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.
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