Our previous blog discussed how oceans have microplastics and how they infiltrate ecosystems.

But what exactly are these microplastics, and how much do they harm us?

Plastic is everywhere around us. A lot of it ends up in the ocean. Most plastics in the ocean break up into tiny particles. These small plastic bits are called "microplastics." They are defined as plastics less than five millimeters (0.2 inches) in diameter, smaller than the standard pearl used in jewelry. There are two categories of microplastics: primary and secondary.(Yu et al., 2018; Alimba and Faggio, 2019) Primary microplastics are tiny particles designed for commercial use, such as cosmetics, microfibers shed from clothing and other textiles like fishing nets. Secondary microplastics are particles that result from the breakdown of more oversized plastic items, such as water bottles. This breakdown is caused by exposure to environmental factors, mainly the sun’s radiation and ocean waves.


The problem with microplastics is that they do not readily break down into harmless molecules like plastic items of any size. Plastics can take hundreds or thousands of years to decompose and, in the meantime, wreak havoc on the environment. On beaches, microplastics are visible as tiny multicolored plastic bits in the sand. In the oceans, microplastic pollution is often consumed by marine animals. Some of this environmental pollution is from littering, but much results from storms, water runoff, and winds that carry plastic, intact objects, and microplastics into our oceans. Single-use plastics, as they are meant to be used just once and then discarded, such as straws, are the primary source of secondary plastics in the environment. But how do they harm us, and how did we know? Human Health Implications: A few years ago, as microplastics began turning up in the guts of fish and shellfish, the concern was focused on seafood safety. Shellfish were a particular worry because, in their case, unlike fish, we eat the entire animal—stomach, microplastics and all. In 2017, Belgian scientists announced that seafood lovers could consume up to 11,000 plastic particles a year by eating mussels, a favorite dish in that country. By then, however, scientists already understood that plastics continuously fragment in the environment, shredding over time into fibers even smaller than a strand of a human hair —particles so tiny they quickly become airborne. Microplastics are everywhere around us. They can be found in salt, beer, fresh fruit and vegetables, and drinking water. Airborne particles can circle the globe in a matter of days, fall from the sky like rain, and enter the human body through inhalation, ingestion, and dermal absorption.


Measuring the possible adverse effects of plastics on humans is far more complex than on animals, as human subjects can’t intentionally be fed a diet of plastics for experimentation. However, in 2022, scientists from the Netherlands and the U.K. announced they had found tiny plastic particles in living humans in two places where they hadn’t been seen before: deep inside the lungs of surgical patients and in the blood of anonymous donors. A 2018 study found microplastics in the feces of eight people. Another study documented the presence of microplastics in the placentas of unborn babies. They all show how deep the microplastics have entered our bodies and can cause severe damage to us.


Humans have inhaled various foreign particles every day since the dawn of the Industrial Revolution. The body’s first response is to find a way to expel them. Large particles in airways are typically coughed out. Mucus forms around particles further down the respiratory tract, creating a mucus “elevator” that propels them back up to the upper airway to be expelled. Immune cells surround those that remain to isolate them. Over time, those particles could irritate, leading to a cascading range of symptoms from inflammation to infection to cancer. The particles are made of plastics known to be toxic to humans and have caused lung irritation, dizziness, headaches, asthma, and cancer. MPs are easily found in the fishes, a significant source of proteins for humans. These MPs enter the human body through biomagnification ( as discussed in the previous blog). They can cause growth retardation, hormone disruption, metabolic perturbation, oxidative stress, immunological and neurotoxicity malfunction at the primary level, and can also lead to cancer. Microplastics, tiny fragments of plastic that result from the breakdown of more oversized items, have become pervasive in our environment, particularly in the ocean. To protect our planet and ensure our well-being, we must reduce plastic consumption, improve waste management practices, and actively support initiatives to minimize microplastics' presence in our environment.