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Description of key information

According to the guideline ISO 8192 (Test for Inhibition of Oxygen Consumption by Activated Sludge) a 3h-EC50 of 857 mg/l was observed for 44.6% aqueous solution of SMBT (Bayer AG, 1990). To exclude the dilution effect of water, the effect concentration of pure SMBT of 382 mg/l should be used. For the nitrification inhibition by 2 -mercaptobenzothiazole an EC75 of 3 mg/L during a 2 -4 h incubation period was obtained (Tomlinson et al., 1966). The effect concentration of MBT is lower than the one of SMBT; and hence it is used as a worst case consideration for the further risk assessment of SMBT.

Key value for chemical safety assessment

Additional information

SMBT is an organic salt of strong base NaOH and weak acid of MBT and it is solely marketed as aqueous solution. The presence of MBT determines the hazard profile of SMBT aqueous solution; and hence the read-across approach is used to support the risk assessment of SMBT.