Microplastics have been found in historic soil samples for the first time, according to a new study, potentially upending the way archaeological remains are preserved.

Researchers found microplastics in soil deposits more than seven meters (23 feet) underground, which were deposited in the first or second century CE and excavated in the 1980s, a team led by researchers from the University of York in the United Kingdom said in a statement published Friday.

In total, the study identified 16 different microplastic polymer types in contemporary and archived soil samples, the statement adds.