Latest research: Microplastics found in human carotid arteries! Will they increase the risk of heart disease and stroke?

Nowadays, plastic has become an indispensable material in our lives: shopping bags, food on supermarket shelves, kitchen appliances at home... and even in laboratories filled with various sophisticated instruments, you can see plastic.

At the same time, the idea that plastics are harmful to the human body has been circulating. Are they really that harmful?

Not long ago, a study in the New England Journal of Medicine revealed its possible impact on the human body: people with microplastics or nanoplastics in their carotid artery tissue are twice as likely to have a heart attack, stroke, or die from other causes in the next three years as those without microplastics or nanoplastics.

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Microplastics are invisible to the naked eye.

But it is common in the body

Microplastics are non-uniform plastic particles smaller than 5 mm. They often come from fibers such as nylon, polyester, and acrylic in textiles, or are formed by weathering and degradation of "large plastics" such as plastic bottles. If these microplastics are smaller than 1,000 nanometers, they have a new name: nanoplastics.

How small is it? If you divide the cross section of a hair into 1,000 equal parts, that's roughly the size of it. This is enough for them to pass through the digestive tract or lung tissue and enter the blood. These microplastics of all sizes also have a scientific name, collectively known as MNPs.

Over the past decade, multiple studies conducted around the world have confirmed that microplastics are widely present in the ocean, air, and terrestrial ecosystems, and that they can invade human tissues and organs, such as the stomach, lungs, liver, and placenta.

There are also studies that have verified that after they invade animals, they affect their heart function. So, do they also affect human cardiovascular function? In order to answer this question, a number of scholars from different universities and hospitals organized an experiment. They continued to track 300 patients with carotid artery stenosis to explore the relationship between the progression of the patients' diseases and microplastics.

The research process sounds a bit "bloody": surgeons open the patients' carotid arteries, dissect all the blood clots and plaques accumulated inside, and scholars then use the cut tissues for research. But don't worry, this is just a normal treatment plan.

Atherosclerosis refers to the process in which the originally elastic arterial walls become rigid, leading to lipid accumulation, fibrosis and calcium deposition, forming plaques that look a bit like yellow rice porridge at first glance. It is the most common cardiovascular disease and affects many large and medium arteries in the body. For such patients, doctors often perform carotid endarterectomy to remove the diseased tissue and restore the artery to normal.

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It can be said that this study is based on "waste utilization". The first conclusion of the study is surprising enough: 150 of the 257 patients were found to contain polyethylene, which is used to make plastic wrap, plastic bags and beverage containers in our daily lives. Among them, 31 patients were also found to contain polyvinyl chloride.

Will microplastics entering the human body lead to premature death?

After testing the patients for microplastics, the researchers followed up for three years and found that the probability of death from non-fatal myocardial infarction, non-fatal stroke, etc. in patients with plastics was very different from that in patients without microplastics.

Of the 150 patients with microplastics in their bodies, 30 died of non-fatal myocardial infarction and other causes, with a probability of 20%. Among the 107 patients without microplastics detected, 8 died of such causes, with a probability of about 7.5%. The proportion of the former is nearly three times that of the latter.

At first glance, this data is really scary. But if you carefully check the process of this study, you will find that it has many shortcomings, and the results cannot fully prove the causal relationship between microplastics and heart disease and stroke.

First, the authors acknowledged in the paper that the study did not control for some important variables, such as the patients’ exposure levels to PM2.5 and PM10, which are important risk factors for cardiovascular disease. No one can say for sure whether the patients who were found to have microplastics in their bodies had a higher mortality rate because they were exposed to more PM10.

Secondly, the population of this case study were all asymptomatic patients who underwent carotid endarterectomy. This limitation was too special, so the conclusion was not representative. Of course, this cannot be blamed on the research team. After all, the experiment still needs to pay attention to ethics. Only patients whose human tissues were removed due to surgical needs can be found, and patients cannot be forcibly harmed for scientific research.

In addition, there are many types of plastics, and the degree of penetration of each type of plastic in the human body is different. The fact that no microplastics were detected in atherosclerotic plaque tissue does not mean that there are no microplastics in the body. Some past studies have suggested that microplastics may exist in everyone's body, but the content is different.

Finally, there is one very important point. Over the years, the use of plastic products has been increasing, and the risk of exposure to microplastics has continued to increase. Even washing clothes in the washing machine several times may produce more microplastics. But overall, the incidence of cardiovascular disease in various places has continued to decline.

Do microplastics need to be avoided?

Let me give you the answer first: There is currently no research that can confirm its specific harm to the human body, but based on research on animals, it is still necessary to reduce the intake of microplastics.

In fact, since 2004, when scholars first proposed the concept of microplastics, various studies on whether microplastics will affect human health have been ongoing. Although scholars have found microplastics in human blood and organs in the past two years, their harm is difficult to verify.

Some scholars have adopted the most common method of scientific research: studying animals and found that animals with excessive microplastic content in their bodies are at greater risk of disease, but this still cannot be applied to humans. After all, compared with humans, these animals living in nature are relatively small in size and are more likely to be affected by plastic waste in the long term. Some studies believe that the current level of microplastics ingested by the human body is still at a safe level.

But this still reminds us: when the intake of microplastics reaches a certain proportion, the impact on the body may change from quantitative change to qualitative change. In order to minimize the intake of microplastics, we can reduce direct contact with plastic products in our daily lives, such as using less plastic bags to pack cooked food, using less plastic straws when drinking milk tea, and reducing the intake of seafood offal.

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References

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Reviewer: Tang Qin, Director and Researcher of the Science Popularization Department of the Chinese Medical Association