From Bakelite to Biohazard: The Century-Long Rise of Microplastics.

The invention of Bakelite in 1907 marked the dawn of the synthetic polymer era, leading to exponential plastic production and widespread microplastic (MP) pollution. MPs (<5 mm) now permeate ecosystems and human tissues, and emerging evidence suggests that they may pose health risks ranging from reproductive to cardiovascular effects. This narrative review aims to connect the historical growth of plastic production, the environmental spread of micro- and nanoplastics, evidence on human health effects, the development of candidate safer polymers, and the main policy responses. The specific objective is to identify key points for prevention, gaps in the evidence base, and priorities for future research and policy intervention. A targeted literature search was conducted to identify studies on plastic production, micro- and nanoplastic pollution, human exposure and health effects, and policy responses. Literature was sourced from PubMed, Scopus, and Web of Science for articles published between January 1, 2010, and June 30, 2025, using combinations of the terms "microplastics," "nanoplastics," "plastic pollution," "polymer production," "human exposure," "health effects," and "policy responses." Major reports from UNEP and WHO were also reviewed. Eligible were peer‑reviewed, English‑language articles reporting primary environmental or human health data, quantitative syntheses, or policy analysis relevant to human exposure/outcomes. We excluded non‑human studies without clear human relevance, conference abstracts, non‑English publications, and non‑seminal work before 2010. Screening yielded 250 records; 162 met criteria for narrative synthesis. Due to heterogeneity in designs, exposure metrics, and outcomes, no risk-of-bias assessment or meta-analysis was conducted. Quantitative findings are summarized descriptively with effect sizes and confidence intervals when available. Global plastic production increased from about 2 million metric tons in 1950 to more than 450 million metric tons by 2018, while only 9-20% of plastic waste underwent recycling. Most waste entered landfills, incinerators, or the environment. Mismanaged waste adds an estimated 4.8 to 12.7 million metric tons of plastic to the oceans each year, where larger items fragment into MPs and nanoplastics that persist, accumulate across food webs, and carry co-pollutants. Human studies now detect these particles in blood, placenta, lung tissue, and atherosclerotic plaques, and one cohort reported higher rates of myocardial infarction, stroke, or death among patients whose carotid plaques contained MPs or nanoplastics. Additional evidence links exposure with endocrine disruption and reduced sperm quality, yet effect sizes vary, and most data remain observational, which underscores the need for longitudinal and mechanistic research that defines causal pathways from particle characteristics and dosimetry to specific health outcomes. The available evidence indicates that historical decisions about polymer design and plastic production now drive widespread micro- and nanoplastic exposure with plausible cardiovascular, endocrine, and reproductive consequences, although causal pathways remain incompletely defined. Coordinated action that aligns safer polymer design, exposure reduction, longitudinal health research, and binding international policy will be necessary to curb micro- and nanoplastic contamination and to protect human health.