A first-of-its-kind study reveals that classroom air carries more microplastics than outdoor air, raising urgent questions about children’s daily exposure to hidden pollutants.
Study: Airborne microplastics and plastic additives in a school environment: identification, quantification, and associated inhalation risks. Image Credit: Drazen Zigic / Shutterstock
In a recent study published in the journal Environment International, researchers from Spain and Portugal investigated the content of circulating air in four classrooms in Portugal to identify microplastics (MPs) and other potential chemical contaminants present in this air. Notably, the school in Estarreja, Portugal, was situated near an industrial complex that manufactures polyvinyl chloride (PVC), a likely contributor, as suggested by wind-direction analyses, rather than a validated source.
The study leveraged cutting-edge analytical techniques (pyrolysis–gas chromatography coupled to Orbitrap-mass spectrometry (Pyr-GC-Orbitrap-MS) to investigate the presence and concentration of 10 common polymers. Study findings revealed that six of these polymers (polymethyl methacrylate, polypropylene, nylon-6,6, nitrile butadiene rubber, polystyrene, and polyvinyl chloride) were present in the classroom PM₁₀ samples. Additionally, phthalates, nicotine, and pesticides were identified through non-targeted screening; however, their levels were not quantified under the pyrolysis conditions.
Most alarmingly, average concentrations of MPs were substantially higher inside the classrooms (21.8 ± 16.3 ng/m³, n = 35) than outdoors (13.4 ± 13.6 ng/m³, n = 36). Together, these findings paint a concerning picture of the complex airborne exposures children face in educational settings, highlighting the necessity of routine air quality monitoring and prompting future research aimed at mitigating these pollutants.
Background
Microplastics (MPs) are a term used to describe minute plastic particles less than 5 millimeters in size. A growing body of research highlights the increasingly severe threat posed by these ubiquitous pollutants, which have even been detected at the summit of Mt. Everest and the deepest point of the Mariana Trench. While much attention has focused on MPs and their impacts on oceans and food, a relatively nascent body of research aims to investigate their prevalence in the air we breathe, with few prior studies measuring indoor PM₁₀ microplastics in schools.
Studies have demonstrated that MPs suspended in circulating air can be inhaled and may reach deep into the respiratory system, with experimental and observational evidence of inflammatory responses. Children with underdeveloped immune and respiratory systems have been identified as a high-risk cohort for exposure to air-suspended MP. Children are known to breathe more air relative to their body weight than adults, resulting in a higher potential exposure to airborne pollutants.
Unfortunately, the air quality and potential contaminant load of school classrooms, locations where children spend a substantial portion of their childhood, remain poorly characterized.
About the study
The present study addressed this knowledge gap by conducting an in-depth air quality analysis at a primary school in Estarreja, Portugal, a first-of-its-kind study. The school's location is significant to the study's design, as it sits just one kilometer from a large industrial complex that has been producing polyvinyl chloride (PVC) and other potentially toxic airborne chemicals for decades.
The study aimed to identify and quantify the types of airborne microplastics (or chemical pollutants) present in the classroom air and to estimate the daily inhalation doses to which students are exposed. Study data was collected over two campaigns (winter and spring) and comprised 70 air samples from four different classrooms (students ages 3-11) and the adjacent outdoor schoolyard.
Experimental procedures involved characterizing breathable particulate matter (PM₁₀) by leveraging Pyrolysis-Gas Chromatography-Orbitrap Mass Spectrometry (Pyr-GC-Orbitrap-MS) and Regions of Interest-Multivariate Curve Resolution-Alternating least squares (ROIMCR) to estimate the presence and concentrations of MPs and chemical contaminants, respectively.
Study findings
Study analyses confirmed the presence of six (polymethyl methacrylate, polypropylene, nylon-6,6, nitrile butadiene rubber, polystyrene, and polyvinyl chloride) out of the ten targeted MPs, and several plastic-related chemical additives (seven different types of phthalates, nicotine, and pesticides such as propoxur) in the PM₁₀ samples evaluated. Of these, nitrile butadiene rubber (NBR) was found to be the most prevalent, while polystyrene (PS) showed the highest detection frequency.
Alarming, MP concentrations were found to be significantly higher in classrooms than outdoors, with measurements of 21.8 ng/m³ inside compared to 13.4 ng/m³ outside (p = 0.010). Concentrations were also observed to be higher during the spring campaign than in winter, likely due to warmer, more humid conditions, which have previously been shown to accelerate the fragmentation of plastic materials.
Computations leveraging MP measurements revealed that children, on average, are exposed to ~1.57 nanograms of plastic per kilogram of body weight per day, with the highest exposure documented in the first-grade classroom (ages 6-7). The authors noted that this estimate is conservative, as it is based on PM₁₀, which also contains non-respirable fractions.
Conclusions
Polystyrene never left the room: Unlike other plastics, polystyrene was detected in every single indoor sample, making it the most consistent pollutant in the school air.
As the first study of its kind, the present research provides a uniquely detailed snapshot of the air quality inside a school, demonstrating that children are continuously exposed to a complex cocktail of multiple types of microplastics and their associated chemical additives.
These findings underscore the importance of conducting frequent and in-depth air quality monitoring and management, particularly in settings such as schools that cater to high-risk sub-adult populations. While the long-term health effects of inhaling this complex mixture are still being investigated, this study provides a crucial baseline and a stark reminder that the threats posed by plastic pollution extend beyond our oceans to the very air our children breathe.
Journal reference:
- Torres-Agullo, A., Karanasiou, A., Charres, I., Alves, C., & Lacorte, S. (2025). Airborne microplastics and plastic additives in a school environment: identification, quantification, and associated inhalation risks. Environment International, 203, 109753. DOI – 10.1016/j.envint.2025.109753, https://www.sciencedirect.com/science/article/pii/S0160412025005045