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Workers - Hazard via inhalation route

Systemic effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
10 mg/m³
Acute/short term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
10 mg/m³
DNEL related information

Local effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
1 mg/m³
Most sensitive endpoint:
skin irritation/corrosion
Acute/short term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
1 mg/m³
Most sensitive endpoint:
skin irritation/corrosion
DNEL related information

Workers - Hazard via dermal route

Systemic effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
2.8 mg/kg bw/day
Acute/short term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
2.8 mg/kg bw/day
DNEL related information

Local effects

Long term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available
Most sensitive endpoint:
skin irritation/corrosion
Acute/short term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available
Most sensitive endpoint:
skin irritation/corrosion

Workers - Hazard for the eyes

Local effects

Hazard assessment conclusion:
medium hazard (no threshold derived)

Additional information - workers

Acute/short-term local effects/ Long-term exposure local effects

SMBT is a strong base (pH 10, as discussed in chapter 1.3) and is classified as corrosive (R34/Skin Corr. 1B). The corrosive character of SMBT is the predominant local effect and determines the local DNEL. According to ECHA Guidance Document Part E: Risk Characterisation, substances with R-phrases R34 (causes burs)/ Skin Corr. 1B are allocated to the moderate hazard category.

SMBT is corrosive, as discussed above. According to REACH regulation Annex VII, chapter 8.3. skin sensitization, column 2, in vivo testing does not need to be conducted.

However, as discussed above (endpoint summary toxicokinetics) SMBT is the sodium salt of MBT. MBT is classified as sensitizing to skin (R43/ category 1). Based on read-across data with MBT, a skin sensitizing potential of SMBT is suggested.

Acute/short-term exposure systemic effects

The acute dermal and oral toxicity of the test substance SMBT (50%) is very low, indicated by LD50 values greater than 2000 mg/kg. The acute oral LD50 value in rats is 2100 mg/kg bw (Bayer AG 1978) and the dermal LD50 value in rabbits is greater than 7940 mg/kg bw for SMBT (50%) (Monsanto Co. 1974).

Since SMBT, in contrast to MBT, is corrosive to the high pH, local irritation is the predominant toxicological effect. Overall, the local long-term and short-term DNEL for worker is 1 mg/m3 based on the corrosive properties of the compound (VCI 2010). No additional short-term peak exposure factor is suggested.

DNEL long-term exposure systemic

There are no repeated dose toxicity study data available for SMBT that can be used as a starting point for DNEL calculation. SMBT is composed of one MBT molecule associated with a sodium ion (mass content SMBT: 88% MBT, 12% Na+). The DNEL calculation is based on a read-across approach with MBT. The following strategy was followed: 1) derive a DNEL for MBT, 2) adopt the DNEL for MBT to SMBT, 3) consider potential toxicity of the sodium ion present in SMBT, 4) define DNEL for SMBT.

Start point MBT: Several repeated dose toxicity data of MBT were used in a weight of evidence approach to assess a NOAEL for DNEL calculation (for more details see chapter repeated dose toxicity). Mild toxic effects, like body weight reduction and/or increase in kidney and liver weights were noted in a concentration range of 150 to 375 mg/kg bw and day. Following the recommendation given in MAK (1999) a NOAEL of 50 mg/kg bw and day was suggested, which based on data from the two-generation toxicity study and the observed LOAEL of 2500 ppm (ca. 150 to 250 mg/kg bw and day) (CMA 1990).

Worker DNEL long-term systemic for oral route

Start point MBT: NOAEL 50 mg/mg bw and day (2-generation study with Sprague-Dawley rats, CMA 1990 according to MAK 1999).

Differences in absorption Abs (oral-rat) / Abs (oral-human): 1

=> Corrected NOAEL 50 mg/kg bw/day

Interspecies differences: Allometric scaling: 4

Remaining interspecies differences: 1*

Intraspecies differences: 5

Differences in duration of exposure (2-generation study to chronic): 1**

Dose response and endpoint specific/severity issues: 1

Quality of database: 1

Overall factor (product of individual factors): 20

=>Worker DNEL long-term based on the MBT content for oral route-systemic: 2.5 mg/kg bw/day

The precise composition of SMBT has to be taken into account to derive a DNEL for systemic toxicity of SMBT based on a read-across approach with MBT. SMBT is composed to 88% of MBT and, consequently, the SMBT dose which corresponds to 2.5 mg MBT/kg bw/day is equal to 2.8 mg SMBT/kg bw/day (2.5/0.88 = 2.8 mg/kg bw/day).

2.8 mg SMBT/kg bw/day is composed of 2.5 mg MBT/kg bw/day and 0.3 mgNa+/kg bw/day; the Na+value is below the recommended daily intake 575 mg Na+/day (ca. 8.2 mg/kg bw/d) (SCF 2003).

Consequently, based on the read-across approach to MBT the worker DNEL long-term of SMBT for oral route-systemic is 2.8 mg/kg bw/day.

* Repeated dose toxicity data from different rat and mice strains available

** In several repeated dose studies the NOAEL and or LOAEL are in the same range; consistent findings in, subchronic, chronic and reproduction/ developmental toxicity study

Worker DNEL long-term sytemic for dermal route

Start point MBT: NOAEL 50 mg/mg bw and day 2-generation study with Sprague-Dawley rats (CMA 1990 according to MAK 1999).

Differences in absorption Abs (oral-rat) / Abs (dermal-human): 1*

=> Corrected NOAEL 50 mg/kg bw/day

Interspecies differences: Allometric scaling: 4

Remaining interspecies differences: 1**

Intraspecies differences: 5

Differences in duration of exposure (2-generation study to chronic): 1***

Dose response and endpoint specific/severity issues: 1

Quality of database: 1

Overall factor (product of individual factors): 20

=>Worker DNEL long-term based on the MBT content for dermal route-systemic: 2.5 mg/kg bw/day

The precise composition of SMBT has to be taken into account to derive a DNEL for systemic toxicity of SMBT based on a read-across approach with MBT. SMBT is composed to 88% of MBT and, consequently, the SMBT dose which corresponds to 2.5 mg MBT/kg bw/day is equal to 2.8 mg SMBT/kg bw/day (2.5/0.88 = 2.8 mg/kg bw/day).

2.8 mg SMBT/kg bw/day is composed of 2.5 mg MBT/kg bw/day and 0.3 mgNa+/kg bw/day; the Na+value is below the recommended daily intake 575 mg Na+/day (ca. 8.2 mg/kg bw/d) (SCF 2003).

Consequently, based on the read-across to MBT the worker DNEL long-term of SMBT for dermal route-systemic is 2.8 mg/kg bw/day.

* Toxicokinetic data revealed low dermal absorption of MBT, because of the corrosive character of SMBT a factor of 1is used instate of 2 originally used for MBT DNEL calculation

** Repeated dose toxicity data from different rat and mice strains available

***In several repeated dose studies the NOAEL and or LOAEL are in the same range; consistent findings in, subchronic, chronic and reproduction/ developmental toxicity study

Worker DNEL long-term systemic for inhalation route

Start point MBT: NOAEL 50 mg/mg bw and day 2-generation study with Sprague-Dawley rats (CMA 1990 according to MAK 1999).

Respiratory volume rat (sRV) (worker (8 h): 1/0.38): 2.632

Differences in respiratory volume (default factor "light activity worker"): 0.67

Differences in absorption Abs (oral-rat) / Abs (inhalation-human): 1

=> Corrected NOAEC: 88.2 mg/m3

Interspecies differences: Allometric scaling: 1

Remaining interspecies differences: 1*

Intraspecies differences: 5

Differences in duration of exposure (2-generation study to chronic): 1**

Dose response and endpoint specific/severity issues: 1

Quality of database: 2***

Overall factor (product of individual factors): 10

=>Worker DNEL long-term based on the MBT content for inhalation route-systemic: 8.8 mg/m3

The precise composition of SMBT has to be taken into account to derive a DNEL for systemic toxicity of SMBT based on a read-across approach with MBT. SMBT is composed to 88% of MBT and, consequently, the SMBT dose which corresponds to 8.8 mg MBT/m3 is equal to 10 mg SMBT/m3 (8.8/0.88 = 10 mg/m3).

10 mg SMBT/m3 is composed of 8.8 mg MBT/m3 and 1.2 mg Na+/m3.

Consequently, based on the read-across approach to MBT the worker DNEL long-term of SMBT for inhalation route-systemic is 10 mg/m3.

* Repeated dose toxicity data from different rat and mice strains available

** In several repeated dose studies the NOAEL and or LOAEL are in the same range; consistent findings in, subchronic, chronic and reproduction/ developmental toxicity study

*** Repeated dose toxicity inhalation study MBT: no valid data available

DNEL fertility

There are no reproduction toxicity study data available for SMBT. A read across approach (systemic effects) was conducted with study data from MBT (benzothiazole-2-thiol) (data matrix analogue approach see discussion endpoint summary toxicokinetic).

A two-generation reproduction toxicity study (CMA 1990) was performed to evaluate the potential of MBT on reproduction toxicity. No adverse effects on reproductive functions of the F0 or F1 generation were indicated up to highest dose evaluated (15000 ppm, ca 778 to 2633 mg/kg bw/d F0 and F1 males, ca. 745 to 1770 mg/kg bw/d F0 and F1 females). Minimal to mild toxic effects occurred in all treated groups in both F0 and F1 parental animals. Based on the reduction of body weight noted in F0 males and F1 males and females at the lowest dose group a LOAEL of 2500 ppm (ca. 150 to 250 mg/kg bw and day) was suggested. These data were used in a weight of evidence approach for systemic DNEL calculation (as discussed above). No additional DNEL fertility was calculated because the systemic DNEL covers the maternal toxic effects.

DNEL developmental toxicity

There are no developmental toxicity study data available for SMBT. A read across approach (systemic effects) was conducted with study data from MBT (benzothiazole-2-thiol) (data matrix analogue approach see discussion endpoint summary toxicokinetics).

The developmental toxicity of MBT was evaluated in a teratology study with New Zealand White rabbits (CMA 1989). The oral administration of MBT up to the highest dose group evaluated (300 mg/kg bw and day) during major organogenesis did not induce any developmental toxicity or teratogenicity. Maternal toxicity was evident only at 300 mg/kg bw and day as slightly decreased body weight gain and slightly elevated liver weight. Based on these findings a NOAEL maternal/foetal of 300 mg/kg bw and day was suggested. Both NOAEL values are above the suggested NOAEL systemic (50 mg/kg bw/and day) and thus it was concluded that the DNEL for long-term exposure covers the DNEL developmental toxicity.

General Population - Hazard via inhalation route

Systemic effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
2.5 mg/m³
Acute/short term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
2.5 mg/m³
DNEL related information

Local effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
1 mg/m³
Most sensitive endpoint:
skin irritation/corrosion
Acute/short term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
1 mg/m³
Most sensitive endpoint:
skin irritation/corrosion
DNEL related information

General Population - Hazard via dermal route

Systemic effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
1.5 mg/kg bw/day
Acute/short term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
1.5 mg/kg bw/day
DNEL related information

Local effects

Long term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available
Most sensitive endpoint:
skin irritation/corrosion
Acute/short term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available
Most sensitive endpoint:
skin irritation/corrosion

General Population - Hazard via oral route

Systemic effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
1.5 mg/kg bw/day
Acute/short term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
1.5 mg/kg bw/day
DNEL related information

General Population - Hazard for the eyes

Local effects

Hazard assessment conclusion:
medium hazard (no threshold derived)

Additional information - General Population

Acute/short-term local effects/ Long-term exposure local effects

SMBT is a strong base (pH 10, as discussed in chapter 1.3) and is classified as corrosive (R34/Skin Corr. 1B). The corrosive character of SMBT is the predominant local effect and determines the local DNEL. According to ECHA Guidance Document Part E: Risk Characterisation, substances with R-phrases R34 (causes burs)/ Skin Corr. 1B are allocated to the moderate hazard category.

SMBT is corrosive, as discussed above. According to REACH regulation Annex VII, chapter 8.3. skin sensitization, column 2, in vivo testing does not need to be conducted.

However, as discussed above (endpoint summary toxicokinetics) SMBT is the sodium salt of MBT. MBT is classified as sensitizing to skin (R43/ category 1).Based on read-across data with MBT, a skin sensitizing potential of SMBT is suggested.

Acute/short-term exposure systemic effects

The acute dermal and oral toxicity of the test substance SMBT (50%) is very low, indicated by LD50 values greater than 2000 mg/kg. The acute oral LD50 value in rats is 2100 mg/kg bw (Bayer AG 1978) and the dermal LD50 value in rabbits is greater than 7940 mg/kg bw for SMBT (50%) (Monsanto Co. 1974).

Since SMBT, in contrast to MBT, is corrosive to the high pH, local irritation is the predominant toxicological effect. Overall, the local long-term and short-term DNEL for worker is 1 mg/m3based on the corrosive properties of the compound (VCI 2010). No additional short-term peak exposure factor is suggested.

DNEL long-term exposure systemic

There are no repeated dose toxicity study data available for SMBT that can be used as a starting point for DNEL calculation. SMBT is composed of one MBT molecule associated with a sodium ion (mass content SMBT: 88% MBT, 12% Na+). The DNEL calculation is based on a read-across approach with MBT. The following strategy was followed: 1) derive a DNEL for MBT, 2) adopt the DNEL for MBT to SMBT, 3) consider potential toxicity of the sodium ion present in SMBT, 4) define DNEL for SMBT.

General public long-term systemic for oral route

Start point MBT: NOAEL 50 mg/mg bw and day 2-generation study with Sprague-Dawley rats (CMA 1990 according to MAK 1999).

Differences in absorption Abs (oral-rat) / Abs (oral-human): 1

=> Corrected NOAEL 50 mg/kg bw/day

Interspecies differences: Allometric scaling: 4

Remaining interspecies differences: 1*

Intraspecies differences: 10

Differences in duration of exposure (2-generation study to chronic): 1**

Dose response and endpoint specific/severity issues: 1

Quality of database: 1

Overall factor (product of individual factors): 40

=> General Public long-term DNEL based on the MBT content for oral route-systemic: 1.3 mg/kg bw/day

The precise composition of SMBT has to be taken into account to derive a DNEL for systemic toxicity of SMBT based on a read-across approach with MBT. SMBT is composed to 88% of MBT and, consequently, the SMBT dose which corresponds to 1.3 mg MBT/kg bw/day is equal to 1.5 mg SMBT/kg bw/day (1.3/0.88 = 1.5 mg/kg bw/day).

1.5 mg SMBT/kg bw/day is composed of 1.3 mg MBT/kg bw/day and 0.2 mgNa+/kg bw/day; the Na+ value is below the recommended daily intake 575 mg Na+/day (ca. 8.2 mg/kg bw/d) (SCF 2003).

Consequently, based on the read-across approach to MBT the general public DNEL long-term of SMBT for oral route-systemic is 1.5 mg/kg bw/day.

* Repeated dose toxicity data from different rat and mice strains available

** In several repeated dose studies the NOAEL and or LOAEL are in the same range; consistent findings in subchronic, chronic and reproduction/ developmental toxicity study

General public long-term systemic for dermal route

Start point MBT: NOAEL 50 mg/mg bw and day 2-generation study with Sprague-Dawley rats (CMA 1990 according to MAK 1999).

Differences in absorption Abs (oral-rat) / Abs (dermal-human): 1 *

=> Corrected NOAEL 50 mg/kg bw/day

Interspecies differences: Allometric scaling: 4

Remaining interspecies differences: 1**

Intraspecies differences: 10

Differences in duration of exposure (2-generation study to chronic): 1***

Dose response and endpoint specific/severity issues: 1

Quality of database: 1

Overall factor (product of individual factors): 40

=>General public long-term DNEL based on the MBT content for dermal route-systemic: 1.3 mg/kg bw/day

The precise composition of SMBT has to be taken into account to derive a DNEL for systemic toxicity of SMBT based on a read-across approach with MBT. SMBT is composed to 88% of MBT and, consequently, the SMBT dose which corresponds to 1.3 mg MBT/kg bw/day is equal to 1.5 mg SMBT/kg bw/day (1.3/0.88 = 1.5 mg/kg bw/day).

1.5 mg SMBT/kg bw/day is composed of 1.3 mg MBT/kg bw/day and 0.2 mgNa+/kg bw/day; the Na+ value is below the recommended daily intake 575 mg Na+/day (ca. 8.2 mg/kg bw/d) (SCF 2003).

Consequently, based on the read-across approach to MBT the general public DNEL long-term of SMBT for dermal route-systemic is 1.5 mg/kg bw/day.

* Toxicokinetic data revealed low dermal absorption of MBT, because of the corrosive character of SMBT a factor of 1is used instate of 2 originally used for MBT DNEL calculation

**Repeated dose toxicity data from different rat and mice strains available

*** In several repeated dose studies the NOAEL and or LOAEL are in the same range; consistent findings in subchronic, chronic and reproduction/ developmental toxicity study

General public long-term systemic for inhalation route

Start point MBT NOAEL: 50 mg/kg bw and day, 2 -generation study with Sprague-Dawley rats (CMA 1990 according to MAK 1999).

Respiratory volume rat (sRV) general public 1/1.15: 0.87

Differences in absorption Abs (oral-rat)/ Abs (inhalation-human): 1

Corrected NOAEC: 43.5 mg/m3

Interspecies differences: Allometric scaling: 1

Remaining interspecies differences: 1*

Intraspecies differences: 10

Differences in duration of exposure (2 -generation study to chronic): 1**

Dose response and endpoint specific/severity issues: 1

Quality of database: 2***

Overall factor (product of individual factors): 20

General Public DNEL long-term based on the MBT content for inhalation route-systemic: 2.2 mg/m3

The precise composition of SMBT has to be taken into account to derive a DNEL for systemic toxicity of SMBT based on a read-across approach with MBT. SMBT is composed to 88% of MBT and, consequently, the SMBT dose which corresponds to 2.2 mg MBT/m3 is equal to 2.5 mg SMBT/m3 (2.2/0.88 = 2.5 mg/m3). 2.5 mg SMBT/m3 is composed of 2.2 mg MBT/m3 and 0.3 mg Na+/m3 .

Consequently, based on the read-across to MBT the general public DNEL long-term of SMBT for inhalation route-systemic is 2.5 mg/m3.

*Repeated dose toxicity data from different rat and mice strains available

**In several repeated dose studies the NOAEL and or LOAEL are in the same range; consistent findings in subchronic, chronic and reproduction/developmental toxicity study

***Repeated dose toxicity inhalation study MBT: no valid data available

DNEL fertility

There are no reproduction toxicity study data available for SMBT. A read across approach (systemic effects) was conducted with study data from MBT (benzothiazole-2-thiol) (data matrix analogue approach see discussion endpoint summary toxicokinetic).

A two-generation reproduction toxicity study (CMA 1990) was performed to evaluate the potential of MBT on reproduction toxicity. No adverse effects on reproductive functions of the F0 or F1 generation were indicated up to highest dose evaluated (15000 ppm, ca 778 to 2633 mg/kg bw/d F0 and F1 males, ca. 745 to 1770 mg/kg bw/d F0 and F1 females). Minimal to mild toxic effects occurred in all treated groups in both F0 and F1 parental animals. Based on the reduction of body weight noted in F0 males and F1 males and females at the lowest dose group a LOAEL of 2500 ppm (ca. 150 to 250 mg/kg bw and day) was suggested. These data were used in a weight of evidence approach for systemic DNEL calculation (as discussed above). No additional DNEL fertility was calculated because the systemic DNEL covers the maternal toxic effects.

DNEL developmental toxicity

There are no developmental toxicity study data available for SMBT. A read across approach (systemic effects) was conducted with study data from MBT (benzothiazole-2-thiol) (data matrix analogue approach see discussion endpoint summary toxicokinetics).

The developmental toxicity of MBT was evaluated in a teratology study with New Zealand White rabbits (CMA 1989). The oral administration of MBT up to the highest dose group evaluated (300 mg/kg bw and day) during major organogenesis did not induce any developmental toxicity or teratogenicity. Maternal toxicity was evident only at 300 mg/kg bw and day as slightly decreased body weight gain and slightly elevated liver weight. Based on these findings a NOAEL maternal/foetal of 300 mg/kg bw and day was suggested. Both NOAEL values are above the suggested NOAEL systemic (50 mg/kg bw/and day) and thus it was concluded that the DNEL for long-term exposure covers the DNEL developmental toxicity.