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The study substance, mono-, and di-(sec-hexadecyl)naphthalene, does not produce acute or chronic toxicity in freshwater aquatic organisms (e. g., fish, invertebrates and algae). The absence of toxicity demonstrated by mono-, and di-(sec-hexadecyl)naphthalene is due in part to low water solubility, resulting in low exposure potential in the aqueous compartment as well as the ability of organisms to metabolize the study substance at a rate which prevents a critical body burden from being reached. The data show that mono-, and di-(sec-hexadecyl)naphthalene is not toxic at their maximum water solubility limit [expected in the water accommodated fractions (WAF), water soluble fractions (WSF) or oil-in-water dispersions (OWD) ] under the conditions of the tests. Since the study substance does not cause acute or chronic toxic effects at the limits of water solubility, it was not possible to derive NOEC or PNEC values needed for quantitative risk assessment. However, it was possible to qualitatively conclude that based on low water solubility and the observed lack of acute and chronic aquatic toxicity, that mono-, and di-(sec-hexadecyl)naphthalene does not pose an unacceptable risk to the aquatic compartment. 

Owing to the inherently low water solubility of the study substance and the analytical limitations to measure its concentrations in the dosed water solutions, the reported NOEL, EL50 or LL50 values (nominal concentrations) are not true measured concentrations and are not applicable for quantitative PNEC derivation or risk assessments.