3,5-dimethylpyrazole

Endpoint summary

Description of key information

ORAL

Key study; Parcell (1994a), performed to GLP, OECD 401 and EU B.1, Klimisch 1, LD50 = 1717 mg/kg bw. in rats.

Supporting studies;

Wallace (1976a), performed to sound scientific principles, Klimisch 2, LD50 > 2140 (1530 – 3000) mg/kg b.w. in rats.

Dewitt (1953), data presented as an abstract with no recorded methodology, Klimisch 4, minimum lethal dose > 500 mg/kg bw. in rats.

Material safety data sheets have been provided from Alfa Aesar (2007), Sigma Aldrich (2009) and Fischer Scientifics (2008), as there is no record of study protocol they have been assigned a Klimisch score of either 3 or 4.

INHALATION

A data waiver has been provided to cover this endpoint.

DERMAL

Key study; Hutchinson (2002a), performed to GLP, OECD 402, EU Method B.3 and EPA OPPTS 870.1200, Klimisch 1, LD50 > 2000 mg/kg b.w. in rats.

OTHER ROUTES

Supporting study; Vetulani (1996), non-GLP compliant study performed to a non-standard protocol, Klimisch 3, LD50 of 570 mg/kg bw when administered via intraperitoneal injection in mice.

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:

22nd February to 13th April 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

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. The study report was conclusive, done to a valid guideline and the study was conducted under GLP conditions.

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

not applicable

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: 4-7 weeks.
- Weight at study initiation: 96 to 119 g.
- Fasting period before study: Overnight prior to and approximately 4 hours after dosing.
- Housing: In treatment groups, up to 5 individuals of the same sex. In metal ages with wire mesh floors.
- Diet (e.g. ad libitum): Standard laboratory rodent diet, Biosure LAD 1, ad libitum except for fasting period.
- Water (e.g. ad libitum): Drinking water, ad libitum except for fasting period.
- Acclimation period: Minimum 7 days.
- Routine analysis was carried out on water and died.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): mean daily minimum and maximum 21 ºC and 22 ºC.
- Humidity (%): av. 47%.
- Air changes (per hr): 10 to 15 per hour.
- Photoperiod (hrs dark / hrs light): Artificial light between 0700 - 1900, in each 24 hour period

Route of administration:

oral: gavage

Vehicle:

other: Methycellulose.

Details on oral exposure:

VEHICLE
- Concentration in vehicle: 1% w/v aqueous methylcellulose.

MAXIMUM DOSE VOLUME APPLIED: 10 ml/kg

Doses:

Preliminary Study - 500 mg/kg bw.
Main Test - Single dose of 1260, 1600 and 2000 mg/kg bw.

No. of animals per sex per dose:

Preliminary Study: 2 males and 2 females.
Main Study: 5 males and 5 females at 2000 mg/kg bw. 5 females only at 1600 and 1200 mg/kg bw as these were determined as the most sensitive sex.

Control animals:

no

Details on study design:

Preliminary Study:
- A single dose was administered.

Main Study:
- Males and females were initially exposed at 2000 mg/kg bw of the test material.
- Based on the response of the first dose, two further groups of female rats were dosed, to obtain a dose response curve and allow calculation of a lethal dose. A single dose was administered at 1260 and 1600 mg/kg bw.

Observations:
- Mortality, time of death was recorded.
- Clinical signs, observations were recorded soon after dosing and at frequent intervals on Day 1. Then for the remainder of the study observations were made twice daily. Nature and severity were recorded.
- Bodyweight, recorded on Days 1, 8 and 15 or at death. Individual weekly bodyweight changes and group mean bodyweights were calculated.
- Macroscopic examinations, necropsy was performed on Day 15. The cranial, abdominal and thoracic cavities were examined.

Statistics:

Acute median lethal oral dose in females was calcualted using the Finney (1971) method.

Preliminary study:

Results indicated that the LD50 > 500 mg/kg bw in females.

Key result

Sex:

female

Dose descriptor:

LD50

Effect level:

1 717 mg/kg bw

Based on:

test mat.

95% CL:

1 360 - 2 269

Mortality:

Results from the preliminary study showed that the acutre lethal oral dose was greater than 500 mg/kg bw.
In the main study, all deaths occurred within the period ranging from 3 hours to 2 days post exposure.
The mortalities were as follows; two females at 1600 mg/kg bw and two males and four females at 2000 mg/kg bw.

Clinical signs:

other: Piloerection, abnormal body carriage (hunched posture), lethargy, decreased respiratory rate, partially closed eyelids, pallor of the extremities, unsteadiness and increased lacrimation, abnormal gait (waddling), increased salivation, walking on toes, pro

Gross pathology:

A darkened appearance of the kidney cortex and spleen were observed in one female at 1600 mg/kg bw.
Thickening of the stomach walls and fluid contents in the stomach and intestines was observed in individuals at both 1600 and 2000 mg/kg bw.

Other findings:

- Females were more sensitive than males.
- Recovery of surviving rats, judged on external appearance, occurred by Day 3 in the 1260 mg/kg bw group, Day 4 in the 1600 mg/kg bw group and Day 5 for the 2000 mg/kg bw group.
- No abnormalities were recorded in microscopic examinations.

Table 1. Time and Number of Deaths During the Main Study

Sex	Dose (mg/kg bw)	Number of deaths in a group of 5	Day
			1							2		3 to 15
			Hours after dosing							Observation
			< 1/2	1	2	3	4	5	6	1st	2nd	1st	2nd
Male	2000	2								2
Female	1260	0
	1600	2								1	1
	2000	4				1	1			1	1

Interpretation of results:

Category 4 based on GHS criteria

Conclusions:

The LD50 in female rats was determined, using the standard acute toxicity method, to be 1717 mg/kg bw.

Executive summary:

In a GLP compliant study performed in accordance with the standardised guideline EU Method B.1, the acute oral toxicity of the test material was determined in female Sprague-Dawley rats following the standard acute method. Male and female rats were exposed to the test material via oral gavage, females were found to be more sensitive and were used in further testing to determine the LD₅₀. Under the conditions of the test the LD₅₀ was determined to be 1717 mg/kg bw.

According to Regulation (EC) 1272/2008 the test material requires classification as Acute oral toxicity category 4 "H302: Harmful if swallowed" with the signal word "Warning".

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

1 717 mg/kg bw

Quality of whole database:

Two further studies and the information from three MSDS sheets have been provided as supporting data.
Wallace (1976a) is a non-GLP study performed to sound scientific principles with a sufficient level of detail to the quality of the presented data. The study was assigned a reliability score of 2, in accordance with Klimisch (1997). The LD50 was determined to be greater than 2140 (1530 – 3000) mg/kg b.w. in rats.
Dewitt (1953) presented data from an abstract with no recorded methodology. The study was assigned a reliability score of 4, in accordance with Klimisch (1997). The minimum lethal dose was recorded to be greater than 500 mg/kg bw. in rats.
Alfa Aesar (2007) recorded the LD50 in rats to be 2140 mg/kg b.w. and the minimum lethal dose in mice to be greater than 500 mg/kg b.w. The study was assigned a reliability score of 4, in accordance with Klimisch (1997) as it is not possible to assess the quality of the information provided.
Sigma Aldrich (2009) and Fischer Scientifics (2008) both recorded the LD50 in mice to be 1060 mg/kg b.w. These studies were assigned a reliability score of 3, in accordance with Klimisch (1997) as the data is presented on a non standard species.

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Data waiving:

exposure considerations

Justification for data waiving:

the study does not need to be conducted because exposure of humans via inhalation is not likely taking into account the vapour pressure of the substance and/or the possibility of exposure to aerosols, particles or droplets of an inhalable size

other:

Endpoint conclusion

Endpoint conclusion:

no study available

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

01 April 2002 to 16 April 2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

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. The study report was conclusive, done to a valid guideline and the study was conducted under GLP conditions.

Qualifier:

according to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Deviations:

yes

Remarks:

Animals were younger and lighter than specified by the guidelines.

Qualifier:

according to guideline

Guideline:

EU Method B.3 (Acute Toxicity (Dermal))

Deviations:

yes

Remarks:

Animals were younger and lighter than specified by the guidelines.

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.1200 (Acute Dermal Toxicity)

Deviations:

yes

Remarks:

Animals were younger and lighter than specified by the guidelines.

Principles of method if other than guideline:

Deviation from guideline: Animals were younger and lighter than specified by the guidelines, however this deviation is not considered to have affected the outcome of the study.

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: Harlan UK Limited, Shaw's Farm, Blackhorn, Bicester, OX6 0TP. Animals arrived on 06 March 2002.
- Age at study initiation: Approximately 7 weeks old, on arrival.
- Weight at study initiation: 164 - 205g, on arrival.
- Housing: Individually in cages (dimensions 42 x 27 x 20 cm), with stainless steel grid tops and solid bottoms. Wood shavings were used as bedding.
- Diet: Rat and mouse no. 1 maintenance diet, supplied by Special Diets Services Limited. The diet was feed ad libitum throughout the study.
- Water: Supplied from the domestic mains and was available ad libitum throughout the study.
- Analysis for significant contaminants was performed on both the diet and water supplied to the test animals. Both were considered not to contain any additional substances in sufficient concentrations to have any influence on the outcome of the study.
- Acclimation period: Animals were allowed to acclimatise for at least 3 weeks.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): Mean minimum and maximum temperatures, 21 ºC and 19 ºC, respectively.
- Humidity (%): Mean relative humidity, 48% (ranged from 36 – 56%).
- Air changes (per hr): Minimum of 15 air charges per hour.
- Photoperiod (hrs dark / hrs light): 12 hr light/dark cycle (light 0700-1900 hrs).

Type of coverage:

occlusive

Vehicle:

unchanged (no vehicle)

Details on dermal exposure:

TEST SITE
- Area of exposure: The exact area was not recorded, however an area of approximately 7 cm x 8 cm was prepared for application on the dorsal trunk and a covering of 5 cm x 6 cm was used.
- Site preparation: The hair was clipped, taking care not to abrade the skin.
- Application: The test material was applied on to the water moistened skin of the test animals.
- Type of wrap if used: A water moistened gauze patch was secured with semi-occlusive tape, and a strip of non-irritating occlusive tape was wrapped around the trunk to secure the test site.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): The site was wiped with distilled water.
- Time after start of exposure: 24 hours, immediately after the patch was removed.

Duration of exposure:

24 hour in a single application.

Doses:

2000 mg/kg b.w.

No. of animals per sex per dose:

5 animals per sex per dose.

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing:
> Viability: Animals were checked twice daily,
> Clinical observations: Animals were examined for reaction to treatment frequently on the day of dosing and daily thereafter. The onset, intensity and duration of any signs were recorded.
> Bodyweights: Recorded weekly, on Day 1, Day 8 and Day 15.
- Necropsy of survivors performed: Yes, all animals were subjected to necropsy on Day 15.
> Sacrifice: Animals were killed by exposure to carbon dioxide and exsanguinated.
> Detailed examinations were made of the thoracic and abdominal organs and tissue in situ. All gross lesions were recorded in descriptive terms including location, size, shape, colour, consistency and number.

Statistics:

No formal statistical analysis was conducted.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

No mortality was observed during the observation period.

Clinical signs:

other: No clinical signs were noted during the study.

Gross pathology:

One male was noted to have developed an oval mass on the median lobe of the liver. This was not noted in any of the other test animals, and thus not considered to be related to treatment.

Table 1. Individual Body Weighs (g)

Dose Level (mg/kg)/Sex	Animal	Body weight (g)
		Day 1	Day 8	Day 15	Change (Days 1 – 15)
2000/M	1	301	308	317	16
	2	309	320	336	27
	3	302	312	321	19
	4	345	355	379	34
	5	311	320	335	24
	Mean	314	323	338	24
	SD	18	19	25	7
2000/F	1	229	229	232	3
	2	212	219	219	7
	3	258	255	270	12
	4	225	227	234	9
	5	236	237	247	11
	Mean	232	233	240	8
	SD	17	14	19	4

SD - standard deviation from the mean.

Interpretation of results:

GHS criteria not met

Conclusions:

Under the conditions of the test, the LD50 of the test material was determined to be > 2000 mg/kg.

Executive summary:

The acute dermal toxicity of the test material was determined in a study conducted according to GLP and in line with the standardised guidelines OECD 402, EU Method B.3 and EPA OPPTS 870.1200.

Ten Sprague-Dawley rats, 5 male and 5 female, were exposed to the test material in a limit test at 2000 mg/kg. The animals were exposed in a single application for 24 hours under an occlusive dressing. Animals were observed for 14 days post application and then subjected to necropsy.

Under the conditions of the test, no mortalities, signs of toxicity or abnormal pathology were observed. Thus the LD₅₀ was determined to be greater than 2000 mg/kg. Consequentially the test material will not require classification according to Regulation (EC) No. 1272/2008.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

Only one study is available which has been assigned a Klimisch score of 1, therefore the quality of the data is high.

Additional information

In accordance with point 8.5.2, Column 2, Annex VIII of Regulation 1907/2006, an acute inhalation study does not need to be performed as the use of this substance will not result in aerosols, particles or droplets of an inhalable size, therefore exposure to humans via the inhalatory route is unlikely to occur. The acute toxicity endpoint has been addressed by assessing the toxicity via the oral and dermal routes, which is more appropriate when considering the properties of this substance.

Justification for selection of acute toxicity – oral endpoint

The key study for acute oral toxicity (Parcell, 1994a) was determined in a GLP compliant study performed in accordance with the standardised guidelines OECD 401 and EU Method B.1. The study was performed to a good standard with a sufficient level of detail to assess the quality of the data presented. The study was assigned a reliability score of 1, in accordance with Klimisch (1997) and considered suitable to fulfil the data requirement. The acute oral LD50 of the test substance was determined to be 1717 mg/kg bw.

Justification for selection of acute toxicity – inhalation endpoint

In accordance with Column 2 of Annex VIII of Regulation (EC) No. 1907/2006, the acute inhalation study, required under information point 8.5.2, does not need to be performed as the use of this substance will not result in aerosols, particles or droplets of an inhalable size, therefore exposure to humans via the inhalatory route is unlikely to occur. The acute toxicity endpoint has been addressed by assessing the toxicity via the oral and dermal routes, which are more appropriate when considering the properties of this substance.

Justification for selection of acute toxicity – dermal endpoint

The key study for acute dermal toxicity (Hutchinson, 2002a) was determined in a GLP compliant study performed in accordance with the standardised guidelines OECD 402, EU Method B.3 and EPA OPPTS 870.1200. The study was performed to a good standard with a sufficient level of detail to assess the quality of the data presented. The study was assigned a reliability score of 1, in accordance with Klimisch (1997) and considered suitable to fulfil the data requirement. The acute oral LD50 of the test substance was determined to be > 2000 mg/kg bw.

Justification for classification or non-classification

ORAL

According to Regulation EC 1272/2008 , the test material meets the criteria for classification as Acute toxicity category 4 (H302: Harmful if swallowed) and Harmful (R22: Harmful if swallowed), respectively.

DERMAL

According to Regulation EC 1272/2008 , the test material does not meet the criteria for classification as Acute toxicity.