How micro- and nanoplastics may worsen non-communicable diseases

In a recent study published in Cell Reports Medicine, researchers review and assess the potential exacerbation of non-communicable diseases (NCDs) by micro- and nanoplastics (MnPs) through their impact on inflammation and disease mechanisms.

Study: The potential of micro- and nanoplastics to exacerbate the health impacts and global burden of non-communicable diseases. Image Credit: chaiyapruek youprasert / Shutterstock.com

What causes NCDs?

The global incidence of NCDs, such as cardiovascular diseases, cancers, diabetes, and chronic lung diseases, is rising. Current estimates indicate that NCDs are responsible for about 71% of annual deaths and will be responsible for an economic burden exceeding $30 trillion USD over the next two decades.

Environmental pollution exacerbates NCD burden, with MnPs now ubiquitous throughout nature. Despite their prevalence in lungs, blood, breast milk, placenta, and stool samples, the health risks of MnP exposure remain unclear due to the lack of standardized protocols and mechanistic understanding. Thus, further research is needed to accurately assess the health risks of MnP exposure and their potential role in exacerbating NCDs.

Human exposure to MnPs

Environmental prevalence of MnPs

Since the 1950s, many studies have indicated a significant rise in MnP concentrations in the environment, reflecting the increase in the production, use, and disposal of plastics worldwide. Plastics are integral to daily life, thus leading to widespread exposure and potential health risks. MnP toxicity, like other pollutants such as soot and lead, is linked to exposure and dosage.

Routes of MnP exposure

Humans encounter MnPs through various pathways, including outdoor air, indoor environments, food, water, and even cosmetics. Direct sources include MnPs in food and beverages, inhalation of particles from local emissions, and household items like plastic clothing and furniture. Indirect sources include contamination from fertilizers, soil, and atmospheric deposition, which can lead to MnP uptake in food crops.

Inhalation of MnPs

MnP inhalation has been confirmed by several studies identifying the presence of MnPs in human lungs, with polypropylene and polyethylene terephthalate fibers being the most common. These particles can induce cytotoxicity, inflammation, and oxidative stress in the lungs.

Human exposure to airborne MnPs varies by location, with higher concentrations present in urban areas. Indoor air often contains higher MnP levels than outdoor air, primarily from household sources like carpets and furnishings.

Ingestion of MnPs

MnPs have been found in human feces, indicating ingestion and entry into the gastrointestinal (GI) tract. Infants exhibit higher MnP concentrations due to exposure to plastics in food preparation and storage. Furthermore, MnPs have been found in breast milk and formula, highlighting exposure from early life.

MnPs are also present in various foods and beverages, including seafood, salad, salt, and bottled water. Previous studies suggest that food preparation and packaging also contribute to MnP exposure.

MnP material properties and health risks

MnP properties such as size, shape, and surface conditions influence human health risks. While larger particles are less likely to penetrate biological barriers, smaller particles can enter the bloodstream and other tissues, potentially causing inflammation and oxidative stress.

MnPs have been detected in human blood, stool, placenta, and breast milk, thus indicating systemic circulation. However, understanding of retention and egestion rates in the human body remains limited.

Potential impacts of MnPs on NCDs

MnP exposure can exacerbate symptoms of NCDs like inflammation, oxidative stress, and cell damage. Initial evidence links MnPs to inflammation in the GI tract and respiratory system, which can potentially worsen conditions like Crohn’s disease and chronic obstructive pulmonary disease (COPD), respectively.

MnPs may also disrupt tight junctions in epithelial membranes, thereby increasing permeability and facilitating further MnP uptake. This cycle can aggravate pre-existing NCDs and contribute to new health issues.

Pre-existing NCDs can increase MnP uptake due to inflammation and dysregulation of epithelial barriers. This can lead to further translocation of MnPs throughout the body, thereby exacerbating health impacts. For example, colon and liver inflammation from MnP exposure has been linked to insulin resistance in mice, which suggests similar risks in humans.

Health risks from MnP leachates

In addition to their physical effects, MnPs exposure is also associated with chemical risks through their leachates, which include harmful substances like bisphenols and phthalates. These chemicals can cause endocrine disruption, reproductive issues, and cancer. MnPs can also act as carriers for environmental contaminants and subsequently introduce additional health risks upon entering the body.

Future directions

A transdisciplinary one-health approach that integrates ecology, chemistry, biology, and other fields is essential to study MnP transport, fate, dose-response effects, as well as particle and leachate mechanisms. Improved analytical methods, such as micro Raman (μRaman) spectroscopy and mass spectrometry, are also needed to detect smaller MnPs in the environment and human tissues.

Additionally, the utilization of advanced models like organ-on-a-chip and three-dimensional (3D) cell culture can elucidate MnP interactions with human tissues. The insights provided by these studies have the potential to guide risk assessments and interventions to understand MnP impacts on NCDs.

Conclusions 

There remains an urgent need for the systematic investigation of MnP impacts on NCD prevalence and severity. Understanding the links between MnP exposure and NCDs is crucial, especially in low-income countries, to designing effective risk reduction strategies and mitigating global health burdens. Taken together, these efforts will align with the United Nations (UN) Sustainable Development Goal Target 3.4 to reduce premature mortality from NCDs.