A toxic industrial chemical that has never before been measured in the air above the Western Hemisphere turned up over an Oklahoma wheat field during a routine air study in Lamont, detected by an instrument that was not deployed to find it.
Findings published in ACS Environmental Au in 2025 recorded the first confirmed airborne detection of medium chain chlorinated paraffins, known as MCCPs, anywhere in the Americas. The University of Colorado Boulder team ran continuous air measurements at the Lamont agricultural monitoring station for a full month using a nitrate chemical ionization mass spectrometer, a device sensitive enough to identify individual chemicals present at parts per quadrillion in the air, a concentration so small it is roughly equivalent to detecting a single drop of liquid dissolved across 20 Olympic swimming pools. Lead researcher Daniel Katz was cataloguing patterns in the incoming data when he noticed signatures that matched nothing in the instrument’s reference library. He pulled the spectra manually, cross-checked them against known compounds, and matched the peaks to at least 18 distinct variants of MCCPs drifting through the air above the surrounding farmland. No monitoring programme in the Western Hemisphere had ever recorded MCCPs in outdoor air before that month.
To understand why this matters, it helps to know what MCCPs actually are. They are synthetic chlorinated chemicals, meaning they are built in factories from carbon chains with chlorine atoms bonded along their length, and they are manufactured at very high volumes for use across multiple industries. They go into metalworking fluids as lubricants during metal cutting, into PVC plastic as softening agents that keep cables, flooring, and window frames flexible, and into industrial coatings and sealants as flame retardants. The broader chemical family they belong to, collectively called chlorinated paraffins, is among the highest-production groups of industrial chemicals in the world, with an estimated 33 million metric tons generated and consumed globally between the 1920s and 2020. Most people have never heard of them because they are not in consumer products in a visible way; they are inside the materials that consumer products are made from.
The most probable route from factory product to Oklahoma air runs through sewage sludge. Wastewater treatment plants across the United States process industrial and domestic effluent, and one of the byproducts of that process is a semi-solid material called biosolid fertiliser, commonly referred to as sewage sludge. MCCPs enter the wastewater stream from industrial discharge, from surfaces coated with MCCP-containing products being washed in municipal drainage, and from PVC materials breaking down in the waste system. Treatment concentrates the compounds into the resulting solid. That solid is then legally spread onto agricultural fields across the country as a licensed soil amendment, a practice that is widespread and routine in American farming. Once on the field, the compounds sit bound in the soil until temperatures rise high enough to release them through volatilisation, the process by which a solid or liquid compound converts to airborne vapour when heat supplies enough energy to free it from the surface. Concentrations in the Oklahoma air peaked at approximately 3 nanograms per cubic meter during the hottest daylight hours, thousands of times above the trace background levels recorded at remote Antarctic monitoring stations, then dropped each night as temperatures fell. That daily cycle, driven by temperature, is the same physical process by which many other persistent industrial pollutants move from contaminated land into the air that people living and working nearby actually breathe.
The detection in Oklahoma is not evidence that MCCPs recently arrived in American air. It is evidence that nobody was looking. MCCPs had already been measured in air above Antarctica and at monitoring sites across several Asian cities, establishing that they are capable of travelling long distances through the atmosphere. The assumption in Western Hemisphere monitoring was that local airborne levels were negligible, but that assumption rested on the absence of a dedicated search rather than on actual negative measurements. No instrument capable of detecting MCCPs continuously in real outdoor field conditions had ever been deployed in the Americas before Katz’s team set up in Lamont. The Oklahoma readings were the first time the question was properly asked, not the first time the chemical was present. No federal air quality standard for MCCPs exists in the United States, and no routine EPA air monitoring programme tests for them at any chain length.
Manufacturers turned to MCCPs as a direct workaround after the EPA banned short chain chlorinated paraffins, SCCPs, from new US production in 2009. That ban was based on solid evidence: SCCPs travel long distances, persist in the environment, accumulate in biological tissue, and cause measurable harm. The industrial functions SCCPs performed did not disappear because the compound was banned. Manufacturers needed lubricants for metal cutting, plasticisers for PVC, and flame retardants for cables and coatings. MCCPs, which have slightly longer carbon chains of 14 to 17 atoms compared to the 10 to 13 in SCCPs, slotted into many of the same formulations without triggering the existing regulatory restriction. Global MCCP production volumes now exceed those of both the shorter and longer variants of the same family. Monitoring data from soils, surface water, and biological tissue at sites worldwide now record higher MCCP concentrations than SCCP concentrations, a direct numerical outcome of that substitution running unchecked for over a decade.
The health picture for MCCPs is built from animal studies and human tissue sampling rather than from long-term population studies, because population-level research at environmentally relevant doses has not been completed. What the animal data shows is consistent across several organ systems. Repeated MCCP exposure in laboratory settings damages the liver, kidneys, and thyroid. MCCP mixtures have produced decreased pup survival and internal bleeding in animal studies. At the cellular level, the compounds activate oxidative stress pathways, meaning they trigger a chemical state in cells that damages proteins, fats, and DNA over time, and they disrupt immune signalling in fat tissue in ways linked to metabolic disorders including insulin resistance. Critically, MCCPs have already been detected in human cord blood, breast milk, placenta, hair, and nail samples across multiple countries. Those detections confirm the compounds already cross biological barriers and are present inside human bodies at population scale, before any inhalation exposure from farm air has been formally assessed.
The comparison to PFAS is chemically grounded rather than rhetorical, though the two classes are structurally distinct. PFAS, the group of synthetic chemicals that has driven lawsuits, congressional hearings, and widespread public alarm over contaminated drinking water across the United States, are persistent because their carbon-fluorine bonds are among the strongest in chemistry and resist breakdown in the environment and the body. MCCPs belong to a separate chemical class and are built around carbon-chlorine bonds rather than carbon-fluorine bonds, but the practical outcome is similar: both resist enzymatic breakdown, both accumulate in fat tissue with repeated low-level exposure, and both concentrate up the food chain. Bioaccumulation factors measured in Great Lakes aquatic food webs place MCCPs at log values between 6.3 and 6.8, meaning organisms higher up the food chain carry body burdens of MCCPs millions of times higher than the concentration in the surrounding water. Humans, sitting at the top of that food chain, receive that accumulated load through diet before any contribution from farm air is added on top.
The gap the Lamont detection exposes is geographic and seasonal as much as regulatory. The Oklahoma data covers one monitoring station operating across one month in warm weather. Volatilisation peaks when temperatures are high, so winter readings, when colder conditions keep more of the compound locked in soil or settled as dust, do not yet exist for any American site. Whether the 3 nanogram per cubic meter daytime peak at Lamont reflects conditions typical of American agricultural air generally, or an unusually heavy local load from nearby field applications, cannot be determined without measurements at additional sites and across additional seasons. The instrument method Katz developed for continuous real-time MCCP detection in open field conditions is the first of its kind anywhere, and deploying equivalent instruments at existing EPA National Ambient Air Monitoring System stations would establish what a national baseline actually looks like.
As of April 2026, no federal exposure guideline for airborne MCCPs exists in the United States. The Stockholm Convention evaluation of MCCPs for global restriction is ongoing. In Oklahoma, legislation to restrict and ultimately ban the land application of biosolid fertiliser has passed the Senate Energy Committee and advances to the Senate floor, with a conditional prohibition tied to the outcome of an Oklahoma State University study due by December 1, 2029. The University of Colorado Boulder team is continuing analysis of the Lamont dataset, with seasonal monitoring planned to track how MCCP concentrations shift across temperature cycles and how the compounds transform chemically once airborne.
