Should we be worried about the microplastics in our bodies?

Microplastics and nanoplastics are almost everywhere—even in human bodies. Over the past 5 years or so, scientists have found them in the blood and brain, heart and kidneys, liver and lungs, human milk and placenta, and testicles and semen. If and how these plastic particles—defined as smaller than 5 mm in size—harm our health remains unclear, but clues are emerging. In the laboratory, scientists are feeding mice microplastics to understand whether these particles pose risks to the animals’ health. Researchers are also tracking health outcomes in relation to the microplastics they find in human bodies. “It’s just such a new field,” says Matthew Campen, a toxicologist at the University of New Mexico who studies micro- and nanoplastics in human tissues. But even as the research continues to evolve from its early stages, the widespread presence of these plastic fragments in humans and the environment is already something “we absolutely need