Use of fluorescent-labelled nanoplastics (NPs) to demonstrate NP absorption is inconclusive without adequate controls.

Whether nanoplastics (NPs) are able to be absorbed across epithelial membranes and accumulate within internal tissues of organisms is an important determinant of their potential toxicity. Evidence of absorption and accumulation requires detection of NPs within internal tissues, and investigations with fluorescently labelled NPs have attempted to provide this information. We hypothesize that studies that do not control for the fluorescent dye leachate and/or cellular autofluorescence are inconclusive and can be misinterpreted.