Toxicity Assessments of Micro- and Nanoplastics Can Be Confounded by Preservatives in Commercial Formulations

Abstract

Micro- and nanoplastics derived from environmental degradation of larger plastic debris can be ingested and accumulate in aquatic organisms, raising growing global ecological concerns. Toxicology studies of aquatic organisms predominantly use commercial formulations of micro- and nanosized polystyrene particles as model plastics. However, many of these commercially available formulations contain different preservatives, antimicrobials, or surfactants such as sodium azide, Tween 20, and sodium dodecyl sulfate, which may introduce artifacts in toxicity assessments. In this study, we carried out acute toxicity tests on Daphnia magna, using commercial 20 and 200 nm polystyrene nanoparticles (PS-NPs) containing 2 mM sodium azide as an antimicrobial preservative. The acute toxicities of nondialyzed PS-NPs, dialyzed PS-NPs, and sodium azide alone were compared. The results reveal that the acute toxicity of the complete commercial formulation of PS-NPs was mainly associated with sodium azide and not the particles themselves. The dialyzed PS-NPs did not cause mortality but significantly disrupted the swimming behavior of D. magna. As commercial PS-NPs are commonly and increasingly used in plastic toxicity assessments, these results highlight the importance of considering the impacts of the suspension matrix.

Biofilm formation by marine bacteria is impacted by concentration and surface functionalization of polystyrene nanoparticles in a species‐specific manner

“…B), suggesting the presence of CNP does not kill the cells. Thus, even though the fluorescently‐labelled CNP used in the biofilm experiments were not washed to remove any additives present in the stock suspension (Pikuda et al ., ), those additives remaining did not impact cell viability.…”

Single particle-resolution fluorescence microscopy of nanoplastics

“…At this pH, the NHS group reacts with the amine groups on the surface of the plastic, covalently binding the dye to the plastic (31). The excess dye was removed from the suspension via dialysis using a 12-14 kDa MWCO dialysis membranes (Frey Scientific) for 7 days with daily water changes in stirred 2 L glass beakers (16).…”

“…Consequently, fluorescence imaging has been widely applied to localize labeled microplastic particles used in exposure studies to track uptake and potential translocalization in live organisms (13)(14)(15)(16). Typically, microplastics are large enough to be individually resolved with light microscopy (13)(14)(15)(16). Consequently, localization of fluorescentlylabeled microplastics is possible even if there is significant background signal from autofluorescence or dye leaching (17,18).…”

A Meta‐analysis of Ecotoxicological Hazard Data for Nanoplastics in Marine and Freshwater Systems

“…It is crucial to note that most of the published nanoplastic ecotoxicity studies were conducted using pristine polystyrene nanoparticles because they are commercially available as nanoplastic suspension with well‐characterized particle sizes (Pikuda et al 2019). However, 2 independent studies have shown that the presence of biocides in these suspensions is seriously affecting the interpretation of the toxicity studies (Pikuda et al 2019; Heinlaan et al 2020).…”

“…It is crucial to note that most of the published nanoplastic ecotoxicity studies were conducted using pristine polystyrene nanoparticles because they are commercially available as nanoplastic suspension with well‐characterized particle sizes (Pikuda et al 2019). However, 2 independent studies have shown that the presence of biocides in these suspensions is seriously affecting the interpretation of the toxicity studies (Pikuda et al 2019; Heinlaan et al 2020). It was shown that after dialysis of the suspension and consequently removal of the sodium azide (NaN 3 ) stabilizer, the pristine polystyrene nanoplastics were no longer toxic at the levels reported before (Pikuda et al 2019; Heinlaan et al 2020).…”