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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

Direct results from the short-term toxicity studies with rainbow trout and sheepshead minnow indicate that mono-, and di-(sec-hexadecyl)naphthalene does not cause acute toxicity in fish at the maximum loadings in the OWD solutions investigated in these tests (i.e., assumed to be at the maximum water solubility limit).  The use of NOEL values reported for risk assessment are nominal concentrations and not the true NOEC because of the substance's extremely low water solubility and the analytical detection limitations could not reliably determine the exact concentration of the test material in the water samples. 
Key values for CSA for short-term toxicity to fish are:
Acute fish toxicity   96h  LL50 > 5014 mg/L (nominal)  for sheepshead minnow -  No acute toxicity at its water solubilityminal
Acute fish toxicity   96h LL50 > 5173 mg/L (nominal) for rainbow trout)  - No acute toxicity at its water solubility
Acute fish toxicity   96h  NOEL > 5014 mg/L (nominal)  for sheepshead minnow  - No acute toxicity at its water solubility
Acute fish toxicity   96h  NOEL > 5173 mg/L (nominal) for rainbow trout) - No acute toxicity at its water solubility

Key value for chemical safety assessment

Additional information

Short-term fish toxicity studies have been carried out with the study substance, mono-, and di-(sec-hexadecyl)naphthalene, and the results have been summarized in the table.   


The study substance has been evaluated for acute toxicity in sheepshead minnow in saltwater (Mobil Business Resources Corp. 1996) using an oil-in-water dispersion (OWD) technique. At loadings up to 5014 mg/L, no mortality was observed. The 96-hr LL50 was determined to be greater 5014 mg/L and the 96-hr NOEL was greater than 5014 mg/L in sheepshead minnow. In addition, mono-, and di-(sec-hexadecyl)naphthalene, was also evaluated in rainbow trout (Salmo gairdneri) in freshwater. The study substance produced no statistically significant mortality in rainbow trout at any of the exposure concentrations including the highest load of 5173 mg/L (OWD). The 96-hr LL50 was determined to be > 5173 mg/L OWD loading and the 96hr NOEL > 5173 mg/L OWD loading, based on mortality (Mobil Environmental and Health Science Laboratory, 1989). Overall, based on these data, mono-, and di-(sec-hexadecyl)naphthalene was not acutely toxic to fish at the water solubility limit.


Overall, the study substance is not acutely toxic to sheepshead minnow or to rainbow trout at its water solubility.