Estimates of AgNP toxicity thresholds in support of environmental safety policies.

Silver nanoparticles (AgNPs) currently possess widespread applications in many products. Although there is an increase in the evaluation of their potential environmental risks and toxicity, the data available on AgNP safety levels are limited. Studies on the ecotoxicological and environmental risks of AgNPs, then, are still a requirement. In the present study, AgNPs sized at 82.8 nm were synthetized with an aim to assess their effect on some organisms including algae, plants, microcrustaceans, cnidaria, nematodes, aquatic insects, earthworms, and fish embryos. In addition, some ecotoxicity data obtained from the literature were also used. The non-observed-effect concentration (NOEC) was then calculated for each organism using a log-logistic function. Additionally, the stability of AgNPs in contact with the culture media throughout the analyzed period and conditions employed was evaluated in order to ensure their availability for the organisms tested. The AgNPs remained stable, presenting a dispersion rate of less than 20%, except for the A. salina medium, which presented a dispersion of approximately 25% but did not display differences in AgNP size. The predicted no-effect concentration (PNEC) in the aquatic and sediment compartment was estimated to lie in a concentration range from 0.07 to 0.35 µg L−1. A risk quotient (RQ) of 28.6 was derived for the NPs tested in relation to a maximum AgNP predicted environmental concentration (PEC) estimate. Since an RQ value superior to 1 indicates an occurrence of risk and, consequently, the need for management measures to be implemented, the present data, in conjunction with the expected increase in AgNP use, reinforce the importance of the establishment of AgNP safety levels that can contribute to AgNP risk assessment studies. [ABSTRACT FROM AUTHOR]