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The global production of plastic has surged from a modest 2 million tons in 1950 to an astounding 460 million tons in 2019, with projections indicating a tripling of these levels by 2060. This dramatic increase is not just a testament to the versatility and utility of plastic but also a harbinger of environmental and health crises.
Plastic is comprised of over 10,000 chemicals, many of which are known carcinogens and endocrine disruptors. The widespread use of plastic has led to pervasive pollution, contaminating aquatic, terrestrial, and atmospheric environments globally. Atmospheric concentrations of plastic particles are rising, and studies have found that in the remote Eastern Alps of Austria, the contribution of micro- and nanoplastics (MNPs) to organic matter is comparable to levels found in urban areas.
The ocean is the final resting place for much of the world’s plastic. Plastic debris is found on the surface and in the depths of all oceans, including in polar sea ice. These plastics resist decomposition and can persist in the environment for decades, impacting marine life. Hundreds of marine species, including those consumed by humans, have been found to contain macro- and microplastic particles.
The fate of microplastic particles (MPs) larger than 10 micrometers and smaller nanoplastics (less than 10 micrometers) in aquatic environments remains poorly understood. However, their ability to cross biological barriers and potentially harm biological systems is particularly concerning.
Human Exposure to MNPs
MNPs come from various sources, including food, beverages, and food packaging. Water bottles are a significant source, with recent estimates indicating approximately 2.4 ± 1.3 × 10^5 particles per liter of bottled water, 90% of which are nanoplastics. This is two to three orders of magnitude higher than previously reported for larger MPs.
MNPs enter the human body primarily through ingestion and inhalation. Drinking liquids or eating food stored or heated in plastic containers, and using products like toothpaste containing MNPs, are common exposure routes. Infants are particularly at risk, with artificial milk prepared in polypropylene baby bottles exposing them to higher levels of MPs—ranging from 14,600 to 4,550,000 particles per capita per day.
MNPs in Biological Systems
The analysis of MNPs in biological systems is challenging due to the formation of hetero-aggregates with natural organic matter and the label-free, heterogeneous nature of environmental nanoplastics. Studies on murine models have shown significant effects on glucose metabolism, reproduction, oxidative stress, and lipid metabolism due to MNP exposure.
MNPs can enter the body through the digestive tract, respiratory tract, and skin contact. Humans could ingest between 0.1 to 5 grams of MNPs per week through various exposure routes.
Health Implications
A recent study on 257 patients with carotid atheromatous plaques suggested a potential link between MNPs and cardiovascular diseases. Polyvinyl chloride was detected in the carotid artery plaque in 58.4% of cases, with patients showing a higher risk of cardiovascular events.
A possible link between inflammatory bowel disease (IBD) and MPs has also been hypothesized. A study found higher fecal MP concentrations in IBD patients compared to healthy individuals, correlating with disease severity.
Future Research
The current evidence confirms the fragmentation of plastic beyond the micrometer level, with nanoplastics detected in real-world samples. Future research will focus on the accumulation of MNPs in human tissue over a lifetime and how their characteristics influence organs and tissues. Understanding the harm MNPs can cause, including effects on the immune system and microbiome, is crucial. As the Organization for Economic Cooperation and Development’s global policy forum on plastics states, “Plastic pollution is one of the great environmental challenges of the 21st century, causing wide-ranging damage to ecosystems and human health.”
