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A New Worry: Microplastics in Human Placenta

In a study released out of Italy on December 2, 2020, researchers found microplastics embedded in human placenta, exposing an entirely new concern surrounding improper plastic disposal. 

About 320 million tons of plastic are produced annually around the world, 40% of which are single-use and thus cannot be recycled. Often, people improperly dispose of these plastics, and they end up in waterways that lead to the ocean. Secondary microplastics (MPs) can form from these plastics when photooxidation and biodegradation pull apart their structural integrity, creating small (less than 5 millimeters) plastics. Commercially produced MPs are considered primary MPs, and they’re commonly used in cosmetic products like exfoliants, toothpastes, and concealers. Both primary and secondary MPs can enter the human body, but primary ones have a direct and ultimately avoidable access point via various cosmetic products. 

Researchers previously found MPs present in marine animals, but now they have found them penetrating human cells and organs as well. Inhalation and ingestion are the main pathways for MPs to enter the human body. MPs float in the air, especially where air pollution levels are high, so inhabitants of regions with poor air quality constantly inhale MPs. This is mostly seen in larger cities with heavy traffic and greater population densities. Ingestion of MPs is also particularly common among seafood-lovers. The marine animal ingests the MPs while alive in the ocean, and the MPs present remain inside the animal’s body even after it’s prepared for consumption. When the seafood is eaten by a human, the MPs migrate into the new host. The average quantity of MPs ingested annually by humans ranges from 39,000 to 52,000 particles per person per year. 

Once in the human gastrointestinal tract, MPs can dramatically disturb normal bodily functions. The most common bodily reaction to the introduction of foreign particles is a general inflammatory response. The inflammation can increase the human organs’ permeability by MPs and change gut microbial composition, which can ultimately affect metabolism. People can also experience lesions in the respiratory system due to the inhalation of MPs. Organs have trouble removing the foreign toxins because the particles are persistent by nature. The MPs’ persistence in the body leads to the aforementioned chronic inflammation, which can actually increase the likelihood of developing cancer. Similarly, large quantities of particulate matter can also increase the chances of developing immune and/or neurodegenerative diseases. In particular, elderly people have a higher risk of developing Alzheimer’s disease and dementia after inhaling high levels of traffic pollution. 

The Italian researchers of last December’s “Plasticenta” study found many dyed MPs in small portions of women’s placentas. A total of 6 women’s placentas were studied following normal and healthy pregnancies. The researchers ordered that all 6 women follow a restricted diet, and product consumption was limited in order to reduce the risk of contamination by MPs in foods or cosmetics. The researchers found 12 total MP fragments in 4 of the 6 placentas. The three different sides of the placenta were studied: fetal side, maternal side, and the chorioamniotic membranes. In the fetal sides, the part attached to the umbilical cord, 5 MPs were found. The maternal sides, the portion attached directly to the mother, contained 4 MP fragments. And finally, 3 MPs were found in the chorioamniotic membranes, more commonly known as the amniotic sac, in which the fetus grows in utero. These numbers may seem small, but it’s important to note that in each placenta studied, only 23 grams out of the total 600 grams were sampled. This leads to the reasonable assumption that, if the researchers had studied the rest of the placenta, they would have found many more MPs.

The discovery of MPs inside human placentas indicates that, once they’ve entered the human body, MPs can enter organs. Specifically, the small size of the MPs discovered suggests they were transported to the placenta via the bloodstream. As of now, it is unknown how MPs initially enter the bloodstream. The body’s natural defense against MPs can depend upon physiological and genetic differences, which vary from person to person. This sheds light on why there were no MPs found in two of the women’s placentas. 

The fetus’ health can be negatively impacted by the introduction of MPs into their tiny system. An important part of fetal growth is learning the identification between the self and non-self. The normal progression of this identification process can be impeded when foreign objects, like MPs, are introduced. When accumulated in large quantities, MPs can become toxic and change immune responses, ultimately decreasing the fetus’ defenses against possible pathogens or viruses. In utero, the fetus’ health can be put at risk when MPs disrupt the maternal-fetal communication lines and the transportation of important nutrients. Preeclampsia and fetal growth restriction can even develop.

Additionally, a study conducted in France found that, when pregnant women were exposed to particulate matter less than 2.5 micrometers in diameter, their children had higher risks of low birth weights and intellectual disabilities. 

The fetus’ health isn’t the only thing at risk—MPs can also disrupt the normal bodily functions of the mother. Many of the risks discussed above also apply to pregnant mothers. For example, preeclampsia affects both mother and child, posing severe health risks to both. Since MPs can interrupt communication processes between organs and parts of the body, they can cause fetal growth issues, severe maternal organ damage leading to pregnancy complications, and decreased immune responses in the mother. 

This new study sheds light on a growing issue across the globe. As plastic and air pollution continue, people will continue to eat MP-contaminated seafood, which will inevitably lead more and more people to experience the negative side effects of MP ingestion. Cosmetics manufacturers and other MP producing companies would need to make massive changes to prevent this issue from worsening further.

 

Sources: 

 

Prata JC, da Costa JP, Lopes I, Duarte AC, Rocha-Santos T. 2019. Environmental exposure to microplastics: An overview on possible human health effects. Science of the Total Environment, 702. 

 

Rafenberg C, and Annesi-Maesano I. 2018. Cost of hypertrophy due to intrauterine growth restriction attributable to air pollution in France. Archives de Pédiatrie, 25, 256-262.

 

Ragusa A, Svelato A, Santacroce C, Catalano P, Notarstefano V, Carnevali O, Papa F, Rongioletti MCA, Baiocco F, Draghi S, D’Amore E, Rinaldo D, Matta M, and Giorgini E. 2021. Plasticenta: First evidence of microplastics in human placenta. Environment International, 146.

 

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