Your expensive new workout socks may be toxic—at least, if you are a tiny fish* downstream from the washing machines used to wash those socks! Researchers from Purdue University found that the silver nanoparticles added to socks to prevent bacterial growth (and resulting stink) leach out of the socks when washed. Disturbingly, this wash water killed the embryos of zebrafish, a small freshwater fish commonly used in experiments. Even when the researchers diluted the wash water, the surviving zebrafish developed abnormalities like curved spines and fluid around their hearts. But were the fish being poisoned by the nanoparticles—or by silver leached from the nanoparticles? To finger the culprit, the researchers tried growing the zebrafish embryos in the wash water; in wash water from which they’d removed the nanoparticles; and in water with dissolved silver but no nanoparticles. Even when the nanoparticles were removed from the wash water, it still killed the zebrafish embryos and caused deformities in the survivors. Surprisingly, the water with just dissolved silver didn’t cause deformities. While the researchers claimed that the nanoparticles and silver were likely innocent of poisoning the zebrafish—that another chemical leached from the socks is guilty—I’m not convinced. I would need to see what happens to zebrafish grown in fresh water with just silver nanoparticles. If the zebrafish grow up healthy, then I’d agree with their conclusions about the culprit. If not, I’d be more suspicious of the silver nanoparticles—and I would wonder if the researchers did a thorough job at removing the nanoparticles from the wash water in their experiments! However, I do agree with the researchers about this conclusion: we need for more studies of wash water toxicity to determine its effects on wild fish and animals—effects which may already be happening, given that over 400 consumer products (and not all of them socks!) contain silver nanoparticles.
* A tiny fish owning a pair of silver nanoparticle-coated socks, that is.
Citation: Gao J, Sepúlveda MS, Klinkhamer C, Wei A, Gao Y, & Mahapatra CT (2014). Nanosilver-coated socks and their toxicity to zebrafish (Danio rerio) embryos. Chemosphere, 119C, 948-952 PMID: 25303653