Methomyl

Endpoint summary

Description of key information

Duration/Value Type	Species	Value	Guideline	Reliability
Oral LD50	Rat, female	17.98 mg/kg	OECD 425, EPA OPPTS 870.1100	1
Oral LD50	Rat, male/female	32 mg/kg	EPA OPP 81-1	1
Oral Lethal Dose	Dog	20 mg/kg	no guideline	2
Oral Minimum Lethal Dose	rabbit	30 mg/kg	no guideline	2
Oral Minimum Lethal Dose	guinea pig	15 mg/kg	no guideline	2
Oral LD50	Adult hen	28 mg/kg	no guideline	2

Duration/Value Type	Species	Value	Guideline	Reliability
Inhalation 4 -hr LC50	Rat, male/female	0.258 mg/L	OECD 403, EPA OPP 81-3, MAFF Testing Guideline for Acute Inhalation Toxicity Study (59 NohSan No. 4200)	1
Inhalation 4 -hr LC50	Rat	0.28 - 0.30 mg/L	no guideline	2

Duration/Value Type	Species	Value	Guideline	Reliability
Dermal LD50	Rat	> 5000 mg/kg	OECD 402, OPPTS 870.1200, Ministry of Agriculture, Forestry and Fisheries of Japan 12-Nouan-8147	1
Dermal LD50	Rabbit	> 5000 mg/kg	no guideline	2
Dermal LD50	Rabbit	> 2000 mg/kg	EPA 81-2	1

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 425 (Acute Oral Toxicity: Up-and-Down Procedure)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.1100 (Acute Oral Toxicity)

Deviations:

no

GLP compliance:

yes

Test type:

up-and-down procedure

Specific details on test material used for the study:

Methomyl Technical
Lot number: DPX-X1179-599
Purity: 99.6%

Species:

rat

Strain:

Sprague-Dawley

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Ace Animals, Inc., Boyertown, Pennsylvania.
- Females nulliparous and non-pregnant: Yes
- Age at study initiation: Young adult (9-12 weeks)
- Weight at study initiation: 190-232 grams
- Fasting period before study: Yes
- Housing: Animals were singly housed in suspended stainless steel caging with mesh floors. Enrichment (e.g. nylabone) was placed in each cage. Litter paper was placed beneath the cage and was changed at least three times per week.
- Diet: Purina Rodent Chow #5012
- Water: Filtered tap water, ad libitum
- Acclimation period: 8-28 days

ENVIRONMENTAL CONDITIONS
- Temperature: 18-21ºC
- Humidity: 34-65%
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

other: 2.5% w/v mixture in distilled water

Doses:

3.2, 10.1, 32 and 101 mg/kg b.wt.

No. of animals per sex per dose:

3.2 mg/kg: 1
10.1 mg/kg: 3
32 mg/kg: 3
101 mg/kg: 1

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: The animals were observed for mortality, signs of toxicity, and behavioral changes changes within 30 minutes of dosing and during the first several hours post-dosing and at least once daily thereafter for 14 days after dosing of until death occurred. Individual weights of the animals were recorded prior to test substance administration (initial) and again on Days 7 and 14 following dosing or after death.
- Necropsy of survivors performed: Yes

Key result

Sex:

female

Dose descriptor:

LD50

Effect level:

17.98 mg/kg bw

Based on:

test mat.

Mortality:

One animal dosed at 10.1 mg/kg and two dosed at 32 mg/kg died within one hour of test substance administration. The rat dosed at 101 mg/kg died within 30 minutes of test substance administration.

Clinical signs:

other: Clinical signs noted in the decedents prior to death of animals dosed at 10.1 mg/kg and 32 mg/kg included hypoactivity, tremors and/or prone posture. The surviving rats from these dose groups exhibited clinical signs including hypoactivity, tremors and/or

Gross pathology:

Gross necropsy of the decedent animals dosed at 10.1 mg/kg and 32 mg/kg revealed discoloration of the intestines. No gross abnormalities were noted for any of the euthanized animal dosed at 10.1 mg/kg and 32 mg/kg necropsied at the conclusion of the 14-day observation period. Gross necropsy of the decedent animal at 101 mg/kg revealed discoloration of the intestines.

Interpretation of results:

Category 2 based on GHS criteria

Conclusions:

Oral LD50 (Rat, female): 17.98 mg/kg

Executive summary:

An acute oral toxicity test (Up and Down Procedure) was conducted with rats to determine the potential for the test substance to produce toxicity from a single dose via the oral route in accordance with the OECD Guideline 425 and U.S. EPA Guideline OPPTS 870.1100.

Based on an estimated LD50 of 32 mg/kg, a Main Test was conducted using a default starting dose level of 10.1 mg/kg administered to one healthy female rat by oral gavage. Following the Up and Down procedure, two additional females were dosed at 10.1 mg/kg, one female was dosed at 3.2 mg/kg, three females were dosed at 32 mg/kg and one female was dosed at 101 mg/kg. Females were selected for the test because they are frequently more sensitive to the toxicity of test compounds than males. All animals were observed for mortality, signs of gross toxicity, and behavioral changes at least once daily for 14 days after dosing or until death occurred. Body weights were recorded prior to administration and again on Days 7 and 14 (termination) following dosing or after death. Necropsies were performed on all animals.

The animal dosed at 3.2 mg/kg survived and exhibited no clinical signs or body weight loss during the study. No gross abnormalities were noted for this animal when necropsied at the conclusion of the 14-day observation period.

One animal dosed at 10.1 mg/kg and two dosed at 32 mg/kg died within one hour of test substance administration. Clinical signs noted in the decedents prior to death included hypoactivity, tremors and/or prone posture. The surviving rats from these dose groups exhibited clinical signs including hypoactivity, tremors and/or piloerection on the day of dosing. All surviving animals recovered from these signs within one day post-dosing and appeared active and healthy for the remainder of the 14-day observation period, showing no body weight loss during the study. Gross necropsy of the decedents revealed discoloration of the intestines. No gross abnormalities were noted for any of the euthanized animal necropsied at the conclusion of the 14-day observation period.

The rat dosed at 101 mg/kg died within 30 minutes of test substance administration. Clinical signs noted in the decedent prior to death included hypoactivity and prone posture. Gross necropsy of the decedent revealed discoloration of the intestines.

Under the conditions of this study, the acute oral LD50 of the test substance is estimated to be 17.98 mg/kg of body weight (based on maximum likelihood) in female rats with a 95% profile-likelihood based confidence interval of 0 mg/kg (lower) to greater than 20000 mg/kg (upper).

Reference 2

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 81-1 (Acute Oral Toxicity)

Deviations:

no

GLP compliance:

yes

Test type:

standard acute method

Specific details on test material used for the study:

Methomyl Technical
Lot number: DPX-X1179-394
Purity: 98.35%

Species:

rat

Strain:

other: Crl:CD BR

Sex:

male/female

Route of administration:

oral: gavage

Vehicle:

other: deionized water

Doses:

20, 40 and 80 mg/kg b.wt.

No. of animals per sex per dose:

10

Control animals:

no

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

32 mg/kg bw

Based on:

test mat.

95% CL:

> 26 - < 39

Interpretation of results:

Category 2 based on GHS criteria

Conclusions:

Oral LD50 (rat): 32 mg/kg (95% CL of 26-39 mg/Kg)

Executive summary:

The purpose of this study was to determine the LD50 of the test substance in male and female rats according to the guideline U.S. EPA OPP 81-1. Three groups of 10 male and 10 female rats each were administered single doses of the test substance by intragastric intubation. The doses administered ranged from 20 to 80 mg/kg of body weight. Clinical signs of toxicity and mortality were observed over a 14 day observation period. Deaths occurred within 1 day after dosing. 2, 5 and 10 males and 1, 8 and 10 females died in 20, 40 and 80 mg/kg groups respectively. Clinical signs of toxicity most often observed in male and female rats dosed at 20 or 40 mg/kg included tremors, low posture, or salivation. These clinical signs of toxicity were only apparent one hour after dosing. All rats dosed at 80 mg/kg exhibited convulsions and were found  dead on the day of dosing. The LD50 for male and female rats was 32 mg/kg. Gross pathologic examinations of found dead rats revealed stress-related acute systemic toxicity. No specific target organ was identified. This substance is considered to be highly toxic (LD50 less than 50 mg/kg of body weight) when administered as a single oral dose.

Reference 3

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The test substance was administered orally to male beagle dogs in gelatin capsules in doses of 10 or 20 mg/kg. In some cases blood was taken from the femoral vein just prior to dosing and at various time intervals thereafter for cholinesterase activity measurements.

GLP compliance:

no

Test type:

standard acute method

Specific details on test material used for the study:

S-Methyl N-[(methylcarbamoyl)oxy]thioacetimidate
Lot number: INX-1179-35
Purity: Not reported

Species:

dog

Strain:

other: Beagle

Sex:

male

Route of administration:

oral: capsule

Doses:

10 and 20 mg/kg

Control animals:

no

Key result

Sex:

male

Dose descriptor:

other: Lethal Dose

Effect level:

20 mg/kg bw

Based on:

test mat.

Conclusions:

Lethal dose (dog, oral): 20 mg/kg

Executive summary:

The test substance was administered orally to male beagle dogs in gelatin capsules in doses of 10 or 20 mg/kg. In some cases blood was taken from the femoral vein just prior to dosing and at various time intervals thereafter for cholinesterase activity measurements. Atropine sulfate, way given by various routes after the oral administration of the test substance to ascertain whether it had antidotal properties; in one test, tetraethylammonium chloride (TEAC) was examined for the antidotal properties.

The test substance is highly toxic when administered orally to male dogs in single doses, its Lethal Dose being 20 mg/kg; it produces clinical signs of toxicity that have been associated with anticholinesterase compounds. Atropine sulfate appears to be an antidote in the dog, for the test substance if administered very quickly after exposure; intravenous administration is more efficacious than oral or intramuscular administration. The oral administration of the test substance to dogs is accompanied by a lowering of blood cholinesterase activity. This depression in activity occurs very rapidly after exposure to the test substance, but its return to pre-exposure values is also rapid; this occurs 0.5 to 1.5 hours after exposure, depending upon the magnitude of the administered dose of the test substance. Although atropine sulfate does protect against the toxic and lethal action of the test substance, it does not appear to prevent the lowering of blood cholinesterase activity.

Reference 4

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The test substance, as a solution in acetone peanut oil (1:10), was administered by intragastric intubation to male guinea pigs in single doses. At the various dose levels, some guinea pigs, serving as controls, were, after being dosed, immediately given an intraperitoneal injection of physiological saline, while others were given an intraperitoneal injection of atropine sulfate (50 mg/kg) dissolved in physiological saline. Survivors were sacrificed 14 days later.

GLP compliance:

no

Test type:

standard acute method

Specific details on test material used for the study:

S-Methyl N-[(methylcarbamoyl)oxy]thioacetimidate
Lot number: INX-1179-35
Purity: Not reported

Species:

guinea pig

Strain:

not specified

Sex:

male

Route of administration:

oral: gavage

Vehicle:

other: Acetone:peanut oil (1:10)

Doses:

5, 10, 15, 30 and 60 mg/kg

No. of animals per sex per dose:

3

Control animals:

no

Key result

Sex:

male

Dose descriptor:

other: Minimum Lethal Dose

Effect level:

15 mg/kg bw

Based on:

test mat.

Conclusions:

Minimum Lethal Dose (Guinea pig, oral): 15 mg/kg of body weight

Executive summary:

The test substance, as a solution in acetone peanut oil (1:10), was administered by intragastric intubation to male guinea pigs in single doses. At the various dose levels, some guinea pigs, serving as controls, were, after being dosed, immediately given an intraperitoneal injection of physiological saline, while others were given an intraperitoneal injection of atropine sulfate (50 mg/kg) dissolved in physiological saline. Survivors were sacrificed 14 days later.

The test substance is very toxic for the male guinea pig when administered orally in single doses, its minimum lethal dose being 15 mg/kg of body weight. Mortality observed in 15, 30 and 60 mg/kg groups within 1 day of dosing. Clinical signs observed were fasciculations, salivation, pallor, irregular respiration, slight hyperemia. Atropine sulfate appears to have antidotal activity against the toxic and lethal action of the test substance in guinea pigs.

Reference 5

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The test substance, as a 5% Suspension in acetone:water (1:10) was administered in single doses directly into the crop of ten sex-linked hens approximately one year old. The LD50 values were calculated from mortality data.

GLP compliance:

no

Test type:

standard acute method

Specific details on test material used for the study:

S-Methyl N-[(methylcarbamoyl)oxy]thioacetimidate
Lot number: INX-1179-68
Purity: Not reported

Species:

hen

Strain:

not specified

Route of administration:

oral: unspecified

Vehicle:

other: acetone:water (1:10)

Doses:

20 and 40 mg/kg

No. of animals per sex per dose:

5

Control animals:

no

Key result

Dose descriptor:

LD50

Effect level:

28 mg/kg bw

Based on:

test mat.

Conclusions:

LD50 (Adult hen): 28 mg/kg of body weight

Executive summary:

The test substance, as a 5% Suspension in acetone:water (1:10) was administered in single doses directly into the crop of ten sex-linked hens approximately one year old. 1 and 4 animals died in 20 and 40 mg/kg groups respectively. The LD50 was 28 mg/kg in adult hens.

Reference 6

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The test substance, as a solution in acetone:peanut oil (1:10), was administered by intragastric intubation to male rabbits in single doses. At the various dose levels tested, some rabbits, serving as controls, were, after being dosed, immediately given an intraperitoneal injection of physiological saline, while others were given intraperitoneal injections of atropine sulfate (50 mg/kg) dissolved in physiological saline. Survivors were sacrificed 14 days after dosing.

GLP compliance:

no

Test type:

standard acute method

Specific details on test material used for the study:

S-Methyl N-[(methylcarbamoyl)oxy]thioacetimidate
Lot number: INX-1179-35
Purity: Not reported

Species:

rabbit

Strain:

not specified

Sex:

male

Route of administration:

oral: gavage

Vehicle:

other: Acetone:peanut oil (1:10)

Doses:

15, 30 and 60 mg/kg

Control animals:

no

Key result

Sex:

male

Dose descriptor:

other: Minimum Lethal Dose

Effect level:

30 mg/kg bw

Based on:

test mat.

Conclusions:

Minimum lethal dose (rabbitt, oral): 30 mg/kg of body weight

Executive summary:

The test substance, as a solution in acetone:peanut oil (1:10), was administered by intragastric intubation to male rabbits in single doses. At the various dose levels tested, some rabbits, serving as controls, were, after being dosed, immediately given an intraperitoneal injection of physiological saline, while others were given intraperitoneal injections of atropine sulfate (50 mg/kg) dissolved in physiological saline. Survivors were sacrificed 14 days after dosing.

Mortality observed only in 30 and 60 mg/kg groups within 30 min of dosing. Clinical signs included fasciculations, salivation, constricted pupils, bulging eyes, convulsions, cyanosis, rapid respiration. The test substance is very toxic when administered orally to male rabbits in single doses, its minimum lethal dose being 30 mg/kg of body weight. Atropine sulfate appears to act as an antidote against the lethal action of the test substance in rabbits

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

17.98 mg/kg bw

Quality of whole database:

Seven acute oral studies were available in rats, two conducted by guidelines. Additional oral studies were available in rabbits, dog, guinea pig and hens. LD50 values all fell within the same GHS category. The most current rat study was selected as the key study as it was conducted via OECD guidelines.

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

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

Qualifier:

according to guideline

Guideline:

EPA OPP 81-3 (Acute inhalation toxicity)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: MAFF Testing Guideline for Acute Inhalation Toxicity Study (59 NohSan No. 4200)

Deviations:

no

GLP compliance:

yes

Test type:

acute toxic class method

Limit test:

no

Specific details on test material used for the study:

- Substance name: Ethanimidothioic acid,N-[[(methylamino)carbonyl]oxy]-, methyl ester
- Substance ID: DPX-X1179
- Lot#: X1179-427
- Purity: 97.7%

Species:

rat

Strain:

other: Crl:CD BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Kingston, New York
- Age at study initiation: Approximately 8 weeks
- Weight at study initiation: Males: 223 to 272 grams; Females: 183 to 219 grams
- Fasting period before study: Not specified
- Housing: Rats were housed either singly or in pairs (sexes separate) in 8" x 14" x 8" suspended, stainless steel, wire-mesh cages.
- Diet: Purina Certified Rodent Chow # 5002 ad libitum
- Water: Tap water ad libitum
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature: 23 ± 2°C
- Humidity: 50 ± 10%
- Photoperiod: 12 hrs dark / hrs light

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

other: Distilled water

Mass median aerodynamic diameter (MMAD):

>= 1.3 - <= 3.8 µm

Geometric standard deviation (GSD):

>= 2.3 - <= 2.9

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: An atmosphere of test substance was generated by suspending the solid in distilled water at a concentration of 3% and generating an aerosol using an Airlife Solo-Sphere nebulizer.
- Exposure chamber volume: 29-L
- Method of holding animals in test chamber: During exposure, rats were restrained in perforated, polycarbonate cylinders with conical nose pieces. The restrainers were inserted into the face plate of a 29-L, cylindrical, glass exposure chamber so that only the nose of each rat protruded into the chamber.
- Source and rate of air: Pressurized air introduced at the Solo-Sphere (7.8-12 L/min) atomized the test material and swept the resulting aerosol into the 29-L, cylindrical, glass exposure chamber. Filtered dilution air was introduced into the chamber at rates of 4.5-13 L/min.
- System of generating aerosols: Using Airlife Solo-sphere nebulizer
- Method of particle size determination: Gravimetric analysis
- Treatment of exhaust air: The chamber atmosphere was exhausted through a glass bubbler filled with water and an MSA particulate filter prior to being discharged in to the fume hood.
- Temperature, humidity, pressure in air chamber: Airflow during the exposures ranged from 14.4-22.4 L/min. Chamber temperatures ranged from 21 to 25°C, relative humidity ranged from 70% to 100%, and the oxygen concentration was 21%.

TEST ATMOSPHERE
- Brief description of analytical method used: Chromatographic analyses of the gravimetric filters from exposures are used for measuring mean total analyrtical concentration.
- Samples taken from breathing zone: yes. The atmospheric concentration of test substance was determined at approximately 30-minute intervals during each exposure using gravimetric
analysis. Four to 10 litre samples of chamber atmosperes were drawn from breathing zone of the rats through a 25 mm filter cassette that contained a preweighed Gelman glass fiber (Type A/E) filter. Cahn Model C-31 Microbalance and then placed in a dessicator. Concentration of test subatnce was calculated from the difference in the preand post-sampling dry filter weights.

TEST ATMOSPHERE
- Particle size distribution: Chamber test atmospheres consisted of 6.2 to 40% of the particles less than 1 µm, 38 to 84% less than 3 µm, and 85 to 99% less than 10 µm.
- MMAD (Mass median aerodynamic diameter) and Geometric standard deviation: 1.3 to 3.8µm and GSD ranged from 2.3 to 2.9

Analytical verification of test atmosphere concentrations:

yes

Remarks:

The mean analytical concentrations of test substance were 0.126, 0.160, 0.179, 0.215, and 0.304 mg/L for 0.137, 0,181, 0.182, 0.232, and 0.326, respectively.

Duration of exposure:

4 h

Concentrations:

0.137, 0.181, 0.182, 0.232, and 0.326 mg/L

No. of animals per sex per dose:

5

Control animals:

yes

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Rats were weighed and observed for clinical signs of toxicity daily, excluding test Days 5, 11, and 12 for the 0.137 mg/L group, test Days 4, 10, and 11 for the 0.181 mg/L group, test Days 6, 7, 13, and 14 for the 0.182 mg/L group, test Days 4 , 5, 11, and 12 for the 0.232 group, and test Days 6, 7, 13, and 14 for the 0.326 mg/L group.
- Necropsy of survivors performed: yes

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

0.258 mg/L air

Based on:

test mat.

Exp. duration:

4 h

Mortality:

No rats died that were exposed to concentrations of 0.137 or 0.181 mg/L. In other exposures, 1 of 10 rats died at 0.182 mg/L, 6 of 10 rats died at 0.232 mg/L, and 7 of 10 rats died at 0.326 mg/L. All rats that died did so during the exposures. There was no difference between the response of the male and female rats based on mortality.

Clinical signs:

other: Clinical signs of toxicity assessed during the exposure included nasal discharge and salivation. Nasal movement was assessed to determine mortality of the rats. Upon removal of the rats from the restrainers immediately following exposure, the clinical sig

Body weight:

By the first day post exposure, most of the rats exhibited weight loss. Rats began gaining weight by the second day of recovery and despite some transient weight losses experienced an overall gain by the end of recovery.

Gross pathology:

All exposed rats were sacrificed and subjected to a gross pathological examination 14 days after exposure. Gross abnormalities found in rats which were found dead included expanded lungs and edema of the pleural cavity. These abnormalities are considered to be associated with stress resulting from systemic toxicity. Gross observations included small bilateral testes and seminal vesicles in 1 male rat and a unilateral dilatation of the renal pelvis in another male rat. These findings were considered to be incidental. No target organ was identified in these rats.

Interpretation of results:

Category 2 based on GHS criteria

Conclusions:

LC50 Rat (Male/Female): 0.258 mg/L

Executive summary:

The study was conducted according to test guideline OECD 403 and US EPA 81-3 to determine the acute inhalation toxicity of test substance in rats. Five groups of 5 male and 5 female CRL:CD BR rats each were exposed to an atmosphere of test substance for a single, 4-hour exposure period. The test atmosphere was generated by suspending the test material in distilled water and aerosolizing the mixture. During the exposure, the concentration of the test aerosol was determined by gravimetric analysis A subsequent liquid chromatographic analysis of the eluent from the desorption of select gravimetric filters was carried out to determine the amount of test substance collected. In the pursuant 14-day recovery period, rats were weighed and observed for clinical signs of toxicity. All rats underwent gross pathological examination at the end of the recovery period.

Rats were exposed to dry weight concentrations of 0.137, 0.181, 0.182, 0.232, and 0.326 mg/L of test substance. Total particulate was determined to be homogeneously distributed in the exposure chamber. The test aerosol during the exposure was characterized by measurement of a mass median aerodynamic diameter (MMAD). The MMAD of the aerosols generated ranged from 1.3 to 3.8 µm with 6.2 to 40% of the particles being less than 1 µm and 38 to 84% of the particles being less than 3 µm.

1 of 10 rats exposed to test substance died following exposure at 0.182 mg/L. 6 of 10 rats exposed at 0.232 mg/L died and 7 of 10 rats died following exposure at 0.326 mg/L. All rats exposed to test substance at 0.137 or 0.181 mg/L survived exposure and pursuant recovery period.

Clinical signs of toxicity observed immediately following exposures included diarrhea, lethargy, and ocular or nasal discharge. Rats surviving exposures at levels which produced mortality also showed signs of abnormal gait or mobility, low posture, tremors, hyperactivity, hyperreactivity, and muscle fasciculations. These clinical signs were transient and were absent on the day following their initial observation. These clinical signs are consistent clinical signs commonly observed in materials from the family of methyl carbamate insecticides. Wet fur, a common sign associated with the restrainers used for nose-only exposure, was noted in most of the rats immediately following the exposure. Other clinical signs observed during the recovery period included stained and/or ruffled fur, diarrhea, hunched posture, ocular and/or nasal discharge, irregular respiration, and lethargy. Corneal opacity was noted in one animal exposed to 0.232 mg/L of test substance. Rats that survived exposures experienced some weight loss immediately following exposure and some transient weight loss later in the recovery, but all rats showed an overall weight gain by the end of the 14-day recovery period. Gross pathological examination revealed no evidence of organ-specific toxicity in any rats.

Under the conditions of this test, the LC50, for test substance was 0.258 mg/L. On an acute inhalation basis, test substance was considered to have moderate toxicity (LC50, between 0.2 mg/L and 0.8 mg/L).

Reference 2

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The study was conducted to compare two different lots of test substance for inhalation toxicity of respirable sized aerosols prepared from melted material at 100°C. 6 rats were exposed at different concentrations of test substance for 4 hours. Surviving rats were maintained for 2 weeks and observed for moratlity, clinical signs and adverse toxic reactions.

GLP compliance:

no

Specific details on test material used for the study:

Test substance Nmae: Methyl O-(Methylcarbamyl)thioacetohydroxamate
Substance ID: INX-1179
Lot#: B-11 (H-5402); B-12 (H-5403)
Purity: Not reported

Species:

rat

Strain:

not specified

Sex:

not specified

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

not specified

Vehicle:

air

Mass median aerodynamic diameter (MMAD):

>= 3.3 - <= 5.7 µm

Geometric standard deviation (GSD):

>= 2.6 - <= 3.1

Analytical verification of test atmosphere concentrations:

not specified

Duration of exposure:

4 h

Concentrations:

Lot#B-11: 0.11, 0.27, 0.30, 0.45, 0.59 and 0.92 mg/L; Lot#B-12: 0.12, 0.24, 0.28 and 0.40 mg/L

No. of animals per sex per dose:

6

Control animals:

yes

Key result

Sex:

not specified

Dose descriptor:

LC50

Remarks:

Approximate

Effect level:

0.3 mg/L air

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

other: For Lot#B-11

Key result

Sex:

not specified

Dose descriptor:

LC50

Remarks:

Approximate

Effect level:

0.28 mg/L air

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

other: For Lot#B-12

Interpretation of results:

Category 2 based on GHS criteria

Conclusions:

LC50 values of the two lots of test substance in rats were 0.28 (B-12) and 0.30 mg/L (B-11).

Executive summary:

The study was conducted to compare two different lots of test substance for inhalation toxicity of respirable sized aerosols prepared from melted material at 100°C. 6 rats were exposed at different concentrations of test substance for 4 hours. Surviving rats were maintained for 2 weeks.

The results showed delayed deaths and progressive weight loss which were associated with exposures at the higher levels. Most of deaths, however, were during the exposures. The clinical signs observed included salivation, lacrimation, fasciculations, tremors, gasping, irregular breathing and exopthalmos. The toxic signs were consistent with those expected for an anticholinesterase agent. The LC50 value of two lots were not significantly different (0.28 and 0.30 mg/L).

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LC50

Value:

258 mg/m³ air

Quality of whole database:

Two acute inhalation calculating 4-hr LC50 values were available. One was conducted by OECD guidelines and therefore used as the key study.

Acute toxicity: via dermal route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.1200 (Acute Dermal Toxicity)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Ministry of Agriculture, Forestry and Fisheries of Japan 12-Nouan-8147

Deviations:

no

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Specific details on test material used for the study:

- Substance name: Methomyl Technical
- Substance ID: DPX-X1179
- Lot#: X1179-599
- Purity: 99.6%

Species:

rat

Strain:

Sprague-Dawley

Remarks:

albino

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Ace Animals, Inc., Boyertown, Pennsylvania
- Females nulliparous and non-pregnant: Yes
- Age at study initiation: Young adult (8-9 weeks)
- Weight at study initiation: Males 259-273 grams and females 189-217 grams
- Housing: One animal per cage
- Diet: Purina Rodent Chow #5012
- Water: ad libitum
- Acclimation period: 9 days

ENVIRONMENTAL CONDITIONS
- Temperature: 19-22°C
- Humidity: 46-67%
- Photoperiod: 12-hour light/dark cycle

Type of coverage:

semiocclusive

Vehicle:

water

Details on dermal exposure:

TEST SITE
- Area of exposure: Dorsal area and the trunk
- % coverage: Approximately 10% of the body surface
- Type of wrap: 3-inch Durapore tape

REMOVAL OF TEST SUBSTANCE
- Washing: Test sites were gently cleansed of any residual test substance
- Time after start of exposure: 24 hours

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 1.3-1.9 g
- For solids, paste formed: Yes

Duration of exposure:

24 hours

Doses:

5000 mg/kg body weight

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: The animals were observed for mortality, signs of toxicity, and behavioral changes 1 and 5 hours after application and at least once daily thereafter for 14 days. Individual weights of the animals were recorded prior to test substance application (initial) and again on Days 7 and 14 (termination).
- Necropsy of survivors performed: Yes
- Examinations performed: Observations included gross evaluation of skin and fur, eyes and mucous membranes, respiratory, circulatory, autonomic and central nervous systems, somatomotor activity and behavior pattern. Particular attention was directed to observation of tremors, convulsions, salivation, diarrhea, and coma. Gross necropsies were performed on all animals. Tissues and organs of the thoracic and abdominal cavities were examined.

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 5 000 mg/kg bw

Based on:

test mat.

Mortality:

All animals survived during the study

Clinical signs:

other: Erythema was observed at the application site of one female on Day 1 following patch removal. There were no signs of gross toxicity, adverse clinical signs, or abnormal behavior.

Gross pathology:

No gross abnormalities were noted for any of the animals when necropsied at the conclusion of the 14-day observation period.

Interpretation of results:

GHS criteria not met

Conclusions:

LD50 (Rat): > 5000 mg/kg bw

Executive summary:

An acute dermal toxicity test was conducted with rats to determine the potential for test substance to produce toxicity from a single topical application. This study was conducted according to OECD guideline 402 and OPPTS 870.1200.

Five thousand milligrams of the test substance per kilogram of body weight was moistened with distilled water and then applied to the skin of ten healthy rats (five male and five female) for 24 hours. The animals were observed for mortality, signs of toxicity, and behavioral changes 1 and 5 hours post-dosing and at least once daily for 14 days. Body weights were recorded prior to application and again on Days 7 and 14. Necropsies were performed on all animals at terminal sacrifice.

All animals survived and gained body weight during the study. Erythema was observed at the application site of one female on Day 1 following patch removal. There were no signs of gross toxicity, adverse clinical signs, or abnormal behavior. No gross abnormalities were noted for any of the animals when necropsied at the conclusion of the 14-day observation period.

Under the conditions of this study, the single dose acute dermal LD50 of the test substance is greater than 5000 mg/kg of body weight in male and female rats.

Reference 2

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

supporting study

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

Specific details on test material used for the study:

- Substance name: Ethanimidothioic acid, N-[[(methylamino)carbonyl]oxy]-, methyl ester
- Substance ID: DPX-X1179
- Lot#: T00620-06
- Purity: 98.35%

Species:

rabbit

Strain:

New Zealand White

Sex:

male/female

Type of coverage:

occlusive

Vehicle:

water

Duration of exposure:

24 hours

Doses:

2000 mg/kg bw

No. of animals per sex per dose:

5

Control animals:

no

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Interpretation of results:

GHS criteria not met

Conclusions:

LD50 (Rabbit): > 2000 mg/kg bw

Executive summary:

The study was conducted following the guideline, EPA OPP 81-2. A single dose of the test substance was applied to the shaved, intact skin of 5 male and 5 female New Zealand White rabbits at a dosage of 2000 mg/kg bw. The application site was occluded for 24 hours. The rabbits were observed for 14 days following application.

No rabbits died within 14 days after dosing. Slight weight loss (up to 3% of initial body weight) occurred in some rabbits the day following treatment. Slight erythema but no edema was observed in 2 rabbits the day following treatment. No dermal irritation was observed by Day 2 following treatment.

Under the conditions of this test, the skin absorption LD50 for the test substance was greater than 2000 mg/kg of body weight.

Reference 3

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The test substance was applied on the clipped area on the back of six male albino rats at the maximum dose of 5000 mg/kg bw. After 24 hours of exposure, the treated area was washed and observed for 14-days.

GLP compliance:

no

Test type:

fixed dose procedure

Limit test:

yes

Specific details on test material used for the study:

Substance name: INX-1179
Batch No.: 2606
Purity: 98.5%

Species:

rabbit

Strain:

other: albino

Sex:

male

Type of coverage:

occlusive

Vehicle:

water

Remarks:

distilled

Duration of exposure:

24 hours

Doses:

5000 mg/kg bw

No. of animals per sex per dose:

6

Control animals:

not specified

Key result

Sex:

male

Dose descriptor:

LD50

Effect level:

> 5 000 mg/kg bw

Based on:

test mat.

Interpretation of results:

GHS criteria not met

Conclusions:

LD50 (Rabbit): > 5000 mg/kg bw

Executive summary:

Six male albino rabbits with previously clipped back areas were treated with a dose level calculated on body weight. The maximum level of 5000 mg/kg (16.8 g) was applied to their skin by means of a polyethylene pouch, held in place with Elastoplast and adhesive tape with 15 mL of distilled water (52.8% slurry) injected into the pouch to wet the test material for better skin contact. The pouch offered approximately 10 x 10 cm skin contact. After 24 hours, the pouch was removed, animals were washed and dried and returned to their cages for a 14-day observation period.

All six animals survived the test. No weight loss or significant signs were observed.

As a result of the test, the LD50 for the test substance has been determined to be > 5000 mg/kg bw.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

5 000 mg/kg bw

Quality of whole database:

Two acute dermal LD50 studies were available in rat, one of which was conducted via OECD guidelines. One acute dermal LD50 study was available in rabbits which was conducted according to EPA 81-2 guidelines.

Additional information

Rats were tested in an acute oral toxicity up and down procedure according to OECD guideline 425 and EPA OPPTS 870.1100. A default starting dose level of 10.1 mg/kg was used. Subsequently two additional females were dosed at 10.1 mg/kg, one female at 3.2 mg/kg, three females at 32 mg/kg and one female at 101 mg/kg. One animal dosed at 10.1 mg/kg and two dosed at 32 mg/kg died within one hour of test substance administration. Clinical signs noted in the decedents prior to death included hypoactivity, tremors and/or prone posture. The surviving rats from these dose groups exhibited clinical signs including hypoactivity, tremors and/or piloerection on the day of dosing. All surviving animals recovered from these signs within one-day post-dosing and appeared active and healthy for the remainder of the 14-day observation period, showing no body weight loss during the study. Gross necropsy of the decedents revealed discoloration of the intestines. No gross abnormalities were noted for any of the euthanized animal necropsied at the conclusion of the 14-day observation period. The rat dosed at 101 mg/kg died within 30 minutes of test substance administration. Clinical signs noted in the decedent prior to death included hypoactivity and prone posture. Gross necropsy of the decedent revealed discoloration of the intestines. The acute oral LD50 of the test substance was estimated to be 17.98 mg/kg of body weight.

In an acute 4-hour inhalation study, groups of five male and five female rats were exposed for a single four-hour period to the test substance (MMAD > 1.3 to < 3.8 µm) at a concentration of 0.137, 0.181, 0.182, 0.232, and 0.326.  The test was conducted according to OECD guideline 403 and EPA 81-3. One of 10 rats exposed to test substance died following exposure at 0.182 mg/L. Six of 10 rats exposed at 0.232 mg/L died and 7 of 10 rats died following exposure at 0.326 mg/L. All rats exposed to test substance at 0.137 or 0.181 mg/L survived exposure and pursuant recovery period. Clinical signs of toxicity observed immediately following exposures included diarrhea, lethargy, and ocular or nasal discharge. Rats surviving exposures at levels which produced mortality also showed signs of abnormal gait or mobility, low posture, tremors, hyperactivity, hyperreactivity, and muscle fasciculations. These clinical signs were transient and were absent on the day following their initial observation. These clinical signs are consistent clinical signs commonly observed in materials from the family of methyl carbamate insecticides. Wet fur, a common sign associated with the restrainers used for nose-only exposure, was noted in most of the rats immediately following the exposure. Other clinical signs observed during the recovery period included stained and/or ruffled fur, diarrhea, hunched posture, ocular and/or nasal discharge, irregular respiration, and lethargy. Corneal opacity was noted in one animal exposed to 0.232 mg/L of test substance. Rats that survived exposures experienced some weight loss immediately following exposure and some transient weight loss later in the recovery, but all rats showed an overall weight gain by the end of the 14-day recovery period. Gross pathological examination revealed no evidence of organ-specific toxicity in any rats. The 4-hour LC50 for test substance was determined to be 0.258 mg/L.

In an acute dermal toxicity study in rats, five rats per sex were administered 5000 mg/kg according to OECD guideline 402 and OPPTS 870.1200. All animals survived and gained body weight during the study. Erythema was observed at the application site of one female on Day 1 following patch removal. There were no signs of gross toxicity, adverse clinical signs, or abnormal behavior. No gross abnormalities were noted for any of the animals when necropsied at the conclusion of the 14-day observation period. Under the conditions of this study, the single dose acute dermal LD50 was greater than 5000 mg/kg. In an acute dermal test in rabbits conducted according to EPA 81-2, 5 the test substance was applied to the skin of 5 male and 5 female rabbits at a dose of 2000 mg/kg body weight. No rabbits died within 14 days after dosing. Slight weight loss (up to 3% of initial body weight) occurred in some rabbits the day following treatment. Slight erythema but no edema was observed in 2 rabbits the day following treatment. No dermal irritation was observed by Day 2 following treatment. Under the conditions of this test, the skin absorption LD50 for the test substance was greater than 2000 mg/kg of body weight.

Justification for classification or non-classification

Based on dermal LD50s in rats and rabbits of >5000 and >2000 mg/kg, no classification is required for the acute dermal toxicity endpoint according to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008. Based on the acute oral LD50 of 17.98 mg/kg in rats and a 4-hour acute inhalation LC50 of 0.258 mg/L, classifications of acute oral Category 2 and acute inhalation Category 2 are warranted.