In total, two studies were carried out, forming the basis of a major report. As part of this study, scientists used cave isolation as a way to measure how deep microplastics had penetrated into the environment and, more specifically, into groundwater systems.

Results

Much research has focused on surface waters. But one of the least studied areas in this field concerns what happens to groundwater in terms of microplastic pollution.
says St. Elizabeth Hasenmueller, a geochemistry researcher at the Water Resources Institute at St. Louis University.

Microplastics are considered small plastic particles of 5 millimeters or less (up to microscopic size). Today we find them everywhere; in clouds, on snow-capped mountain peaks, and even in human hearts.

The area chosen for the new study is called Cliff Cave. It is located in the US state of Missouri. It has been closed to visitors since 1993, but since there is a residential area close to the cave, it was a good option to test the impact of human settlement on the surrounding ecosystems.

99 percent of the microplastic debris we found in the cave was stored in the sediment. There was only a very small percentage of plastic in the water.
Hasenmüller said:

Plastic that accumulates over time is stored for long periods of time (decades or longer). It remains even after the water has receded. Researchers also say that airborne particles may also settle to the bottom of the cave.

This shows once again how much plastic has spread across the planet, reaching the most unexpected and inaccessible places. It can affect our health and animal habitats by seeping into groundwater that people use for drinking.

The authors of the study are confident that it will be very difficult to stop this trend. One solution, according to Hasenmüller, is that society as a whole should abandon synthetic clothing, because most of the particles found in the cave were synthetic fibers derived from textiles.