A preliminary study on the natural aging behavior of microplastics in indoor and outdoor environments

The aging of microplastics (MPs) due to environmental abiotic effects in diverse habitats, which might negatively affect the environment and human health, is a rising issue. The major concern is the release of additives and plasticizers and their fragmentation into nanoplastics which are more harmful due to their larger surface area. The virgin MPs (low-density polyethylene, polyethylene, polystyrene, polyethylene terephthalate, high-density polyethylene, and polypropylene) were kept for natural aging in indoor and outdoor environments for one year. They showed morphological changes like racks, broken edges, ridges, grooves, and rough and uneven surfaces. It was also discovered that MPs had lost weight. The highest weight reduction in outdoor MPs was recorded in polypropylene (18.52%), with the least weight loss in polyethylene (0.69%). The highest weight loss in indoor MPs was seen in low-density polyethylene (6.54%), while the lowest was for polyethylene terephthalate (0.04%). Change in the chemical composition in these virgin MPs also showed the formation of additional peaks or the disappearance of some main peaks, like in high-density polyethylene additional peak was found at 2345.44 cm−1. In polystyrene, CH bending peak, CH2 bending peak, aromatic ring stretching peak, C–H stretching at 2847 cm−1, and aromatic C–H stretching were not seen. In polypropylene, the CH2 twisting and rocking peaks were not found. In polyethylene, the additional peak was found at 871.82 cm−1. The morphological and chemical alterations in the MPs can enhance the possibility of bioaccumulation, alter their capacity to adsorb chemicals and make them more harmful.