Developed following the 19th century Industrial Revolution, plastics are synthetic or semi-synthetic polymers, categorised according to the chemical composition of their primary polymer and any side chains. These include acrylics, polyesters, silicones, polyethylenes (PE), polypropylenes (PP), polyurethanes, and halogenated plastics. Due to their many useful characteristics, including being lightweight, infinitely mouldable, low-cost to produce, chemically resistant, and easy to manufacture and transport, plastics are widely used in food packaging (e.g. containers, plastic bags), building products (e.g. pipes, vinyl cladding), electronics, and transport materials. The development of plastics has also revolutionised medicine, providing life-saving devices and enabling the availability of sterile, single use instruments and personal protective equipment.
However, the excessive use of plastics has created a throw-away culture, resulting in growing amounts of environmental pollution that resist degradation. Plastic degradation is a very slow process, with fragmentation and breakdown occurring via physical forces, ultraviolet (UV) radiation, temperature fluctuations, and biodegradation, potentially allowing plastics to persist in the environment for hundreds of years. The accumulation of synthetic plastic products disrupts habitats and threatens the health of wildlife and humans, representing one of the most urgent environmental challenges.
In 2023 alone, the world produced 400.3 million metric tonnes of plastic, with waste present in rivers and oceans, soil, air, and even glaciers. Between 4.8 and 12.7 million metric tonnes reach the oceans each year, contributing to 80% of the plastic pollution in the world’s seas.
Microplastics and nanoplastics
Microplastics (MP) are water-insoluble synthetic solid particles or polymer matrices, of either primary origin (originating directly from sources such as clothing or industrial nanoparticles) or secondary origin (resulting from the breakdown of larger plastic items), with regular or irregular shapes and sizes ranging from 1 μm to 5 mm.
Nanoplastics (NP) arise from the further breakdown of MP. The precise definition of nanoplastics remains debated. Some scholars define them as particles sized between 1 nm and 1,000 nm (or 1 μm), while others align with the European Commission’s definition of engineered nanomaterials (ENMs) – particles measuring 1 nm and 100 nm in at least one dimension.
Routes of exposition and uptake
MP and NP can enter the human body through two primary routes: ingestion (e.g. drinking liquids stored in plastic containers), and inhalation. A secondary route is direct skin contact (via cosmetics and personal care products such as facial scrubs). They have been detected in numerous human samples, including lungs, breast milk, liver, spleen, blood, sputum, colon, saliva, faces, urine, testes, and semen. More recently, MP have been identified in human placental tissue and meconium, demonstrating direct fetal exposure and raising concerns about developmental toxicity and long term health consequences for offspring.
In addition, MP possess a unique surface area that allows them to absorb contaminants, including microorganisms (bacteria, fungi, and viruses) and heavy metals.
Human exposure and potential consequences: What do we know?
It is estimated that an individual may be exposed to approximately 74,000-121,000 MP per year. As this estimate does not consider NP, total micro- and nanoplastics (MNP) exposure is likely considerably higher.
Research into MP and their health effects in humans is still in its infancy. A growing body of evidence, however, indicates adverse effects of MP exposure on living organisms. For example, these particles increase the susceptibility of fish and seabirds to infections. They have also been shown to accumulate in human tissues, including the womb, and to induce biological changes such as oxidative stress and inflammation in human cell lines. Exposure to MP has been associated with adverse cardiovascular and respiratory outcomes, metabolic disorders, gastrointestinal and reproductive effects, and cancer in humans.
Conclusion
Despite the expanding evidence linking MP to adverse health outcomes, limitations in the evidence base remain. Risk assessment studies are essential to understand the implications of these particles for human health; however, comprehensive assessments are still in early development. Given the emerging nature of this research, regulatory and policy responses are still being formulated. There is increasing awareness among policymakers of the need to address plastic pollution and its potential impact on human health.
There are clear opportunities for future research, including:
- Epidemiological studies and the standardization of analytical methods to investigate the health impacts of MP exposure.
- Investigation of other health outcomes potentially affected by MP exposure.
- Evaluation of the impact of MP exposure on susceptible populations due to developmental stage or other socio-environmental stressors.
Finally, research should focus on identifying and assessing strategies to mitigate or prevent exposure to these particles.
Sources :
- Blackburn K, Green D. The potential effects of microplastics on human health: What is known and what is unknown. Ambio 2022, 51:518–530.
- Chartres N. et al. Effects of Microplastic Exposure on Human Digestive, Reproductive, and Respiratory Health: A Rapid Systematic Review. Sci. Technol. 2024, 58, 22843-22864.
- Voelker R. What Are Microplastics? JAMA Published Online: February 19, 2026. doi:10.1001/jama.2025.25534
- Winiarska E. et al. The potential impact of nano- and microplastics on human health: Understanding human health risks. Environmental Research 251 (2024) 118535.
- Zurub RE et al. (2024) Microplastics exposure: implications for human fertility, pregnancy and child health. Front. Endocrinol. 14:1330396. doi: 10.3389/fendo.2023.1330396
