Microplastics are everywhere—human bodies included. But it’s unclear what health effects these particles might have on organs and tissues, not least because researchers have struggled to track the plastics as they move through living organisms. Outi Keinänen aims to fill that knowledge gap.

Her research lab at the University of Alabama at Birmingham (UAB) is using radiochemical methods to understand the fate of microplastics in mammals. These studies in living creatures are important “because any toxicological evaluation begins with determining the biodistribution—determining where the contaminants go,” Keinänen says.

It’s an idea she first developed as a postdoctoral researcher at Hunter College after reading a paper from a group that was using fluorophore imaging to try to accomplish the same thing. Fluorophores are fluorescent chemical compounds that can be attached to molecules or tiny particles, which enables scientists to follow their movements with a microscope or spectrometer. But the fluorescence signal doesn’t penetrate strongly through tissue, so the researchers couldn’t determine where the microplastics had accumulated until after they sacrificed the animal and collected tissue samples. This shortcoming of the fluorescence method limited how well the team could link the microplastics with potential health impacts.

Keinänen wondered if she could instead use positron emission tomography (PET), a common medical imaging technique, to track microplastics in living lab animals. PET relies on radioisotope tracers that emit positrons, the antimatter counterpart to electrons. When these positrons meet electrons, they annihilate to produce gamma rays that reveal the precise location of the tracer and whatever it’s attached to.

Keinänen was already developing ways to target tumors with these kinds of radioisotopes so that the cancerous tissue could be imaged and treated more effectively. She realized that if she could use a similar approach to radiolabel plastic particles before feeding them to mice, she could determine where they accumulate in the body—in real time.

Keinänen brought the idea to her postdoc mentor, Brian Zeglis. “She saw the opportunity and the utility and the innovation” to combine her background in radiopharmaceutical chemistry with microplastics research, he says. “What I think really sets her apart is that, as a postdoc, she conceived and executed and pioneered what I’d argue is almost entirely a completely new field.”

In 2021, Keinänen published a paper in Scientific Reports describing her method for radiolabeling polystyrene particles. By doing so, she could follow their journey through mice using a combination of PET imaging and X-ray-based computed tomography (CT) scans. “It feels good to be the first one to publish something like that,” she says.

Keinänen’s work has been well recognized. In 2022, she received a National Institutes of Health Pathway to Independence Award (K99/R00) and made the Society of Nuclear Medicine and Molecular Imaging’s Ones to Watch list.

Despite her success in science, there’s a version of reality in which Keinänen never becomes a researcher. “I was really considering becoming a travel guide,” she says. Instead, she ended up studying chemistry as an undergraduate at the University of Helsinki, where she became intrigued by radiochemistry. “It felt like the right fit,” she says.

She then worked part time at the radiopharmaceutical company MAP Medical Technologies, now a subsidiary of Curium Pharma, while finishing up her bachelor’s and master’s degrees; she transitioned to a full-time position after she graduated.

But after a few years in industry, she began to miss academic research, and she returned to the University of Helsinki for a PhD. “I’ve never been a person who has 5-year plans,” Keinänen says. “I kind of go where the opportunity takes me.”

That personality trait might explain why she has managed to carve out such a unique path in her research. “That’s who Outi is,” says Mirkka Sarparanta, one of Keinänen’s PhD supervisors. “She’s not asking, ‘Am I allowed to do this?’ There is this boldness to just go and apply and do.”

Keinänen joined UAB in 2023, and Sarparanta has no doubt that her microplastics work will continue to flourish there. “She is going to be a leader,” Sarparanta says.

Zeglis agrees. “I think she is going to be the person leading the field of using molecular imaging for pollutants,” he says. “I can’t think of a better person to be the standard-bearer than Outi.”