It’s no secret that microplastics are everywhere—in Earth’s soils, waters, oceans, air; in plants, and animals—including inside our human bodies. Yet plastic also embeds itself in our history: Scientists are now discovering microplastics in ancient and contemporary archeological digs.
Archeologists working with the universities of York and Hull have published research showing that microplastics are present in archeological soil samples. The sites were as old as the late first century CE, and excavated from as far as 7.35 meters (more than 24 feet) below Earth’s surface. How is plastic—a material only mass-produced since the 1940s—becoming a part of ancient history?
Microplastic Pollutes Archeological Dig Sites
The researchers focused their study on two archeological sites in the historic town of York, England: Queen’s Hotel and Wellington Row. These urban sites have been occupied continuously for an estimated two thousand years, encompassing England’s early Roman and Viking periods. While shallower soils are typically representative of more recent occupants, deeper soils have preserved artifacts from ancient times. Microplastics and even smaller nanoplastics are now found in soils around the world, reflecting our modern plastic lifestyles in Earth’s geological record.
The researchers analyzed sediment samples collected during archeological excavations conducted in 1988, 1989, 1990, and 2023. The archeologists expected to find that the number of microplastics in the most contemporary soil samples—taken in 2023—would contain more microplastics than their archived counterparts, as plastic pollution has only increased over time. They were surprised to find that the archived deeper samples from the 1980s contained similar amounts of microplastics to the contemporary samples.
These findings suggest that microplastics and nanoplastics are constantly moving and interacting with the Earth. Soils experience erosion, subsistence, and deeper archeological sites are easily contaminated by shallow soils. How can archeologists be sure that a sample contains sediment dating from the era represented by other remains with microplastics getting in the way of their analysis?
How Deep Can Microplastics Go?
The existence of microplastics in archeological remains, the researchers emphasize, is not a sudden occurrence. Over time, microplastics have built up in sediment due to increased human activities such as agriculture, industry, and transportation. In their report, the researchers listed three main sources of microplastics in soil: landfill, fertilizer, and mulch degradation. A related study done in the Santa Barbara Basin in California and published in ScienceAdvances corroborates this.
Microplastics have been found in sediment cores, which are pieces of the earth’s crust extracted with a long, cylindrical tool. They illuminate how geology and climate have developed over time. The sediment cores examined in this study were taken from the benthic zone—the bottom of a body of water, like the seafloor. This essentially means that plastic pollution is not just deposited in water and remains at the surface. It makes its way to the bottom and finds a place for itself among the sediment, disrupting the thriving ecosystem existing there.
The Potential Damage to Archeological Samples by Microplastics
Scientists are still determining the extent of the potential damage microplastics in archeological samples can cause. Right now, they hypothesize that microplastics could affect the accuracy of radiocarbon dating. The 5.33 meters of archeological sediment taken from the 1980s were previously dated to be from between the late first century CE all the way to the twentieth century. However, with microplastics being an unforeseen (and unwelcome) addition to the soil, scientists worry that microplastics have caused a change in the physical and chemical traits of the soil structure. These alterations hinder the processes of soil enzymes and organisms, which act as clues to aid scientists in concluding the age of soil samples. They now have to wonder how accurate their methods remain with microplastics being present.
This may decide the fate of archeology. In Western archeological practices, a particular method is used called in situ preservation. This method prioritizes preserving archeological remains at the site where they are excavated rather than transporting them to be preserved elsewhere, thereby risking the loss of valuable information. This process becomes obsolete, however, if the soil samples are already being compromised by microplastics. Thus, countries like England, where this study occurred, could determine that spending money on these excavations is not worth poor results. We would then, as a society, be deprived of enjoying history and all its wonders.
The Evolution of Plastic Production: How Did We Get Here?
To fully understand how plastic has become such a pervasive and invasive substance, we must first understand its origins. In 1863, the first strain of plastic, celluloid, was invented in America when people sought a replacement for the original material of billiard balls—ivory. Celluloid did not become a suitable substitute for ivory. Yet once people realized that it could be dyed to mimic other, more expensive materials, celluloid propelled the world into what is now known as the Plastic Age.
Plastics evolved as the demand for them increased, and many more variations were created. Bakelite emerged as celluloid’s less flammable successor, molded from oil and formaldehyde, and used to make radios and telephones in the early twentieth century. Vinyl and acrylics were popular in the 1920s. In the 1930s, nylon exploded as a cheaply-produced, plastic-based fabric. Plastic truly solidified its role in human consumption when polyethylene came onto the scene. Polyethylene became ubiquitous, used in everything from the helmets of World War II soldiers to plastic water bottles and meat packaging.
Polyethylene, a widely used plastic, has achieved what its makers hoped for—making previously unaffordable products accessible. However, its success has also led to global plastic saturation, clogging once-pristine oceans and creating mountains of waste. Even history itself has not been spared from its contamination.
Take Action
With world leaders about to wrap up UN Plastics Treaty talks in the coming months, we have the opportunity to address plastic pollution at the source—starting with its fossil fuel ingredients. The U.S. is the world’s biggest plastic and fossil fuel producer, and this is a critical time to push our leaders to do more to solve these interconnected crises. Join us in calling on U.S. Government leaders to take a strong stance on the UN Global Plastics Treaty.
