Scientists find microplastics in cave closed to humans for 30 years: Study

Researchers in the US state of Missouri found high concentrations of microplastics in a cave system that has been closed off to visitors for the past three decades. 

The recent study is an addition to worrisome research which shows the extent of microplastic contamination which has been found in clouds, rain and even in several parts of the human body. 

The findings related to the significant microplastic levels in the cliff cave in the city of St Louis were detailed in two new research papers, published in Science of the Total Environment and Water Research. 

This time around, microplastics were found in the water and sediment in the cave system in Missouri, according to the scientists studying student-collected samples. 

Microplastics have been defined as tiny chunks of less than five millimetres long pieces of plastic and microfibres from clothes that get caught in the Earth’s atmosphere. However, they are also formed after the breakdown of other plastic products like plastic bags due to ocean currents. 

What makes this study exceptional is that no one had been able to enter the cave system since 1993 allowing the researchers to eliminate human presence as a possible cause of microplastic contamination. Additionally, most of the research on microplastics in this context has been focused on surface water settings but not the subsurface level. 

“A lot of research has been focused on surface water settings…one of the most understudied areas in this field relates to what’s happening to the subsurface in terms of microplastic contamination,” said Dr Elizabeth Hasenmueller of St Louis University whose team published findings, adding that this is because of the highly visible problem of large plastic pollution in the ocean.  

Hasenmueller and her team discovered that the flooding not only contributed to higher levels of microplastics but also brought a higher diversity of microplastics to the cave water. 

Furthermore, when it receded, more microplastic was deposited near the cave’s mouth than in locations deeper in the cave. The study also found that microplastics were 100 times more concentrated in sediment than in the water of the cave. 

According to Hasenmueller, as much as 99 per cent of the microplastic debris present in the cave was found stored in the sediment and “only a very small fraction” was in the water.

“As the waters recede, that material remains in the cave sediment, potentially for decades or longer,” said the researcher. 

Researchers also warned that these microplastics could enter the groundwater, a common drinking water resource, or caves which are home to fragile ecosystems. So far, there is very little known about the impact of microplastics on human health. 

The cliff caves located near residential areas could have contributed to the high concentration of microplastic, according to Hasenmueller. She went on to warn that it could disrupt the delicate habitat of bats, amphibians, and other animals in the cave. 

“On a larger scale, we, as a society, could move away from synthetic clothing, because a lot of the debris that we found in this cave was synthetic fibers from textiles,” said Hasenmueller. 


 

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