Exploration of microplastic concentration in indoor and outdoor air samples: Morphological, polymeric, and elemental analysis

Khadija Sharaf Din; Muhammad Fahim Khokhar; Shahid Ikramullah Butt; Abdul Qadir; Farhan Younas

doi:10.1016/j.scitotenv.2023.168398

Exploration of microplastic concentration in indoor and outdoor air samples: Morphological, polymeric, and elemental analysis

Sci Total Environ. 2024 Jan 15:908:168398. doi: 10.1016/j.scitotenv.2023.168398. Epub 2023 Nov 11.

Authors

Khadija Sharaf Din¹, Muhammad Fahim Khokhar², Shahid Ikramullah Butt³, Abdul Qadir⁴, Farhan Younas⁵

Affiliations

¹ Institute of Environmental Sciences and Engineering (IESE), SCEE, National University of Sciences and Technology, Islamabad 44000, Pakistan.
² Institute of Environmental Sciences and Engineering (IESE), SCEE, National University of Sciences and Technology, Islamabad 44000, Pakistan. Electronic address: fahim.khokhar@iese.nust.edu.pk.
³ Department of design and manufacturing Engineering (DME), SMME, National University of Sciences and Technology, Islamabad 44000, Pakistan.
⁴ College of Earth and Environmental Sciences, University of the Punjab, Lahore 54000, Pakistan.
⁵ Center for Interdisciplinary Research in Basic Science (CIRBS), Faculty of Sciences, International Islamic University, Islamabad 44000, Pakistan.

PMID: 37952657
DOI: 10.1016/j.scitotenv.2023.168398

Abstract

Microplastics are ubiquitously pervasive throughout the environment, but unlike aquatic and terrestrial microplastics, airborne microplastics have received less scientific attention. This study is the first of its kind to explicitly examine microplastics in the indoor and outdoor air (PM_2.5) samples collected using active air samplers in Islamabad, Pakistan. The suspected synthetic particles were analyzed using ATR-FTIR, μ-Raman and SEM-EDX to categorize them based on their morphological characteristics, polymeric composition, and elemental makeup. Microplastics were found in all indoor and outdoor air samples, with indoor air samples (4.34 ± 1.93 items/m³) being significantly more contaminated than outdoor air samples (0.93 ± 0.32 items/m³) (P < 0.001). Among all the indoor air samples, samples taken from classroom (6.12 ± 0.51 items/m³) were more contaminated than samples taken from hallway (4.94 ± 0.78 items/m³) and laboratory (1.96 ± 0.44 items/m³). Fibers were found to be the prevalent shape type in indoor and outdoor airborne microplastics followed by fragments. Transparent- and black colored microplastic particles were predominant in both indoor and outdoor air samples. According to ATR-FTIR analysis, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), and polystyrene (PS) were the most prevalent polymer types in both indoor and outdoor environments. Results from μ-Raman analysis corroborated the presence of the polymers identified by ATR-FTIR. Morphological analysis of particles by SEM indicated signs of weathering on particles' surface i.e., grooves, breaks, shredded edges, pits etc. SEM-EDX of randomly chosen particles unraveled the presence of C and O as core elements, along with the presence of heavy metals at some spots due to foreign material adhering to their surface. Correlation analysis of environmental factors i.e., PM_2.5, relative humidity, temperature, and wind speed with MPs abundance revealed non-significant relationships. The findings of this study call for further research on airborne MPs to better comprehend their dispersion, toxicity, interactions with other air pollutants, and attributable health risks.

Keywords: ATR-FTIR; Airborne microplastics; Particulate matter (PM(2.5)); Raman spectroscopy; SEM-EDX; Synthetic particles.