Microplastic Transfer Pathways in Rural Household Environments Through Integrated Compartmental Analysis

Microplastic (MP) pollution is a serious environmental and public health concern. However, the mechanisms governing MP distribution and transport in rural household environments remain poorly understood. This study presents the first integrated compartmental analysis of MP transfer between outdoor and indoor matrices, including soil, indoor air (inlet and outlet), and reused cooking oil in households located in Karunya Nagar (10.938523°N, 76.743782°E), a rural area in India. Samples were selected based on waste mismanagement profiles and analyzed using Fourier transform infrared spectroscopy. High plastic loads detected in the soil samples consisted of polypropylene (PP, 38.21%), polyethylene terephthalate (PET, 32.85%), polyethylene (22.78%), and polystyrene (PS, 6.16%), likely originating from agricultural films, packaging, and burned household waste. Samples from the air inlet predominantly contained PP (41.72%) and PET (33.94%), suggesting resuspension from contaminated soil due to wind action. Substantial concentrations of PET (42.4%) and PS (25.4%) were detected in reused indoor cooking oil, representing increases of 29.1% and 14.2%, respectively, relative to the air inlet samples. This suggests sorption and thermal transfer during cooking processes in open containers. Increases of 9.4% PP and 0.27% PET in air outlet profiles provide evidence of re-aerosolization during heating and inefficient ventilation. Polymer aging and oxidative degradation were confirmed by spectral intensities at 1783.1 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>, 1161.15 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>, and 509.21 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>. These results reveal a continuous, cyclic pathway of MP entry, accumulation, and secondary emission within rural households, demonstrating an overlooked but critical exposure route that necessitates targeted waste management and health interventions.