, Greifensee, Switzerland). The weight percentage of each stage to the total amount of the trapped test substance was calculated. The dust of the test substance was trapped on a glass fiber filter. Then the test substance on the filter was extracted with acetonitrile, and analysed by high-performance liquid chromatography (HPLC). The atmospheric concentration of the test article was calculated by dividing the weight of the test substanced by the sample air volume. The concentration was calculated as follows: Concentration (mg/L) = Weight of test article supplied (g) x 1000 / time (minutes) x airflow (L/minute).

PARTICLE SIZE DETERMINATION: The aerodynamic particle size distribution of the test atmosphere was measured twice during the exposure period, using an Andersen personal sampler, at one and three hours after the initiation of exposure. The amount of the test substance trapped on each stage of the sampler was determined gravimetrically with a balance. The amount of the test substance, by weight, in each size range, was then used to calculate the aerodynamic particle size distribution. The cumulative weight percentage was plotted on a logarithmic-probability paper to obtain the mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) of the test substance dust.

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

- Measured particulate concentration: 3.72 mg/L
- Nominal concentration: 1.02 mg/L
- Analysed concentration: mean 1.02 mg/L (group 1) and 3.72 mg/L (group 2)

No. of animals per sex per dose:

5

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Prior to the start of the study animals were examined to ensure that they were physically normal and exhibited normal activity.
- During exposure they were observed frequently and, at 2 hours after initial exposure and immediately, at 2 and 4 hours after the termination of exposure.
- The animals were subjected to detailed clinical observations, daily during a 14-day observation period.
- Body weights of the animals were individually measured just prior to exposure and on post-exposure days 7 and 14.
- All animals were necropsied at the end of the observation period.

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 3.72 mg/L air

Based on:

test mat.

Exp. duration:

4 h

Mortality:

No animals were killed as a result of exposure to the test substance.

Clinical signs:

other: After termination of exposure, soiled fur in the nasorostral region was observed at the slight degree in all animals in both groups. This slight sign disappeared by post-exposure day 1 in both group 1 and day 3 in the group 2.

Body weight:

Although 2 females in the group 2 showed slight decreases in body weight on day 7, they recovered their weights by day 14.

Gross pathology:

There were no macroscopic abnormalities.

Interpretation of results:

GHS criteria not met

Conclusions:

It is concluded that the acute inhalation LC50 of the test substance exceeds 3.72 mg/L.

Executive summary:

In an acute inhalation toxicity study, groups of young adult SPF Sprague-Dawley (Crj:CD) rats (10 male and 10 female) were exposed by inhalation route to pulverized test substance (purity: 98.60%) in the form of a dust for 4 hours (in a nose only exposure chamber) at concentrations of 1.02 (group 1) and 3.72 mg/L (group 2). Animals then were observed for 14 days. Two groups of five male and five female SPF Sprague-Dawley were exposed nose-only for a four-hour period to the test substance at a target formulation concentration of 5 mg/L. Test atmospheres were analysed for particulate concentration. The particle size distribution of the test atmosphere was analysed twice during the exposure period. Following exposure, the animals were retained without treatment for 14 days. Clinical observations and body weights were recorded throughout the study and at the end of the scheduled period, the animals were killed and subjected to a gross examination post mortem. The achieved test atmosphere had the following characteristics: Target concentration (mg/L) = 5; achieved particulate concentration (mg/L) = 3.72 ± 0.73; MMAD (µm) = 5.1, 5.6; GSD = 2.1, 1.8.There were no deaths in either sexes throughout the observation in both groups. The median lethal concentration of the test substance for male and female rats was more than 3.72 mg/L. No abnormalities were found in the major organs in the cranial, thoracic, and abdominal cavities in any animal of either group at necropsy. From these results, it was concluded that the acute inhalation toxicity of the test substance in Sprague-Dawley rats was virtually nontoxic at the atmospheric concentration of 3.72 mg/L and the LC50 for male and female rats was more than 3.72 mg/L.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating conc.

Value:

3 730 mg/m³ air

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:

not specified

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Version / remarks:

1987

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

Crj: CD(SD)

Remarks:

SPF rats

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: 7 weeks old
- Weight at study initiation: 212 to 230 g in males and 160 to 181 g in females
- Housing: Individually in stainless steel wire mesh cages
- Diet: A pellet diet ad libitum
- Water: Tab water ad libitum
- Acclimation period: Approximately 1 week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23 ± 3
- Humidity (%): 50 ± 20
- Air changes: 11 to 13 minutes per hour
- Photoperiod (hrs dark / hrs light): 12 / 12

IN-LIFE DATES: Start: 6 Oct. 1995 End: 23 May 1996

Type of coverage:

occlusive

Vehicle:

unchanged (no vehicle)

Details on dermal exposure:

PRELIMINARY DERMAL TOXICITY STUDY
In a preliminary acute dermal toxicity study, a group of three male and three female 7 week old CD(SD) rats had the test article administered at a dose level of 2000 mg/kg bw. No deaths were observed in either sex and therefore a single dose of 2000 mg/kg bw of the test material was administered dermally to a group of 5 male and 5 female (both 7 weeks old) CD(SD) rats.

TEST SITE & TEST ARTICLE
On the day prior to application of the test article, the dorsal area (approximately 30cm2 5 x 6cm) of each animal was clipped with an electric clipper. Immediately before administration, requisite amount of the test article was weighed for each animal and impasted by addition of 0.5 mL of distilled water. The test article was applied evenly to a gauze sheet (approximately 20cm2 4 x 5cm), placed on the application site and then covered with a polyethylene-film plaster and fixed with surgical tape.

REMOVAL OF TEST SUBSTANCE
After 24 hours of application, the dressing was removed and the application site was wiped with a gauze sheet. The reaction sites were then assessed.

Duration of exposure:

24 h

Doses:

2000 mg/kg bw

No. of animals per sex per dose:

5

Control animals:

yes

Remarks:

distilled water

Details on study design:

- Duration of observation period following administration: 14 days
- The animals were examined frequently for the first six hours after dosing and twice daily in the morning and afternoon thereafter for 14 days for mortality and clinical abnormalities during the study.
- Body weights were recorded throughout the study.
- At the end of the scheduled observation period, all animals were necropsied and examined macroscopically.

Statistics:

For body weights, group mean values with standard deviation were calculated.

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

No deaths occured during the study.

Clinical signs:

other: No abnormalities were observed in any animal.

Gross pathology:

No abnormalities were observed in any of the organs of the animals. Neither was there any change at the application site.

Other findings:

IRRITATION
There were no signs of irritability at the application site (dorsal skin).

Interpretation of results:

GHS criteria not met

Conclusions:

The acute dermal LD50 of the test substance after a single dermal application to rats of both sexes, observed over a period of 14 days is greater than 2000 mg/kg body weight.

Executive summary:

In an acute dermal toxicity study, groups of 7 week old Crj:CD (SD) strain SPF rats (each group consisting of 5 animals of each sex) were dermally exposed to the test substance (purity 98.60%) for 24 hours via a gauze sheet of 20 cm2 to the rodent dorsal area at doses of 0 or 2000 mg/kg bw. Animals then were observed for 14 days. The animals were examined frequently for the first six hours after dosing and twice daily in the morning and afternoon thereafter for 14 days for mortality and clinical abnormalities during the study. Body weights were recorded throughout the study. No death was observed in any animal at 2000 mg/kg bw. There were no treatment related clinical signs, necropsy findings or changes in body weight. The acute dermal LD50 of the test substance after a single dermal application to rats of both sexes, observed over a period of 14 days is in excess of 2000 mg/kg bw. In the clinical signs, no abnormalities were observed in any animal, nor was there any sign of irritability at the application site.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating dose

Value:

2 000 mg/kg bw

Additional information

Acute oral toxicity rat:
In a GLP compliant acute oral toxicity study (Oda, 1996), 6 groups of 7 week old rats of Crj:CD (SD) strain (each group consisting of 5 animals of each sex), were given a single oral dose of the test substance (98.60%.) in methylcellulose at doses of 900, 1500, 2300, 3800 or 6000 mg/kg bw. Animals were observed for 14 days. A control group consisting of 5 male and 5 female rats were treated with 0.5% methylcellulose solution alone and were also observed. The animals were examined frequently for the first six hours after dosing and twice daily in the morning and afternoon thereafter for 14 days for mortality and clinical abnormalities during the study. Body weights were recorded throughout the study. In the males and females in each group, ptosis was observed beginning from one hour after dosing. In each sex in the 1500 mg/kg bw and above groups, decrease in spontaneous movement and tonic convulsion were also observed. Initial deaths were seen at the 1500 mg/kg group with 3 animals of each sex, this was also seen with 4 animals of each sex in the 2300 mg/kg bw group and all animals in the 3800 and 6000 mg/kg group. The oral LD50 for males and for females is 1563 mg/kg bw (95% CI 1086 – 2174 mg/kg bw). The combined (males and females) oral LD50 is 1563 mg/kg bw (95% CI 1267 – 1905 mg/kg bw).

Acute oral toxicity mouse:
The acute oral toxicity of the test substance was assessed in a GLP compliant standard guideline study (OECD 401) in mice, Crj:CD-1 (ICR) strain (Oda, 1996a). Based on the results of a preliminary study, one control group and 5 test groups receiving dose levels of 500, 700, 1000, 1400 and 2000 mg/kg were selected for both sexes (5 animals/sex/group) in the main study. No deaths were observed in the 500 mg/kg group in either sex, however, 2 males and 1 female in the 700 mg/kg group, 4 males and 3 females in the 1000 mg/kg group, all males and 4 females in the 1400 mg/kg group, and all animals in the 2000 mg/kg group died. The acute oral LD50 of the test substance in mice is 783 mg/kg (95% confidence limits 619 – 1000 mg/kg) in males and 964 mg/kg (729 – 1271 mg/kg) in females, and 871 mg/kg (735 – 1028 mg/kg) in both sexes combined. 

Acute inhalation toxicity:
In a GLP compliant acute inhalation toxicity study (Shutoh, 1996), performed according to OECD 403, groups of young adult SPF Sprague-Dawley (Crj:CD) rats (10 male and 10 female) were exposed by inhalation route to pulverized test substance (purity: 98.60%) in the form of a dust for 4 hours (in a nose only exposure chamber) at concentrations of 1.02 (group 1) and 3.72 mg/L (group 2). Animals then were observed for 14 days. Two groups of five male and five female SPF Sprague-Dawley were exposed nose-only for a four-hour period to the test substance at a target formulation concentration of 5 mg/L. Test atmospheres were analysed for particulate concentration. The particle size distribution of the test atmosphere was analysed twice during the exposure period. Following exposure, the animals were retained without treatment for 14 days. Clinical observations and body weights were recorded throughout the study and at the end of the scheduled period, the animals were killed and subjected to a gross examination post mortem. The achieved test atmosphere had the following characteristics: Target concentration (mg/L) = 5; achieved particulate concentration (mg/L) = 3.72 ± 0.73; MMAD (µm) = 5.1, 5.6; GSD = 2.1, 1.8. There were no deaths in either sexes throughout the observation in both groups. The median lethal concentration of the test substance for male and female rats was more than 3.72 mg/L. No abnormalities were found in the major organs in the cranial, thoracic, and abdominal cavities in any animal of either group at necropsy. From these results, it was concluded that the test substance was non-toxic to Sprague-Dawley rats at the atmospheric concentration of 3.72 mg/L and the LC50 for male and female rats was greater than 3.72 mg/L.

Acute dermal toxicity:
In a GLP compliant acute dermal toxicity study (Oda, 1996), performed according to OECD 402, groups of 7 week old rats of Crj:CD (SD) strain SPF (each group consisting of 5 animals of each sex) were dermally exposed to the test substance (purity 98.60%) for 24 hours via a gauze sheet of 20 cm2 to the rodent dorsal area at doses of 0 or 2000 mg/kg bw. Animals then were observed for 14 days. The animals were examined frequently for the first six hours after dosing and twice daily in the morning and afternoon thereafter for 14 days for mortality and clinical abnormalities during the study. Body weights were recorded throughout the study. No death was observed in any animal at 2000 mg/kg bw. There were no treatment related clinical signs, necropsy findings or changes in body weight. The acute dermal LD50 of the test substance after a single dermal application to rats of both sexes, observed over a period of 14 days is in excess of 2000 mg/kg bw. In the clinical signs, no abnormalities were observed in any animal, nor was there any sign of skin irritation at the application site.

Justification for classification or non-classification

Based on the available data on acute oral toxicity the substance is classified as Acute Tox. 4, H302: Harmful if swallowed according to the EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.

Based on the result of the available studies classification for acute inhalation and acute dermal toxicity is not warranted in accordance with EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation No. (EC) 1272/2008.