Microplastics Pose Risks to Lungs

When Laura Sadofsky, PhD, a senior lecturer in Respiratory Medicine at the University of Hull, Hull, England, began looking at the effects of microplastic exposure on respiratory health 6 years ago, there were few scientific papers in the literature. “There was very little known about microplastics in the air we breathe,” she told Medscape Medical News. “Now, there’s a huge amount of work being done, and it’s all important data that we need to collect and learn from.”

Microplastics are tiny plastic particles created when larger plastic items degrade over time due to environmental factors such as ultraviolet radiation, wind, and friction. As these larger plastics disintegrate, they produce particles small enough to be inhaled.

Contrary to what most people think, we might breathe as much microplastic as we drink or eat. “Air is at least an equal source of microplastics into the human body than water,” said Chris Carlsten, MD, director of the Centre for Lung Health and professor and head of the Respiratory Medicine Division at The University of British Columbia, Vancouver, British Columbia, Canada, at European Respiratory Society (ERS) 2024 Congress, held in Vienna in September.

Now, researchers are trying to understand how microplastics in our airways might affect respiratory health.

The Health Risks of Breathing Plastic

In the 1990s, researchers found that workers at a plant in Rhode Island producing flocks (synthetic fibers used for padding, insulation, or creating textures) inhaled these fibers in large amounts, leading to health issues like bronchiolitis and hypersensitivity pneumonitis. Gwenda Vasse, PhD, a postdoctoral researcher at the University of Groningen, Groningen, the Netherlands, said we have known for a while that high concentrations of microplastics can cause lung disease. But we still don’t know to what extent typical levels of microplastics can be harmful.

The first description of airborne microplastics was reported in 2016, using atmospheric precipitation from Paris. Other studies have now confirmed the presence of these pollutants in the atmosphere. They are more abundant in indoor environments, where people spend the majority of their time than outside. They are also more common in highly populated cities than in rural places.

Only 2 years ago, researchers demonstrated that microplastics we inhale can reach the deepest regions of the human respiratory system, based on samples from bronchoalveolar lavage and lung biopsies. “Microplastics have likely been present in the air we breathe for a long time, but we have only recently become aware of their existence,” Carlos Baeza-Martínez, MD, a pulmonology specialist at the Hospital General Universitari d’Elx, Alicante, Spain, and one of the authors of the study told Medscape Medical News. “Perhaps it was difficult to imagine. It is almost sinister to think that we are breathing plastic.”

However, researchers don’t yet fully understand the consequences of microplastic inhalation on respiratory health.

Most available information comes from in vitro and animal studies. These studies have shown that when plastic comes into contact with the bronchial epithelium, it promotes the release of reactive oxygen species and cytokines, triggering a local inflammatory response. Chronic oxidative stress can lead to the loss of alveolar units, contributing to the development of pulmonary diseases. Another observed effect is the disruption of cellular metabolism, which impairs cell proliferation and hampers regeneration after damage.

Microplastics have also been found to cause DNA damage and promote genetic mutations, increasing the risk for neoplasms. They can alter the immune function of the respiratory system, reducing its ability to eliminate pathogenic microorganisms.

Evidence of the link between microplastics in the airways and human disease has also begun to emerge. Baeza-Martínez and his colleagues have observed that patients with higher concentrations of microplastics in their airways tended to show more lung lesions on chest CT scans, such as nodules or masses. They also had a higher concentration of harmful bacteria, which could indicate that microplastic inhalation plays an important role in the development and severity of some respiratory infections. This could happen by delivering these germs deeper into the airways or promoting their growth within the lungs. “We know that plastic is a good surface for bacteria and other microorganism to attach and grow,” Sadofsky said.

Vasse explained that not just the plastic itself but also the numerous chemicals, such as phthalates and bisphenol A, used to modify the material’s properties, cause concern. “In our study, we have seen that an unknown compound leaching from nylon microplastics is responsible for the detrimental effect on airway organoid formation,” she said.

Microplastics can also carry other substances they have absorbed from their surroundings, including polycyclic aromatic hydrocarbons, heavy metals, and antibiotics.

Complex Challenges in Microplastic Research

Studying the effects of microplastics on respiratory health is challenging, Vesse explained. First, individual exposure levels are difficult to determine. The mixtures of plastics each of us are exposed to also vary. “We don’t know exactly how much microplastic we are exposed to on a daily basis in a normal situation. Or how much actually reaches deep in our lungs,” she said.

Other factors, like smoking, can increase the amount of microplastic people are exposed to. In one study led by Baeza-Martínez, researchers observed that smokers have significantly higher concentrations of microplastics in their respiratory airways than nonsmokers or even those who have quit smoking. They found that rayon, a plastic commonly used in cigarette filters, was the most frequently found in smokers’ lungs.

The heterogeneous nature of microplastics complicates research further. Different sizes and shapes determine how deep in the lungs microplastics travel. For example, fibers have a greater capacity to infiltrate the respiratory system and are more challenging for the body’s defense mechanisms to eliminate than spherical or other-shaped particles, Baeza-Martínez explained. “In our studies, the vast majority of microplastics identified in the airways of our patients were fiber-shaped,” he said. His team also observed significantly higher concentrations of these microplastics in people older than 60 years than in younger people. This could indicate an accumulative effect over a person’s lifetime and suggest that fiber-shaped microplastics may persist in the respiratory system for extended periods.

There is also a need for comprehensive comparative data, as most studies focus on specific types of plastic rather than examining multiple types simultaneously, limiting the ability to draw broader conclusions about their health impacts.

What’s Next?

Plastic is an incredibly versatile material that has significantly improved human life over the past century, said Baeza-Martínez. “The problem likely lies in our indiscriminate use of these materials and poor waste management, which has turned plastic and microplastic pollution into one of the most pressing environmental and, likely, health challenges we face in the current era.”

Projections indicate that global plastic production will continue to rise sharply in the coming decades, increasing human exposure to microplastics. In response, the United Nations Environment Assembly 2022 pledged to create a legally binding framework to combat plastic pollution, while countries like the United States, Canada, and members of the EU have banned microbeads in cosmetics and other products.

Carlsten advocated for air filtration systems in buildings and vehicles and called for improved methods to assess individual microplastic exposure and their health impacts.

“There’s been a lot of work done in this area every week,” said Sadofsky. “But there’s still a lot of work to be done.”

Sadofsky, Carlsten, Vasse, and Baeza-Martíne reported no relevant financial relationships.

Manuela Callari is a freelance science journalist specializing in human and planetary health. Her words have been published in The Medical Republic, Rare Disease Advisor, The Guardian, MIT Technology Review, and others.