Vascular effects of micro- and nanoplastics in humans: Systematic review

Plastics have been accumulating in the environment for over 100 years and are environmental pollutants already recognized as relevant risk factors for human health, including the cardiovascular system. Plastics break down into smaller particles called microplastics (with diameters ranging from 1 micrometer to 5 millimeters) and nanoplastics (with diameters smaller than 1 micrometer), which are resistant to natural degradation. Micro- and nanoplastics (MNPs) enter the human body through ingestion, inhalation, dermal penetration, injection, and implantation. MNPs are heterogeneous in their origins, chemical compositions, and structures. Their toxicity varies according to the type of plastic (most prevalent polymers being polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and polyvinyl chloride), the plastic micro-additives like bisphenols and phthalates, the size of the particles, the other non-organic and organic substances, which they transfer (heavy metals, polycyclic aromatic hydrocarbons, bacteria, viruses, antibiotics), etc. In this review, we will focus on the known vascular effects of these particles - on the coronary arteries, visceral arteries and peripheral arteries, and the methods of MNPs detection. We will also discuss their penetration pathways, measures to reduce exposure, the role of a healthy gut microbiome in the absorption of these particles, investigational approaches to reducing damage, and new biodegradable alternatives (e.g., polyhydroxyalkanoates). Additionally, we will discuss the existing scientific evidence, particularly from the Bulgarian database. Finally, we will discuss the major knowledge gaps involving MNPs clinical research. Current evidence of vascular toxicity in humans is still with limited mechanistic validation.