Numerous plastic additives were found in microplastic samples taken from various marine and river environments around Japan in a new study.
Led by Go Suzuki of the National Institute for Environmental Studies, Japan, in collaboration with the Tokyo University of Marine Science and Technology and Nagasaki University, a research team analysed additive-derived chemicals in microplastics and larger plastic waste collected from coastal, offshore, riverine and seafloor environments around Japan including Tokyo Bay, the Genkai Sea, Pacific coastal waters, waters off Hokkaido and Sea of Japan coastal waters.
Larger plastic debris collected included bags, ropes, nets and hard fragments, recovered from across coastal Japan, as well as from a river drainage pump station in Tokyo.
Gas chromatography–mass spectrometry was used to analyse samples
As described in Environmental Science & Technology, researchers identified polymer types within the samples taken, finding antioxidants, plasticizers, ultraviolet stabilizers, flame retardants and polycyclic aromatic hydrocarbons.
The study focused on three groups of chemicals due to their high frequency and relevance to pollution management: Irgafos 168-related compounds, di(2-ethylhexyl) phthalate (DEHP) and hexabromocyclododecane (HBCD).
Irgafos 168
This is an antioxidant used to reduce the oxidative degradation of plastics such as polyethylene and polypropylene. Distribution and products of oxidation varied by polymer type and particle size, but the observed patterns of Irgafos 168 were consistent with leading and transformation from within the plastic matrix.
DEHP
This plasticizer is the third most-produced synthetic polymer of plastic and is used to add flexibility to polyvinyl chloride products, such as plumbing cables, inflatables and vinyl records.
This chemical was widely detected in both the larger plastic debris and microplastics (plastic particles smaller than 5 millimetres), with some samples found to have a concentration higher than 1,000 micrograms per gram (equivalent to 0.1% by weight).
Concentrations of DEHP were also higher in floating microplastics than in larger plastic debris sourced from the seafloor, compared to both polyethylene and polypropylene samples. This suggests that DEHP present in surrounding water, suspended particles and organic matter may be sorbed to microplastics from the surrounding environment.
HBCD
A brominated flame retardant, HBCD is primarily used in insulating and cushioning materials in construction as expanded polystyrene. It is regulated as a persistent organic pollutant due to it’s long life, bioaccumulative properties.
HBCD was detected at concentrations of 110–590 micrograms per gram in microplastics collected from the Genkai Sea, Pacific coastal waters and Sea of Japan coastal waters. This suggests that plastic particles containing HBCD can act as a secondary source of exposure in marine environments through their mobility.
Plastic pollution continues after fragmentation
Exposure to the elements causes degradation and fragmentation of plastics, breaking them down into smaller pieces. This process also increases the surface area of plastics relative to mass, which changes how chemicals in the plastics can be transferred into surrounding particles and contaminate environments.
The findings suggest that after fragmentation, chemicals can still leach from plastic matrices in concerning concentrations. Further studies are needed on how this impacts marine environments specifically, as well as informing future regulation around plastic waste management.
