sodium 2-{N-[(3,5-difluorophenyl)carbamoyl]ethanehydrazonoyl}nicotinate

Endpoint summary

Description of key information

In two acute oral toxicity studies with the test substance and the read-across test substance similar results were obtained with LD50 values of 4000 mg/kg bw and greater than 5000 mg/kg bw respectively. In an acute oral toxicity study that examined the neurotoxicity potential of the read-across test substance, no evidence of neurotoxicity at dosages up to 2000 mg/kg bw was found. An acute inhalation toxicity study (limit test) was performed with the read-across test substance (free acid of Diflufenzopyr sodium salt). The LC50 value determined was greater than 2.93 mg/L. In two acute dermal toxicity studies with the test substance and the read-across test substance (free acid of Diflufenzopyr sodium salt) an LD50 value of greater than 5000 mg/kg bw was obtained.

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:

1995-05-10 until 1995-06-26

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Scientifically valid study

Qualifier:

according to guideline

Guideline:

EPA OPP 81-1 (Acute Oral Toxicity)

Version / remarks:

November 1984

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: Harlan Olac Ltd, Bicester, Oxon, England
- Age at study initiation: 7 - 10 weeks
- Weight at study initiation: 192 - 260 g
- Housing: metal cages with wire mesh floors
- Diet: a standard laboratory rodent diet (SDS LAD 1), ad libitum
- Water: ad libitum
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature: 22 ± 3°C
- Humidity: 30 - 70 %
- Air changes: 10 - 15 air changes per hour
- Photoperiod: 12 hours of artificial light

Route of administration:

oral: gavage

Vehicle:

other: 1 % w/v aqueous methylcellulose

Details on oral exposure:

MAXIMUM DOSE VOLUME APPLIED: 10 mL/ kg

Doses:

5000, 3200, 1600 mg/kg bw

No. of animals per sex per dose:

10 rats per dose: 5 males, 5 females

Control animals:

other: not required

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: daily - clinical signs - daily and weighing 3 times during the observation period (once a week)
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight, organ weights

Statistics:

The acute median lethal oral dose (LD50) to male and female rats was calculated using the method of Finney [FINNEY, D.J. (1971) Probit Analysis, 3rd Cambridge University Press, Cambridge].

Sex:

male/female

Dose descriptor:

LD50

Effect level:

4 000 mg/kg bw

Based on:

test mat.

Sex:

male

Dose descriptor:

LD50

Effect level:

4 800 mg/kg bw

Based on:

test mat.

Sex:

female

Dose descriptor:

LD50

Effect level:

3 300 mg/kg bw

Based on:

test mat.

Mortality:

Two females at 3200 mg/kg bw and 3 males and all females at 5000 mg/kg died during the study. Deaths occurred between 24 to 48 hours of dosing.

Clinical signs:

Clinical signs of reaction to treatment included piloerection and soft to liquid faeces, seen among rats at all three dosages. In addition, abnormal body carriage, abnormal gait, lethargy, decreased respiratory rate, partially closed eyelids, pallor of the extremities, increased urine production, increased salivation, gasping, walking on toes, unsteadiness, increased lacrimation, bluish colour to skin/extremities, cold body surfaces, prostration, brown staining around nose and mouth and red stained urine were seen among rats at one or more dose levels. Recovery of surviving rats was complete in all instances by day 7.

Body weight:

Slight bodyweight losses were recorded for all decedents. A slightly low bodyweight gain was recorded on day 8 for one male at 5000 mg/kg and two females at both 1600 and 3200 mg/kg. A similar trend was noted on day 15 for two males and one female at 1600 m g/kg, with one further female at 1600 mg/kg showing a slight bodyweight loss at this time. All other surviving animals achieved satisfactory bodyweight gains throughout the study.

Gross pathology:

Macroscopic examination revealed changes to all major organs and tissues of animals who died during the observation period. No abnormalities were recorded at the macroscopic examination on day 15.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

4 000 mg/kg bw

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

1996-06-21 until 1995-07-12

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Scientifically valid study, OECD guideline study. Please refer to IUCLID section 13 for read-across justification.

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPP 81-3 (Acute inhalation toxicity)

Deviations:

no

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River UK Ltd, Manston Road, Margate, Kent, England
- Age at study initiation: 8 weeks
- Weight at study initiation: 200 - 300 g
- Housing: The holding cages were made of stainless steel sheet and wire mesh and were suspended on a movable rack.
- Diet: SDS RM1
- Water: tap water
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature: 18 - 24°C
- Humidity: 45 - 78 %

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose only

Vehicle:

air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: A Wright dust generator was used to produce the test atmospheres containing the dust of the test substance
- Exposure chamber volume: 5 L
- Method of holding animals in test chamber: The snout-only exposure chambers were of cylindrical form and made of aluminium alloy. The rats were held for exposure, individually, in polycarbonate restraining tubes attached at one of the ports in the cylindrical section of the chamber. The tube was tapered at one end to allow the snout only to project into the chamber. The other end was closed by insertion of an expanded plastic bung. A push rod passed through the centre of the bung and was adjustable to maintain the position of the rats during exposure.
- Source and rate of air: A supply of clean dried compressed air was connected to the dust generator and the supply pressure was adjusted to give a flow rate of 14 litres per minute measured at the generator outlet nozzle. The total chamber air supply was made up to 15 1/minute with an additional flow of 11/minute into the diluent port of the chamber.
- Method of conditioning air: The test atmosphere was passed through an elutriation column to reduce, by sedimentation, the amount of non-respirable particulate in the test atmosphere.
- Temperature, humidity: 21°C, 25 %

TEST ATMOSPHERE
- Brief description of analytical method used: Five air samples were taken from the chamber during the exposure to determine the concentration of the test substance in the chamber air by chemical analysis. Samples were collected at 30, 60, 120, 180 and 235 minutes following the equilibrium period. Each air sample was withdrawn, at 4 litres per minute, through a weighed glass fibre filter mounted in an open face filter holder. The volume of the air sample was measured with a wet-type gas meter. Two additional air samples were taken during each exposure using a Marple cascade impactor. The samples were taken approximately 1.5 and 3.5 hours after the start of exposure. The material collected on the stages of the sampler was analysed to determine the particle size distribution of the test subsrance in the test atmospheres.
- Samples taken from breathing zone: yes

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

Mean analysis concentration: 2.93 mg/L
Mean gravimetric concentration: 3.14 mg/L
Nominal concentration (the nominal concentration is calculated from the amount of the test substance disperrsed and the total volume of air supplied to the exposure system): 17.5 mg/L

No. of animals per sex per dose:

10 animals: 5 males, 5 females

Control animals:

yes

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: daily
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight, organ weights, histopathology

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 2.93 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Mortality:

No mortality was observed

Clinical signs:

other: During exposure - There were no signs attributable to exposure to the test substance in the test rats. Soiling of the fur with as a consequence of the method of restraint was seen in control and test rats. During observation period - The only sign was exc

Body weight:

Reduced bodyweight or a reduced rate of bodyweight gain was seen in rats exposed to the test substance for 1 day. Subsequently, weight gain was similar to that of control rats.

Gross pathology:

- The lung weight to bodyweight ratios for rats exposed to the test substance were similar to those of the control rats
- There were no internal or external macroscopic abnormalities detected in rats exposed to the test substance
- No treatment-related changes were detected.

Other findings:

Water consumption:
Water consumption was slightly increased for 2 days following exposure to the test substance. Subsequently, water consumption for test rats was similar to that of the control rats.

- The size distribution results from the chemical analysis: 3.5 µm (MMAD) and 80.8 % of respirable particles (< 7 µm)

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating conc.

Value:

2 930 mg/m³

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:

1995-05-18 until 1995-05-19

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Scientifically valid study similar to current OECD guideline

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:

rabbit

Strain:

New Zealand White

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Froxfield (U.K.) Ltd., Petersfield, Hampshire, England
- Age at study initiation: 10 - 13 weeks
- Weight at study initiation: 2.2 - 2.9 kg
- Housing: metal cages with wire mesh floors
- Diet: a standard laboratory rodent diet (SDS Rabbit diet SQC), ad libitum
- Water: drinking water, ad libitum
- Acclimation period: 8 days

ENVIRONMENTAL CONDITIONS
- Temperature: 19°C
- Humidity: 30 - 70 %
- Air changes: 10 - 15 air changes per hour
- Photoperiod: 12 hours of artificial light

Type of coverage:

semiocclusive

Vehicle:

other: 1 % w/v aqueous methylcellulose

Details on dermal exposure:

TEST SITE
- Area of exposure: dorso-lumbar region
- % coverage: 10 %
- Type of wrap if used: The treated area (approximately 50 mm x 50 mm) was promptly covered with two layers of gauze which were held in place with a non-irritative elastic adhesive bandage encircled firmly around the trunk. This bandage was secured with waterproof strapping BP tape to provide a semi-occlusive wrapping which inhibited evaporation and inhalation of the test material or wetting agent and also prevented the animal from ingesting the test substance.

REMOVAL OF TEST SUBSTANCE
- Washing: with warm water
- Time after start of exposure: 24 hours

TEST MATERIAL AND VEHICLE
The test substance was prepared at a maximum practical concentration of 83.33 % w/v in 1 % w/v aqueous methylcellulose and administered at a volume of 6 mL/kg bw.

Duration of exposure:

24 hours

Doses:

5000 mg/kg bw

No. of animals per sex per dose:

10 animals: 5 males, 5 females

Control animals:

not required

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: daily - for clinical signs. Body weights were recorded on days 1, 8, and 15
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight, organ weights, histopathology

Sex:

male/female

Dose descriptor:

LD50

Effect level:

5 000 mg/kg bw

Based on:

test mat.

Mortality:

No mortality was observed.

Clinical signs:

There were no signs of systemic reaction to treatment.

Body weight:

A slight bodyweight loss was recorded for one male on day 8 and for one female on day 15. In addition, one further male showed a slightly low bodyweight gain on day 15. All other rabbits achieved satisfactory bodyweight gains throughout the study.

Gross pathology:

Macroscopic examination on day 15 revealed congestion in the kidney of one female only.

Other findings:

Dermal responses:
A residual (yellow/brown) staining from the test substance was evident at all treatment sites following the removal of the dressings and over the following days. This did not inhibit assessment for dermal responses. Slight to well-defined erythema and oedema were evident in all rabbits during the first week of the study. These reactions were accompanied in three females by desquamation (characterised by dryness and localised spots/scab formation). There were no other dermal responses and reactions gradually subsided in the majority of instances during the latter part of week 1, with recovery complete in all instances by day 13.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating dose

Value:

5 000 mg/kg bw

Additional information

Acute oral toxicity

Key study

A study (Sandoz, 1995) was performed to assess the acute oral toxicity of a formulation of the test substance to the rat, according to the Pesticide Assessment Guidelines, EPA 81-1. A group of ten fasted rats (five males and five females) was given a single dose by oral gavage of the test substance, formulated in 1 % w/v aqueous methylcellulose, at a dose level of 5000 mg/kg bw. On the basis of findings at this level, further dosages at 1600 and 3200 mg/kg bw were investigated to obtain a dose response curve and permit estimation of a median lethal dose. All animals surviving treatment were killed and examined macroscopically on day 15. Two females at 3200 mg/kg and three males and all females at 5000 mg/kg died during the study. Deaths occurred between 24 to 48 hours of dosing. Slight bodyweight losses were recorded for all decedents. Macroscopic examination revealed changes to all major organs and tissues. Various clinical signs of reaction to treatment were observed in the surviving rats in all doses tested. Recovery was complete in all instances by day 7. A slightly lower bodyweight gain/ loss was recorded by 6 rats. All other surviving animals achieved satisfactory bodyweight gains throughout the study. No abnormalities were recorded at the macroscopic examination. The acute median lethal oral dose (LD50) values estimated in the study: males and females combined: 4000 mg/kg bw, males: 4800 mg/kg bw, females: 3300 mg/kg bw

Supporting study

In this study (Sandoz, 1995) a read-across test substance (free acid of Diflufenzopyr sodium salt) was assessed for its neurotoxicity potential in rats. Three groups of 10 male and 10 female were administered with the read-across test substance in a single oral dose at levels of 125, 500 and 2000 mg/kg bw. A similar sized group was given the vehicle and acted as controls. All of these animals were subjected to a functional observational battery prior to treatment and at 3 hours post-dosing and on days 7 and 14 post-dosing. Motor activity of each animal was also quantitatively assessed at the same time points. Throughout the study, clinical signs, body weights and food consumption were monitored. Administration of the test substance was not associated with any clinical signs nor were there any notable effects on food consumption or bodyweight gain. There were a few changes on the functional observational battery on the day of dosing but these were interpreted as indicating an acute systemic response and not a neurotoxic response. Although lower brain weights were recorded for treated females, in the absence of any treated behavioural changes or neuropathology, this was not considered to be of toxicological importance. Based on these findings there was no evidence of neurotoxicity at dosages up to 2000 mg/kg bw.

Supporting study

A study (Sandoz, 1995) was performed to assess the acute oral toxicity of a read-across test substance (free acid of Diflufenzopyr sodium salt) according to the Pesticide Assessment Guidelines, EPA 81-1. A group of ten fasted rats (five males and five females) was given a single dose by oral gavage of the test substance, formulated in 1 % w/v aqueous methylcellulose, at a dose level of 5000 mg/kg bw. All animals surviving treatment were killed and examined macroscopically on day 15. There were no deaths. Several clinical signs were observed in all or the majority of rats. Recovery was complete in all instances by day 2. A slightly low bodyweight gains were noted in 5 rats. No abnormalities were recorded at the macroscopic examination. The acute lethal oral dose was determine to be greater than 5000 mg/kg bw.

Acute toxicity inhalation

Key study

An inhalation toxicity study was performed with the read-across test substance (free acid of Diflufenzopyr sodium salt). Ten rats were administered by snout-only exposure to a test atmosphere containing dust generated from the test substance for 4 hours. The test group and the control group were observed for fourteen days. There were no clinical signs or differences in bodyweights and food or water consumption that could be attribuated to exposure to the test substance. The lung weight to bodyweight ratios for rats exposed to the test substance were similar to those of the control rats. There were no internal or external macroscopic abnormalities detected in exposed rats and no treatment-related changes were detected. The LC50 value determined was greater than 2.93 mg/L.

Acute demal

Key study

A study was performed to assess the acute dermal toxicity of a formulation of the test substance to the rat, according to the Pesticide Assessment Guidelines, EPA 81-2. A group of ten rabbits (five males and five females) was given a single dermal application of the test substance, at a maximum practical concentration of 83.33 % w/v in 1 % w/v aqueous methyicellulose, and administered at a dose level of 5000 mg/kg bw. All animals were killed and examined macroscopically on day 15. There were no deaths and no signs of systemic reaction to treatment. Slight to well-defined dermal irritation was evident in all rabbits during the first week of the study. These responses were accompanied by desquamation in three females. There were no other dermal responses and reactions had resolved in all instances by day 13. Three rabbits showed a slight bodyweight gain/ loss. All other rabbits achieved satisfactory bodyweight gains throughout the study. No abnormalities were revealed at the macroscopic examination. The acute lethal dermal dose of the test substance was found to be greater than 5000 mg/kg bw.

Supporting study

A study was performed to assess the acute oral toxicity of the read-across test substance (free acid of Diflufenzopyr sodium salt) to the rat, according to the Pesticide Assessment Guidelines, EPA 81-2. A group of ten rabbits (five males and five females) was given a single dermal application of the test substance, at a maximum practical concentration of 66.67% w/v in 1 % w/v aqueous methylcellulose, and administered at a dose level of 5000 mg/kg bw. All animals were killed and examined macroscopically on day 15. There were no deaths and no signs of systemic reaction to treatment.

Slight to well-defined dermal irritation was evident in all rabbits during the early part of the study, persisting in the occasional animal through to day 8. There were no other dermal responses and reactions had resolved in all instances by day 9. Four rabbits showed a slight bodyweight gain/ loss. All other rabbits achieved satisfactory bodyweight gains throughout the study. Macroscopic examination revealed congestion in the kidney of one female. The acute lethal dermal dose to rabbits of the read-across test substance was found to be greater than 5000 mg/kg bw.

Justification for selection of acute toxicity – oral endpoint
Most reliable study

Justification for selection of acute toxicity – inhalation endpoint
The only reliable and compliant study available

Justification for selection of acute toxicity – dermal endpoint
Most reliable study

Justification for classification or non-classification

Based on data available on the test substance and the read-across test substance, the test substance is not classified for acute toxicity according to the criteria of Directive 67/548/EEC (DSD) and Regulation (EC) No 1272/2008 (CLP).