Nanosilver-coated socks and their toxicity to zebrafish (Danio rerio) embryos

Silver nanoparticles (AgNPs) are being incorporated and are known to be released from various consumer products such as textiles. However, no data are available on the toxicity of AgNPs released from any of these commercial products. In this study, we quantified total silver released from socks into wash water by inductively coupled plasma mass spectrometry (ICP-MS) and determined the presence of AgNPs using transmission electron microscopy (TEM). We then exposed zebrafish (Danio rerio) embryos for 72 h to either this leachate ("sock-AgNP") or to the centrifugate ("spun-AgNP") free of AgNPs and compared their toxicity to that of ionic silver (Ag(+)). Our data suggest that AgNPs do get released into the wash water, and centrifugation eliminated AgNPs but did not decrease total silver concentrations, indicating that most of the silver in the sock-AgNP solution was in the ionic form. All embryos died during the first 24 h when exposed to undiluted sock-AgNP and spun-AgNP solutions resulting in significantly lower LC50 values (0.14 and 0.26 mg L(-1)) compared to AgNO3 (0.80 mg L(-1)). Similarly, at 72 hpf, both sock-derived solutions were more potent at affecting hatching and inducing abnormal development. These results suggest that both sock-AgNP and spun-AgNP solutions were more toxic than AgNO3. Previous studies have consistently shown the opposite, i.e., AgNPs are about 10 times less toxic that Ag(+). All together our results show that the high toxicity induced by the leachate of these socks is likely not caused by AgNPs or Ag(+). More studies are needed to evaluate the toxicity of the myriad of AgNP-coated commercial products that are now estimated to be close to 500.