Key Takeaways & Executive Findings
- •• • Atmospheric MPs predominantly measure <700 μm, with fibrous shapes dominating; this size fraction is inhalable and can penetrate deep into the respiratory system, posing significant human health risks. • • Over 20 polymer types have been identified in atmospheric samples, with textiles, tire wear, and dust as major contributors; this chemical diversity complicates source apportionment and necessitates polymer-specific risk assessments. • • Sampling methods are categorized as passive or active; active sampling is essential for quantifying deposition fluxes, yet no standardized protocol exists, leading to data incomparability across studies. • • Analytical techniques include μ-FTIR, μ-Raman, LDIR, and mass spectrometry; each has detection limits and resolution trade-offs, and method selection critically influences reported concentrations and polymer distributions.
Abstract
Microplastics (MPs), defined as plastic particles smaller than 5 mm, are ubiquitous environmental contaminants with documented presence in urban, rural, marine, remote, and polar atmospheres. The atmosphere serves as a primary medium for their long-range transport, raising concerns regarding climate interactions and human health. This review synthesizes recent advances in atmospheric MPs research, encompassing sampling strategies, pretreatment protocols, analytical techniques, occurrence characteristics, and ecological ramifications. Passive and active sampling methods are delineated, with active samplers enabling quantitative flux measurements. Pretreatment typically involves sequential steps of sieving, density separation, digestion, staining, and filtration to isolate MPs from complex matrices. Identification relies on visual inspection, micro-Fourier transform infrared spectroscopy (μ-FTIR), micro-Raman spectroscopy, laser direct infrared imaging (LDIR), and mass spectrometry. Reported atmospheric MPs predominantly exhibit dimensions below 700 μm, with fibrous morphologies being most prevalent. Color distribution is dominated by black, followed by white and transparent particles. Over 20 polymer types have been identified, with textiles, tire wear, and dust identified as principal sources. Atmospheric MPs can influence solar radiation balance, cloud formation processes, and pose risks to flora, fauna, and human health. However, research remains nascent; standardization of sampling and analytical protocols, along with comprehensive toxicological assessments, are critical knowledge gaps requiring urgent attention.
1. Introduction
Atmospheric microplastics (MPs) have emerged as a distinct environmental compartment, yet their study lags behind aquatic and terrestrial systems. The primary bottleneck is methodological: sampling and analytical protocols are not standardized, leading to wide variability in reported concentrations and characteristics. Passive samplers, such as deposition jars, are simple but provide only integrated fallout, while active samplers, like cascade impactors, offer size-resolved data but require calibration and power. Furthermore, pretreatment steps—sieving, density separation, digestion—must balance removal of organic matter against preservation of polymer integrity. Identification techniques, from visual sorting to spectroscopic methods, vary in sensitivity and throughput, with μ-FTIR and μ-Raman capable of detecting particles down to ~10 μm, but LDIR offers faster mapping. This lack of harmonization impedes global comparisons and risk assessments.
This review addresses these bottlenecks by systematically evaluating current methodologies and synthesizing occurrence data from diverse environments. It highlights that atmospheric MPs are not a homogeneous pollutant; their size, shape, and polymer composition vary spatially and temporally, influenced by sources such as textile fibers, tire wear, and resuspended dust. The reported predominance of particles <700 μm and fibrous morphologies underscores the potential for inhalation exposure. Moreover, the presence of MPs in remote and polar regions confirms long-range atmospheric transport, implicating them in climate feedback loops. By consolidating existing knowledge, this review identifies critical research needs, including standardized protocols and comprehensive toxicological studies, to advance the field and inform policy.
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WANG Bo, WANG Kai, QU Kaijing, ZHANG Jinrui, LONG Xin, XU Li, HOU Junxian, LI Ben, PAN Xianhui, LI Xin, HU Junli, LIU Xuejun (2026). Research Progress on Atmospheric Microplastics: Sampling, Analytical Methods, Occurrence, and Ecological Impacts. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025041502
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Frequently Asked Questions
What are the main limitations of current sampling methods for atmospheric microplastics, and how do they affect data comparability?
Passive sampling (e.g., deposition jars) collects only falling particles, while active sampling (e.g., cascade impactors) provides size-segregated data but requires flow calibration. The lack of standardized protocols leads to variations in reported deposition fluxes and size distributions, making cross-study comparisons difficult. For instance, studies using active samplers report higher concentrations of smaller particles (<100 μm) compared to passive methods, which may underestimate these due to wind effects.
Which analytical technique offers the best balance between sensitivity and throughput for routine monitoring of atmospheric microplastics?
μ-FTIR and μ-Raman provide chemical identification with particle size limits down to ~10 μm, but are time-consuming. LDIR (laser direct infrared imaging) can rapidly map large areas, but may miss particles <20 μm. Mass spectrometry (e.g., TED-GC-MS) offers high sensitivity for mass quantification but lacks spatial resolution. For routine monitoring, a tiered approach is recommended: visual pre-screening followed by μ-FTIR for confirmation, with LDIR for high-throughput screening when particle loading is high.
What are the dominant polymer types found in atmospheric microplastics, and what do they imply about sources?
Common polymers include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), and polyamide (PA). PET and PA are indicative of textile fibers, while tire wear contributes styrene-butadiene rubber (SBR) and other elastomers. The presence of these polymers in remote areas suggests long-range transport, with atmospheric residence times influenced by particle size and density.
How do atmospheric microplastics potentially affect cloud formation and climate?
Microplastics can act as cloud condensation nuclei (CCN) or ice nucleating particles (INP), altering cloud microphysics and radiative properties. Their hydrophobic surfaces may inhibit water uptake, while additives could leach and affect droplet surface tension. However, quantitative assessments are lacking; current estimates suggest that MPs contribute negligibly to global CCN concentrations compared to natural aerosols, but local impacts in polluted regions may be significant.
What are the key knowledge gaps in assessing the health risks of atmospheric microplastics?
Critical gaps include: (1) exposure assessment—accurate measurement of inhalation doses, especially for particles <10 μm; (2) toxicological data—limited studies on cellular uptake, inflammatory responses, and translocation; (3) additive leaching—the role of plasticizers and flame retardants in toxicity; and (4) mixture effects—interactions with other pollutants. Standardized reference materials and dose-response studies are urgently needed.
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