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The acute toxicity of 1-naphthol has been studied in eight species representing three trophic levels. The catfish Mystus cavasius had a 96 hour LC50 of 0.33 mg/L (95% confidence limits 0.25 -0.4 mg/L, flow-through exposure (key). The 96 hour LC50 for four additional fish species ranged from 1.1 – 4.63 mg/L (Geiger et al 1984, Holcombe et al 1984, Tilak et al 1981) (supporting). The invertebrate Daphnia magna had a 48 hour EC50 of 2.51 mg/L (Beasley 2016) and the 72 hours EC50 value for inhibition of specific growth rate in the green algae Pseudokrichneriella subcapitata was >2.18 mg a.i./L. 

The algae ErC10 and NOEC values for inhibition of specific growth were > 2.18 and 0.0173 mg a.i./L respectively (Bergfield 2016).

1-naphthol tested in a 21-day Daphnia magna study gave an EC 50 > 1 mg/L (immobilization), NOEC 0.25 mg/L (reproduction rate), LOEC 0.5 mg/L (reproduction rate) and MATC 0.38 mg/L (reproduction rate).

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