Infants have an average of 10 times the concentration of a type of microplastic in their poop than adults, a pilot study released Wednesday found. The research, published in the journal Environmental Science and Technology Letters, follows previous studies reflecting the ubiquity of microplastics—small fibers less than 5 mm in size originating from everyday objects like plastic bottles and polyester clothing and that end up in the planet's waterways and human guts. "Human exposure to microplastics is a health concern," said lead author Kurunthachalam Kannan, a professor at the NYU Grossman School of Medicine's Department of Pediatrics. Researchers focused on two types of common microplastics—polyethylene terephthalate (PET) and polycarbonate (PC)—and measured feces from six infants and 10 adults.