Researchers at Michigan State University have discovered that neurons in a locust’s brain can distinguish among multiple PFAS compounds, including PFOS, one of the world’s most common “forever chemicals,” at environmentally relevant concentrations.

PFAS, or per- and polyfluoroalkyl substances, are used in products ranging from nonstick cookware and waterproof fabrics to firefighting foams. Because they break down very slowly, they persist in water, soil and living organisms, making contamination difficult to monitor and clean up.

A woman sits in front beside a microscope. Behind her, a man is standing. — Summer McLane-Svoboda and Debajit Saha. Photo by Derrick L. Turner.

“PFAS are extremely difficult to detect,” said Debajit Saha, associate professor in Michigan State University’s College of Engineering and Institute for Quantitative Health Science and Engineering. “There is a tremendous need for technologies that can identify them at very low concentrations.”

Despite decades of engineering, scientists still struggle to build artificial chemical sensors that rival the sensitivity of living organisms. Dogs remain among the best detectors of many chemicals, and insects rely heavily on smell to navigate the world.

To test whether insects could detect PFAS, researchers recorded neural activity from the portion of a locust’s brain that processes odors. The insects were exposed to gases containing several PFAS compounds, including PFOS, one of the most common and heavily regulated PFAS chemicals found in the environment.

“We weren’t sure whether the locust brain would respond to PFAS at all,” said Summer McLane-Svoboda, a doctoral candidate and graduate research assistant in Saha’s lab and lead author of the study. “Once we saw distinct neural patterns for different compounds, we realized biology could become a powerful PFAS-sensing platform.”

Researcher in a lab coat and green gloves adjusts equipment during the experiment. — During the experiment, the green sensor can detect if the locust brain can smell PFAS chemicals. Photo by: Derrick L. Turner

The researchers found that each PFAS compound produced a distinct pattern of neural activity — an “odor fingerprint” that allowed the insects to distinguish between different chemicals. The team also demonstrated that locusts could detect PFOS at concentrations similar to those found in contaminated environmental samples.

This finding bewildered the researchers because PFAS are entirely human-made chemicals. Unlike the natural odors insects have evolved to recognize, PFAS have existed only for decades, making it unclear why the locust’s sensory system responds so strongly to them.

“We were surprised by how strongly the locust brain responded to PFAS compounds,” Saha said. “For some reason, the insect’s sensory system is able to detect these human-made chemicals, even though they don’t naturally occur in the environment.”

Detecting PFAS today typically requires laboratory instruments such as liquid chromatography-mass spectrometry. Although highly accurate, those systems are expensive, require specialized facilities and are not easily deployed in the field. Many existing detection methods are designed to identify specific PFAS compounds, making broad screening for contamination challenging.

The study is a proof of concept. Next, the team is testing environmental water samples collected in Michigan to determine whether the approach can detect PFAS contamination outside the laboratory. Ultimately, the researchers hope to miniaturize the technology into portable biological sensors capable of rapidly screening multiple PFAS compounds in the field.

“Biology may offer a completely different way to detect PFAS,” Saha said. “If living sensory systems can recognize these chemicals, we may be able to build faster, more versatile tools for monitoring contamination.”

The team is now working with environmental samples collected in Michigan to determine whether the approach can identify PFAS contamination outside the laboratory.

The research was published in the Journal of Hazardous Materials Advances.

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