N-butylphosphorothioic triamide

Endpoint summary

Description of key information

Acute toxicity:
Oral (OECD 401), rat: LD50 2823 mg/kg bw 
Dermal (OECD 402), rabbit: LD50 >2000 mg/kg bw
Inhalation (OECD 403), rat, 4 hour exposure: LD50 >2100 mg/m³

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:

The study was performed between 12 August 1994 and 12 December 1994.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not effect the quality of the relevant results.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OTS 798.1175 (Acute Oral Toxicity)

Deviations:

no

GLP compliance:

yes

Test type:

fixed dose procedure

Limit test:

no

Species:

rat

Strain:

other: Cr1:CD®(SD)BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc., Portage, Michigan, USA
- Age at study initiation: Young adult
- Weight at study initiation: 15 male and 15 female rats, weighing from 240 to 294 g
- Fasting period before study: approximately 17 to 20 hours before test material administration
- Housing: the animals were separated by sex and group housed in screen-bottom stainless steel cages in temperature- and humidity-controlled quarters. During the range-finding study, the animals were individually housed.
- Diet (e.g. ad libitum): Laboratory Rodent Diet #5001, PMI Feeds, Inc.
- Water : Ad libitum from an automatic system. Samples of the water are analyzed by HWI for total dissolved solids, hardness, and specified microbiological content and for selected elements, heavy metals, organophosphates, and chlorinated hydrocarbons.
- Acclimation period: At least 7 days
-Contaminants: There were no known contaminants in the feed or water at levels that would have interfered with or affected the results of the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 - 25
- Humidity (%): 50 ± 20
- Air changes (per hr): Not stated
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES:
In-life Start Date: 18 August 1994
In-life Termination Date: 4 October 1994

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

VEHICLE
- Concentration in vehicle: Not reported
- Amount of vehicle (if gavage): Not reported
- Justification for choice of vehicle: Not reported

MAXIMUM DOSE VOLUME APPLIED:
20 mL/kg of body weight

DOSAGE PREPARATION:
The test material was mixed with distilled water to a specific concentration for each dose level. Each prepared test mixture appeared to be a suspension. An individual dose of each respective test mixture was calculated for each animal based on its fasted body weight and administered by gavage to a volume of 20 mL/kg of body weight. The test mixtures were stored at room temperature until administration.

Doses:

Range-Finding Study: 500, 1000, 3000, and 5000 mg/kg bw

Definitive Study:
1000, 2500, and 5000 mg/kg bw (males)
1000, 2500, and 3000 mg/kg bw (females)

No. of animals per sex per dose:

Range-finding Study:
eight healthy, acclimated rats (one/sex/dose level)

Definitive Study:
5 males and 5 females per dose level

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days

- Frequency of observations and weighing: The range-finding animals were observed for mortality only on the day of treatment and for 14 days thereafter. Clinical observations and mortality checks for the definitive study animals were conducted at approximately 1, 2.5, and 4 hours after test material administration. Additional clinical observations and twice a day mortality checks (morning and afternoon) were conducted daily thereafter for 14 days.

Body weights for range-finding and definitive study animals were determined before test material administration (Day 0). Additional body weights were determined at Day 7, at termination of the experimental phase (Day 14), or at death when survival exceeded 1 day.

- Necropsy of survivors performed: Yes

- Other examinations performed: Clinical signs

Statistics:

The LD50 value for males, females, and the sexes combined was determined by a computer program using a modified Behrens-Reed-Muench cumulant method. No other statistical analyses were required by the protocol.

Preliminary study:

Not applicable.

Sex:

male

Dose descriptor:

LD50

Effect level:

3 536 mg/kg bw

Based on:

test mat.

95% CL:

2 147 - 5 824

Sex:

female

Dose descriptor:

LD50

Effect level:

2 603 mg/kg bw

Based on:

test mat.

95% CL:

1 885 - 3 595

Sex:

male/female

Dose descriptor:

LD50

Effect level:

2 823 mg/kg bw

Based on:

test mat.

95% CL:

2 823 - 3 652

Mortality:

All mortality occurred within 2 days of test material administration. Based on the observed mortality, the estimated oral LD50 in rats was determined to be 3536, 2603, and 2823 mg/kg for males, females, and the sexes combined, respectively.

Clinical signs:

Clinical signs of toxicity included thin appearance, hunched posture, staggered gait, hypoactivity, absence of pain and/or righting reflex, hypothermic to touch, prostration, red or yellow-stained face, lacrimation, miosis, excessive salivation, dyspnoea, bradypnoea, soft stool, wet urogenital area, and dark- or yellow-stained urogenital area. All surviving animals returned to a normal appearance by Day 5 after treatment.

Body weight:

There was no meaningful effect on body weight gain in surviving animals.

Gross pathology:

There were 10 rats (five males and five females) each from dose levels of 1000 and 2500 mg/kg, five females from a dose level of 3000 mg/kg, and five
males from a dose level of 5000 mg/kg necropsied. Some animals died on test (DOT) and the remaining surviving animals were euthanized and necropsied at
the termination of the study.

At necropsy, the most prominent finding in the DOTs pertained to coloration changes and the contents of the gastrointestinal tract. The stomach and small intestines contained yellow oily semifluid which possibly represented test material mixed with ingesta. The urinary bladder in some animals were apparently distended with yellow or red fluid. The bladder wall or mucosa in two animals given 5000 mg/kg was diffusely dark red or had multiple dark red areas of variable size. These changes were possibly caused by the test material but may also be related to post mortem autolysis. All remaining observations in these animals andthe animals surviving to study termination were considered incidental findings and unrelated to the test material.

Other findings:

- Organ weights: Not recorded

- Histopathology: Not recorded

- Potential target organs: Not recorded

- Other observations: Not recorded

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The acute oral median lethal dose (LD50) of the test material in the female Wistar strain rat was estimated to be greater than 2000 mg/kg bodyweight.

Executive summary:

Introduction. 

The study was performed to assess the acute oral toxicity of the test material in the young adult albino rats of the Crl:CD®(SD)BR strain procured from Charles River Laboratories, Inc., Portage, Michigan. The method was designed to meet the EPA Guidelines: EPA OTS 798.1175 (Acute Oral Toxicity).

Method. 

The objective of this study was to assess the acute oral toxicity produced when the test material is administered by the oral route (gavage) to rats.

The test material, N-(n-butyl) thiophosphoric triamide (NBPT), was evaluated for its acute oral toxicity potential in male and female rats when administered as a single gavage dose at levels of 1000, 2500, and 5000 mg/kg of body weight in males and at 1000, 2500, and 3000 mg/kg in females. The estimated oral LD50 in rats was determined to be 3536, 2603, and 2823 mg/kg for males, females, and the sexes combined, respectiv

Mortality. 

All mortality occurred within 2 days of test material administration.

Clinical Observations. 

Clinical signs of toxicity included thin appearance, hunched posture, staggered gait, hypoactivity, absence of pain and/or righting reflex, hypothermic to touch, prostration, red or yellow-stained face, lacrimation, miosis, excessive salivation, dyspnoea, bradypnoea, soft stool, wet urogenital area, and dark- or yellow-stained urogenital area. All surviving animals returned to a normal appearance by Day 5 after treatmen

Bodyweight. 

There was no meaningful effect on body weight gain in surviving animal.

Necropsy. 

Test material-related findings observed at necropsy were limited to those animals dying during the study and pertained to coloration changes and the contents of the gastrointestinal tract.

Conclusion. 

The acute oral median lethal dose (LD₅₀) of the test material in the female Wistar strain rat was estimated to be greater than 2000 mg/kg bodyweight.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 823 mg/kg bw

Quality of whole database:

The study is a GLP compliant and has Klimisch score 1.

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:

The study was performed between 15 November 2010 and 20 December 2010.

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted in compliance with agreed protocols, with no/or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

yes

Remarks:

(the achieved particle size (9.4 µm) and GSD range (5.3) were larger than generally acceptable for this type of study (MMAD: 1 -4 µm, GSD: 1.5-3.0, respectively)).

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.1300 (Acute inhalation toxicity)

Deviations:

yes

Remarks:

(only six animals (three males and three females) were used)

GLP compliance:

yes (incl. QA statement)

Remarks:

Date of Inspection: 20 July 2010, date of signature: 29 October 2010

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

other: HsdHan™ : WIST

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories UK Ltd, Oxon, UK.
- Age at study initiation: eight to twelve weeks old
- Weight at study initiation: 200 g to 350 g
- Fasting period before study: Not reported
- Housing: solid-floor polypropylene cages with stainless steel lids, furnished with softwood flakes (Datesand Ltd., Cheshire, UK) and provided with environmental enrichment items: wooden chew blocks (B & K Universal Ltd, Hull, UK) and cardboard “fun tunnels” (Datesand Ltd., Cheshire, UK).
- Diet: Harlan 2014C Rodent Diet, Harlan Laboratories UK Ltd, Oxon, UK
- Water: free access to mains drinking water
- Acclimation period: at least five days

ENVIRONMENTAL CONDITIONS
- Temperature: 19 - 25°C
- Humidity: 30 - 70%
- Air changes (per hr): at least fifteen changes per hour
- Photoperiod (hrs dark / hrs light): 12/12

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 SAG 410 Solid Aerosol Generator (TOPAS GmbH, Dresden, Germany) plus cylindrical exposure chamber
- Exposure chamber volume: approximately 30 litres
- Method of holding animals in test chamber: Each rat was individually held in a tapered, polycarbonate restraining tube fitted onto a single tier of the exposure chamber and sealed by means of a rubber ‘O’ ring. Only the nose of each animal was exposed to the test atmosphere.
- Source and rate of air: Compressed air was supplied by means of an oil free compressor and passed through a water trap and respiratory quality filters before it was introduced to the SAG 410. 35 L/min providing 70 air changes per hour.
- Method of conditioning air: water trap and respiratory quality filters
- System of generating particulates: SAG 410 Solid Aerosol Generator (TOPAS GmbH, Dresden, Germany)
- Method of particle size determination: Marple Personal Cascade Impactor (Westech IS Ltd, Beds., UK)
- Treatment of exhaust air: filtered
- Temperature, humidity, pressure in air chamber: temperature and relative humidity inside the exposure chamber were measured by an electronic thermometer/humidity meter (Hanna Instruments Ltd, Beds., UK) located in a vacant port in the animals’ breathing zone of the chamber and recorded every thirty minutes throughout the four-hour exposure period.

TEST ATMOSPHERE
- Brief description of analytical method used: glass fibre filters (Gelman type A/E 25 mm) placed in a filter holder. The holder was temporarily sealed in a vacant port in the exposure chamber in the animals’ breathing zone and a suitable, known volume of exposure chamber air was drawn through the filter using a vacuum pump (Gravimetric).
- Samples taken from breathing zone: yes

VEHICLE
- Composition of vehicle (if applicable): Not applicable
- Concentration of test material in vehicle: Not applicable
- Justification of choice of vehicle: Not applicable
- Lot/batch no. (if required): Not applicable
- Purity: Not applicable

TEST ATMOSPHERE (if not tabulated)
- Particle size distribution: Inhalable fraction (% <4 µm) 30.3
- MMAD (Mass median aerodynamic diameter: 9.40 µm; Geometric Standard Deviation (GSD):
5.30

CLASS METHOD (if applicable)
- Rationale for the selection of the starting concentration: Not applicable

Analytical verification of test atmosphere concentrations:

no

Remarks:

Gravimetric only

Duration of exposure:

4 h

Concentrations:

Mean Achieved (mg/L) = 2.10
Mean Mass Median Aerodynamic Diameter (µm) = 9.40
Inhalable Fraction (% <4 µm) = 30.3
Geometric Standard Deviation (GSD) = 5.30

No. of animals per sex per dose:

3 males and 3 females

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: All animals were observed for clinical signs at hourly intervals during exposure, immediately on removal from the restraining tubes at the end of exposure, one hour after termination of exposure and subsequently once daily for fourteen days. Individual bodyweights were recorded prior to treatment on the day of exposure and on Days 1, 3, 7 and 14 or at death.
- Necropsy of survivors performed: yes

Statistics:

Data evaluations included the relationship, if any, between the animals’ exposure to the test material and the incidence and severity of all abnormalities including behavioural and clinical observations, necropsy findings, bodyweight changes, mortality and any other toxicological effects.
Using the mortality data obtained, an estimate of the acute inhalation median lethal concentration (LC50) of the test material was made.

Preliminary study:

Not applicable

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 2.1 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Mortality:

No deaths occurred in a group of six rats exposed to a mean achieved atmosphere concentration of 2.10 mg/L for four hours.

Clinical signs:

other: Signs of hunched posture and pilo-erection are commonly seen in animals for short periods on removal from the chamber following 4-Hour inhalation studies. Wet fur is commonly recorded during exposure. These observations are considered to be associated wit

Body weight:

All animals exhibited a slight bodyweight loss or no bodyweight gain on the first day postexposure. Normal bodyweight development was noted for all animals during the remainder of the recovery period.

Gross pathology:

With the exception of one instance of dark patches on the lungs, no macroscopic abnormalities were detected amongst animals at necropsy.

Other findings:

Not applicable.

DISCUSSION

It is recognized that the achieved particle size and GSD range are larger than would generally be acceptable for this type of study (1 -4 µm and 1.5-3.0, respectively). During the method development phase of the study, changes were made to the generation system (addition of a particle size separator in an attempt to remove larger particles and thereby increasing the percentage of particles <4 µm) and variations in grinding techniques were implemented in an attempt to increase the inhalable portion of the test item. However, changing the generation system markedly reduced the achieved atmosphere concentration (maximum attainable concentration with the particle separator added was approximately 0.26 mg/Lwith a particle size distribution of ~ 5.5 µm and therefore, also reduced the actual concentration of particles <4 µm. It was, therefore, preferable to expose the animals to a higher concentration of test item (target concentration of 2 mg/L) as this resulted in the animals being exposed to the highest possible concentration of particles <4 µm.

 

During the method development phase of the study it proved impossible to achieve consistent particle size distributions. These could be described as being random at best. A target concentration of 2 mg/L was therefore set for the formal exposure. This target concentration was considered to be the most likely concentration that would allow the largest concentration of particles < 4 µm to be generated. It is considered that running at this concentration (2 mg/L) provided a much smaller particle size than generating at a target concentration of 5mg/L(the original target concentration for this study) where data from the method development phase showed that the achieved particle size was much greater than 13 µm. The large particle sizes achieved are considered to be due to the physical characteristics of the test item. It appears to clump together making it extremely difficult to reduce the achieved particle size. It is therefore considered that the particle size achieved during this study is the optimum attainable and provided approximately 0.64 mg/L of test item at <4 µm (30.3% of the mean achieved atmosphere concentration).

 

It is also worth mentioning that the atmospheres has been generated by specialist equipment which has been proven over many years to generate test atmospheres from the majority of test items at <4 µm. It can, therefore, be concluded that it would be highly unlikely in a real world situation that anyone would be exposed to atmospheres of this test item containing particle size' distributions quoted in this test report. The nominal concentration also shows that the test item would be very unlikely to form an atmosphere in the real world as it is shown to be 775% of the actual achieved concentration.

Exposure Chamber Concentration

The test atmosphere was sampled eighteen times during the exposure period and the actual concentration of the test material calculated.The mean values obtained were:

Atmosphere Concentration
Mean Achieved (mg/L)	Standard Deviation	Nominal (mg/L)
2.10	0.16	16.3

The chamber flow rate was maintained at 35 L/min providing 70 air changes per hour.The theoretical chamber equilibration time (T₉₉) was 4 minutes.

Particle Size Distribution

The particle size analysis of the atmosphere drawn from the animals’ breathing zone, was as follows:

Mean Achieved Atmosphere Concentration (mg/L)	Mean Mass Median Aerodynamic Diameter (µm)	Inhalable Fraction (% <4 µm)	Geometric Standard Deviation
2.10	9.40	30.3	5.30

Mortality Data

The mortality data are summarised as follows:

Mean Achieved Atmosphere Concentration (mg/L)	Deaths
	Male	Female	Total
2.10	0/3	0/3	0/6

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

No deaths occurred in a group of six rats (3 males /3 females) exposed to a mean achieved atmosphere concentration of 2.10 mg/L for four hours. It was therefore considered that the acute inhalation median lethal concentration (4 hr LC50) of NBPT, in the HsdHan™ : WIST strain rat, was greater than 2.10 mg/L.

Executive summary:

Introduction.

A study was performed to assess the acute inhalation toxicity of the test item. The method used was compatible with that described in the OECD Guidelines for Testing of Chemicals (2009) No. 403 "Acute Inhalation Toxicity" referenced as Method 82 (Inhalation) of Commission Regulation (EC) No. 440/2008. The method was also designed to be compatible with the US Environmental Protection Agency (EPA) Health Effects Test Guidelines, OPPTS 870.1300, Acute Inhalation Toxicity, August 1998, with the exception that only six animals (three males and three females) were utilized during the "limit test".

Methods.

A group of six HsdHan™ : WIST strain rats (three males and three females) was exposed to a dust atmosphere. The animals were exposed for four hours using a nose only exposure system, followed by a fourteen day observation period.

Results. The mean achieved atmosphere concentration was as follows:

Atmosphere Concentration
Mean Achieved (mg/L)	Standard Deviation	Nominal (mg/L)
2.10	0.16	16.3

The characteristics of the achieved atmosphere were as follows:

Mean Achieved Atmosphere Concentration (mg/L)	Mean Mass Median Aerodynamic Diameter (µm)	Inhalable Fraction (% <4 µm)	Geometric Standard Deviation
2.10	9.40	30.3	5.30

The mortality data were summarised as follows:

Mean Achieved Atmosphere Concentration (mg/L)	Deaths
	Male	Female	Total
2.10	0/3	0/3	0/6

Clinical Observations.

Common abnormalities noted during the study included increased respiratory rate, hunched posture, pilo-erection and wet fur. Animals recovered quickly to appear normal on Day 3 post-exposure.

Bodyweight.

All animals exhibited a slight bodyweight loss or no bodyweight gain on the first day post-exposure. Normal bodyweight development was noted for all animals during the remainder of the recovery period.

Necropsy.

With the exception of one instance of dark patches on the lungs no macroscopic abnormalities were detected amongst animals at necropsy.

Conclusion.

No deaths occurred in a group of six rats (3 males / 3 females) exposed to a mean achieved atmosphere concentration of 2.10 mg/L for four hours. It was therefore considered that the acute inhalation median lethal concentration (4 hr LC50) of NBPT, in the HsdHan™ : WIST strain rat, was greater than 2.10 mg/L. 

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Value:

2 100 mg/m³

Quality of whole database:

The study is a GLP compliant and has Klimisch score 2.

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:

Between 12 August and 11 November 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Deviations:

yes

Remarks:

(occlusive conditions)

Qualifier:

according to guideline

Guideline:

EPA OTS 798.1100 (Acute Dermal Toxicity)

Deviations:

yes

Remarks:

(occlusive conditions)

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:
Animals: Hra:(NZW)SPF strain

Rationale: Historically, the New Zealand White albino rabbit has been the animal of choice because of the large amount of background information on this species.

- Source: from HRP, Inc., Kalamazoo, Michigan

- Age at study initiation: Adult albino rabbits
- Weight at study initiation: 2.4 to 2.8 kg
- Fasting period before study: Not stated
- Housing: animals were individually housed in screen-bottom stainless steel cage
- Diet: a measured amount of Laboratory Rabbit Diet HF #5326, PMI Feeds
- Water: ad libitum
- Acclimation period: at least 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19° to 23°C
- Humidity (%): relative humidity of 50% ±20%
- Air changes (per hr): Not stated
- Photoperiod (hrs dark / hrs light): 12-hour light/12-hour dark lighting cycle

IN-LIFE DATES: From: To:
In-life Start Date: 17 August 1994
In-life Termination Date: 31 August 1994

Type of coverage:

occlusive

Vehicle:

other: Each dose was thoroughly moistened with distilled water before application

Details on dermal exposure:

TEST SITE
- Area of exposure:
- % coverage: not less than 10% of the total body surface

- Type of wrap if used: The area of application was covered with a 10-cm x 10-cm gauze patch secured with paper tape and overwrapped with Saran Wrap® and Elastoplast® tape to provide an occlusive dressing.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): the test sites were washed using tap water and disposable paper towels.

- Time after start of exposure: 24 hours

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 0.05 g/cm²

- Concentration (if solution): Not applicable
- Constant volume or concentration used: yes
- For solids, paste formed: yes

VEHICLE
- Amount(s) applied (volume or weight with unit): Not applicable
- Concentration (if solution): Not applicable
- Lot/batch no. (if required): not applicable

Duration of exposure:

24 hours

Doses:

2000 mg/kg body weight

No. of animals per sex per dose:

5 per sex per dose

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days

- Frequency of observations and weighing: Clinical observations and mortality checks were conducted at approximately 1, 2.5, and 4 hours after test material administration. Additional clinical observations and twice a day mortality checks (morning and afternoon) were conducted daily thereafter for 14 days.

Body weights were determined before test material application (Day 0), at Day 7, and at termination of the experimental phase (Day 14).

The initial dermal irritation reading was made approximately 30 minutes after removal’of the test material according to the Draize technique (recorded as the Day 1 score). Subsequent readings of dermal irritation were made on Days 3, 7, 10, and 14.

- Necropsy of survivors performed: yes

- Other examinations performed: clinical signs, body weight,organ weights, histopathology, other:

Statistics:

No statistical analysis was performed.

Preliminary study:

Not applicable

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Remarks on result:

other: 95% confidence limits not reported.

Mortality:

No mortality was observed during the study.

Clinical signs:

All animals appeared normal with the exception of 4 animals which exhibited soft stool on Days 1 and/or 2. All animals returned to a normal appearance by Day 3 after treatment.

Body weight:

All animals showed expected gains in bodyweight over the study period.

Gross pathology:

There were 10 rabbits (five males, and five females) euthanized and necropsied at the termination of the study. There were no visible lesions in any of the animals.

Other findings:

None.

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The test material, N-(n-butyl) thiophosphoric triamide (NBPT), was evaluated for its acute dermal toxicity potential in male and female rabbits when administered as a single topical application at a level of 2000 mg/kg of body weight. The estimated dermal LD50 for male and female rabbits was determined to be greater than 2000 mg/kg.

Executive summary:

The study was conducted in accordance with the EPA Guidelines, EPA OTS 798.1100 (Acute Dermal Toxicity)

The objective of this study was to assess the systemic toxicity and relative skin irritancy of a test material when applied to the skin of adult albino rabbits of the Hra:(NZW)SPF strain procured from HRP, Inc., Kalamazoo, Michigan. The test material, N-(n-butyl) thiophosphoric triamide (NBPT), was evaluated for its acute dermal toxicity potential in male and female rabbits when administered as a single topical application at a level of 2000 mg/kg of body weight. The estimated dermal LD₅₀ for male and female rabbits was determined to be greater than 2000 mg/kg. All animals appeared normal with the exception of 4 animals which exhibited soft stool on Days 1 and/or 2. All animals returned to a normal appearance by Day 3 after treatment.

Mortality. There were no deaths.

Clinical Observations. There were no signs of systemic toxicity.

Dermal Irritation.  The test material produced slight to severe dermal irritation.

Bodyweight. All animals exhibited body weight gain throughout the study.

Necropsy.  The gross necropsy at termination revealed no visible lesions.

Conclusion.  The test material, N-(n-butyl) thiophosphoric triamide (NBPT), was evaluated for its acute dermal toxicity potential in male and female rabbits when administered as a single topical application at a level of 2000 mg/kg of body weight. The estimated dermal LD50 for male and female rabbits was determined to be greater than 2000 mg/kg.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Value:

2 000 mg/kg bw

Additional information

The acute oral toxicity study was performed in accordance with OECD 401 (Glaza, 1994a). The substance formulated in water was administered by gavage to rats in a doses of 1000, 2500 and 5000 mg/kg bw for males and 1000, 2500 and 3000 mg/kg bw for females. Mortality occured within 2 days after test material administration. Clinical signs of toxicity included thin appearance, hunched posture, staggered gait, hypoactivity, absence of pain and/or righting reflex, hypothermic to touch, prostration, red or yellow-stained face, lacrimation, miosis, excessive salivation, dyspnoea, bradypnoea, soft stool, wet urogenital area, and dark- or yellow-stained urogenital area. All surviving animals returned to a normal appearance by Day 5 after treatment. There was no meaningful effect on body weight gain in surviving animals. Test material-related findings observed at necropsy were limited to those animals dying during the study and pertained to coloration changes and the contents of the gastrointestinal tract. The oral LD50 in rats was estimated to be 3536, 2603, and 2823 mg/kg for males, females, and the sexes combined, respectively.

Equivalent to OECD 402, 2000 mg/kg bw of the test substance were dermally applied to the intact skin of 5 male and 5 female rabbits (Glaza, 1994b). The test substance was placed on a wet gauze patch and applied to the skin for 24 h under occlusive conditions. After the exposure period, the gauze patch was removed and the treated skin was rinsed with tap water. There were no deaths during the study. All animals appeared normal with the exception of 4 animals which exhibited soft stool on Days 1 and/or 2. All animals returned to a normal appearance by Day 3 after treatment. Gross examination of organs and tissues at necropsy did not reveal any abnormalities. The LD50 of the test substance was > 2000 mg/kg bw.

The acute inhalation toxicity of the test substance on rats was conducted in accordance with OECD 403 (Griffiths, 2010). The rats (3 males and 3 females) were nose-only exposed to a mean dust concentration of 2.1 mg/L (=2100 mg/m³). The inhalable fraction (% < 4 µm) was 30.3% (MMAD 9.4 µm, GSD 5.3). Running at a higher target concentration of 5 mg/L showed that the achieved particle size was much greater than 13 µm. However, methodological efforts were made to remove larger particles and thereby increasing the percentage of inhalable particles. Changing the system reduced the achieved atmosphere concentration to 0.26 mg/L with a particle size distribution of ~5.5 µm and also reduced the actual concentration of particles < 4 µm. Therefore, it was preferred to expose the animals to a higher concentration of test item as this resulted in the animals being exposed to the highest possible concentration of particles < 4 µm. The actual concentration of 2.1 mg/L did not cause mortality. Nonspecific clinical signs included increased respiratory rate, hunched posture, pilo-erection and wet fur. Animals recovered quickly to appear normal on Day 3 post-exposure. All animals exhibited a slight bodyweight loss or no bodyweight gain on the first day post-exposure. Normal bodyweight development was noted for all animals during the remainder of the recovery period. With the exception of one instance of dark patches on the lungs no macroscopic abnormalities were detected amongst animals at necropsy. The LC50 of the test substance was therefore determined to be > 2.1 mg/L (=2100 mg/m³).

 

 

Justification for selection of acute toxicity – oral endpoint
Only one study available

Justification for selection of acute toxicity – inhalation endpoint
Only one study available

Justification for selection of acute toxicity – dermal endpoint
Only one study available.

Justification for classification or non-classification

The available data on acute toxicity (oral, dermal and inhalation) of the test substance do not meet the criteria for classification according to Regulation (EC) 1272/2008 and Directive 67/548/EEC, and are therefore conclusive but not sufficient for classification.