Sodium dibutyldithiocarbamate

Endpoint summary

Description of key information

No data on repeated dose toxicity of SDBC are available. However, a reliable 90-day study is available for a structural analogue of SDBC, sodium dimethyldithiocarbamate (SDMC), in which a NOAEL of 10 mg/kg bw/day (calculated for pure (anhydrous) substance) was established, based on haemolytic effects manifested as an increase in mean corpuscular haemoglobin and mean corpuscular volume in both sexes, decreased hepatopoisis in spleen and signs of bone marrow hyperplasia in females. Applying a correction factor for the difference in molecular weight for SDBC (227/143), this leads to a NOAEL of 16 mg/kg bw/day for isolated (anhydrous) SDBC. This corresponds to a NOAEL of 34 mg/kg bw/day for its aqueous solution (47%). The value for the pure substance shall be used for DNEL derivation.

NOAEL pure substance = 16 mg/kg bw/d

NOAEL 47% aq.solution = 34 mg/kg bw/d

LOAEL pure substance = 79 mg/kg bw/d

LOAEL 47% aq.solution = 169 mg/kg bw/d

Key value for chemical safety assessment

Toxic effect type:

dose-dependent

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP-compliant guideline study, available as unpublished report, no restrictions, fully adequate for assessment.

Qualifier:

according to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Qualifier:

according to guideline

Guideline:

EU Method B.26 (Sub-Chronic Oral Toxicity Test: Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.3100 (90-Day Oral Toxicity in Rodents)

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River (UK) Limited, Margate, Kent, UK
- Age at study initiation: 5-8 weeks
- Weight at study initiation: males: 164-217 g, females: 143-193 g
- Housing: in groups of 5 by sex in polypropylene grid-floor cages suspended over trays lined with absorbent paper.
- Diet: a pelleted diet (Rat and Mouse SQC Diet No. 1, Special Diets Services Limited, Witham, Essex, UK), ad libitum
- Water: Mains drinking water from polycarbonate bottles attached to the cage, ad libitum
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 ± 2
- Humidity (%): 55 ± 15
- Air changes (per hr): at least 15 per hour
- Photoperiod (hrs dark / hrs light): 12/ 12

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: the test material was prepared at the appropriate concentrations as solution in distilled water. Formulations were stable for at least 3 days. Fresh formulations were therefore prepared daily and used wherever possible within 3 hours of preparation. Correction for 41% purity was taken into account.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples were taken once weekly of each test material formulation and analysed for concentration of SDDC at Safepharm Analytical Laboratory by gas chromatography. The results indicate that the prepared formulations were on most occasions within ±10% of nominal.

Duration of treatment / exposure:

90 consecutive days

Frequency of treatment:

Daily

Remarks:

Doses / Concentrations:
0. 10, 50 and 250 mg/kg bw/day
Basis:
nominal in water

No. of animals per sex per dose:

10/sex/dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: based on the results of a range-finding study
- Rationale for animal assignment (if not random): the animals were randomly allocated to treatment grouops using random letter tables and the group mean bodyweights were then determined to ensure similarity between the treatment groups

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: all animals were examined for overt signs of toxicity, ill-health or behavioural change immediately before dosing and one and 5 hours after doing during the working week. Animals were observed immediately before dosing and one hour after dosing at weekends and public holidays.

DETAILED CLINICAL OBSERVATIONS: Yes
Detailed individual clinical observations were performed on each animal using a purpose built arena. The following parameters were observed: gait, tremors, twitches, convulsions, bizarre/abnormal/stereotypic behaviour, salivation, piloerection, exophthalmia, lachrymation, hyper/hypothermia, skin colour, respiration, palpebral closure, urination, defecation, trasfer arousal, tail elevation.

BODY WEIGHT: Yes
- Time schedule for examinations: at day 0 (the day before the start of treatment) and at weekly intervals thereafter. Bodyweights were also recorded at terminal kill.

FOOD CONSUMPTION: yes
Food consumption was recorded for each group at weekly intervals throughout the study.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: daily, by visual inspection of the water bottles for any overt change.

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: pre-treatment and before termination of treatment (during week 12)
- Dose groups that were examined: control and high-dose animals

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the end of the study (day 90); where necessary, repeat were obtained on day 21.
- Anaesthetic used for blood collection: No data
- Animals fasted: No
- How many animals: all animals from each test and control groups
- Parameters examined: haemoglobin (Hb), erythrocyte count (RBC), haematocrit (Hct), erythrocyte indices (mean corpuscular haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin concentration), total leucocyte count (WBC), differential leucocyte count (neutrophils, lymphocytes, monocytes, eosinophils, basophils), platelet count (PLT), reticulogyte count (Retic, prothrombin time and activated partial thromboplastin time.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the end of the study (day 90); where necessary, repeat were obtained on day 21.
- Anaesthetic used for blood collection: No data
- Animals fasted: No
- How many animals: all animals from each test and control groups
- Parameters examined: urea, glucose, total protein, albumin, albumin/globulin ratio, sodium, potassium, chloride, calcium, inorganic phosphorus, aspartate aminotransferase, alanine aminotransferase, alkalline phosphatase, creatinine, total cholesterol, total bilirubin, cholinesterase

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: prior to the start of treatent and at weekly intervals thereafter, all animals were observed for signs of functional/behavioural toxicity. During Week 12 functional performance tests were also performed on all animals together with an assessment of sensory reactivity to different stimuli.
- Dose groups that were examined: all
- Battery of functions tested: sensory reactivity, forelimb/hindlimb grip strength, motor activity

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes. Samples of the following tissues were removed from all animals and preserved in buffered 10% formalin: adrenals, aorta (thoracic), bone & bone marrow (femur including stifle joint, sternum), brain (including cerebrum, cerebellum and pons), caecum, colon, duodenum, epididymides, eyes, gross lesions, heart, ileum (including Peyer's patches), jejunum, kidneys, liver, lungs (with bronchi), lymph nodes (cervical and mesenteric), mammary glands, muscle (skeletal), oesophagus, ovaries, pancreas, pituitary, prostate, rectum, salivary glands (submaxillary), sciatic nerve, seminal vesicles, skin (hind limb), spinal cord (cervical, mid-thoracic and lumbar), spleen, stomach, testes, thymus, thyroid/parathyroid, tongue, trachea, urinary bladder, uterus

Statistics:

Haematological, blood chemical, organ weight, weekly bodyweight gain and quantitative functional performance and sensory reactivity data were assessed for control and test material treatment groups for dose response relationships by linear regression analysuis followed by one way analysis of variance (ANOVA) incorporating Levene's test for homogeneity of variance. Wheere variances were shown to be homogenous pairwise comparisons were conducted using Dunnett's test. Where Levene's test showed unequal variances the data were analysed using non-parametric methods: Kruskal-Wallis ANOVA and Mann-Whitney "U" test.

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

no effects observed

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

not examined

Behaviour (functional findings):

effects observed, treatment-related

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
There were no deaths. Increased salivation around the time of dosing was detected for animals of either sex treated with 250 mg/kg bw/day from day 1 or day 2 onwards, accompanied in females with associated isolated findings of red/brown staining and/or wetness of the external body fur and generalised fur loss. Females treated with 250 mg/kg bw/day also showed hunched posture and isolated signs of tiptoe gait from day 28. Instances of transient increased salivation were also seen in either sex treated with 50 mg/kg bw/day. Excessive visible salivation and its associated findings are commonly reported following the oral administration of a test material, and are considered to be attributable to the repeated administration of a locally irritant test material formulation by gavage rather than an indication of systemic toxicity. No treatment-related clinical signs were observed at 10 mg/kg bw/day.

BODY WEIGHT AND WEIGHT GAIN
Animals of either sex treated with 250 mg/kg bw/day showed reductions in bodyweight gain throughout the study period compared with controls. No adverse bodyweight effect was noted at the other dose levels.

FOOD CONSUMPTION:
A reduction in dietary intake was detected for animals of either sex treated with 250 mg/kg bw/day throughout the study period compared with controls. No noteworthy differences in food consumption were observed at the other dose levels.

WATER CONSUMPTION:
Daily visual inspection of water bottles revealed no overt intergroup differences.

OPHTHALMOSCOPIC EXAMINATION
There were no treatment-related ocular effects.

HAEMATOLOGY
A clear haemolytic effect was identified for animals treated with 250 mg/kg bw/day and likely also in animals treated with 50 mg/kg bw/day, characterised by a statistically significant reduction in erythrocyte count in animals treated with 250 mg/kg bw/day together with increases in mean corpuscular haemoglobin (MCH) and mean corpuscular volume (MCV). Males treated with 250 mg/kg bw/day also shwoed an increase in mean corpuscular haemoglobin concentration. An increase in MCH and MCV was also apparent in either sex treated with 50 mg/kg bw/day.

CLINICAL CHEMISTRY
Findings were confined to increases in plasma levels of total protein, sodium and cholesterol in males treated with 250 mg/kg bw/day.

NEUROBEHAVIOUR
Males treated with 250 or 50 mg/kg bw/day showed a statistically significant increase in total activity compared with controls. No treatment-related changes were detected for females or for 10 mg/kg bw/day males.
Females treated with 250 mg/kg bw/day showed statisitically significant increases in startle reflex for percentile average response, root of the mean square and peak response, compared with controls. A slight but statistically significant increase in percentile average response was also noted in females treated with 50 or 10 mg/kg bw/day but this was considered not to be toxicologically significant.

ORGAN WEIGHTS
Increases in kidney, liver and spleen weight were evident in both sexes treated with 250 mg/kg bw/day compared with controls. The other organs were unaffected and there were no other changes in organ weight that could be considered toxicologically important.

GROSS PATHOLOGY
Treatment-related gastric changes were detected in the majority of male animals treated with 250 mg/kg bw/day together with enlarged and darkened spleens in two males treated with 250 mg/kg bw/day. No treatment-related macroscopic abnormalities were detected for animals treated with 50 or 10 mg/kg bw/day.

HISTOPATHOLOGY: NON-NEOPLASTIC
The following treatment-related changes were detected:
Spleen: higher severities of extramedullary haemopoiesis were observed in relation to treatment for rats of either sex dosed at 250 mg/kg bw/day. A similar effect was also seen for male rats dosed at 50 mg/kg bw/day and 10 mg/kg bw/day. In addition, higher severities of pigment accumulation were seen for rats of either sex dosed at 250 mg/kg bw/day or at 50 mg/kg bw/day. The pigment was determined to be haemosiderin by Perl's staining technique.
Kidneys: a higher incidence and greater severity of pigment accumulation was seen in the renal tubules of rats of either sex dosed at 250 mg/kg bw/day and for male rats dosed at 50 mg/kg bw/day. The pigment was determined to be haemosiderin by Perl's staining technique.
Urinary bladder: there were indications of an effect of treatment on the transitional epithelium of the bladder resulting in hyperplasia. This is reasonably convincing for male rats dosed at 250 mg/kg bw/day, but for females, this condition is also present among control animals.
Thyroids: higher severities of follicular cell hyperthrophy were observed for male rats dosed at 250 mg/kg bw/day. A higher incidence of associated colloird depletion was also seen.
Stomach: acanthosis and heperkeratosis of the epithelium of the forestomach was seen among rats of either sex dosed at 250 mg/kg bw/day. Similar effects were also seen for male rats receiving 50mg/kg bw/day of the test material.
Duodenum: mucosal hypertrophy was seen for four males and for 1 female rat dosed at 250 mg/kg bw/day. This condition was considered to be related to treatment for male rats, but probably not for females.
Salivary glands: treatment-related atrophy of the serous acini of the submaxillary salivary glands was seen for rats of either sex receiving 250 mg/kg bw/day of the test material.
Bone marrow: lower severities of adipose infiltration of the bone marrow indicative of marrow hyperplasia were seen in female rats dosed at 250 mg/kg bw/day and 50 mg/kg bw/day.
All remaining morphological changes were those commonly observed in laboratory maintained rats of the age and strain employed. Although group differences in the incidence or severity of lesions occasionally attained statistical significance, none was considered to be related to treatment.

HISTOPATHOLOGY: NEOPLASTIC (if applicable)

HISTORICAL CONTROL DATA (if applicable)

OTHER FINDINGS

Dose descriptor:

NOAEL

Effect level:

10 mg/kg bw/day (actual dose received)

Based on:

act. ingr.

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

50 mg/kg bw/day (actual dose received)

System:

haematopoietic

Organ:

bone marrow

kidney

spleen

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Conclusions:

Based on the results of this repeated dose toxicity study the NOAEL of SDMC is 10 mg/kg bw.

Executive summary:

A reliable GLP-compliant 90 -day study, performed according to OECD Guideline 408, was performed with SDMC. In this 90-day study, groups of 10 male and 10 female rats were daily administered the test substance in water by gavage at dose levels of 10, 50 and 250 mg/kg bw/d. A clear haemolytic effect was identified for animals of both sexes treated with 50 and 250 mg/kg/d, characterized by a statistically significant reduction in erythrocyte count in animals treated with 250 mg/kg bw/d together with an increase in mean corpuscular haemoglobin (MCH) and mean corpuscular volume (MCV) in animals treated with 50 mg/kg bw/d. Males treated with 250 mg/kg bw/d also showed a slight increase in mean corpuscular haemoglobin concentration (MCHC). Lower severities of adipose infiltration of the bone marrow indicative of marrow hyperplasia were seen for female rats dosed at 250 mg/kg/day and 50 mg/kg/day. Increases in relative kidney, liver and spleen weight were evident in both sexes treated with 250 mg/kg/day compared with controls. Increased haemosiderin deposition in spleen was observed in females dosed with 50 mg/kg bw/day, while increased haemosiderin deposition in kidneys was observed in males at the same dose level. Males dosed with 250 mg/kg bw/day also showed increased follicular cell hypertrophy in thyroid gland and hyperplasia of the transitional epithelium of urinary bladder. Based on the results of the study, the NOAEL for repeated dose toxicity for pure SDMC was established at 10 mg/kg bw/day. 

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

16 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

OECD TG 408 study performed under GLP

System:

haematopoietic

Organ:

bone marrow

spleen

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

No data on repeated dose toxicity of sodium dibutyldithiocarbamate (SDBC) are available for assessment. However, Article 13 of REACH states that, in case no appropriate animal studies are available for assessment, information should be generated whenever possible by means other than vertebrate animal tests, i. e. applying alternative methods such as in vitro tests, QSARs, grouping and read-across.

A reliable GLP-compliant 90 -day study, performed according to OECD Guideline 408, is available for a structural analogue of SDBC, sodium dimethyl dithiocarbamate (SDMC). In the 90-day study, groups of 10 male and 10 female rats were daily administered the test substance in water by gavage at dose levels of 10, 50 and 250 mg/kg bw/day (corresponding to 24.4, 122 and 610 mg/kg bw/day for the substance as manufactured, i.e. 41% solution). Animals were observed for clinical signs and signs of functional/behavioral toxicity, and gross pathological, histopathological, haematological and clinical chemistry examinations were performed at terminal sacrifice. A clear haemolytic effect was identified for animals of both sexes treated with 50 and 250 mg/kg/day, characterized by a statistically significant reduction in erythrocyte count in animals treated with 250 mg/kg bw/day together with an increase in mean corpuscular haemoglobin (MCH) and mean corpuscular volume (MCV) in animals treated with 50 mg/kg bw/day. Males treated with 250 mg/kg bw/day also showed a slight increase in mean corpuscular haemoglobin concentration (MCHC). Lower severities of adipose infiltration of the bone marrow indicative of marrow hyperplasia were seen for female rats dosed at 250 mg/kg/day and 50 mg/kg/day. Increases in relative kidney, liver and spleen weight were evident in both sexes treated with 250 mg/kg/day compared with controls. Increased haemosiderin deposition in spleen was observed in females dosed with 50 mg/kg bw/day, while increased haemosiderin deposition in kidneys was observed in males at the same dose level. Males dosed with 250 mg/kg bw/day also showed increased follicular cell hypertrophy in thyroid gland and hyperplasia of the transitional epithelium of urinary bladder. Based on the results of the study, the NOAEL for repeated dose toxicity for pure (anhydrous) SDMC was established at 10 mg/kg bw/day. 

In addition to SDMC, data are also available for the other structural analogue SDEC. In an NTP subchronic feeding study with SDEC trihydrate, groups of five  Fischer 344 rats of each sex were fed diets containing SDEC trihydrate at doses 1250, 2500, 5000, 10000, 20000 and 40000 ppm. The period of administration of the test chemical was 7 weeks, followed by 1 week of additional observation. At the end of the study, all animals were killed and necropsy and histopathological examinations were performed. Effects were seen in the body weight of animals due to treatment. A 10% depression in body weight was used for the estimation of the maximum tolerated dose (MTD) of SDEC. In the histopathology examination a very slight increase in splenic hematopoiesis and a very small amount of vacuolation of renal tubular epithelium were noted at 10000 ppm and above. Based on this the NOAEL of this study for SDEC trihydrate was 425 mg/kg bw (5000 ppm), while the respective NOAEL for the anhydrous SDEC is 332 mg/kg bw/d.

In an NTP subchronic feeding study with SDEC, groups of five B6C3F1 mice of each sex were fed diets containing SDEC trihydrate at doses 2500, 5000, 6000, 8000 and 10000 ppm. The period of administration of the test chemical was 7 weeks, followed by 1 week of additional observation. For female mice the period of administration of the test chemical was 12 weeks.  At the end of the study, all animals were killed and necropsy and histopathological examinations were performed. No effects of any toxicological significance were seen up until and including the highest dose level. Therefore, the NOAEL of this study for SDEC was 1305 mg/kg bw (10000 ppm), while the respective NOAEL for the pure SDEC is 1019 mg/kg bw/d.

The three substances are structural homologues of each other, differing only in the length of alkyl substituents at the amine function of the dithiocarbamate moieties (butyl vs. methyl and ethyl). As SDMC is a smaller molecule than SDEC and SDBC, it is expected that its absorption from the gut shall occur at least as fast, if not faster. Therefore it is considered acceptable to derive the data on repeated dose toxicity of SDBC by read-across to SDMC, as a worst-case scenario. The SMDC NOAEL of 10 mg/kg bw/day wil be used as a point of departure after application of a correction for molecular weight: NOAEL of 10 x (227.37/143.21) = 16 mg/kg bw/day for pure (anhydrous) SDBC. For the 47% aqueous solution this would be 34 mg/kg bw/day for the substance as manufactured.

Applying the correction for molecular weight, the LOAEL of 50 x (227.37/143.21) = 79.4 mg/kg bw/day and of 168.9 mg/kg bw/day have been calculated for the pure substance and its 47% solution, respectively.

 

Justification for classification or non-classification

Based on the calculated NOAEL of 16 mg/kg bw/day and a LOAEL of 79.4 mg/kg bw/day for anhydrous SDBC, established based on the read-across of the results of 90 -day oral toxicity study from a structural analogue sodium dimethyldithiocarbamate (SDMC), associated with haemolytic effects and indirect evidence of bone marrow hyperplasia, sodium dibutyldithiocarbamate (SDBC) in its anhydrous form should be classified as Specific Target Organ Toxicity - Repeated Exposure Cat. 2, H373 (may cause damage to cardiovascular/hematological organs, including bone marrow, through prolonged or repeated exposure) according to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008. 

This classification is not applicable for the 47% aqueous solution, with a calculated NOAEL of 34 mg/kg bw/day and a LOAEL of 168.9 mg/kg bw/day. As the observed LOAEL is above the cut-off limits of 100 mg/kg bw/day, established by EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008, classification of the substance as manufactured (as ca. 47% aqueous solution) for repeated dose toxicity is not warranted.