Atmospheric deposition of anthropogenic microfibers in different indoor environments of Chennai, India

Microplastics, particularly microplastic fibers, are an emerging pollutant of growing concern, frequently detected in the atmosphere. However, recent studies emphasized the predominance of artificial and natural microfibers over microplastic fibers. Despite this, research focusing on all types of microfibers, commonly grouped as anthropogenic microfibers (MFs) remains limited, especially in residential indoor environments. Therefore, this study explored the indoor atmospheric deposition of microfibers, in the residential homes of Chennai, India, marking the first such study in the country. Additionally, workplaces, including offices, laboratories, and hostel rooms, were examined. Bedrooms (16,736±7,263 MFs/m²/day) and student hostels (5,572±2,898 MFs/m²/day) recorded the highest contamination in respective categories, and this could be attributed to the abundance of textile products, such as bedsheets, carpets, quilts, towels, and curtains in the indoors of both the rooms. MFs shorter than 500 µm dominated the samples, comprising 78.8 and 65.9 % of total MFs in residential and workplace categories, respectively. The diameter of MFs ranged from 2.02–23 µm in residential spaces and 2.04–36.4 µm in workplaces, indicating their potential to penetrate human lungs. µ-FTIR analysis revealed the predominance of semi-synthetic MFs (48.2 %), followed by natural (29.3%) and synthetic (22.5 %) MFs, underscoring the need to consider all categories of MFs. Further classification revealed rayon (94.5±6.40 %), cotton (68.1±6.12 %), and polyethylene terephthalate (PET) (48.1±11.5 %) as major MFs, indicating textiles as a significant contamination source. The detection of black rubber/latex MFs indicates additional contributions from road dust. Surface morphological analysis, correlations with environmental and meteorological factors, and backward trajectory analysis further highlighted the primary role of indoor/local sources in MFs contamination. Overall, the study emphasizes the need to monitor all categories of MFs and calls for comprehensive investigations into the impact of indoor textile products and road dust on indoor atmospheric contamination in future research.