BERLIN (AP) — Scientists in Austria say they've detected tiny bits of plastic in people's stool for the first time, but experts caution the study is too small and premature to draw any credible conclusion.

Presenting their findings at a congress in Vienna on Tuesday, researchers from the Medical University of Vienna and the Environment Agency Austria said their pilot study detected nine types of so-called microplastic in all samples taken from eight volunteers living in Europe, Russia and Japan.

While the study's authors don't know how the plastic got there, food diaries kept by the volunteers...