In recent years, release of silver nanoparticles (AgNPs) to the aquatic environment increased with wide usage in consumer products. In the present study acute toxicity of AgNPs was investigated in a freshwater snail, Lymnaea sp. according to OECD test guideline number 243. Snails were divided to two groups and each group exposed to incremental concentrations of AgNPs including 0, 0.05, 0.07, 0.10, 0.20, 0.50, 1.00 mg/L. In the first group, snails were permitted to exit freely from the exposure media; but in the second group test chambers were covered with a synthetic mesh fabric to prevent escape of the snails. Exposures were conducted in triplicate and ten animals were exposed per replicate in 1000 mL glass vessels under 16 h light: 8 h dark. The numbers of dead animals were recorded at 24, 48, 72, and 96 hours and lethal concentrations (LCs) were estimated using Probit analysis program. In the group that snails could not escape from the exposure media, no observable effect concentration (NOEC), lowest observable effect concentration (LOEC), maximum acceptable toxicant concentration (MATC), and median effective concentration (LC50) of AgNPs were 0.01, 0.05, 0.044, and 0.104 mg/L respectively. While in the group with escape permission, NOEC, LOEC, MATC, and LC50 were 0.075, 0.10, 0.10, and 0.227 mg/L respectively. Based on the results of this study, escaping from the polluted water is a preventive strategy against AgNPs toxicity and can reduce short term effects of this nanomaterial.
