Recent headlines (including in this publication) have raised concerns about microplastics in our bodies and the harm they may be doing.

Scientists say it could be years before we have a full understanding of how these tiny plastic particles are affecting human health. But we do know they have been found from the depths of the Mariana Trench to the heights of Mount Everest. And we know that plastic is accumulating in our bodies, too.

“The air we breathe, the water we drink, the food we eat — it’s in it,” said Richard Thompson, a marine biologist at the University of Plymouth who coined the term “microplastics” in a 2004 paper. “We’re exposed.”

What are microplastics?

Scientists generally define “microplastics” as pieces less than 5 millimeters long. Nanoplastics, which measure less than 1 micrometer, are the smallest of these and the most likely to get into our blood and tissues.

Microplastics mostly come from larger plastics, which degrade with use or when they aren’t disposed of properly, said Jeffrey Farner, an assistant professor of civil and environmental engineering at the Florida A&M University-Florida State University College of Engineering.

“We use plastics in areas or in ways that lend themselves to the production of microplastics or to the breakdown over time,” Dr. Farner said — for example, in construction materials that are weathered outdoors, in tubing that generates microplastics when it is cut and in agriculture, as plastic mulch or in irrigation systems.