By: Adam Gushgari, Senior Director of Emerging Contaminants, Eurofins Environment Testing
Microplastics research is still a young field. The term itself wasn't coined until 2004, and the science largely stayed confined to marine research until the latter half of the 2010s. In the years since, our understanding has grown quickly, but the gap between what we know and what we still need to know remains significant.
What we do know is that microplastics are everywhere. They've turned up in soils, water, and air, including in some of the most remote locations on Earth. They're present in cosmetics, food products, and everyday household items, and they've been detected in biota across the globe and in human tissue samples. Taken together, the literature points to one clear conclusion: this contaminant is far more widespread than most people realize.
That's only half the picture, though. There's legitimate question today around the accuracy of a number of published microplastics studies, largely due to a lack of QA/QC practices that would otherwise be standard for a high-impact journal. And while correlations between microplastics exposure and adverse outcomes have been demonstrated repeatedly, most studies stop short of establishing causality because enough evidence doesn’t yet exist in many cases. And underneath nearly every open question in this field sits one common variable: particle size. It shapes how these contaminants move through the environment.
Redefining How These Particles Move
Plastic particles below 5 mm are broadly categorized as micro- or nanoplastics, though where exactly that internal line falls depends on which definition you use. For this discussion, we'll treat anything below 1 µm as a nanoplastic.
The critical thing to understand is that nanoplastics, and microplastics at the smallest end of their range, aren't just smaller versions of the same problem. They can behave in fundamentally different ways, and that changes how we need to think about their environmental fate and transport.
Take airborne transport. We've known for a while that air is a meaningful transport mechanism, since airborne microplastics have been detected in some of the most remote corners of the planet. But most of the models used to estimate that transport have historically treated microplastic particles as simple spheres, which doesn't reflect how they actually behave. A 2023 study found that microplastic fibers have settling velocities up to 76% lower than a sphere of equivalent volume [1]. Modeling from that same work suggested the smallest fibers, up to 100 µm in length, settle slowly enough to potentially reach the stratosphere, where they could damage the ozone layer through UV-driven release of chlorine and bromine. The authors were careful to note that how much microplastic actually reaches the stratosphere depends heavily on emission size distribution, data we don't yet have at a global scale, so this remains a plausible, well-supported risk rather than a settled one. Separately, particle size has also been shown to govern how microplastics deposit within human and avian respiratory systems [2].
The subsurface tells a similar story. Microplastics can migrate through saturated porous media, with movement influenced by particle size, surface charge, and reactivity [3]. But a comprehensive 2026 modeling review found that microplastics don't move through the subsurface the way conventional contaminant transport models assume [4]. The environmental pathway a particle takes before it ever reaches the subsurface may impact how it moves once it's there, and existing models don't yet capture that complexity. Closing that gap is essential before subsurface transport modeling can meaningfully inform policy or remediation decisions.
Where That Movement Leads
All of this transport complexity matters most when you consider where it ends up, and one of the more striking findings in recent years is uptake into plants. This represents a potential direct exposure pathway, carrying subsurface contamination straight into the human food supply.
Research has shown nanoplastics entering the root systems of edible crops, primarily at the points where new lateral roots break through the outer root tissue, creating a natural entry point [5]. More notably, those nanoplastics didn't stay in the roots. They migrated into the edible portions of the plants themselves across many different examined vegetables, including asparagus, radish, pak choi, and tomatoes. Root uptake isn't the only pathway either. Nanoplastics applied directly to leaves have also been shown to enter plant systems, and a comprehensive review confirmed that both root and foliar uptake allow these contaminants to redistribute throughout the plant once absorbed [6]. So, this isn't only a subsurface exposure story. It's also a pathway that starts in the air and ends up on the plate.
The Bigger Picture
The environmental transport and fate of this contaminant class, particularly at the nanoscale, is proving far more complex than originally anticipated, and it doesn't necessarily follow the same patterns we've used to regulate previous classes of emerging contaminants. That mismatch, between how we've historically modeled contaminant transport and how these particles actually move through our environmental matrices is one of the more important gaps this field still needs to close.
References
[1] Tatsii, Daria, et al. "Shape matters: long-range transport of microplastic fibers in the atmosphere." Environmental Science & Technology 58.1 (2023): 671-682.
[2] Huang, Xinlei, et al. "Transport and deposition of microplastics and nanoplastics in the human respiratory tract." Environmental Advances 16 (2024): 100525.
[3] Shaniv, Dotan, Ishai Dror, and Brian Berkowitz. "Effects of particle size and surface chemistry on plastic nanoparticle transport in saturated natural porous media." Chemosphere 262 (2021): 127854.
[4] Cai, Fangfei, et al. "Microplastics transport in subsurface environments: Mechanisms and multi-scale modeling." Ecotoxicology and Environmental Safety 322 (2026): 120362.
[5] Zytowski, Eric, Mohanna Mollavali, and Susanne Baldermann. "Uptake and translocation of nanoplastics in mono and dicot vegetables." Plant, Cell & Environment 48.1 (2025): 134-148.
[6] Arshad, Muhammad, et al. "Micro-and nanoplastics-induced stress in plants: uptake, physiological disruption, and toxicity mechanisms." Frontiers in Plant Science 17 (2026): 1772615.