Low concentration effects and different outcome in repeated reproduction tests with silver nanoparticles, silver nitrate and Folsomia candida (Collembola)

Xin Zhang,Juliane Filser

doi:10.1186/s12302-020-00413-7

Abstract

BackgroundToxicity of silver nanoparticles (AgNP) has been studied frequently due to a rise in application in various products. Various studies on AgNP toxicity with terrestrial and aquatic organisms confirmed their negative effects. In our previous experiments, strong variability was observed in the reproduction of Collembola (Folsomia candida) in different repeats. To investigate the effects of silver on the reproduction of Folsomia candida, they were exposed in laboratory-controlled conditions to AgNP and silver nitrate (AgNO3) at a concentration of 30 mg/kg dry soil for 28 days and compared to controlled individuals not exposed to silver. We repeated reproduction tests on the toxicity of silver to Folsomia candida four times throughout one year (April, July, October and January) in order to explore the temporal variability of their outcome.ResultsWhile adult survival was similar in all treatments and seasons, reproduction in the control increased from April to October. Significantly lower reproduction was found in January with only 385–424 juveniles per vessel, compared to 504–633 individuals in other months. Strong toxic effects of both silver treatments were observed in July, April and October. However, AgNP showed no toxic effects on the reproduction of F. candida in January. The relative toxicity of both substances varied between single experiments: AgNP were more toxic than AgNO3 in April and July, and less toxic in October and January.ConclusionThese findings indicate that the reproduction of F. candida in the control had a significant effect on the results of the toxicology experiments. Moreover, we demonstrated the reproductive toxicity of AgNP in soil at a much lower concentration than reported thus far. Therefore, to guarantee reliability and reproducibility, we recommend to disregard any test results where the reproduction rate of F. candida in the control is significantly different from the average in the respective laboratory, even if the validity criteria of the test are met.

Highlights

Toxicity of silver nanoparticles (AgNP) has been studied frequently due to a rise in application in various products
The toxicity of Silver nanoparticles (AgNP) for Collembola was first reported by Waalewijn-Kool et al [25], who observed no effect on survival and reproduction for Folsomia candida (F. candida) exposed to AgNP (3–8 nm coated with paraffin) at a measured concentration of 673 mg Ag/kg dry soil
Does this difference in reproduction affect the results of the toxicity test? To test the accuracy and reproducibility of the test, we evaluated the toxicity of AgNP and Silver nitrate (AgNO3) on the reproduction of F. candida throughout one year

Summary

Introduction

Toxicity of silver nanoparticles (AgNP) has been studied frequently due to a rise in application in various products. Various studies on AgNP toxicity with terrestrial and aquatic organisms confirmed their negative effects. To investigate the effects of silver on the reproduction of Folsomia candida, they were exposed in laboratory-controlled conditions to AgNP and silver nitrate (AgNO3) at a concentration of 30 mg/kg dry soil for 28 days and compared to controlled individuals not exposed to silver. The application of silver nanoparticles (AgNP) is strongly increasing in several areas such as electrical, medicine, food and textile products. The toxicity of AgNP for Collembola was first reported by Waalewijn-Kool et al [25], who observed no effect on survival and reproduction for Folsomia candida (F. candida) exposed to AgNP (3–8 nm coated with paraffin) at a measured concentration of 673 mg Ag/kg dry soil. Mendes et al [26] reported a negative effect of AgNP (NM-300 K) on the reproduction of F. candida, with EC20 and EC50 values of 173 and 540 mg Ag/kg, respectively

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Discussion

Conclusion