The research team set out to answer a deceptively simple question: what exactly is floating in and settling out of the air inside the buildings where people work and live? To find out, they collected settled indoor dust from three contrasting urban microenvironments in Tiruchirappalli, a major city in the southern Indian state of Tamil Nadu. The sampling sites included an academic office, a residential dwelling located near a busy traffic corridor, and a second residence situated close to a small-scale industrial area with comparatively lighter traffic. By choosing locations that differed in both their surrounding land use and their internal activity patterns, the researchers could probe whether outdoor pollution sources or indoor behaviors dominate the microplastic burden that people actually breathe and swallow.

Identifying plastics at the microscopic scale requires more than a good magnifying glass. The team used micro-Fourier transform infrared spectroscopy, or µ-FTIR, a technique that shines infrared light on individual particles and reads the characteristic vibrational fingerprints of the chemical bonds within them. Because every polymer absorbs infrared radiation at a distinctive set of wavelengths, the method allows researchers to distinguish polyethylene terephthalate from nylon, polystyrene, polyethylene, polyurethane, and polyvinyl chloride with high confidence. This chemical specificity matters enormously for risk assessment, because different polymers carry different hazard profiles based on the monomers, additives, and residual catalysts they contain.

The polymer analysis revealed a familiar cast of characters. Polyethylene terephthalate, the plastic of beverage bottles and synthetic textiles; nylon, ubiquitous in carpets, clothing, and furnishings; polystyrene, common in packaging and disposable containers; and polyethylene, the world’s most produced plastic, all appeared consistently in the dust across all three sites. These findings align with what indoor air studies in cities from Tehran to Birmingham to Dhaka have reported, reinforcing the picture of indoor environments as reservoirs of plastic fragments shed from fabrics, furniture, packaging, and countless everyday objects that slowly degrade into inhalable and ingestible particles.

But the numbers told a more surprising story. Microplastic deposition differed significantly among the three sites, a difference confirmed statistically with a Kruskal-Wallis test yielding a p-value of 0.027. The academic office, designated Site A, recorded the highest mean deposition at 241 plus or minus 23 particles per square meter per day. The traffic-adjacent residence, Site C, came in second at 151 plus or minus 24 particles per square meter per day, while the residence near the small-scale industrial zone, Site B, showed by far the lowest deposition at just 54 plus or minus 3 particles per square meter per day. If outdoor sources were the primary driver, one might have expected the industrial-adjacent home to fare worst. Instead, the office dominated, suggesting that occupant activity, source diversity, and cleaning frequency inside a building can outweigh the industrial or traffic influences just beyond its walls.

Particle size added another layer of concern. The size distribution varied significantly among sites, with a p-value below 0.001, and the office again stood out for the wrong reasons. Particles at Site A averaged just 18.9 plus or minus 11.2 micrometers, markedly smaller than the 33 to 36 micrometer particles typical of the two residences. The authors attribute this to greater occupant activity, less frequent cleaning, and a wider diversity of plastic sources in the office environment. The size difference is toxicologically important: smaller particles can penetrate deeper into the respiratory tract, reaching the lower airways more readily, and they also remain suspended in air longer, increasing the chance of inhalation before they ever settle into dust. Children and infants, who play on floors and frequently bring hands to mouths, are considered especially vulnerable to ingesting dust-bound particles.

Perhaps the study’s most consequential finding concerns risk. When the researchers weighted their polymer identifications by hazard scores, drawing on established chemical-composition-based ranking frameworks for plastic polymers, the pattern of danger did not follow the pattern of abundance. Site A, the academic office, recorded the highest potential exposure risk associated with polyurethane and polyvinyl chloride, reaching 1,750 hazard units. Polyurethane appears in foams, coatings, and adhesives, while polyvinyl chloride is notorious for its additive suite, including plasticizers and stabilizers of toxicological concern. Site C, the traffic-side residence, registered a potential polyurethane-associated hazard ranking of 1,500 hazard units. Site B, the industrial-adjacent home, exhibited a negligible polymer-associated potential hazard score despite its proximity to industrial activity.

This inversion carries a blunt message: site classification based on outdoor environment, whether traffic-dominated or industrial-influenced, does not align with actual indoor exposure risk. A building next to a small factory can be safer to breathe in than an ordinary office, if the office harbors more hazardous polymers in its dust. The authors emphasize that mere particle counts cannot determine risk, and that a comprehensive understanding and characterization of indoor microplastic sources is essential for designing targeted mitigation strategies. Counting particles alone, in other words, tells only half the story; knowing whether that count is dominated by relatively benign polyethylene or by additive-laden PVC changes the entire risk calculus.

The study arrives amid a rapidly expanding global literature on airborne microplastics, which have now been documented in indoor air and dust across five megacities in China, in subway stations in Istanbul, in classrooms in Shiraz and Dhaka, in hospitals in India, and in homes from Pakistan to Barcelona. Researchers have also shown, using breathing thermal manikins, that humans inhale measurable quantities of indoor airborne microplastics under ordinary conditions, and that plastic particles can act as vectors, carrying adsorbed contaminants and associated microorganisms into the body. What the Tiruchirappalli study adds is a tropical savanna data point, a region and climate underrepresented in the existing literature, along with a methodological argument that hazard-weighted assessment should become standard practice in exposure studies.

For readers wondering what to do with this information, the findings point toward practical, source-focused interventions. Frequent and thorough cleaning, careful selection of furnishings and textiles, reduced use of plastic packaging indoors, and attention to ventilation all plausibly reduce the reservoir of settled particles that resuspension turns into breathable air. But the deeper lesson is structural. The plastic burden of indoor dust reflects the materials we choose to surround ourselves with, and the polymers that shed from foams, coatings, and synthetic fabrics can be more hazardous than their abundance suggests. As the authors conclude, understanding what the particles are made of, not merely how many there are, is the key to protecting the people who live and work among them.

Subject of Research: Microplastic contamination of indoor dust and associated human health risks in a tropical savanna urban environment

Article Title: Indoor exposure to microplastics in dust: polymeric composition and health risks in a tropical savanna climatic region

Article References: Sibhi M, R., Mohan V, L., & Passi, A. (2026). Indoor exposure to microplastics in dust: polymeric composition and health risks in a tropical savanna climatic region. Air Quality, Atmosphere & Health, 19(10), Article 210. https://doi.org/10.1007/s11869-026-02107-0

Image Credits: AI Generated

DOI: 10.1007/s11869-026-02107-0

Keywords: microplastics, indoor dust, polymer composition, µ-FTIR spectroscopy, inhalation exposure, polyurethane, polyvinyl chloride, PET, health risk assessment, Tiruchirappalli, tropical savanna climate, indoor air quality