Plastic was invented in the early 1900s and since the second half of the 20th century production—and subsequently disposal—rates have skyrocketed. As of 2015, approximately 8,300 million metric tons of plastic had been produced and 70% of that was already considered waste. Most of that waste—an estimated 4,900 million metric tons—has ended up in landfill or as pollution1 (Figure 1). Once in the environment, plastics break down into micro- (<5 mm) and then nanoplastic (<1 µm) particles, undergoing ‘aging’ through exposure to UV light, water, salt, oxidation and temperature changes. Consequently, aged microplastics and nanoplastics (MNPs) are now found everywhere—in water2, air3 and soil4; from the deep ocean5, to mountain tops6; and from pole to pole7. The question is, what does this mean for our ecosystems, and for human health?
Does environmental contamination with MNPs matter?
Whilst we know there is plastic pollution everywhere, the specifics of its impact remain uncertain—how big the problem is, what the long-term impacts will be, and when and where they might be felt. However, a couple of research papers have hit the headlines in 2025 that suggest it’s rather important we find out. The first, by Nihart and colleagues8, found that the amount of MNPs in human brains is increasing over time, with as yet unknown neurological consequences. They hypothesise that this increasing trend could continue, given rising levels of environmental exposure8. The second, published by Zhu et al.9 explored the impact of microplastics on photosynthesis, the scale of potential crop losses and the knock-on effect on food security. They estimated that microplastic pollution causes crop losses exceeding 100 million metric tons per year - a concerning risk for global food production9.
Should we be paying more attention to nanoplastics?
More research is needed to understand the full picture of MNP pollution. There is a need for methods to map MNP levels and characterise the particles found, as well as a need for studies of dose-effect relationships. However, most techniques currently available for plastic particle analysis measure in the microplastic range10, so data on the prevalence and effects of nanoplastics is lagging behind (Figure 2).
Many studies suggest there are likely to be more smaller particles than larger ones11-13, meaning that nanoplastics may be the most numerically prevalent form of plastic pollution. This will only increase as existing plastic continues to break down. As well as being more numerous, nanoplastics may also pose a higher risk, as smaller particles are more likely to penetrate the body14-16, circulating in the bloodstream17, accumulating in organs18 and even being taken up inside cells19, 20. Mounting evidence suggests, perhaps unsurprisingly, that this accumulation of foreign bodies could have a variety of negative effects on health21, 22. It is therefore critical to develop techniques for nanoplastic characterisation and enable further research.
Could tunable resistive pulse sensing (TRPS) have a role in nanoplastic analysis?
There are many properties of MNPs that must be measured to understand environmental distribution and toxicity. These include their composition, size, shape, concentration, surface charge and adsorption of hazardous substances. Multiple complementary methods are needed to perform a complete analysis of MNPs, as no single method can provide all the necessary information. For example, gas chromatography—mass spectrometry can determine the quantity (mass) and type of plastics present, while scanning electron microscopy can provide images of particle size and shape.
Techniques that have been used for concentration, size and/or surface charge analysis of nanoplastics include dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA)16, 23, 24. Previous comparisons show TRPS has advantages over both DLS and NTA. A comparison of nine methods’ ability to analyse polystyrene particles found that TRPS accurately measures particle concentration and size, even in polydisperse mixtures and mixtures spanning the nano- to microplastic size range25. While several techniques, including DLS and NTA, already struggled with this challenge, it is simplistic compared to the complexity of nanoplastics in environmental samples. A more advanced test, using polyethylene, doped polystyrene and non-spherical (elongated) iron oxide particles, concluded that TRPS was suitable for measuring the size and concentration of each of these complex samples. However, this study did identify the potential of the electrolyte used for TRPS to induce sample agglomeration of polyethylene, leading to measurement of agglomerates rather than single particles26.
A major challenge when analysing environmental samples is the low concentration of particles compared to the lower limit of detection of measurement techniques. Microplastic concentrations in water range from up to 10 particles per litre for surface water and bottled water to 100 particles per litre for tap water2, 12. Even though these estimates are based on the detection of microplastics, and nanoplastics are thought to be more prevalent, concentrations are likely below the input specifications of 107 particles/mL or more for techniques such as TRPS and NTA.
As dose-effect studies are required, alongside data on exposure levels, to understand the effects of nanoplastic exposure on living organisms, the characterisation of MNP samples for laboratory experiments may be a more feasible, but no less important use case for nanoplastic profiling. It is critical that such samples are shown to be representative of the diversity and complexity of environmental contamination, in order to accurately reflect the behaviour and biological effects of MNP pollution27.
A key feature of TRPS is its ability to measure zeta potential, which is dependent on particle surface charge, as well as the electrolyte it is suspended in (Figure 3). Surface charge affects the uptake and toxicity of nanoplastics28, 29 and behaviours such as adsorption and aggregation in the environment30. It is therefore a crucial factor to include when characterising both environmental samples and materials used in laboratory studies of nanoplastic effects. As only a very limited number of techniques can measure zeta potential, this may be an important driver for the use of TRPS in nanoplastic research.
Ongoing challenges in nanoplastic monitoring
Ultimately, there are still problems to be solved before we can routinely and reproducibly analyse nanoplastic particles, particularly in environmental samples. Methodologies for MNP extraction, concentration, distinguishing between plastic and other particles, size fractionation prior to analysis of populations of interest, and contamination prevention are works in progress that will make nanoplastic characterisation easier. The understanding of MNP pollution that all these efforts will provide is an important step towards managing the problem.
Interested in reading more about the comparison of methods for nanoplastic analysis? See The Expanding Landscape of Techniques for Nanoplastic and Microplastic Analysis: A Comparative Study.
