HIDDEN AIRBORNE TOXINS DISCOVERED

Something strange is floating through the air above Oklahoma farmland—and scientists didn’t even know to look for it. When a research team from the University of Colorado Boulder set out to study tiny particles in rural air, they stumbled onto a surprise. For the first time in the Western Hemisphere, toxic Medium Chain Chlorinated Paraffins (MCCPs) were drifting overhead.

The twist? These chemicals likely didn’t come from smokestacks or factories, but from the ground itself—specifically, fields treated with fertilizer made from sewage sludge. This points to a hidden, overlooked path for pollution.

Chance Discovery in the Heartland

Fieldwork rarely goes exactly as planned. Researchers often chase one question, only to get sidetracked by the data. That’s what happened in Oklahoma, where scientists were using high-tech sensors to track the evolution of airborne particles. Instead, they found unmistakable chemical fingerprints of MCCPs—pollutants usually associated with heavy industry and previously found only in places like Asia or even Antarctica, but never before in North or South America’s air.

“It’s exciting as a scientist to find something you weren’t expecting,” said Daniel Katz, a chemistry PhD student at CU Boulder and the study’s lead author. “We know these pollutants are out there, but understanding how they move and where they show up is crucial.”

Why MCCPs Matter

MCCPs are under global scrutiny as potential threats to human health. They’re being considered for regulation under the Stockholm Convention, the international treaty targeting persistent, widespread chemicals. While they’re common in products like metalworking fluids, PVC, and textiles, MCCPs also sneak into wastewater and, eventually, into biosolid fertilizers spread across farmland.

The Oklahoma findings suggest that when these fertilizers are used, MCCPs can evaporate and be carried by the wind. Katz and his team can’t prove the connection outright, but the evidence lines up—and other studies have shown similar chemicals escaping from sludge-based fertilizers.

A Regulatory Ripple Effect

MCCPs are chemical cousins of Short Chain Chlorinated Paraffins (SCCPs), which have been tightly regulated for years because of their ability to travel long distances, persist in the environment, and pose health risks. But as regulators cracked down on SCCPs, many industries switched over to MCCPs—trading one hazard for another.

“There’s always this dance with regulations: you ban one thing, and something else takes its place,” explained Ellie Browne, chemistry professor and CIRES Fellow at CU Boulder, who co-authored the study.

How They Spotted the Toxin

The research team didn’t just take a few air samples—they set up round-the-clock monitoring, using a sensitive instrument called a nitrate chemical ionization mass spectrometer. Over a month, the machine sniffed out chemical signatures in the air, and eventually Katz noticed odd patterns in the data. After digging deeper, he traced them to MCCPs.

Echoes of “Forever Chemicals”

MCCPs share some nasty traits with PFAS—the infamous “forever chemicals” that barely break down in nature. In fact, growing concern over PFAS in Oklahoma’s soil recently pushed state lawmakers to ban biosolid fertilizers.

Now, with a method to spot MCCPs in the air, scientists want to know how these toxins ebb and flow with the seasons, and what happens once they’re airborne. Do they linger? Do they pose health risks? No one knows yet.

“We’ve figured out how to find them,” Katz said. “But we still don’t know what these chemicals do once they’re swirling in the atmosphere. There’s a lot more to learn, and it’s vital that agencies keep up with the science so we can protect public health.”

Although this study was conducted in Oklahoma, it is likely an emerging problem nationwide. Recent studies have found that farm workers are at a higher risk of health issues related to pollutants than the general population. This may also be an issue for people who live in farm country.

Pro Tip: Limit time outside on high-impact air quality days. If the air seems stagnant, this is your cue to stay inside, especially if you are elderly, have chronic respiratory issues, or have seasonal allergies. If you live in farm country, the intense smell of fertilizer in the Spring can pose a respiratory threat.