Indoor dust in 600 public buildings in Kerala carries microplastics and chemical additives
Researchers at the Central University of Kerala measured a mean flux of 2,455.6 microplastic particles per m² per day, with plasticizers and other contaminants detected alongside.
A survey of 600 non-residential indoor spaces in the Kasaragod and Kannur districts of northern Kerala, India, found microplastics and emerging chemical contaminants in settled dust. The work, by the Environmental Monitoring and Assessment Research Group at the Central University of Kerala, was published in Frontiers in Nutrition. The mean microplastic deposition flux was 2,455.6 ± 1,290.4 particles per m² per day, with values from 616 to 4,902 frontiersin.org
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Sampling and analysis
The spaces fell into ten facility types: supermarkets, hospitals, textile shops, banks, restaurants, post offices, panchayath administrative offices, footwear stores, gyms and salons. Sixty establishments were sampled in each type, spread across pre-monsoon, monsoon and post-monsoon periods. Dust was collected passively for ten days in glass Petri dishes 11 cm in diameter, with a collection area of 0.0095 m².
Particle shape was examined by stereomicroscopy and polymer type by Raman spectroscopy. Chemical contaminants were screened by gas chromatography–tandem mass spectrometry (GC–MS/MS). The authors omitted chemical digestion and density-separation salts to avoid degrading fragile polymers, and used procedural blanks to control contamination.
Results
Supermarkets had the highest mean flux, 2,981.8 ± 1,201.9 particles per m² per day. Salons (2,117.8) and gyms (2,098.4) had the lowest means. Flux rose with intensive human activity and material use frontiersin.org
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Seasonal differences were significant (Kruskal-Wallis H = 93.51, p < 0.001). The mean flux was 1,742.57 in the pre-monsoon period, 2,937.80 in the monsoon and 2,686.58 in the post-monsoon period.
Fibres were the dominant shape, about 56.92% of particles, followed by fragments at 31.67% and pellets. Raman analysis identified polyethylene, polystyrene, polyester, polymethacrylates and polyhaloolefins. The authors attribute fibres to shedding from synthetic garments, upholstery, carpets and curtains.
The screening also detected plasticizers, personal care product residues, hydrocarbons and aromatic compounds. Statistical analysis showed a strong positive association between microplastic flux and the occurrence of these contaminants, and principal component analysis showed co-occurrence patterns between them frontiersin.org
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The authors describe non-residential indoor dust as a potential route of simultaneous exposure through hand-to-mouth transfer and deposition onto food and food-contact surfaces.
