As microplastics and their smaller, even more insidious counterparts, nanoplastics, have increasingly permeated the environment and our bodies, one of the key challenges facing researchers has been finding inexpensive, rapid, and convenient methods to detect the presence of these tiny particles in the first place.
In a groundbreaking study published in Nature Photonics, researchers revealed a new method for detecting nanoplastics using only a standard microscope, a basic color camera, and a simple tool they referred to as an “optical sieve.”
The study’s findings have the potential to revolutionize the way scientists identify nanoplastics in everything from waterways to human blood.
“Because they’re so tiny, detecting nanoplastics is extremely difficult and expensive. As a result, determining the extent of their impact has been largely guesswork,” Mario Hentschel, one of the study’s authors, wrote in The Conversation. “A cheap, easy, and reliable way to detect nanoplastics is the first step in addressing their potential impact.”
While microplastics have been defined as plastic particles smaller than 5 millimeters in length, nanoplastics are even tinier, measuring less than 1 micrometer, or one-millionth of a meter. They are small enough to cross important biological barriers within the human body, according to Hentschel. It has also made them incredibly difficult to find.
“Today, detecting and sizing particles below a micrometer often relies on complex separation and filtration methods followed by expensive processes, such as electron microscopy,” Hentschel wrote in The Conversation. “These methods are powerful. But they’re also slow, costly, and usually confined to advanced laboratories.”
These limitations have meant that, when it comes to nanoplastic particles, researchers have largely been flying blind. However, the new discovery has the potential to change that on a massive scale.
Despite the complexity of the challenge, the solution, as so often happens, was surprisingly simple and relatively low-tech.
The key component, an optical sieve, is essentially a flat surface containing microscopic holes of various sizes. When light passes through these holes, it takes on a certain color.
To detect nanoplastics, researchers washed a liquid sample over the optical sieve. When nanoplastics encountered a hole of the right size, they became stuck. After removing excess debris from the sample, all that remained were the nanoplastic particles.
When researchers again shone light through the optical sieve, the holes that contained trapped nanoplastic particles changed color, making them easy to identify using nothing more than a standard microscope and a basic camera. Because the holes in the optical sieve were made of various, predetermined sizes, researchers could also measure the size of the nanoplastic particles.
Using this method, the scientists were able to identify nanoplastic particles as small as 200 nanometers, Hentschel explained in The Conversation. Just as importantly, the technique proved effective under real-world conditions, using samples that included sand and organic matter.
“Our new method is a first step in developing a cheap, easy, and portable method for routine monitoring of waterways, beaches, and wastewater, and for screening biological samples where pre-cleaning is difficult,” Hentschel wrote.
“From here, we are exploring paths to a portable, commercially available testing device that can be adapted for a range of real-world samples, especially those like blood and tissue that will be crucial in monitoring the impact of nanoplastics on our health.”
As scientists work to develop new methods for identifying microplastics and nanoplastics and removing them from the environment and our bodies, it is essential that the world also takes meaningful steps to prevent plastic waste from entering the environment in the first place.
A 2024 study found that, globally, humans produced 57 million tons of plastic pollution per year, a figure that experts say will continue to increase unless current trends dramatically change.
To make a difference, you can cut down on your own plastic use by choosing plastic-free options for everyday products and by supporting brands that use plastic-free packaging.
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