Plastics are produced through the chemical and physical processing of naturally occurring constituents. Through polymerization and polycondensation, base constituents react together to form polymer chains, a process that can rarely be reversed. Therefore, once the reaction has occurred, these molecules cannot return to their previous basic form only be further processed or recycled to differing polymeric forms. Industrial chemicals may be added to the reaction to develop harder or more malleable results. Due to chemical stability, the environmental accumulation of plastics is on the rise and the research documenting these increases is receiving mainstream interest. Unfortunately, as identified in a recent editorial in Nature Nanotechnology, the laboratory and environmental toxicological assessments have not been completed, and overall, we simply do not know the outcomes [1].
2. Microplastic verses nanoplastic
The term “nanoplastic” is relatively novel. The first utilization of the term in a Web of Science search was within a 2004 abstract describing computational methods pertaining to material deformation [2]. As such, there has been some discussion in the literature regarding the definition of a ‘nanoplastic’. However, this is an important characterization for clarity as the field moves forward.
By definition, microplastics are plastic pieces that are less 5 millimeters (mm) in one dimension; therefore, nanoplastics would be considered ultrafine plastics that fall under this umbrella term. The discrepancy of terminology lies with how the nanoplastic produced. Nanoplastics in ecotoxicological settings are primarily formed by bulk degredation and have been defined as plastic materials less than 1000 nanometers (nm) [3]. There are secondarily derived through physical and mechanical breakdown, photodegradation, thermodegradation, and biodegradation of larger microplastics [4]. The size definition of nanomaterials is not isolated to plastics, but a symptom of a greater debate between scientists and regulators [5].
Nanomaterials traditionally describe particles that are intentionally produced at the nano-scale to take advantage of the physico-chemical properties available only at that size range [6]. Engineered or primary nanoplastics identified in personal care products, biomedical applications, and laboratory use are defined as less than 100 nanometers (nm) in a single dimension. For the purposes of this manuscript, we will define nanoplastics as particles that are less than 100 nm.
Unfortunately, due to their small size range, the quantity of nanoplastics in the environment currently cannot be measured. This is because the technologies to identify these small particles on a large scale have not yet been formulated. The traditional methodology of filtration cannot be used as the pores in most traditional containment centers are large enough to allow nanoplastics to pass through. Within the laboratory, nanotechnology techniques are in place to assess the small, known quantities to be characterized. These include dynamic light scattering, Raman spectroscopy, transmission electron microscopy, hyperspectral microscopy, and mass or size-based particle counters [7]. Further, laboratory assessments can modify nanoplastics to allow for their identification or quantification. This may be with the addition of a metallic core, or surface modifications including radioactive or fluorescent labelling [8–10]. Therefore, we await the analytic chemistry technologies. Further reading on the challenges of micro-, and subsequently nanoplastic, analyses are discussed here [11,12].
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Toxicological considerations of nano-sized plastics
AIMS Environ Sci. Author manuscript; available in PMC: 2019 Nov 19.
Published in final edited form as: AIMS Environ Sci. 2019 Oct 22;6(5):367–378. doi: 10.3934/environsci.2019.5.367AIMS Environ Sci. Author manuscript; available in PMC: 2019 Nov 19.
Published in final edited form as: AIMS Environ Sci. 2019 Oct 22;6(5):367–378. doi: 10.3934/environsci.2019.5.367
Toxicological considerations of nano-sized plastics
PA Stapleton 1,2,*
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