A pile of assorted shapes and sizes of plastic fragments.


Our ocean and Great Lakes are polluted with a wide variety of marine debris, ranging from large fishing nets and abandoned vessels, down to the smallest plastic particles that can’t be seen with the naked eye. These microplastics are found throughout the ocean and Great Lakes, and are small enough to be eaten by wildlife. 

What are microplastics?

Microplastics are small plastic pieces or fibers that are smaller than 5 mm in size, or about the size of a pencil eraser and smaller. These pieces can be so small that they fit on the tip of your finger, while some can’t even be seen with the human eye! There are many different types of microplastics, including beads, fragments, pellets, film, foam, and fibers.

Some microplastics are made to be small for a specific purpose. These primary microplastics can be plastic pellets that are melted and used to create larger plastic items, or the microbeads that may be found in personal care products, such as toothpaste, face washes, and cosmetics. 

Secondary microplastics come from larger pieces of plastics, such as beverage bottles, bags, and toys. Sun, heat, wind, and waves can cause these plastics to become brittle and break into smaller and smaller pieces that may never fully go away. Microplastics are also created when pieces of plastic break off during use. For example, particles of synthetic tires can break off during regular use and through wear and tear. 

Similarly, our clothing, furniture, and fishing nets and lines may produce plastic microfibers, another type of secondary microplastics. These fibers are extremely common on shorelines across the United States, and are made of synthetic materials, such as polyester or nylon. Through general wear or washing and drying, these tiny fibers break off and shed from larger items.

Why are microplastics a problem? 

Microplastics are found throughout the ocean, from tropical waters to polar ice, fresh water, and the air we breathe. They have even been found in tap and bottled water, sea salt, and other products we eat or drink. 

Because they are so small, wildlife can mistake microplastics for food. Zooplankton, fish, mussels, and even whales have been found to eat microplastics. Microplastics can attract and carry pollutants that are in the water. They can also release the chemicals that are added to plastics to make them colorful or flexible into the water around them. Lab studies have shown that microplastics and chemicals in plastics may impact animals by delaying their developmental stages, cause problems with reproduction, and may even make it difficult for them to fight off disease

This can be bad news for small animals, such as zooplankton, that may not be able to tell the difference between their usual snacks and these plastic pieces. These animals form the base of the food chain and when eaten by larger animals, the impacts of microplastics could be passed on higher in the food chain, including the animals that we eat

These small pieces of debris have quickly become a high research priority for scientists around the world. Although wildlife may ingest or be exposed to microplastics and their contaminants, more research is needed to understand how they might be affected.

How do microplastics get into the environment?

Trash travels, and microplastics are no exception. They have been found on beaches around the world, even in our protected areas, and have been documented in sea ice in the Arctic and on the ocean floor. Once they enter the ocean, it can be difficult to understand where exactly these tiny plastics come from. 

Microbeads, like those found in toothpastes and face washes, can wash down your drain and into a wastewater treatment plant, where they can end up in the solid sludge that is captured during the treatment process, or in the treated wastewater. Once treated, wastewater is released into the marine or freshwater environment or is used in agriculture to water crops, while the sludge can also be used for agriculture or landscaping.  

Plastic pellets, which are used to produce larger plastic items, could directly enter the ocean, waterways, and Great Lakes through a spill during shipping or at a manufacturing facility. 

Plastic fragments come from larger plastic items that could be intentionally or unintentionally littered or dumped in the environment. They can be moved by wind and storms, and travel into the ocean or Great Lakes from rivers and streams. Through exposure to winds, waves, and the sun, these larger, more recognizable plastics can break into smaller and smaller pieces, eventually creating microplastics. 

When in use, fishing nets can shed microfibers directly into the ocean, waterways, and Great Lakes. Our clothes also shed these fibers, releasing them in the wash or directly into the water and air around us during normal wear. In a study of microplastics on 37 National Park beaches, these fibers were found at every site and made up 97% of the microplastic debris.

Last updated Tue, 02/07/2023 - 07:45 am EST