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Description of key information

The 28-day gavage study with Crj: CD (SD) rats (MHWJ 1997) was considered to be the most relevant oral toxicity study for NOAEL determination. CBS-related effects were present in male and female Crj: CD (SD) rats at = 250 mg/kg bw and day. There were signs of a coagulopathy of the blood in both sexes and effects in the kidney of male rats. No relevant systemic effects were observed in male and female rats after repeated oral administration of 80 mg/kg bw and day CBS. Thus, the NOAEL is considered to be 80 mg/kg bw and day.
The inhalation toxicity of CBS was examined in a subacute inhalation study (Monsanto Co. 1981). The study is limited concerning the recommended particle-size distribution given in current guidelines and thus an exposure of all relevant regions of the respiratory tract might not have been given. In light of these limitations the data from the oral subacute toxicity study (NOAEL: 80 mg/kg bw and day, MHWJ 1997) will be used for calculation of the systemic DNEL; whereas local effects noted in the inhalation study will be used as supporting evidence. Based on the fact that signs of nasal irritation observed at clinical examination were reversible, only short in duration and could not be correlated to histopathological effects, no toxicological significance was attached to this finding, and thus, no relevant local effects were observed up to 0.048 mg/l.
In a subacute dermal toxicity study using doses of 125, 500 and 2000 mg/kg bw and day no systemic or local effects were noted in New Zealand White rabbits after repeated dermal exposure for three weeks with 2000 mg/kg bw and day (Monsanto 1981). Thus, the NOAEL is considered to be 2000 mg/kg bw and day.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records
Reference
Endpoint:
short-term repeated dose toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: Guidelines for 28-day repeated dose toxicity testing of chemicals (Japan)
Deviations:
no
Principles of method if other than guideline:
N-cyclohexyl-2-benzothiazolesulfenamide was studied for oral toxicity in rats in a 28-day repeat dose toxicity test at doses of 0, 25, 80, 250 or 800 mg/kg/day.
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Crj: CD(SD)
Sex:
male/female
Route of administration:
oral: gavage
Vehicle:
other: sesame oil
Duration of treatment / exposure:
28 days
Frequency of treatment:
daily
Remarks:
Doses / Concentrations:
25; 80; 250; 800 mg/kg bw/day
Basis:

No. of animals per sex per dose:
Six per dose and sex.
Control animals:
yes, concurrent vehicle
Details on study design:
Post-exposure period: with and without 14 days recovery period
Observations and examinations performed and frequency:
Signs of general condition,food consumption, body weight gain, Hematoloty, urinalysis
Sacrifice and pathology:
Organs weights, histopathological examination.
Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
Signs of loss of general condition like piloerection and siled fur were observed in females of the 800 mg/kg group.
Mortality:
no mortality observed
Description (incidence):
All animals survived until the end of the study.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Suppression of food consumption and body weight gain was noted in females of the 250 mg/kg group and males and females of the 800 mg/kg group.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
Suppression of food consumption and body weight gain was noted in females of the 250 mg/kg group and males and females of the 800 mg/kg group.
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
Shortening of prothrombin time in males of the 250 and 800 mg/kg-groups.  
Decreased hematocrit, reticulocyte count and platelet count in females of  the 800 mg/kg-group.
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
Total protein content was decreased in males of the 250 and 800  mg/kg-groups.
Chloride levels were reduced in males and females of the  800 mg/kg-group. Calcium level was elevated and sodiumlevel reduced in  females of the 800 mg/kg-group.
Urinalysis findings:
effects observed, treatment-related
Description (incidence and severity):
Increase of ketone bodies in males of 250 and 800 mg/kg-groups.  
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
Distended cecum in females of the 800 mg/kg-group. Increased relative kidney weights in males and females of the 800 mg/kg-group.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Increased deposition of hyaline droplets in the renal proximal tubular epithelium in males of the 250 and 800 mg/kg-groups. After the 14 days recovery the histopathological changes in the kidneys tended to recover and the other substance-related changes had disappeared.
Histopathological findings: neoplastic:
not examined
Key result
Dose descriptor:
NOAEL
Effect level:
80 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: no adverse effects
Key result
Dose descriptor:
LOAEL
Effect level:
250 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: signs of a coagulopathy and adverse effects in the kidney of male rats, suppression of food consumption and body weight gain in female rats
Key result
Critical effects observed:
yes
Lowest effective dose / conc.:
250 mg/kg bw/day (nominal)
System:
haematopoietic
Organ:
kidney
Treatment related:
yes
Dose response relationship:
yes

All animals survived until the end of the study.

Males:

25, 80 mg/kg bw: no adverse effects (decrease of GPT* at 25, and 80 mg/kg bw)

250 mg/kg bw: increase of ketone bodies, shortening of the prothrombin time, on blood chemical examination: total protein was decreased,

Histopathology: an increase in deposition of hyaline droplets in the renal proximal tubular epithelium.

800 mg/kg bw: Suppression of food consumption and body weight gain, urin analysis revealted an increase of ketone bodies,shortening of the prothrombin time,on blood chemical examination: total protein was decreased, reduced chloride levels,

Histopathology: an increase in deposition of hyaline droplets in the renal proximal tubular epithelium, increase of the relative kidney weights

No abnormalities were detected in: pancreas, stomach, small intestine, large intestine, thyroid, parathyroid, spleen, lymph node, bone marrow or brain, 1/6 males of the 800 mg/kg bw group + 14 d recovery showed a moderate effect on the testis (atrophy, seminiferous tubule, diffuse).

Females

25,80 mg/kg bw: no adverse effects (decrease of GPT* at 80 mg/kg bw)

250 mg/kg bw: Suppresion of food consumption and body weight gain

800 mg/kg bw: Clinical signs:signs of loss of general conditions like piloerection and soiled fur;

Supression of food consumption and body weight gain; hematology findings: decrease in the hematocrit value, reticulocyte count and platelet count; reduced chlorid levels, calcium elevated and sodium reduced.

Necropsy: cecum was distended;increase in relative kidney weights

No abnormalities were detected: heart, pancreas, stomach, small intestine, large intestine, urinary bladder, ovary, pituitary, thyroid, parathyroid, spleen, lymph node, bone marrow or brain

Remarks: Histopathological changes in the kidney tended to recover and the other changes related to the test substance disappeared after 14 -day recovery period.

The authors consider: NOAEL: 80 mg/kg bw/day for both sexes

*GPT: serum glutamic pyruvic transaminase (synonym: alanine aminotransferase ALAT).

Conclusions:
No relevant systemic toxic effects were observed in male and female rats after repeated oral administration of 80 mg/kg bw and day CBS. Based on these findings, the author considered a NOAEL of 80 mg/kg bw and day for both sexes (MHWJ 1997).
Executive summary:

The test substance CBS was evaluated in a subacute gavage study with Crj: CD (SD) rats, which was performed mostly in accordance to regulation requirements (mostly according to OECD TG 407) (MHWJ 1997). Male and female rats (6 per dose and sex) were administered with 0, 25, 80, 250 and 800 mg/kg bw/day for 28 days and were scarified on day 29. Another control and 800 mg/kg bw/day group were treated for 28 days and then kept for a recovery period of 14 days before sacrifice on day 43. In this study data on haematology, clinical biochemistry, organ weights and incidences of histopathological findings were provided. No mortality occurred during the study period. After administration of 800 mg/kg bw and day signs of loss of general conditions like piloerection and solid fur were observed in female rats. Suppression of food consumption and body weight gain was observed in females given = 250 mg/kg bw and day and in males at 800 mg/kg bw and day. Hematology revealed statistically significant shortening of the prothrombin time in males given = 250 mg/kg bw and day, and statistically significant decrease in hematocrit value, reticulocyte count and platelet count for the 800 mg/kg bw and day females. Clinical biochemistry revealed statistically significant decreases in alanine aminotransferase (ALAT) for males of all CBS treated groups and for females given = 80 mg/kg bw and day, in total protein for males treated at = 250 mg/kg bw and day, in chloride levels in males and females at 800 mg/kg bw and day and in sodium levels in females at 800 mg/kg bw and day. In addition, calcium concentration was elevated in females at the 800 mg/kg bw and day dose group. Urinalysis revealed an increase of ketone bodies in males treated with = 250 mg/kg bw and day. The statistically significant increase in relative kidney weights in the 800 mg/kg bw and day males was considered to be associated with an increase in deposition of hyaline droplets in the proximal tubular epithelium of the kidneys in male rats evident at 250 and 800 mg/kg bw and day. This effect in male kidney showed a clear tendency towards reversibility. All other changes were completely reversible after the 14 day recovery period. In summary, CBS-related effects were present in male and females Crj: CD (SD) rats at = 250 mg/kg bw and day. There were signs of coagulopathy of the blood in both sexes and effects in the kidney of male rats. No relevant systemic toxic effects were observed in male and female rats after repeated oral administration of 80 mg/kg bw and day CBS. Based on these findings, the author considered a NOAEL of 80 mg/kg bw and day for both sexes (MHWJ 1997).

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEL
80 mg/kg bw/day
Study duration:
subacute
Species:
rat

Repeated dose toxicity: dermal - systemic effects

Link to relevant study records
Reference
Endpoint:
short-term repeated dose toxicity: dermal
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study, comparable to guideline study.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 410 (Repeated Dose Dermal Toxicity: 21/28-Day Study)
Deviations:
no
Principles of method if other than guideline:
In a 21-day dermal toxicity study 5 male and 5 female rabbits were treated with 0, 125, 500 or 2000 mg Santocur/kg/day (5 days/weeks) on intact and abraded skin. The animals were observed for mortality, clinical signs, body weight gain and dermal irritation. A gross pathology and microscopic examination was performed at the end of the study.
GLP compliance:
yes
Species:
rabbit
Strain:
New Zealand White
Sex:
male/female
Type of coverage:
semiocclusive
Vehicle:
unchanged (no vehicle)
Details on exposure:
Route of Administration: dermal
Duration of treatment / exposure:
21 d
Frequency of treatment:
Daily (5 days per week).
Remarks:
Doses / Concentrations:
125, 500 or 2000 mg/kg bw/d
Basis:

No. of animals per sex per dose:
Ten per dose and sex (5 per dose and sex intact skin, 5 per dose and sex abraded skin).
Control animals:
yes
Details on study design:
Post-exposure period: no data
Positive control:
None.
Observations and examinations performed and frequency:
Mortality, general observations, body weight gain, dermal irritation .
Sacrifice and pathology:
Gross pathology and microscopic examination.
Clinical signs:
no effects observed
Description (incidence and severity):
No test article-related signs were noted for any animal in the test groups; a few rabbits in the 125 and 500 mg/kg bw test groups exhibited some signs of occular irritation such as injected iris, corneal opacity and conjunctivial redness and swelling. None of the animals in the 2000 mg/kg group were noted for ocular irritation.
Dermal irritation:
no effects observed
Description (incidence and severity):
The majority of the rabbits in both control and test groups (abraded and intact skin) exhibited no dermal irritation during the study period; however during the study period a few rabbits in each CBS dose groups exhibited very slight to slight erythema on the application area of the skin, which was reversible within day 21 of the study; the incidence of very slight to slight desquamation was increased in test compound treated groups; but a dose-response relationship was not noticed.
Mortality:
no mortality observed
Description (incidence):
No test substance related mortality.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
No statistically significant differences were seen.
Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
effects observed, treatment-related
Haematological findings:
no effects observed
Description (incidence and severity):
No changes considered to be related to CBS were seen in the hematologic studies and biochemical studies.
Clinical biochemistry findings:
no effects observed
Description (incidence and severity):
No changes considered to be related to CBS were seen in the hematologic studies and biochemical studies.
Urinalysis findings:
not specified
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Description (incidence and severity):
The body weight means of the different test groups and most of the mean organ weights were simular to the control groups.
Gross pathological findings:
no effects observed
Description (incidence and severity):
No findings related to the test substance were observed.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
no effects observed
Description (incidence and severity):
The main microscopic findings in the skin were slight hyperkeratosis abd acanthosis in the epidermis and infiltration of inflammatory infiltrate in the dermis. These changes were present in control animals and CBS treated animals and were considered as unrelated to the application of CBS.
Histopathological findings: neoplastic:
not examined
Other effects:
no effects observed
Key result
Dose descriptor:
NOAEL
Effect level:
2 000 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No major signs of local or systemic toxicity noted in rabbits treated with CBS at dosage of 125, 500, or 2000 mg/kg bw/day
Key result
Critical effects observed:
no

No test article-related signs were noted for any animal in the test groups; a few rabbits in the 125 and 500 mg/kg bw test groups exhibited some signs of occular irritation such as injected iris, corneal opacity and conjunctivial redness and swelling. None of the animals in the 2000 mg/kg group were noted for ocular irritation.

mortality: control 1/10 males (on day 12); 1/10 males 2000 mg/kg (on day 13)

mortality not test substance related

Dermal Irritation:

the majority of the rabbits in both control and test groups (abraded and intact skin) exhibited no dermal irritation during the study period; however during the study period a few rabbits in each CBS dose groups exhibited very slight to slight erythema on the application area of the skin, which was reversible within day 21 of the study; the incidence of very slight to slight desquamation was increased in test compound treated groups; but a dose-response relationship was not noticed.

Body weight: no statistically significant differences were seen.

Clinical laboratory tests:

No changes considered to be related to CBS were seen in the hematologic studies and biochemical studies.

Gross pathology: No findings related to the test substance were observed.

Organ weights: the body weight means of the different test groups and most of the mean organ weights were simular to the control groups.

Histopathology: the main microscopic findings in the skin were slight hyperkeratosis abd acanthosis in the epidermis and infiltration of inflammatory infiltrate in the dermis. These changes were present in control animals and CBS treated animals and were considered as unrelated to the application of CBS.

Findings on the internal organs were consistent with the usual spontaneous lesions found in this strain of rabbits

No evidence of toxicity related to test material administration.

Conclusions:
No evidence of toxicity related to test material administration.
Executive summary:

In a dermal 21-day toxicity study comparable to OECD TG 100 CBS was applied daily to the intact and abraded skin in doses of 125, 500 and 2000 mg/kg bw and day to each of the male and female adult New New Zealand white rabbits for a period of 3 weeks. Saline was used as negative control. Ground CBS was applied onto the skin moistened and covered with occlusive dressing. No data were available indicating the administered concentrations or surface area doses of CBS. The exposure time was 6 hours per day for a 5-day per week basis, for a period of 21 consecutive days. Two rabbits died during the course of study. One male control rabbit was found dead on day 12 and one male treated with 2000 mg/kg bw and day on day 13, respectively. Neither death was attributed to treatment with CBS. No dose dependent effects were noted for general appearance, behaviour, body weight, haematology, blood biochemistry, gross pathology, absolute and relative organ weights and histopathology. During the study period a few rabbits in each of the CBS dose groups exhibited very slight to slight erythema on the application area of the skin, which was reversible within day 21 of the study. The incidence of very slight to slight desquamation seen as slight scaling was increased in animals of the CBS-dose groups when compared to controls. But a dose-response relationship was not noticed. At microscopy of the skin slight hyperkeratosis and acanthosis in the epidermis and infiltration of inflammatory infiltrate in the dermis were observed. These findings were present in both CBS-treated animals and those of controls. Their incidence and severity did not distinguish CBS-treated rabbits from controls. Therefore, the NOAEL for systemic effects and local effects in rabbits after repeated dermal exposure was 2000 mg/kg bw and day (Monsanto Co.1981).

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
2 000 mg/kg bw/day
Study duration:
subacute
Species:
rabbit
Quality of whole database:
GLP study, comparable to guideline study.

Repeated dose toxicity: dermal - local effects

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Additional information

Repeated dose toxicity: oral

The test substance CBS was evaluated in a subacute gavage study with Crj: CD (SD) rats, which was performed mostly in accordance to regulation requirements (mostly according to OECD TG 407) (MHWJ 1997). Male and female rats (6 per dose and sex) were administered with 0, 25, 80, 250 and 800 mg/kg bw/day for 28 days and were scarified on day 29. Another control and 800 mg/kg bw/day group were treated for 28 days and then kept for a recovery period of 14 days before sacrifice on day 43. In this study data on haematology, clinical biochemistry, organ weights and incidences of histopathological findings were provided. No mortality occurred during the study period. After administration of 800 mg/kg bw and day signs of loss of general conditions like piloerection and solid fur were observed in female rats. Suppression of food consumption and body weight gain was observed in females given >= 250 mg/kg bw and day and in males at 800 mg/kg bw and day. Hematology revealed statistically significant shortening of the prothrombin time in males given >= 250 mg/kg bw and day, and statistically significant decrease in hematocrit value, reticulocyte count and platelet count for the 800 mg/kg bw and day females. Clinical biochemistry revealed statistically significant decreases in alanine aminotransferase (ALAT) for males of all CBS treated groups and for females given >= 80 mg/kg bw and day, in total protein for males treated at >= 250 mg/kg bw and day, in chloride levels in males and females at 800 mg/kg bw and day and in sodium levels in females at 800 mg/kg bw and day. In addition, calcium concentration was elevated in females at the 800 mg/kg bw and day dose group. Urinalysis revealed an increase of ketone bodies in males treated with >= 250 mg/kg bw and day. The statistically significant increase in relative kidney weights in the 800 mg/kg bw and day males was considered to be associated with an increase in deposition of hyaline droplets in the proximal tubular epithelium of the kidneys in male rats evident at 250 and 800 mg/kg bw and day. This effect in male kidney showed a clear tendency towards reversibility. All other changes were completely reversible after the 14 day recovery period. In summary, CBS-related effects were present in male and females Crj: CD (SD) rats at >= 250 mg/kg bw and day. There were signs of coagulopathy of the blood in both sexes and effects in the kidney of male rats. No relevant systemic toxic effects were observed in male and female rats after repeated oral administration of 80 mg/kg bw and day CBS. Based on these findings, the author considered a NOAEL of 80 mg/kg bw and day for both sexes (MHWJ 1997).

These findings were confirmed by an early carcinogenicity study. In this study male and female B6C3F1 and B6AKF1 mice were treated for 18 months with 95.3 mg/kg bw and day CBS. Gross pathology and histological examination of major organs were performed. No substance-related adverse effects were seen in treated B6C3F1 and B6AKF1 mice (for more details see chapter carcinogenicity) (NCI 1968).

In a 28 day feeding study male and female rats were treated with 0, 100, 250, 1000 or 3000 mg/kg bw and day CBS (corresponding to mean compound consumption of 0, 101, 249, 500, 961 and 3208 mg/kg bw and day in males; and 0, 92.5, 229, 459, 910 and 2769 mg/kg bw and day in females). Three female rats given 3000 mg/kg bw and day died during the treatment period. Two deaths occurred during study week two and one death occurred during study week four. CBS-related effects were noted at the highest dose level of 3000 mg/kg bw and day and included hair loss, labored breathing, yellowish staining of the anogenital region and distension of the abdomen. Less frequent findings were abdominal masses and decrease of motor activity. In rats of both sexes statistically significant body weight reduction and a decrease in food consumption were observed at = 500 mg/kg bw and day CBS. No blood biochemistry and haematology parameters were examined, and no histopathology was performed in this study because this study was intended to serve as a dose-range finding study. The NOAEL for systemic effects which could be derived from this study is approximately 250 mg/kg bw and day. The NOAEL based on the reduced body weight gain and food consumption seen at 500 mg/kg bw and day (Monsanto Co. 1980). The lack of blood biochemistry, haematology and histopathology data diminishes the validity of this NOAEL through food consumption and body data are generally as sensitive indicators of systemic toxicity.

Repeated dose toxicity: inhalation

In a 28-day inhalation toxicity study groups of Sprague-Dawley CD rats (10/sex/group) were whole body exposed to atmospheric concentrations of CBS of 0.0043, 0.0144 and 0.048 mg/l (analytic values which represent ca. 9 % of the nominal values) for 6 hours per day and 5 days per week for a period of four consecutive weeks (Monsanto 1981). The equivalent aerodynamic diameter of the CBS dust generated was 7.6 µm with a geometric standard deviation of 2.7 µm. This distribution of CBS particle sizes was above the recommendations in current inhalation guideline tests. Two further groups of rats (10 per sex) acting as control groups were exposed to compressed filter air alone. There were no treatment-related premature deaths. The rats exhibited occasional nasal irritation which appeared to be concentration related in term of severity and number of animals exhibiting the sign (no more data). This finding was observed immediately after the 6-hour exposure period, and disappeared by the next morning. Since the animals recovered from this lesion within 24 hours and these findings could not be correlated to histopathologic effects, the observation of nasal irritation in few CBS-exposed animals was not considered to be toxicologically adverse. No concentration dependent effects were noted for general appearance, behaviour, body weight, food consumption, haematology, urinalysis, gross pathology and absolute and relative organ weights. Clinical biochemistry revealed concentration-related statistically significant increase of serum glutamic oxaloacetic transaminase (SGOT) values in males and females exposed to 0.0144 and 0.048 mg/l compared to control groups. However, these findings were not confirmed by microscopic changes in the liver and should therefore not be regarded as an adverse effect. In addition, there were no changes in organ weights and macroscopic examination that were considered to be an effect of exposure to CBS. A slight increased incidence of brown pigment within sinusoidal macrophages in lymph nodes was present in 2/10 males and 4/10 females exposed to 0.048 mg/l compared to controls (3/20 females). Very slight to slight increase of hemosiderin storage in the spleen was observed in 5/10 females of the 0.048 mg/l concentration group. This finding was not observed in any of the 20 males and females of the internal controls. The author suggested that these lesions may represent a compound effect; however similar lesions were commonly observed in control rats at this facility and therefore the possibility that they were spontaneous in origin cannot be excluded. Microscopic finding was present in the eyes of a few animals exposed to the highest concentration of 0.048 mg/l. There was a slight increased incidence and severity of conjunctivitis in each of 2/10 males and females when compared to control (1/20 males). Because a limited number of animals were affected this finding was considered to be incidental and spontaneous nature. Microscopy of nasal turbinates, olfactory bulb and the lungs showed a number of histopathologically findings. Their type, incidence and severity did not distinguish CBS-exposed rats from controls. Based on the fact that the signs of nasal irritation observed at clinical examination were only short in duration and could not be correlated to histopathological effects, no toxicological significance was attached to this finding.

In summary, the study is limited concerning the recommended particle-size distribution given in current guidelines. To allow for exposure of all relevant regions of the respiratory tract, aerosols with mass median aerodynamic diameters (MMAD) ranging from 1 to 3 µm are recommended. The MMAD used was above the recommendations given (7.6 µm) and therefore, a limited systemic exposure seems reasonable. Thus, the findings of this study are questionable, especially for systemic effects. Whereas the local effects on the respiratory tract noted should be used as supporting evidence.

Repeated dose toxicity: dermal

In a dermal 21-day toxicity study comparable to OECD TG 410 CBS was applied daily to the intact and abraded skin in doses of 125, 500 and 2000 mg/kg bw and day to each of the male and female adult New Zealand white rabbits for a period of 3 weeks. Saline was used as negative control. Ground CBS was applied onto the skin moistened and covered with occlusive dressing. No data were available indicating the administered concentrations or surface area doses of CBS. The exposure time was 6 hours per day for a 5-day per week basis, for a period of 21 consecutive days. Two rabbits died during the course of study. One male control rabbit was found dead on day 12 and one male treated with 2000 mg/kg bw and day on day 13, respectively. Neither death was attributed to treatment with CBS. No dose dependent effects were noted for general appearance, behaviour, body weight, haematology, blood biochemistry, gross pathology, absolute and relative organ weights and histopathology. During the study period a few rabbits in each of the CBS dose groups exhibited very slight to slight erythema on the application area of the skin, which was reversible within day 21 of the study. The incidence of very slight to slight desquamation seen as slight scaling was increased in animals of the CBS-dose groups when compared to controls. But a dose-response relationship was not noticed. At microscopy of the skin slight hyperkeratosis and acanthosis in the epidermis and infiltration of inflammatory infiltrate in the dermis were observed. These findings were present in both CBS-treated animals and those of controls. Their incidence and severity did not distinguish CBS-treated rabbits from controls. Therefore, the NOAEL for systemic effects and local effects in rabbits after repeated dermal exposure was 2000 mg/kg bw and day (Monsanto Co.1981).

In conclusion:

Oral

The 28-day gavage study with Crj: CD (SD) rats (MHWJ 1997) was considered to be the most relevant oral toxicity study for NOAEL determination. In this subacute toxicity study signs of coagulopathy of the blood were observed in both male and female rats. In males shortening of the prothrombine time (statistically significant) was noted after oral administration of = 250 mg/kg bw and day CBS, and in females statistically significant decreased platelet count was noted at 800 mg/kg bw and day. CBS-related effects were present in male and female Crj: CD (SD) rats at = 250 mg/kg bw and day. There were signs of a coagulopathy of the blood in both sexes and effects in the kidney of male rats. No relevant systemic effects were observed in male and female rats after repeated oral administration of 80 mg/kg bw and day CBS. Thus, the NOAEL is considered to be 80 mg/kg bw and day.

Inhalation

The inhalation toxicity of CBS was examined in a subacute inhalation study (Monsanto Co. 1981). The study is limited concerning the recommended particle-size distribution given in current guidelines and thus an exposure of all relevant regions of the respiratory tract might not have been given. The biologically relevance of sporadic findings reported, especially systemic effects are questionable. In light of these limitations the data from the oral subacute toxicity study (NOAEL: 80 mg/kg bw and day, MHWJ 1997) will be used for calculation of the systemic DNEL; whereas local effects noted in the inhalation study will be used as supporting evidence. Based on the fact that signs of nasal irritation observed at clinical examination were reversible, only short in duration and could not be correlated to histopathological effects, no toxicological significance was attached to this finding, and thus, no relevant local effects were observed up to 0.048 mg/l.

Dermal

In a subacute dermal toxicity study using doses of 125, 500 and 2000 mg/kg bw and day no systemic or local effects were noted in New Zealand White rabbits after repeated dermal exposure for three weeks with 2000 mg/kg bw and day (Monsanto 1981). Thus, the NOAEL is considered to be 2000 mg/kg bw and day.

Justification for classification or non-classification

According to CLP classification criteria (Regulation (EC) No 1272/2008) a classification is not justified.