Invisible microplastics in homes and cars may be entering our lungs by the tens of thousands each day, underscoring a hidden risk of modern indoor life, suggest scientists from the Université de Toulouse in France.
In research published in PLOS One, the researchers quantified airborne microplastics in indoor environments (car cabins and homes) to assess inhalation exposure, concluding that the impacts may be far worse than we realise.
They found that indoor air contains significant concentrations of small microplastics, with car cabins showing median concentrations 2 238 MPs/m³, four times higher than homes (median 528 MPs/m³). However, this difference was not statistically significant (p=0.5) due to high variability.
Estimated adult inhalation of microplastics in the 1-10 µm range is around 68 000 ±40 000 particles per day, while children may inhale 47 000 ±28 000 particles daily, highlighting a potentially underestimated health risk.
Widespread
Higher human activity spiked microplastic levels dramatically, with one sample reaching 34 000 particles/m³ when two people were active in a room versus typical levels under 2 500.
Microplastics – plastic particles between 1 µm and 5 mm – have become widespread environmental pollutants, due to extensive plastic use and poor waste management, reports News-Medical.net.
They have been detected in outdoor and indoor air across diverse regions, from urban areas to remote locations.
Indoor air is of particular concern because its microplastic levels are eight times higher than outdoors, and people typically spend 90% of their time indoors, including about 5% in cars. Microplastics vary in size and composition, which affects how they interact with the respiratory system.
Particles smaller than 10 µm (PM10), especially those under 2.5 µm (PM2.5), can reach deep into the lungs and potentially cause inflammation, chronic respiratory conditions, or systemic effects by carrying additives and adsorbed toxins.
Despite the known presence of microplastics in indoor air, research has mostly focused on particles larger than 10–20 µm due to limitations in μFTIR spectroscopy. These methods miss smaller, inhalable microplastics.
Raman spectroscopy (detection limit: 1 µm) allows accurate analysis of these smaller particles.
In this study, the researchers used Raman analysis to quantify microplastics between 1–10 µm in residential and car cabin settings and estimate human exposure.
Analysing just 1 tiny square millimetre of each filter took a painstaking 14 hours due to the Raman microscope's detailed process, highlighting the intensive effort behind detecting these invisible pollutants.
The study examined airborne microplastics in three apartments and two cars, collecting air samples using vacuum pumps at human breathing heights (e.g., 1.6 m in living rooms, 0.5 m in bedrooms).
Twelve samples and four blanks were analysed (January-May 2023). Lower-volume samples (<3 m³ air) underwent sonication in methanol; higher-volume samples (3–10 m³) included calcium chloride density separation to remove inorganic material.
Particles were transferred to filters and analysed via automated Raman microscopy, with only 0.3% of each filter’s surface examined directly (results extrapolated to full surface area).
Quality assurance included positive controls (81% recovery rate for 10-27 µm polyethylene beads), contamination controls (18% blank contribution), and strict cleaning protocols.
Microplastic concentrations were blank- and recovery-corrected. Inhalation exposure was estimated using EU-recommended
breathing rates (adults: 16 m³/day; children: 11 m³/day).
Key findings
• Overall median indoor microplastic concentration: 1,877 MPs/m³
• Car cabins (median: 2,238 MPs/m³) exceeded homes (median: 528 MPs/m³), but variability was high (e.g., sample MP15 during high human activity: 34,404 MPs/m³)
• Polymer types differed: polyethylene dominated homes (76%); polyamide dominated cars (25%)
• 97% of microplastics were fragments (not fibres); 94% were inhalable (1–10 µm), after a power-law size distribution
• Adults may inhale 68 000 ±40 000 MPs/day (1–10 µm) and 3 200 ±2 900 MPs/day (10–300 µm), while children may inhale 47 000 ±28 000 MPs/day (1–10 µm). The larger particles contribute to gastrointestinal exposure via mucociliary clearance
• Consensus estimates (integrating prior studies) suggest higher indoor concentrations (4 300 MPs/m³ for 1–10 µm) than previously extrapolated from larger MPs
Concerns
The study shows that indoor airborne MPs <10 µm are more than 100 times more abundant than earlier estimates. Deep-lung penetration may raise concerns about systemic inflammation, oxidative stress, and endocrine disruption, though health implications require further study, noted the scientists.
The first car cabin measurements underscore vehicle interiors as exposure hotspots. Raman spectroscopy’s ability to detect particles ≥1 µm is a key strength, though limited sample size (n=12) and extrapolated nanoplastic estimates require further validation.
The authors recommend routine Raman-based MP monitoring and inclusion of inhalation exposure in epidemiological studies.
Study details
Human exposure to PM10 microplastics in indoor air
Nadiia Yakovenko, Lucía Pérez-Serrano, Théo Segur et al.
Published in PLOS One on 30 July 2025
Abstract
The ubiquitous presence of airborne microplastics (MPs) in different indoor environments prompts serious concerns about the degree to which we inhale these particles and their potential impact on human health. Previous studies have mostly targeted MP in the 20–200 µm size range, which are less likely to efficiently penetrate into the lungs. In this study, we specifically investigate airborne, indoor suspended MPs in the inhalable 1–10 µm (MP1–10 µm) range in residential and car cabin environments, by using Raman spectroscopy. The median concentration of total suspended indoor MPs for the residential environment was 528 MPs/m3 and 2,238 MPs/m3 in the car cabin environment. The predominant polymer type in the residential environment was polyethylene (PE), and polyamide (PA) in the car cabin environment. Fragments were the dominant shape for 97% of the analysed MPs, and 94% of MPs were smaller than 10 µm (MP1–10 µm), following a power size distribution law (the number of MP fragments increases exponentially as particle size decreases). We combine the new MP1–10 µm observations with published indoor MP data to derive a consensus indoor MP concentration distribution, which we use to estimate human adult indoor MP inhalation of 3,200 MPs/day for the 10–300 µm (MP10–300 µm) range, and 68,000 MPs/day for MP1–10 µm. The MP1–10 µm exposure estimates are 100-fold higher than previous estimates that were extrapolated from larger MP sizes, and suggest that the health impacts of MP inhalation may be more substantial than we realise.
PLOS One article – Human exposure to PM10 microplastics in indoor air (Open access)
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