MCCPs may be less easy to pronounce than PFAS, but they are just as stubborn. Just like the latter chemical substances used in particular in frying pans for their non-stick properties, medium chain chlorinated paraffins (MCCP) can be described as eternal pollutants. Researchers at the University of Colorado Boulder (USA) detected MCCPs in North American air for the first time in 2025, while surveying the presence of aerosols in an agricultural region of Oklahoma. These toxins had previously been found in Asia and even Antarctica.
These chemicals take a very long time to break down in the environment. They could also cause health problems such as liver and kidney toxicity, and certain neurological and thyroid disorders. American scientists discovered MCCPs using a technique known as nitrate ion chemical ionization mass spectrometry. They published their first results in the journal ACS Environmental Au, as reported by Popular Mechanics.
Lubricating, softening and insulating, MCCPs are used in machining fluids, certain textiles and PVC objects. They often end up in wastewater. This is where the problem begins: biosolids are produced from treated sewage sludge which are used as fertilizer in agricultural crops. “When this sludge is spread on fields, MCCPs could be released into the airwrites the lead author of the study, Daniel Katz, in a press release. We cannot yet prove this, but it would be a reasonable explanation for their presence in the atmosphere. We know that other wastewater-based fertilizers already release similar substances.”
The irony is that the creation of this synthetic chemical follows the banning of a cousin toxin: short-chain chlorinated paraffins (SCCP). The American Environmental Protection Agency and the Stockholm Convention on Persistent Organic Pollutants, as well as China, have adopted regulations in this direction in recent years, particularly since the turn of the millennium.
The European Union is slow to ban the substance
In 2025, the Stockholm Convention also included MCCPs on its blacklist, synonymous with a ban. The transition from the short chain to the medium chain will therefore not have been enough. It remains to be seen whether this cat and mouse game will lead to the creation of a new dangerous substance. An endless cycle, all things considered quite representative of the impossible mission represented by the elimination of eternal pollutants. “These are the undesirable effects of regulationdeplores Ellie Browne, co-author of the study. When we ban a substance but we still need the product it was, it just gets replaced by another substance.”
There is still some good news. The European Commission, all members of which are signatories to the Stockholm Convention, announced that it would add MCCPs and two other substances to its list of banned perennial pollutants. The public consultation ended in December 2025. The amendment was then due to come into force at the beginning of 2026, but it is slow to be published in the Official Journal.
The Oklahoma Senate goes even further. It passed a law last year banning the use of biosolids as fertilizer. An environmental association was also created to try to extend the ban to the whole country – the national agency regulates them without banning them. The effort must be continued, because the United States is one of the rare countries not to have ratified the Stockholm Convention.
Still, MCCPs now float in the air. Boulder scientists hope to shed light on their behavior and dangers. “It is important for public health to continue to have government agencies capable of understanding the science and regulating these chemicals”concludes Daniel Katz. Barely disguised response to the Trump administration’s purges of regulatory agencies.
