Toxic particles may cast doubt on known archaeological analysis
Researchers in the UK have found the first evidence of microplastic use at two archaeological sites in York, which have yielded significant finds from the Roman and Viking periods. Microplastic particles have recently received a lot of attention due to their prevalence and abundance in our daily lives.
Photo: University of York
Microplastics less than five millimeters long are known to enter our bodies through plastic packaging, some foods, tap water and even the air, and have been linked to cancer problems. But it can also potentially compromise the surviving remains of antiquities, rendering them useless for science.
A British team found more than 25,000 microplastics in archaeological samples that were the direct result of human activities such as industry, agriculture, transport and everyday life. Particles were also found in almost every corner of the world — from the Mariana Trench to the summit of Mount Everest.
Archaeologist John Schofield said: “This seems to be an important point in confirming what we should have expected: that what was previously thought to be pristine archaeological deposits suitable for exploration, is actually contaminated with plastic, and that this includes sediments collected and stored in the late 1980s.”
While previously scientists were aware of the problem of plastic in oceans and rivers, it is now clear that historical heritage may be exposed to toxic elements.
«To what extent does this contamination jeopardize the evidentiary value of these sediments and their national significance, we will try to find out further,” — explains the scientist.
The team analyzed soil samples taken from Wellington Row in 1989 and from the Queen's Hotel in York the same year and in 1990. The earliest deposits from Wellington Row date from the first or early second century AD and were discovered in the 19th and 20th centuries.
The highest concentration was found in Wellington – 20,588 microplastics per kilogram, and samples from the Queen's Hotel contained 5,910 microplastics per kilogram.
At the site dating back to the Viking period, archaeologists discovered about a ton of animal bones, a quarter of a million pottery and 20 thousand other interesting items.
Excavations at a Roman site at the Queen's Hotel have revealed the remains of an ancient wall, suggesting the area may have been important to the ancient empire.
The team used a technique called Fourier transform infrared spectroscopy ( FTRI), which allows you to identify unknown plastics in materials.
The device detected tens of thousands of microplastics in six small soil samples — and 16 of them could not be classified.
Polyethylene, which is used in water bottles, polypropylene, used in cans, and hydrocarbon resin, which is added to rubbers, printing inks and adhesives, and other plastics were found at the excavation site.
However, 57 percent of the microplastics found were categorized as polytetrafluoroethylene (PTFE) — or what is commonly known as Teflon, which is used in non-stick cookware.
The team theorized that the tiny particles were carried into the archaeological site when it was excavated in the 1980s.
“Plastic storage buckets (PP), coring tubes (polymethacrylate), and a week-long air sample taken from the archival storage facility revealed different predominant polymer types compared to those found in the archival sediments,” ; the researchers report.
The team said the work was a pilot analysis to see if microplastics had entered valuable objects, and noted that “if replicated across the UK, many cultural heritage sites would potentially at risk due to increased wear and loss of information potential.”
Because plastics degrade slowly, particles can affect the chemical and physical composition of the soil.
“Potential of radiocarbon dating or analysis micronutrient residues may be compromised by the presence of microplastics and again requires further study to determine whether these are real risks,” — scientists concluded.
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