In 2017, the world produced over 300 million tons of plastic. The material only breaks down into microplastics, pieces so small—less than 5 millimeters in size—that they can be transported by air, present in the ocean floor, or end up in the food chain.
Until recently, some researchers argued that ingested microplastics posed no harm since they were passing through the body and coming out in the stool. However, two studies published this year in Environment International and Science of The Total Environment respectively, found microplastics in human blood and living lung tissues for the first time.
The authors of the blood study reported that the mean of the sum concentrations of plastic particles they found was 1.6 micrograms of total plastic particles per milliliter of blood sample. Meanwhile, the lung tissue study detected microplastics within all regions of the lungs. Both studies found polyethylene terephthalate (PET) in their samples. A 2021 study published in the Journal of Hazardous Materials previously found the presence of microplastics in human lung tissues obtained from autopsies.
The results of the recent lung tissue study provide information about the size and composition of microplastics retained in the lung and where they can be found, which is useful in determining the extent of their impacts on human health, says Mark E. Hahn, senior scientist at the Woods Hole Oceanographic Institution.
Knowing that microplastics can be found in the blood, researchers may begin trials to study whether they can block blood vessels or disrupt organ functions.
“The levels of exposure (and toxicity) of having microplastics inside the body are not yet understood because they are so difficult to measure, especially the particles smaller than 10 micrometers that are thought to be most easily transported in the body”, says Hahn.
High concentrations of microplastics in the lungs may cause inflammation, asthma-like symptoms, and tissue damage, says Fay Couceiro, biogeochemistry and environmental pollution expert in the School of Civil Engineering and Surveying at the University of Portsmouth. Microplastics in the gut have also been found to cause changes in the human gut microbiome.
Microplastics can also absorb toxic organic substances that may affect human health and function as their carrier. Plastics often contain endocrine-disrupting chemicals (EDCs) that affect the body’s hormone systems and potentially lead to reproductive disorders, diabetes, and cancer. Determining the specific consequences of microplastics on human health is absolutely urgent, says Couceiro.
While exposure to microplastics may be reduced by minimizing the contact of food with plastic and spending more time outdoors, reducing the number of synthetic fabrics, improving ventilation and increasing vacuum cleaner use may lower the concentration of microplastics indoors, the only way to prevent this problem from getting bigger than it already will be is to stop using plastic wherever possible.