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Toxicity to microorganisms

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Description of key information

The 3-hour NOEC for total respiration for Reaction product of naphthalene, propan-2-ol, sulfonated and neutralized by caustic soda to activated sludge microorganisms was 0.16 mg/L.
The 3-hour NOEC for heterotrophic respiration for Reaction product of naphthalene, propan-2-ol, sulfonated and neutralized by caustic soda to activated sludge microorganisms was 0.05 mg/L.
The 3-hour NOEC for nitrification respiration for Reaction product of naphthalene, propan-2-ol, sulfonated and neutralized by caustic soda to activated sludge microorganisms was 1.64 mg/L.
The 3-hour EC50 for Reaction product of naphthalene, propan-2-ol, sulfonated and neutralized by caustic soda to activated sludge microorganisms was determined to be greater than the highest level tested, 5.2 mg/L.
By analogy, the 3-hour NOEC for Reaction product of naphthalene, butanol, sulfonated and neutralized by caustic soda was assumed to be the same value (NOEC = 1.64 mg/L)

Key value for chemical safety assessment

Additional information

The toxicity to microorganisms of Reaction product of naphthalene, butanol, sulfonated and neutralized by caustic soda is determined by a read-across approach based on analogue substance Reaction product of naphthalene, propan-2-ol, sulfonated and neutralized by caustic soda.

A GLP-compliant study (KJ. Muddiman, 2013), scored as Klimisch 2 and flagged as a key study, is available on Reaction product of naphthalene, propan-2-ol, sulfonated and neutralized by caustic soda.

The following results were determined:

 NOEC (mg/L)  LOEC (mg/L)  EC50 (mg/L)
 Total respiration  0.16  0.51  > 5.2
 Heterotrophic respiration  0.05  0.16  > 5.2
 Nitrification respiration  1.64  5.2  > 5.2

The overall NOAEC determined during this study was 0.05 mg/L, based on heterotrophic respiration. The overall EC50 was determined to be greater than the highest level tested, 5.2 mg/L.