New research suggests that microplastics in our oceans might be hundreds of thousands of times more abundant than current detection methods are reporting.

Microplastic particles (MPs) are tiny fragments of plastic, less than 5mm. They result from both commercial production and the breakdown of larger plastics. One of the biggest sources is synthetic fabrics.

Chemicals within microplastics have now made their way into oceans and waterways, and even drinking water, causing concern to scientists and public health officials. The increase of microplastics in aquatic systems is dangerous to both marine life and creatures, including humans, through the consumption of seafood.

Recent reports have also that microplastics themselves are common in every part of the human body, including the testicles.

A new study, published in the Marine Pollution Bulletin, shows that the problem is likely to be even greater than we previously thought.

Using Raman microspectroscopy to determine the chemical makeup of samples, the scientists analysed ocean waters from the Caribbean to the Arctic. Their results show that the most abundant and tiny microplastics aren’t being detected by current methods.

Normally, microplastics in ocean waters are measured using net tow surveys. Tightly meshed “plankton nets” sieve microplastics out of the water, which can then be analysed.

These plankton nets detect particles between 300–500 micrometres in size, where a micrometre is one millionth of a metre. The Raman microspectroscopy technique is able to reveal microplastics much smaller than just 15 micrometres.

“Our results highlight the numerical primacy of small microplastic particles in seawater, and we found that the most abundant microplastics were between 1 and 14 micrometres,” says first author Medina Faull, from Stony Brook University in New York. “60% were under 5 micrometres, and none were larger than 53 micrometres.”

“This size fraction has been totally overlooked in almost all marine microplastics.” Faull adds.

The Raman microspectroscopy based research found microplastics less than 53 micrometres in size hundreds of thousands of times more often than all the combined reports around the globe using traditional detection techniques.

Graphs showing chemicals in microplastic
This image, generated in a lab and based on the Raman spectra, shows a microplastic particle within a 100 micrometer area.
The false-color images of green and red match for specific polymers detected in the particle. Credit: Luis Medina Faull.

“Understanding health risks from exposure to microplastics is a vastly understudied area, and investigations are needed to understand the health impacts from microplastics of different shapes, sizes, and compositions,” says Jaymie Meliker, a public health researcher at Stony Brook University who was not involved in the study.

Faull emphasises the need for wider research on microplastics in the ocean.

“Firstly, most of the ocean is grossly under-sampled, and the majority of existing data is based on towed net studies. And smaller, less buoyant microplastic particles residing below the ocean’s upper few meters are almost never sampled. Secondly, understanding sources of microplastics transport and final landing locations such as ocean floors is crucial to explain the distribution patterns of microplastics throughout the ocean,” he explains.

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