Scientists in the UK have found evidence that microplastics are contaminating archaeological soil samples. The discovery has the potential to upend the way historical remains are preserved.
Tiny particles of microplastics were discovered seven metres underground in samples dating from the first or early second century. They were first excavated in the 1980s.
“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, and that this includes deposits sampled and stored in the late 1980s,” says Professor John Schofield from the University of York’s Department of Archaeology.
Where do microplastics come from?
Microplastics are small plastic particles, ranging in size from one-thousandth of a millimetre to five millimetres. They are formed when chemical degradation or physical wear causes larger plastic pieces to break down. They were also commonly used in beauty products until around 2020.
“We think of microplastics as a very modern phenomenon as we have only really been hearing about them for the last 20 years,” says David Jennings, chief executive of York Archaeology.
But, he adds, research from 2004 revealed that they have been prevalent in our seas since the 1960s due to the post-Second World War boom in plastic pollution.
“This new study shows that the particles have infiltrated archaeological deposits and, like the oceans, this is likely to have been happening for a similar period, with particles found in soil samples taken and archived in 1988 at Wellington Row in York,” Jenning explains.
Why is microplastic contamination a problem for archaeologists?
The study found 16 different kinds of microplastics across both contemporary and archived soil samples.
The team says that the concern for archaeologists is whether microplastics compromise the scientific value of preserved remains. Preserving archaeology in the place where it was found has been the preferred approach to conservation for a number of years. But these new findings could change that.
“Our best-preserved remains - for example, the Viking finds at Coppergate - were in a consistent anaerobic waterlogged environment for over 1,000 years, which preserved organic materials incredibly well,” Jennings says.
“The presence of microplastics can and will change the chemistry of the soil, potentially introducing elements which will cause the organic remains to decay. If that is the case, preserving archaeology in situ may no longer be appropriate.”
The team says further research into the impact of microplastics will be a priority for archaeologists given their potential impact on historical sites.
