Scientific fieldwork does not always go as planned. Researchers often set clear goals, but the data can sometimes lead them in unexpected directions.
That’s exactly what happened during a University of Colorado Boulder field study in an agricultural region of Oklahoma. The research team was using advanced equipment to study how airborne particles form and evolve. Instead, they discovered something surprising. It was the first time medium-chain chlorinated paraffins (MCCPs), a type of toxic organic pollutant, were detected in the air in the Western Hemisphere. The survey results are ACS environmental gold.
“It’s very exciting as a scientist to find something unexpected like this that we weren’t looking for,” said Daniel Katz, a chemistry doctoral student at the University of California, Boulder, and lead author of the study. “We’re starting to learn more about this toxic organic pollutant, but we know it exists and we need to understand it better.”
What is MCCP and why is it important?
MCCP is currently being evaluated for possible regulation under the Stockholm Convention, an international agreement aimed at protecting human health from persistent and widespread chemicals. These pollutants have been detected before in places such as Antarctica and Asia, but until this study, scientists had struggled to measure them in the Western Hemisphere’s atmosphere.
These chemicals are commonly used in industrial processes such as metalworking fluids and PVC and textile manufacturing. They frequently appear in wastewater and can end up in biosolid fertilizers, also called sewage sludge, produced during wastewater treatment. Researchers believe the MCCP detected in Oklahoma likely came from nearby fields where this type of fertilizer was applied.
“When sewage sludge spreads over fields, those toxic compounds can be released into the air,” Katz said. “While we can’t directly show that that’s happening, we think it’s a reasonable possibility that they’re being kicked up into the air. Fertilizers in sewage sludge have been shown to release similar compounds.”
Possible side effects of regulation
MCCP is closely related to short-chain chlorinated paraffins (SCCP), which are already regulated by the Stockholm Convention and since 2009 by the U.S. Environmental Protection Agency. These early regulations were based on evidence that SCCPs can travel long distances, persist in the environment, and pose a risk to human health.
However, researchers suspect that by restricting SCCP, industry has substituted it for MCCP, increasing the presence of these related chemicals.
“There are always unintended consequences of regulation. When you regulate something, there’s still a demand for the product that contained that regulation,” said Ellie Brown, a chemistry professor at the University of California, Boulder, a CIRES fellow, and co-author of the study. “So they’re being replaced by something else.”
How scientists tracked chemicals
This finding comes from continuous air monitoring at a facility in Oklahoma. The research team used a nitrate chemical ionization mass spectrometer, a highly sensitive instrument that can identify specific compounds in the air. Measurements were collected 24 hours a day for one month.
Katz analyzed the data and identified unusual isotopic patterns that did not match any known compounds. Further investigation revealed that these patterns were associated with chlorinated paraffins associated with MCCP.
“Forever Chemicals” and links to future research
Katz noted that MCCPs share similarities with PFAS, a group of chemicals that are often referred to as “forever chemicals” because they break down very slowly in the environment. Concerns about PFAS contamination in soil recently led the Oklahoma State Senate to ban biosolids fertilizers.
Now that scientists have confirmed how to detect MCCP in the air, the next step is to track how its levels change over time. Researchers want to understand how concentrations change with the seasons and what effects these chemicals have when suspended in the air.
“We’ve identified them, but we still don’t know exactly what they’re doing in the atmosphere. Further research is needed,” Katz said. “I think it’s important that we continue to have government agencies that can evaluate the science and regulate these chemicals as necessary for public health and safety.”
