A new study has revealed a startling fact: tiny plastic particles are showing up in lake sediments that pre-date modern mass-industrial plastic production. Researchers diving into the sediment cores of lakes in Latvia uncovered microplastics in layers that go back to the early 1700s — long before the era of synthetic plastics.
The investigation, published in the journal Science Advances, examined multiple lakes and found that microplastics not only exist in the surface layers but were present deeper down in older sediment layers. For example, plastic items like PLA and PHB were detected in layers dating from 1813-1733 in one of the lakes studied.
Why this matters
For years, scientists have debated the best way to mark the beginning of the Anthropocene — the age when human activity began leaving a clear, global stratigraphic signature. Many had hoped plastic pollution might serve as a tidy “timestamp”. But these findings throw that idea into question: if microplastics were already sinking into sediments centuries ago, then plastic can’t reliably mark a modern-start boundary. The study authors even suggest that the ubiquity and persistence of microplastics means our planet has been absorbing plastic debris for far longer than we assumed.
What did the researchers do?
The team collected sediment cores from several lakes in northeastern Europe and used detailed stratigraphic dating and polymer-analysis to locate and identify microplastic particles in the layers. They found that even the deep, older layers—those thought to be undisturbed by modern human activity—contained plastic fragments.
In one lake, for instance, layers dating 1925-1900, 1953-1881 and even 1813-1733 displayed the presence of plastic types including PLA (polylactic acid) and PHB (polyhydroxybutyrate).
So how did plastics get there so early?
The study doesn’t claim that modern plastics (like mass-produced polyethylene or PVC) were around in the 1700s. Instead, the authors point to processes such as downward migration—tiny plastic fragments can move through sediment layers over time, bio-mixing, groundwater transport, and natural sedimentary reworking may carry younger particles deeper than expected.
Also, some of the polymers found (e.g., PLA, PHB) may be older or degrading faster; still, the presence at depth signals the complexity of plastic transport and deposition in natural systems.
Broader implications
The findings raise alarm on several fronts:
Global spread: Microplastics are not just a modern surface phenomenon. They have penetrated environments we thought were pristine and untouched.
Unexpected pathways: The fact that sediments once assumed isolated now bear plastic traces means we need to rethink how plastics move through soil, water and sediment systems.
Environmental health: If microplastics are embedding into layers of sediment previously untouched, then the long-term ecological and chemical effects are largely unknown. They may affect habitats, biogeochemical cycles and even archaeological sites.
Anthropocene marking: Using microplastics to define a boundary for the Anthropocene may be flawed if the deposition began earlier and is more gradual than a single clear “event”.
What we still don’t know
While this study sheds light, it raises many new questions:
Precisely how the particles moved into those older layers remains uncertain.
The rates of downward migration, mixing and sediment disturbance vary by environment and are not yet fully quantified.
The health and ecosystem impacts of such ancient microplastic contamination remain largely unexplored: how do these particles interact with sediments, microorganisms, chemical cycles, and buried organic matter?
The prospects for removal or remediation of microplastics deeply embedded in sediments are currently limited.
What this means for us
For you, me and the broader world, the key takeaway is that plastic pollution is more than just a visible litter problem on beaches or in water. It’s penetrating deep into Earth’s systems, spanning centuries, and embedding in places we once considered “clean”.
It underscores the importance of reducing plastic waste, improving filtration and capture of microplastics, and rethinking how we evaluate environmental contamination over long timelines.
Source:
Adarlo, Sharon. “Microplastics Found in Sediment Layers Untouched by Modern Humans.” Futurism, 23 Feb. Also see the original research article: I. Dimante-Deimantovica et al., “Downward migrating microplastics in lake sediments are a sediment‐marker of modern pollution?”, Science Advances, 2024.