Microplastics Are Contaminating Ancient Archaeological Sites

New research suggests plastic particles may pose a threat to the preservation of historic remains

Two researchers in a lab
In the lab, researchers tested soil samples dating to the first or early second century C.E. York Archaeology

Today, microplastics are found almost everywhere: oceans, food, the atmosphere and even human lungs, blood and placentas. But while they’re thought of as a modern problem, plastic particles are now appearing where one might least expect: ancient archaeological sites.

Researchers found microplastics in soil deposits 7.35 meters (24.11 feet) below the ground, according to a study published this month in the journal Science of the Total Environment. The soil samples date to the first or early second century C.E. and were sourced from two archaeological sites in York, England. Some were excavated in the late 1980s, while others were contemporary samples.

The scientists then used an imaging technique called μFTIR, which can detect microplastics’ quantities, size and composition. Across all samples, they found 66 particles consisting of 16 polymer types.

“This feels like an important moment, confirming what we should have expected: that what were previously thought to be pristine archaeological deposits, ripe for investigation, are in fact contaminated with plastics,” says John Schofield, an archaeologist at the University of York, in a statement.

Microplastics are fragments of plastic that are smaller than five millimeters long, the diameter of a standard pencil eraser. They come from a variety of sources, including laundry, landfills, beauty products and sewage sludge.

“In the last not even 100 years—mostly since the 1950s—we as humans have produced eight billion tons of plastic, and the estimate is only about 10 percent of that has been recycled,” Leigh Shemitz, president of the climate education group SoundWaters, told Yale Sustainability in 2020.

Microplastics have been found in soil samples before. In fact, almost one-third of all plastic waste ends up in soil or freshwater, according to the United Nations Convention to Combat Desertification.

But the new study provides “the first evidence of [microplastic] contamination in archaeological sediment (or soil) samples,” write the researchers. These findings could change how archaeologists protect historic sites.

“While preserving archaeological remains in situ has been the favored approach in recent years, the new findings could trigger a change in approach, as microplastic contamination could compromise the remains’ scientific value,” writes CNN’s Jack Guy.

In situ, Latin for “in the place,” is the term used to describe archaeological objects that have not been moved from their original locations. Leaving remains in situ helps prevent site and artifact damage, preserves contextual setting and allows future researchers to gather information.

“The presence of microplastics can and will change the chemistry of the soil, potentially introducing elements which will cause the organic remains to decay,” says David Jennings, chief executive of York Archaeology, in the statement. “If that is the case, preserving archaeology in situ may no longer be appropriate.”

Now, the researchers will shift their attention toward better understanding the implications of their findings. They know microplastics could threaten the integrity of archaeological samples, but what exactly does that harm look like?

“To what extent this contamination compromises the evidential value of these deposits and their national importance is what we'll try to find out next,” says Schofield.

Get the latest stories in your inbox every weekday.