Plastic pollution may be carrying a hidden chemical payload across Japan’s coastal waters. A study led by researchers at Japan’s National Institute for Environmental Studies has found that floating microplastics and larger plastic debris contain a wide range of additives and environmental contaminants, including antioxidants, plasticizers, ultraviolet stabilizers, flame retardants, and polycyclic aromatic hydrocarbons. The findings suggest that plastic fragmentation does not eliminate chemical risks. Instead, as bottles, ropes, bags, nets, and other discarded products break into smaller pieces, they may continue transporting hazardous substances through marine ecosystems.
The research team, working with scientists from the Tokyo University of Marine Science and Technology and Nagasaki University, examined plastic collected from a range of environments around Japan. Floating microplastics were sampled from Tokyo Bay, the Genkai Sea, Pacific coastal waters, waters off Hokkaido, and coastal areas of the Japan Sea. Larger debris was recovered from offshore and coastal locations, a river drainage pump station in Tokyo, and seafloor environments. By comparing different polymer types and particle sizes, the researchers investigated whether chemical patterns changed as plastics weathered and fragmented.
The scientists identified the polymers in each sample before extracting chemical compounds for analysis by gas chromatography–mass spectrometry, a technique capable of separating complex chemical mixtures and identifying compounds based on their molecular signatures. Among the many substances detected, three groups received particular attention because of their frequency, concentrations, and environmental or regulatory importance: Irgafos 168-related compounds, di(2-ethylhexyl) phthalate, commonly known as DEHP, and hexabromocyclododecane, or HBCD.
Irgafos 168 is an antioxidant added to plastics such as polyethylene and polypropylene to slow oxidative damage caused by heat, oxygen, and processing. The study found that Irgafos 168 and its oxidation products were distributed differently depending on the type and size of the plastic particles. These patterns were consistent with chemicals leaching out of the plastic matrix and changing through environmental transformation. The result offers a chemical record of how plastic products age after entering the environment, rather than simply acting as inert fragments.
DEHP showed an especially broad distribution. This plasticizer was historically used in large quantities, particularly in flexible polyvinyl chloride products, to make them softer and more workable. It was detected in both microplastics and larger debris, with concentrations exceeding 1,000 micrograms per gram in some samples—equivalent to more than 0.1 percent by weight. The researchers found higher DEHP concentrations in floating polyethylene and polypropylene microplastics than in larger pieces of the same polymers recovered from the seafloor.
That difference points to a process more complicated than chemical release from inside the plastic alone. Microplastics have a much larger surface-area-to-mass ratio than larger fragments, allowing them to interact more extensively with seawater, suspended particles, and organic matter. DEHP present in the surrounding environment may therefore adhere to or partition onto the surface of small plastic particles. In effect, microplastics can function not only as sources of additives but also as mobile surfaces that collect chemicals from their surroundings.
The most striking results involved HBCD, a brominated flame retardant formerly used in materials including expanded polystyrene. HBCD is classified as a persistent organic pollutant because it can remain in the environment, accumulate in living organisms, and travel over long distances. Researchers detected concentrations ranging from 110 to 590 micrograms per gram in microplastics collected from the Genkai Sea, Pacific coastal waters, and Japan Sea coastal waters. These particles may remain mobile after the original plastic product has fragmented, creating secondary pathways for exposure far from the material’s initial point of use or disposal.
The study does not establish how much of these chemicals are absorbed by marine organisms or whether the measured concentrations directly cause ecological harm. However, the findings challenge the idea that chemical concerns disappear once plastic waste is weathered or broken down. Additives may leach from the plastic, transform into new compounds, remain trapped in fragments, or accumulate on their surfaces from contaminated water and sediment. These processes can continue while particles move between rivers, coastlines, open water, and the seafloor.
The researchers argue that plastic pollution and chemical management should therefore be addressed as connected problems. Regulations focused only on the manufacture or sale of products may not fully account for what happens after plastics escape into the environment. Preventing leakage, identifying products that contain chemicals of concern, improving selective collection, and ensuring appropriate treatment could reduce both the physical spread of plastic and the movement of associated contaminants. Further work will be needed to trace the original sources of contaminated debris and determine how organisms interact with the chemicals carried by microplastics. The study provides a scientific foundation for linking marine-litter policies with global efforts to control hazardous substances and develop an international agreement on plastic pollution.
Subject of Research: Not applicable
Article Title: Priority Plastic Additives of Environmental Concern in Marine-leaked Micro- and Macroplastics: Occurrence, Distribution, and Management Implications
Web References: https://doi.org/10.1021/acs.est.6c03000
Image Credits: National Institute for Environmental Studies, Japan
Keywords
Plastics, microplastics, marine pollution, environmental chemistry, chemical pollution, marine ecosystems, plastic additives, DEHP, HBCD, Irgafos 168
