Thymidine

Endpoint summary

Description of key information

The test item was assessed in acute oral toxicity and acute dermal toxicity studies according to respective EU Methods, OECD and OPPTS Guidelines. In none of the studies were any treatment related effects observed. The acute oral and acute dermal LD 50-values were determined to be > 2000 mg/kg bw (limit dose). The LD0 value in both studies was 2000 mg/kg bw. A study on acute inhalation toxicity was waived. Instead an acute inhalation LD0-value was calculated based on the results obtained in the acute oral toxicity study. 

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

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

EU Method B.1 tris (Acute Oral Toxicity - Acute Toxic Class Method)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.1100 (Acute Oral Toxicity)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Toxi-Coop ZRT.

Test type:

acute toxic class method

Limit test:

yes

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: Young adult rat, 8 weeks old in first and second step
- Weight at study initiation: Body weight range at starting (first step): 203 - 211 g, body weight range at starting (second step): 195 - 199 g
- Fasting period before study: The day before treatment the animals were fasted. The food, but not water was withheld overnight.
- Housing: Group caging (3 animals/cage), type II polypropylene/polycarbonate cages, laboratory bedding
- Diet: Ad libitum
- Water: Ad libitum
- Acclimation period: 12 days in first step and 13 days in second step

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 30 - 70
- Air changes (per hr): 8-12 air exchanges/hour by central air-condition system
- Photoperiod (hrs dark / hrs light): Artificial light, from 6 a.m. to 6 p.m.

IN-LIFE DATES:
- From: 18 Sept. 2012
- To: 03 Oct. 2012

Route of administration:

oral: gavage

Vehicle:

CMC (carboxymethyl cellulose)

Remarks:

0.5 %

Details on oral exposure:

VEHICLE
- Concentration in vehicle: 200 mg/mL
- Amount of vehicle (if gavage): 10 mL/kg bw
- Lot/batch no.: N83746634

MAXIMUM DOSE VOLUME APPLIED:
- Maximum dose volume: 10 mL/kg bw

DOSAGE PREPARATION:
-Formulations were prepared just before the administration and stirred continuously during the treatment.

CLASS METHOD
- Rationale for the selection of the starting dose: Starting dose was selected on the basis of the available information about the test item.

Doses:

The acute toxic class method was carried out involving a stepwise procedure with the use of 2000 mg/kg bw as the starting dose in three female rats. No animal died in the first step at 2000 mg/kg bw dose level, so treatment with 2000 mg/kg bw was repeated on further three female rats. No animal died in the second step, too. Thus, the study was terminated.

No. of animals per sex per dose:

Three female rats per treatment group.

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Animals were observed individually after dosing at least once during the first 30 minutes, then 1 h, 2 h, 3 h, 4 h after the treatment and twice each day for 14 days thereafter. The body weights were recorded on day 0 (just before the treatment), on day 7 and on day 14 with a precision of 1 g.
- Necropsy of survivors performed: Yes
- Other examinations performed: Individual observations were performed on the skin and fur, eyes and mucous membranes and also respiratory, circulatory, autonomic and central nervous system, somatomotor activity and behaviour pattern. Particular attention was directed to observation of tremors, convulsions, salivation, diarrhoea, lethargy, sleep and coma.

Statistics:

Not applicable.

Sex:

female

Dose descriptor:

LD0

Effect level:

2 000 mg/kg bw

Based on:

test mat.

Sex:

female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

No mortalities occurred at 2000 mg/kg bw single oral dose (limit dose). All female rats in step 1 and also step 2 survived until the end of the 14-day observation period.

Clinical signs:

No treatment related symptoms were observed throughout the 14-day post-treatment period in any of the female animals.

Body weight:

The mean body weight of the animals corresponded to their species and age throughout the study.

Gross pathology:

All animals survived until the scheduled necropsy on Day 14. Slight hydrometra was observed in one treatment group female and moderate hydrometra was recorded in a second treatment group female. The hydrometra is physiological finding and connected to the cycle of the animal. No pathological changes were found related to the effect of the test item during the macroscopic examination of animals.

Interpretation of results:

practically nontoxic

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

No mortalities occurred after a single 2000 mg/kg bw oral dose (limit dose). There were no treatment related clinical or behavioral signs and no effect on body weights and body weight gains during the study. Autopsy revealed no treatment related pathological changes. Based on the results observed the LD50 was determined to be > 2000 mg/kg bw/day. The LD0 was determined to be 2000 mg/kg bw/day.

Executive summary:

A study following the acute toxic class method was carried out according to EU Method B.1 tris, OECD Guideline 401 (Acute Oral Toxicity) and OPPTS 870.1100. In a stepwise experimental procedure animals were treated with a starting dose of 2000 mg/kg bw (limit dose). The test item was administered to three female rats per oral gavage. Over a period of 14 days there were no mortalities observed at the 2000 mg/kg bw dose level. Therefore, treatment with 2000 mg/kg bw was repeated on further three female rats. Again, no mortalities were observed over a period of 14 days. All animals were periodically weighed, observed for clinical and behavioral symptoms. Gross pathological examination was carried out on the 14th day after the treatment.

No lethality was noted at single oral dose (gavage) of 2000 mg/kg bw (limit dose). No clinical symptoms were observed on the day of the treatment and during the 14-day observation period, the general state and behavior of experimental animals were normal. The body weight development was undisturbed in all animals. All animals survived until the scheduled autopsy on day 14. All organs of all experimental animals proved to be free of treatment related gross pathological changes.

Based on the results observed the LD50 was determined to be > 2000 mg/kg bw/day (limit dose). The LD0 was determined to be 2000 mg/kg bw/day (limit dose).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

Study according to GLP.

Acute toxicity: via inhalation route

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

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

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

GLP compliance:

yes (incl. QA statement)

Remarks:

Toxi-Coop ZRT.

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: Young adult rats, females were nulliparous and non-pregnant
- Weight at study initiation: Body weight range in preliminary study at starting: 201 - 205 g, body weight range in main study at starting 270 - 297 g (male) and 219 - 276 g (female)
- Fasting period before study: No
- Housing: During acclimatization 3 animals/sex/cage and during the study animals were housed individually. Housing in type II polypropylene/polycarbonate rat type cages with a solid floor, stainless steel wire covers and self-feeding baskets.
- Diet: Ad libitum
- Water: Ad libitum
- Acclimation period: 12 days in preliminary study, 26 days in main study

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 30 - 70
- Air changes (per hr): 8-12 air exchanges/hour by central air-condition system.
- Photoperiod (hrs dark / hrs light): Artificial light, from 6 a.m. to 6 p.m.

IN-LIFE DATES:
- From: 02 Oct. 2012
- To: 16 Oct. 2012

Type of coverage:

semiocclusive

Vehicle:

CMC (carboxymethyl cellulose)

Details on dermal exposure:

TEST SITE
- Area of exposure: Ca. 10 % area of the total body surface
- Type of wrap if used: Sterile gauze pads were placed on the skin of rats. These gauzes were kept in contact with the skin by a patch with adhesive hypoallergenic plaster. The entire trunk of the animal was wrapped with semi occlusive plastic wrap for 24 hours.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): At the end of the 24-hour exposure period any residual test item was removed using body temperature water.
- Time after start of exposure: 24 hours

TEST MATERIAL
- Amount(s) applied: 2000 mg/kg bw (limit dose)
- For solids, paste formed: No

VEHICLE
- Vehicle used: None, test item was applied as such

Duration of exposure:

24 hour exposure

Doses:

Preliminary study: 5, 50, 300, 2000 mg/kg bw
Main study: 2000 mg/kg bw (limit dose)

No. of animals per sex per dose:

Preliminary study: 2 females
Main study: 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: Inspection for signs of morbidity and mortality were made twice daily at the beginning and end of the working day. The body weight was recorded on day 0 (shortly before the treatment) in preliminary study and on day 0 (just before the treatment), on day 7 and on day 14 with a precision of 1 g in main study.
- Necropsy of survivors performed: Yes
- Other examinations performed: Careful clinical observation was made at the following intervals: 1h, 5h after the treatment and once each day for 14 days thereafter. Individual observations included the skin and fur, eyes and mucous membranes, and also respiratory, circulatory, autonomic and central nervous system, somatomotor activity and behaviour pattern as well. Particular attention was directed to the observation of tremors, convulsions, salivation, diarrhoea, lethargy, sleep and coma.

Statistics:

Not applicable.

Sex:

male/female

Dose descriptor:

LD0

Effect level:

2 000 mg/kg bw

Based on:

test mat.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

No mortality were observed over a 14-day period following a 24-hour dermal exposure to the test item in male and female rats.

Clinical signs:

No behavioural changes, symptoms of dermal irritation and corrosion or signs of systemic toxicity were noted during the study.

Body weight:

The mean body weight of the all animals corresponded to their species and age throughout the study.

Gross pathology:

All animals survived until the scheduled necropsy on Day 14. Pale coloured kidneys as an internal necropsy finding were found in one male animal. Moderate hydrometra was found in two animals. The macroscopic finding in one male could not be related the test item toxic effect, but was regarded an individual variation. Most likely the observation is a congenital anomaly. The observed hydrometra is physiological finding and connected to the cycle of the animal.

Interpretation of results:

practically nontoxic

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

No mortalities occurred after a single 2000 mg/kg bw dermal dose. Throughout the 14-day observation period there were no systemic toxic clinical signs at both sexes and no any related effect of the test item found in body weights and body weight gains of animals. Under the experimental conditions, the acute dermal LD50 value of the test item proved to be greater than 2000 mg/kg bw in male and female Crl:(WI)BR rats. The LD0 was determined to be 2000 mg/kg bw.

Executive summary:

An acute dermal toxicity study was performed according to EU Method B.3, OECD Guideline 402 (Acute Dermal Toxicity) and OPPTS 870.1200. A limit test was carried out. Single groups of male and female Crl:(WI)BR rats (n=5 animals/sex) were exposed to the test item at 2000 mg/kg bw (limit dose) by dermal route. The test item was applied in original form and left in contact with the skin for 24 hours, followed by a 14-day observation period.

No mortality occurred during the study. Neither male nor female animals treated at 2000 mg/kg bw showed behavioral changes. No signs of systemic toxicity were observed during the study. No signs of irritation and corrosion were noted. The body weight development was undisturbed in all animals. No macroscopic alterations of organs related to systemic toxic effects of the test item were noted during necropsy.

Under the experimental conditions the acute dermal LD50 value of the test item proved to be > 2000 mg/kg bw in male and female Crl:(WI)BR rats. The LD0 was determined to be 2000 mg/kg bw.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

Study according to GLP.

Additional information

Acute oral toxicity

A study following the acute toxic class method was carried out according to EU Method B.1 tris, OECD Guideline 401 (Acute Oral Toxicity) and OPPTS 870.1100. In a stepwise experimental procedure animals were treated with a starting dose of 2000 mg/kg bw (limit dose). The test item was administered to three female rats per oral gavage. Over a period of 14 days there were no mortalities observed at the 2000 mg/kg bw dose level. Therefore, treatment with 2000 mg/kg bw was repeated on further three female rats. Again, no mortalities were observed over a period of 14 days. All animals were periodically weighed, observed for clinical and behavioral symptoms. Gross pathological examination was carried out on the 14th day after the treatment.

No lethality was noted at single oral dose (gavage) of 2000 mg/kg bw (limit dose). No clinical symptoms were observed on the day of the treatment and during the 14-day observation period, the general state and behavior of experimental animals were normal. The body weight development was undisturbed in all animals. All animals survived until the scheduled autopsy on day 14. All organs of all experimental animals proved to be free of treatment related gross pathological changes.

Based on the results observed the LD50 was determined to be > 2000 mg/kg bw/day (limit dose). The LD0 was determined to be 2000 mg/kg bw/day (limit dose).

Acute inhalation toxicity

According to REACH Annex VIII, section 8.5 testing by the inhalation route was waived, as an acute oral toxicity study and an acute dermal toxicity study are available. Only two acute dose toxicity studies are required, with test item administration via the most appropriate route.

For risk characterization an inhalation LC0 for workers and general population was derived from the oral acute LC0 in rats of 2000 mg/kg bw (limit dose). The calculation assumed 70 kg bw and 50 % vs. 100 % absorption for the oral and inhalation route, respectively.

The LC0 (acute worker)inhalation was calculated for 8 h exposure and light activity.

LC0 (acute worker)inhalation = 2000 mg/kg bw * 1/0.38 m3/kg bw * 6.7m3 (8 h)/10 m3 (8 h) * 50 % Abs. (oral)/100 % Abs. (inhalation) = 1763 mg/m3

The LC0 (acute general population)inhalation was calculated assuming an equal breathing volume (20 m3) and exposure over 24 h at basal caloric demand:

The LC0 (acute general population)inhalation = 2000 mg/kg bw/4 * 70 kg bw/20 m3/person * 50 % Abs. (oral)/100 % Abs. (inhalation) = 875 mg/m3

Acute dermal toxicity

An acute dermal toxicity study was performed according to EU Method B.3, OECD Guideline 402 (Acute Dermal Toxicity) and OPPTS 870.1200. A limit test was carried out. Single groups of male and female Crl:(WI)BR rats (n=5 animals/sex) were exposed to the test item at 2000 mg/kg bw (limit dose) by dermal route. The test item was applied in original form and left in contact with the skin for 24 hours, followed by a 14-day observation period.

No mortality occurred during the study. Neither male nor female animals treated at 2000 mg/kg bw showed behavioral changes. No signs of systemic toxicity were observed during the study. No signs of irritation and corrosion were noted. The body weight development was undisturbed in all animals. No macroscopic alterations of organs related to systemic toxic effects of the test item were noted during necropsy.

Under the experimental conditions the acute dermal LD50 value of the test item proved to be > 2000 mg/kg bw in male and female Crl:(WI)BR rats. The LD0 was determined to be 2000 mg/kg bw.

Justification for classification or non-classification

Based on the data available the substance is not classified and labeled according to Regulation 1272/2008/EEC (CLP) and Directive 67/548/EEC (DSD).