A review on decoding the cellular and ecological risks of polypropylene microplastics

Polypropylene (PP), which is widely used in packaging, medical devices, and consumer goods, has raised growing concerns owing to its persistence and toxicological impacts. PP feeding bottles can release up to 16.2 million microplastic particles per litre during sterilization and heating, with the estimated infant intake reaching 1.58 million particles daily (range: 14,600–4,550,000). Food containers contribute 0.042–0.14 additional items/kg body weight per day. More recently, pharmaceutical injections packaged in PP bottles were shown to contain 6 × 10⁴–1 × 10⁷ particles/mL (0.02–100 µm), confirming medical contamination. Biologically, polypropylene microplastics (PPMPs) are not inert. Chronic exposure via ingestion, inhalation, or dermal contact disrupts cellular homeostasis, inducing oxidative stress, mitochondrial dysfunction, inflammatory signalling, and premature senescence. Organ-level consequences include gastrointestinal inflammation, hepatic oxidative stress, and pulmonary responses, which may contribute to metabolic disorders, immune dysregulation, and even carcinogenic pathways. Additive leaching, including plasticizers and stabilizers, further amplifies health risks, with infants and children disproportionately affected by higher relative intake. Environmentally, PPMPs persist because of their buoyancy, low density, and resistance to biodegradation, facilitating dispersal in soil and aquatic systems. In marine food webs, they are ingested by plankton, bivalves, and fish, leading to bioaccumulation, trophic transfer, and impaired feeding, growth, and reproduction. PPMPs also act as vectors for heavy metals and organic pollutants, intensifying ecological risks. This review highlights the dual threat posed by PPMPs and suggests the importance of new studies to establish safer alternatives and promote sustainable and healthier practices.