A recent study has revealed a dual nature in the ubiquitous blue plastics that litter the world’s oceans. Scientists have found that a common blue pigment, long considered stable, can leach from degrading plastic and harm marine life in a previously unknown way. This same chemical, however, also carries a unique signature that allows researchers to detect and track plastic fragments down to the nanometer scale, offering a powerful new tool in the fight against plastic pollution.
The discovery recasts certain plastics not merely as inert physical pollutants but as chemical delivery systems, or “Trojan horses,” for other environmental contaminants. Researchers studying heavily weathered plastic fishing gear found that the pigment, copper phthalocyanine (CuPc), creates a secondary threat once it escapes its plastic casing. At the same time, its distinct signal under advanced spectroscopy provides an unexpected method for spotting some of the smallest and most difficult-to-trace plastic particles, fundamentally changing how scientists can monitor the lifecycle of plastic waste in the environment.
The ‘Trojan Horse’ in Blue Plastics
Investigators focused on blue plastic fragments, which are frequently reported in high numbers in environmental surveys. The research identified the synthetic pigment copper phthalocyanine (CuPc), responsible for the vibrant blue color, as a key actor. While CuPc is classified as having low toxicity because of its stability and low solubility, recent findings show it poses a greater risk when it leaches from aged plastics that have spent years degrading in the ocean.
The study highlights a “hidden action” where the pigment itself becomes a secondary environmental threat. As plastics on the seabed are exposed to a combination of mechanical, biochemical, and photo-oxidative processes, they become extremely brittle. This aging allows the CuPc pigment to escape. Once in the water, the pigment was found to exacerbate oxidative stress in cyanobacteria, a vital part of the marine food web. This stress leads to cellular and membrane damage in the microorganisms, demonstrating a direct harmful effect that was previously overlooked.
A New Window into Nanoplastics
One of the most significant challenges in pollution research is the detection of nanoplastics, particles so small they are incredibly difficult to find and analyze. The new research provides a breakthrough by using the very pigment that poses a threat as a beacon for detection. The CuPc chemical gives off a newly discovered, powerful, and specific signal when analyzed with micro-Raman spectroscopy.
This unique spectral signature allows scientists to positively identify plastic particles as small as 500 nanometers. This greatly expands the capability of Raman tools to track the degradation of plastic waste from the macro scale down to the nano scale. By following the persistent signal of the pigment, researchers can now more effectively study how these tiny particles move through the environment and are ingested by living organisms, overcoming a major technical hurdle that has limited the understanding of the full extent of plastic contamination.
From Seabed to Laboratory
The findings were the result of analyzing polypropylene ropes and filaments recovered from the seabed of the Bay of Bistrina on the South Adriatic coast, an area with a long history of intensive shellfish farming. The plastic materials, estimated to have been degrading in marine conditions for about 20 years, were part of discarded fishing nets. They had become so fragile that they spontaneously fragmented into a powder of micro- and nanoparticles simply from being handled and placed in collection vials.
This spontaneous breakdown provided the research team with a ready supply of naturally weathered nanoplastics for analysis. This real-world sourcing is critical, as it ensures the particles studied are representative of what is actually occurring in the marine environment, rather than relying solely on laboratory-generated fragments. The analysis of these powders is what ultimately revealed the unique Raman signal of the CuPc pigment.
Implications for Pollution Monitoring
The dual discovery has profound implications for how plastic pollution is monitored and understood. The “Trojan horse” effect, where the additives within plastic create their own environmental risks, suggests that risk assessments for plastic pollution must evolve. Instead of focusing only on the physical hazards of the plastic polymer, future studies will need to account for the complex cocktail of dyes, stabilizers, and other chemicals that are mixed into plastics during manufacturing.
Furthermore, the novel detection method provides a practical tool that could be widely adopted. By using the blue pigment as an analytical marker, scientists can better track the journey of plastic waste along the entire trophic chain. This could lead to a more accurate understanding of its impact on the health of organisms at all levels, from microbes to large marine animals. The technique offers a robust and selective way to monitor contamination in various environmental matrices, from seawater to sediment and biological tissues.
The Scale of the Invisible Threat
This research into a single blue pigment underscores the broader, often invisible, challenge of nanoplastic pollution. While this study provides a new method for detecting certain types of plastic, it also highlights the immense scale of a problem that is only beginning to be quantified. Other recent research has attempted to measure the total amount of these tiny particles, with one 2025 study estimating that the North Atlantic Ocean alone holds millions of tons of nanoplastics, a figure that may exceed the total mass of larger floating plastic garbage.
Such staggering estimates emphasize the urgent need for innovative detection methods. The lack of standardized protocols for sampling and analyzing micro- and nanoplastics has been a persistent problem in the field. The technique pioneered in this study, leveraging an additive within the plastic itself, represents a creative step forward. It suggests that other chemical components in different colored plastics could potentially be used as markers, opening up new avenues for research and helping to build a more complete and accurate picture of one of the planet’s most pervasive pollution problems.
