An Overview of Microplastic Exposure in Urban, Suburban, and Rural Aerosols

Abstract

This study advances the understanding of atmospheric microplastic (MPs) exposure across urban (US), suburban (SS), and rural (RS) areas of Madrid, Spain, for the first time. Air pollution from MPs remains an understudied issue with broad implications for environmental and human health. Recent evidence highlights the need for multipoint studies to accurately establish atmospheric exposure to MPs, especially during winter seasons in the city. To address this issue, this work conducted active sampling of ≤10 μm aerosol particles, following EN 12341:2014 standards, during the 2024–2025 winter season. A quantitative innovative method using UV-assisted optical microscopy was applied to assess daily MPs exposure. To trace the potential sources and transport pathways, air mass back trajectories were modelled using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) software. The results showed an average exposure (n = 4) of 80 ± 20; 55 ± 9 and 46 ± 20 MPs·m⁻³·day⁻¹ during the sampling period in US, SS, and RS, respectively; and an average exposure (n = 4) of 61 ± 11 MPs·m⁻³·day⁻¹ throughout the winter period between November and December 2024 and January and February 2025. The polymers detected as constituents of MPs were polystyrene, polyethylene, polymethyl methacrylate, and polyethylene terephthalate, achieving a correct identification ratio of 100% for the detected microplastic particles. The HYSPLIT results showed diffuse sources of MPs, especially local, regional, and oceanic sources, in the US. In contrast, microplastic contributions in SS and RS areas originated from local or regional sources, highlighting the need for advanced studies to identify the sources of emissions and transport routes that converge in the occurrence of microplastics in the areas studied. These results demonstrate the atmospheric exposure to microplastics in the city, justifying the need for specialized studies to define the health impacts associated with the inhalation of these emerging pollutants. The findings of this research provide clear evidence of exposure to atmospheric microplastics in urban, suburban, and rural environments in Madrid, suggesting the need for further specialized research to rigorously assess the potential risks to human health associated with microplastic inhalation by the city’s population.

1. Introduction

Microplastic pollution has become a significant environmental issue with serious implications for both the environment and human health. Microplastics (MPs) have been detected in various ecosystems, including terrestrial, aquatic, and atmospheric compartments [1,2]. Pollution associated with these emerging contaminants is considered pervasive and persistent worldwide. The production, transport, and diffusion of MPs is a problem whose complexity is increasing over time owing to the systematic increase in global plastic production, accompanied by intensive accumulation of waste from these polymeric materials. Beyond their hazardous presence on the Earth’s surface, in aquatic ecosystems, and in the atmosphere, multiple studies have highlighted the ability of these micropollutants to infiltrate the tissues of living organisms, including plants [1], animals [2], and humans [1,2]. Recent evidence has shown that MPs have penetrated the food supply chain [3,4], exposing the population to higher levels of these contaminants and increasing the risk of adverse health effects [5].

Within the specialized field of microplastic research, atmospheric MPs raise particular concern due to their ability to travel long distances through long-range atmospheric transport [6,7] and the significant role of inhalation exposure in the incorporation of these contaminants into the human body [6]. The idea that humans might inhale these particles daily is unsettling and raises urgent questions regarding their reach and impact on human health [7]. Nevertheless, despite increasing awareness, comprehensive studies on the occurrence of MPs in the atmosphere remain limited due to analytical challenges, which stem mainly from the lack of harmonized methods [8].

While most existing research has predominantly focused on the occurrence, distribution, and ecological implications of microplastics in aquatic environments, comparatively limited empirical attention has been directed toward their presence in the atmospheric compartment [9]. This research gap is particularly critical in densely urbanized areas, such as Madrid (Spain), where anthropogenic factors, including high vehicular traffic density, substantial industrial activity, and a large resident population, collectively create conditions conducive to the emission, atmospheric transport, and potential inhalation exposure to airborne microplastic particulates.

Previous research conducted with single-point sampling has shown that exposure to atmospheric microplastics in indoor and outdoor environments in Madrid, specifically during winter (2017–2018), is significantly higher than that during the rest of the year. This situation highlights the need to conduct multipoint sampling studies within the city to investigate exposure to atmospheric microplastics more rigorously, specifically in urban, suburban, and rural environments [10].

The concrete determination of the levels of exposure to atmospheric microplastics in urban, suburban, and rural environments in the city of Madrid, especially during the winter season, is essential to establish the risks and impact of the inhalation of these emerging pollutants on the population. This is especially due to the links that have been previously established with regard to the increase in microplastic concentrations in the atmosphere due to the use of warm clothing, which is characteristic of this season, compared to the lower concentrations previously detected in the city during the summer or warm season [10].

Atmospheric exposure to microplastics represents an emerging risk to human health, the magnitude of which has not yet been fully characterized [11]. The documented presence of MPs in urban and indoor aerosols suggests chronic exposure, which is particularly concerning given their potential for deposition in the lower respiratory tract [12]. Preliminary studies have indicated that these particles can induce inflammation, oxidative stress, and cytotoxic effects and act as vehicles for chemical and biological contaminants [13,14,15]. Although direct evidence in humans is limited and safety thresholds have not yet been established, the biological plausibility of their effects and environmental ubiquity justify a precautionary approach to public health. Nevertheless, to date, there is concrete evidence of the presence of microplastics in lower respiratory tract sputum, specifically in residents of Alicante, Spain [16].

This research has focused on defining exposure to atmospheric microplastics in urban, suburban, and rural environments in Madrid during winter, as well as establishing the sources and potential origins of these emerging pollutants. The objective of this research is to consolidate evidence on atmospheric exposure to microplastics, which can serve as a starting point for defining policies aimed at controlling and mitigating the effects of this global environmental problem.

2. Materials and Methods

In general, this research has employed a rapid and easy-to-implement methodological approach, without the use of expensive or polluting reagents or sophisticated instrumentation. While it is true that the study of microplastics generally includes determining polymer identity and particle size, this study was limited to examining exposure to the contaminant and its potential sources. From the authors’ perspective, this methodological approach, specifically designed to define the exposure and sources of microplastics, is a viable alternative for any interested party to provide relevant information on exposure to microplastics in a relatively inexpensive and rapid manner with minimal resources.

2.1. Geographical Context of the Study and Aerosol Sampling Protocol

This investigation was performed in Spain, specifically in the city of Madrid (Figure 1a), located in the central region of the Iberian Peninsula at an altitude of 657 m above sea level. Samples were collected from three different locations representing the urban, suburban, and rural environments of the city, as shown in Figure 1b.

The urban site (US) was the Casa Árabe building, located at Calle Alcalá 62, Salamanca (40.4219° N 3.6817° W), approximately 1.9 km from the city center. The suburban site (SS) was established on the Moncloa Campus of the Complutense University of Madrid, specifically in the Faculty of Chemical Sciences, located at Plaza de las Ciencias 2, Moncloa-Aravaca (40.4506° N 3.7254° W), approximately 4.2 km from the city center. Finally, the rural site (RS) was established in the city hall building located in Torremocha del Jarama (40.8387° N, 3.4989° W), approximately 50 km from the center of Madrid, at an altitude of approximately 707 m above sea level.

Aerosol samples with an aerodynamic diameter <10 μm (PM₁₀) were collected in accordance with standard EN 12341:2014 using a DPE-1 Comde Darenda (Stahnsdorf, Germany) high-volume automatic sampler. The parameters of the autosampler were set to a flow rate of 2.30 m3/h, sampling period of 24 h, and sampling frequency of every three days, resulting in 120 different samples. Aerosols were collected on quartz fiber supports or filters (47 mm). Once collected, the samples were wrapped in aluminum foil and stored in the dark under refrigerated conditions (4 °C). Given that this study focused on determining exposure to atmospheric microplastics during the winter season, samples were collected during the winter of 2024–2025, specifically during November and December 2024, and January and February 2025.

2.2. Methodology for Direct Counting of Microplastics in the Filter

To count the microplastics directly on the filter, circular sections (n = 4) measuring 6 mm were carefully cut from each filter using stainless steel punches of identical diameters. To do this, the punch was placed perpendicular to the 47 mm filter, which was in a glass Petri dish, and gently pressed to delicately cut the sections of the filter. Each cutout (n = 4) from each filter was stored in a glass Petri dish to prevent cross-contamination. Each 6 mm diameter circular slice was then microscopically inspected using a CH30 Olympus biological microscope (Olympus Optical Co., Ltd., Tokyo, Japan) at 40 × magnification.

In terms of the representativeness of the sections analysed, it has been previously shown that a single section of the filter is sufficient to determine the overall representative composition of the particulate matter in the filter [17]. However, in this investigation, microplastic measurements were performed on four different 6 mm circular sections, not only to ensure a representative result of the sample (or total filter) but also to determine the concentration of microplastics in the filter with statistical accuracy.

To help identify plastic particles from other waste materials, the microscopic optical field was irradiated with a 360 nm (120 W) UV lamp. Since microplastics characteristically fluoresce with weak blue light under this wavelength, making them easily discernible from interferences such as biological matter that produces yellow fluorescence [18,19], only particles showing this type of fluorescence were counted.

This innovative methodological approach for counting microplastics directly on the filter using UV-assisted optical microscopy was previously developed by our research group [10]. This method significantly simplifies sample processing and handling, eliminating the need for separation and/or pre-analytical preconcentration steps that are conventionally used in microplastic counting by optical methods [8,20].

The use of the active aerosol sampling method enabled the determination of the occurrence of microplastics in terms of daily exposure (MPs·m⁻³·day⁻¹). This is due to the availability of specific information on the volume of air sampled per day (55.2 m³) measured by the reference autosampler. To quantitatively establish daily exposure, the relationship between the microplastic count in the area of the pre-cut circle with a diameter of 6 mm (28.27 mm² surface area), the original area of the 47 mm diameter filter (1734.9 mm²), and the total volume of air sampled by the filter, which corresponds to a total of 55.2 m³ of sampled air, was determined.

2.3. Microplastic’s Identification

An NTegra Spectra dispersive confocal μRaman spectrometer (NT-MDT, Amsterdam, Netherlands) was used to identify the polymer of the microplastic particles present in the filters. This spectrometer consists of a Solar TII MS5004i Czerny-Turner monochromator with a focal length of 520 mm, a 75/Echelle grating configuration, and a 785 nm laser with 50 mW of power. The instrument detector consists of an Andor iDus DU-420 charge-coupled device (CCD) with a resolution of 1024 × 128 pixels. This μRaman instrument also incorporates an Olympus BXFM microscope (Olympus Optical Co., Ltd., Tokyo, Japan) consisting of a SenTech color CCD camera and halogen illumination (Olympus TH4-200/U-LH100-3-7) with a 50× objective lens.

The polymers were identified directly on each of the replicas (n = 4) of pre-cut 6 mm diameter filters. Each fluorescent particle detected as a microplastic was analyzed directly, in accordance with the procedure described in the previous section. Identification was performed by comparing the spectra of the microplastic particles with those of the polymers used as reference materials. For this purpose, the microplastic standard PY1-4940 from Frontier Lab (Fukushima, Japan) was used.

Conventionally, microplastics are identified using μRaman spectroscopy by assigning discrete signals to functional groups present in polymers. Unfortunately, this strategy can result in incorrect polymer identity assignments due to the interpretation of partial spectral fingerprints, which can be generated, for example, by the aging of microplastics. The methodological approach used in this research allows the identity of microplastics to be established from complete micro-Raman spectra. This enables the unambiguous identification of the chemical or polymeric composition of the analyzed microplastic, especially in situations where the ageing of microplastics can induce signals that do not represent the true identity of the microplastic itself.

2.4. Estimation of Potential Sources of Atmospheric Microplastics

In order to establish the potential emission sources and transport of the identified microplastics, monthly backward air mass trajectory analyses were conducted for aerosol samples collected across the US, SS, and RS. The Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) open-source software was used to model back trajectories. This software was developed by researchers at the US National Oceanic and Atmospheric Administration (NOAA) [14] and can be accessed online at https://www.ready.noaa.gov/HYSPLIT_traj.php (accessed on 17 July 2025). A 24-h interval was used to produce back trajectories for each site studied. In addition, the Global Data Assimilation System (GDAS) was adjusted to 1° global from 2006 to the present, using meteorological files corresponding to the sampling date at the exact location where the aerosol sampling was carried out, as described previously in Section 2.1. The parameters used for the retracement model were (i) the configuration of movement or vertical velocity, (ii) reverse trajectory direction (retracement), and (iii) a height of 657 m AMSL for US and SS, and 707 m AMSL for RS.

2.5. Quality Assurance and Quality Control (QA/QC) Methodological Approach

Due to the potential occurrence of microplastics in the environment in which analytical activities are carried out, analytical control protocols are required to ensure that analysis can be performed without interference from cross-contamination of microplastics from the environment. To this end, specific considerations have been taken into account in this research, as is conventional in the study of microplastics, to avoid cross-contamination of analytes in the samples. This type of control also ensures the validity of the analytical results obtained, with control of all stages of the experimental process to guarantee accurate and reproducible measurements of the microplastics strictly present in the samples. This protocol was carried out in accordance with the guidelines described in previous publications [8,10,11].

More specifically, all materials and utensils used during the study of the samples were thoroughly washed three times with type I water (18.2 MΩ·cm), produced using a Merck Milli-Q Model IQ 7000 ultrapure water system (Darmstadt, Germany), prior to use. Glass materials, in particular, were subsequently washed vigorously with a 1:1 nitric acid solution (Scharlab, Barcelona, Spain) to ensure the removal of any particulate material, especially microplastics. Similarly, the work areas were thoroughly cleaned and prepared before using all materials, devices, and instruments, and covered with aluminum foil (both before and after processing) to prevent the deposition of microplastics present in the laboratory environment. The personnel who handled the samples wore 100% cotton lab coats and clean nitrile gloves throughout the analysis procedure. To evaluate cross-contamination associated with each process, white filters were used before and after each methodological phase to make the corresponding quantitative corrections. However, no microplastics were observed in any of the control filters, demonstrating the rigor of the protocol used to prevent cross-contamination of the samples.

For information on the evaluation of analytical performance, advantages, limitations, scope, and other technical and analytical information of interest regarding the methodological context used in this study, readers may consult reference [10].

3. Results and Discussion

3.1. Atmospheric MPs Exposure

The average (n = 4) MP exposure measured at each sampling location (US, SS, and RS) is presented in Figure 2.

In general terms, the average exposure (n = 4) during the study period was 80 ± 21; 55 ± 9 and 46 ± 20 MPs·m⁻³·day⁻¹ for the US, SS, and RS sites, respectively. This demonstrates that exposure to atmospheric microplastics in Madrid is significant in urban areas characterized by significant anthropogenic activity compared to other regions (suburban or rural), in line with the results of previous studies carried out in different cities around the world, such as Hamburg (Germany) [21], Thulamela (South Africa) [22], Patna (India) [23], Beijing, Chengdu, and Xiamen (China) [24,25,26], among others [27].

Table 1. Microplastic concentrations reported in recent studies conducted in other regions of the world.

City	MPs Concentration Reported a	Site	MPs Collection Method	Reference
Hamburg (Germany)	89 ± 61 MPs·m−2	Urban	Passive	[21]
Bremerhaven (Germany)	91 ± 47 MPs·m−3·day−1	Urban	Active	[28]
Thulamela (South Africa)	212 ± 32 MPs·m−2	Urban	Passive	[22]
Patna (India)	1960 ± 205 MPs·m−2	Urban	Passive	[23]
	1321 ± 126 MPs·m−2	Suburban
Seoul (South Korea)	144 ± 2 MPs·m−3·day−1	Urban	Active	[29]
Incheon (Korea)	192 ± 127 MPs·m−3·day−1	Urban	Active	[30]
Harbin (China)	163 ± 45 MPs·m−3·day−1	Urban	Active	[31]
	64 ± 22 MPs·m−3·day−1	Suburban
	13 ± 6 MPs·m−3·day−1	Rural
Madrid (Spain)	80 ± 21 MPs·m−3·day−1	Urban	Active	This study
	55 ± 9 MPs·m−3·day−1	Suburban
	46 ± 20 MPs·m−3·day−1	Rural

^a Note that the units of volume sampled may vary in m² or m³, depending on the collection method used, whether passive or active (as in this study). Only concentrations obtained using the active method are considered as daily exposure [10].

presents the microplastic concentrations reported in recent studies conducted in other regions of the world.

According to the results obtained (Figure 2), relatively high atmospheric exposure to microplastics was observed in the US area compared to the SS and RS areas, where similar exposure levels were observed. This reflects the fact that even in rural areas, where anthropogenic action is significantly lower, the ubiquitous nature of airborne MPs has widespread effects on the environment. Even at substantially lower concentrations, MPs are present in every environment, and the risks they pose must be evaluated at all sampling sites.

More specifically, a relative difference is observed between exposure in the US and SS, despite only a 2.6 km difference between these two sampling sites. This is indicative of the high anthropogenic activity in the US environment compared to the SS area, which has more green areas and fewer densely distributed buildings. In contrast, the highest exposure was observed at the beginning of the winter season, specifically in November. However, at the RS site, the highest exposure was recorded in December. Specifically, regarding the SS site, a very similar exposure was observed across the months covered by the study. However, at the RS site, a clear trend towards a decrease in daily exposure over time was observed.

An important aspect that should not be overlooked is the difference in altitude between the US (657 m ASML) and RS (707 m ASML) sites, approximately 50 m AMSL, which translates into different meteorological processes, such as the incidence of fog [32], thermal profile, wind direction, thermal inversion [33], and differences in wind gradients [34]. All these meteorological and climatological phenomena significantly influence the emission, transport, and deposition of microplastics in the atmosphere, resulting in differences in exposure to these emerging pollutants in SS and RS due to variations in altitude. With regard to atmospheric exposure to microplastics throughout the study period, considering the months sampled (n = 4), a mean of 61 ± 11 MPs·m⁻³·day⁻¹, was obtained.

It is important to note that, in analytical terms, comparing microplastic concentration results is counterproductive, mainly due to differences in the methodological approaches used in the studies, whether for aerosol sampling or for the qualitative or quantitative determination of microplastics. Specifically, variations in methodological approaches to the qualitative and quantitative methods for determining microplastics, regardless of the matrix, lead to changes in the method’s ability to capture and identify particulate matter, resulting in considerable metrological deviations. Although numerous studies have reported the occurrence of microplastics, whether in terms of concentration, daily exposure, or deposition, these results should be interpreted as merely informative and not as a comparison of the state of microplastic pollution in the atmosphere.

To illustrate this issue, the results of atmospheric exposure to microplastics obtained in Madrid in previous studies provide an appropriate example. A recent study reported daily exposure values from April 2017 to May 2018 [10]. In this study, the researchers used different filter sizes (150 mm) and flow rates (720 m³/day), unlike the 47 mm filter and 55.2 m³/day flow rate used in this research. These differences in the collection method represent analytical limitations that prevent inferences about increases or decreases in exposure levels when comparing the results of the two studies.

This situation exemplifies the difficulties and limitations associated with the lack of harmonized MP detection methods, which prevents data obtained in studies from being compared with more recent evidence. This evidence highlights the importance of incorporating airborne MPs into environmental monitoring and air quality regulations, given their significant presence and potential implications for public health in all zones studied (US, SS, and RS).

3.2. MPs Polymer Identity

Once the concentration (or exposure) of microplastics in the filters was established, the polymers that made up the detected microplastics or particles that emitted fluorescence in the previous counting stage were identified. All fluorescent particles, which constituted 100% of the detected microplastics, were successfully identified. The results obtained through the μRaman spectroscopy technique evidenced that the spectral fingerprints of representative spectra of the detected MPs belong to four different groups of polymers (MPs 1, MPs 2, MPs 3, and MPs 4). Figure 3 shows the representative spectra obtained along with their respective references used for identification.

The identified polymers correspond to polystyrene (PS), polyethylene (PE), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET). Note that the reference spectra of the polymers were observed with a greater relative intensity than the spectra of the detected microplastics. This is due to the characteristic aging of microplastics, generally during transport, unlike the polymers used as references, which have not undergone this type of aging. These results align with the chemical identity of the microplastics detected in Madrid from April 2017 to May 2018 [10]. These results demonstrate the persistence of these four polymers in the atmosphere of Madrid, regardless of the sampling sites. With regard to the potential origin of these polymers,

Table 2. Potential sources of the polymers constituting the detected microplastics.

Polymer	Formulae	Potential Sources	References
Polystyrene (PS)	(C8H8)ₙ	Aquaculture buoys	[35]
		Compact discs (CDs), toys, toothbrushes, etc.	[36]
		Personal care products, cosmetics, disposable plastic tableware, and fishing waste	[37]
		Aggregates, pellets, pre-production materials	[38]
		ion exchange resins for water softening and various industrial wastewater purification processes)	[39]
		Pharmaceuticals	[40]
		Synthetic textiles	[39]
Polyethylene (PE)	(C2H4)ₙ	Personal care products, washing wastewaters, and farming films	[37]
		Synthetic grass and scaffold nets	[41]
		Plastic mulching, mulch film on agricultural land	[42]
		Road dusts	[43]
		Pharmaceuticals	[39]
		Synthetic textiles	[39]
Polymethyl methacrylate (PMMA)	(C5O2H8)n	Personal care products	[37]
		Road dusts	[43]
		Aggregates, pellets, pre-production materials	[38,44]
		Antifouling ship paint and varnishes	[45,46]
		Synthetic textiles and textile softener	[47]
Polyethylene terephthalate (PET)	(C10H8O4)n	Personal care products and sewage sludge	[37]
		Road dusts	[43]
		Synthetic textiles	[48]
		Shopping bags and packaging sacks	[48]

presents the main sources of these polymers, according to previous studies.

Interestingly, all polymers detected in this study are constituents of textile fibers used in the manufacture of conventional and warm clothing for the cold season. This evidence aligns with multiple studies [49,50,51] that indicate textiles and clothing made from polymeric textiles as one of the primary sources of microplastics, particularly in the atmosphere [10,52]. In addition to the data presented in Table 2, it has been shown that sea spray-air-water interfaces, tyre wear, and nail salons are also significant sources of the polymers detected in this study [53].

In addition to the hazards and risks associated with atmospheric exposure to these polymers and their toxicity, some recent studies have pointed to the potential of these chemicals to degrade and produce a new generation of emerging pollutants [54,55,56], exacerbating the global air quality situation and the impact of microplastics on the environment, especially on human health. This highlights the urgent need to develop strategic policies to mitigate microplastic emissions from these key sources.

3.3. MPs Backtrajectories and Potential Sources and Transport

The results obtained using the HYSPLIT software are shown in Figure 4.

For the US, local (terrestrial) contributions are observed, as well as oceanic contributions derived from long-range transport, which MPs generally experience due to their light weight and micrometric size [57,58]. In contrast, the air mass contributions to SS and RS originate strictly from local terrestrial sources. These data highlight the variability and complexity of the meteorological processes involved in MPs transport, despite the small differences in distance observed between urban and suburban sites, which were approximately 2.6 km apart. HYSPLIT modelling results also suggest that synoptic-scale meteorology plays a significant role in the aerial dispersion process of microplastics. These observations emphasize the importance of considering both primary emission sources and air circulation patterns when examining atmospheric microplastics, their transport, and potential sources.

Collectively, the outcomes of this study represent an important initial contribution to the knowledge of microplastic air pollution in Madrid and provide preliminary insights into the daily exposure levels faced by residents of the assessed areas. This type of data provides essential information for justifying more advanced and sophisticated studies aimed at more accurately defining the potential effects of microplastics on human health, especially those associated with the inhalation of these emerging pollutants. In contrast, the results of this research demonstrate that exposure to microplastics is not limited to urban and suburban sites but also extends to rural environments. These findings represent pioneering advances in the study of atmospheric microplastic pollution in Madrid.

Furthermore, consolidating this evidence represents a technical and scientific milestone of particular interest to authorities, government agencies, and stakeholders responsible for developing policies, programs, and regulations to combat both the uncontrolled spread of MPs and their effects on the environment and human health.

From an analytical perspective, this study presents a rapid, simple, and relatively inexpensive methodological approach for determining atmospheric exposure to microplastics, serving as a reference for researchers in other cities and countries who wish to address this issue but lack the advanced technology typically required for such studies.

This also coincides with the critical need to develop harmonized methods for studying microplastics in the air, which will enable the collection of comparable data and results, allowing inferences to be made about the regions in which this type of atmospheric microcontaminant study is conducted.

4. Conclusions

Microplastic pollution poses a significant threat to air quality, the sustainability of terrestrial, marine, and atmospheric ecosystems, and human health. This pollution menace is evident not only in densely populated urban areas with intensive anthropogenic activity but also in rural zones with lower populations and limited human activity, highlighting the pervasive nature of this environmental issue. This finding contradicts the common misconception that rural areas’ atmospheres are free from significant air pollution. Although MPs’ exposure is lower in rural environments, these regions are also polluted with MPs, and their air quality should be monitored with the same rigor as that in urban areas.

From the standpoint of atmospheric quality, this study offers compelling evidence supporting the urgent need for regulatory measures targeting microplastic emissions, as well as the development of tailored mitigation strategies to reduce their environmental and public health impacts, particularly in light of the current global environmental challenges exacerbated by the climate change crisis.

At the same time, the findings of this research represent pioneering data on the specific definition of exposure of city dwellers to microplastic air pollution. This initial information provides a clear justification and a starting point for more advanced studies aimed at establishing the toxicological effects of inhalation exposure to microplastics on human health with greater scientific rigor. This is particularly important given that the daily exposure to atmospheric microplastics has been demonstrated.

Finally, the results of this research provide critical information for future toxicological studies and reaffirm the importance of developing research projects with a comprehensive and integrative view of the study of microplastics in the environment, so that the dynamics of these pollutants in the compartments of the biosphere and in the organisms that inhabit them can be understood with greater precision.