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Short-term toxicity to aquatic invertebrates

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Description of key information

Collectively, based on the mysid data and the read-across Daphnia magna data, the study substance, mono-, and di-(sec-hexadecyl)naphthalene, would not expected to produce acute toxicity at its maximal water solubility level in these invertebrate tests. 
Key values for short-term toxicity to aquatic invertebrates for CSA: 
96 h LL50 > 2002 mg/L WAF  Mysidopsis bahia (EPA OTS 797.1930 TG) - not acutely toxic at its water solubility 
48 h EL50 >5029 mg/L WSF  Daphnia magna read-across data (OCED 202 TG)  - not acutely toxic at its water solubility 

Key value for chemical safety assessment

Additional information

The acute toxicity of the study substance as measured by mortality to the mysid shrimp,Mysidopsis bahia, was evaluated in salt water.  The 96 hr LL50 value was determined to be 5028 mg/L WAF loading while the 96-hr NOEL (no observed effect loading) was estimated be 2002 mg/L WAF loading. Overall, the study substance is not expected to produce acute toxicity at its water solubility level (WAF) under the conditions of the test. The study substance has not been evaluated in Daphnia magna, a freshwater invertebrate. However, read-across data are available for a structurally related alkylnaphthalene, MCP 968. MCP 968 (naphthalene reaction products with tetradecene) is the tetradecyl naphthalene structural analog of the study substance (mono-, and di-(sec-hexadecyl)naphthalene) and because of their structural similarities (C14- versus C16- alkyl group), read-across is appropriate. Ecotoxicity effects are expected to be similar since there is only two carbon differences in the alkyl group substituents. Water soluble fractions solutions of the surrogate material did not produce any acute toxicity to Daphnia even at the highest nominal loadings of 5029 mg/L under the conditions of this study. It was determined that the 48 hr EL50 value was > 5029 mg/L WSF and the NOEL was > 5029 mg/L WSF since no immobilization and no adverse effects were observed. Collectively, based on the mysid data and the read-across Daphnia magna data, the study substance, mono-, and di-(sec-hexadecyl)naphthalene, would not be expected to produce acute toxicity at its water solubility level in these invertebrate test.

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