In a Penn Engineering lab, postdoctoral fellow Derek Ho uses Nile Red dye and acetone to identify microplastics in water samples, including one taken from Cobbs Creek.
"And this red particle over here, that's a microplastic," Ho said while examining a sample.
Nearby, an array of plastics from drinking water sources - including water bottles and canned water - glowed under specialized lighting.
"If you see very carefully, you'll be able to see those little yellow specks," said Ho.
Ho and Assistant Professor Samantha McBride have spent the past two years refining a staining method that makes microplastics visible under a microscope.
"We found that acetone and water were able to make sure that the plastics glow for us as brightly as they need to be, and for it to show some kind of trend for us to be able to differentiate it by its color," said Ho.
Their findings show how widespread the particles have become.
"We are looking at tap water. We are looking at environmental water, and we are finding microplastics pretty much everywhere we look," McBride said.
Researchers say exposure may carry health risks.
"The more that you're exposed to, the more it stays in your body. And at this point, we are now learning all of the new, different effects that this might have on human health," McBride said, noting possible cardiovascular or reproductive impacts.
Last month, the White House announced a $144 million investment to measure, research, and remove microplastics from the human body - funding that Penn researchers are applying for.
Asked about the long-term goal, McBride said the team hopes to make detection tools widely accessible.
"We are working on a simplified version of our detection that can be distributed to schools so that we can really alleviate some of these myths and show people that tap water is safe compared to single-use plastics, so they can make more informed choices," said McBride.
The research continues as scientists work to better understand how microplastics move through water systems - and the human body.