The tiny pieces of plastic drifting in the sea carry more than just plastic. Japanese researchers detected numerous chemicals added during the manufacture of consumer goods. Some can persist during their journey through the ocean, adding a chemical dimension to microplastic pollution.
Manufacturers incorporate various substances into plastics to modify their properties. Some slow down their aging, while others make them more flexible or less flammable. These molecules do not necessarily remain trapped in the material when the object is discarded, exposed to sunlight, battered by waves, and gradually fragmented.
Microplastics
Oregon State University · CC BY-SA 2.0 · Wikimedia
Go Suzuki and colleagues analyzed plastic waste collected in coastal areas and offshore waters around Japan. They compared microplastics, very small fragments, with larger pieces. The analyses revealed antioxidants, phthalates used in particular as plasticizers, and brominated flame retardants in both groups.
A compound called DEHP was frequently detected in particular. It is a phthalate whose use is regulated.
The fragments can release certain additives incorporated during their manufacture. The nature and size of the plastic influence these releases. A study of an antioxidant called Irgafos 168 and its oxidation product indicates in particular that its leakage from the material accompanies the fragmentation and aging of the plastic.
The scientists also found hexabromocyclododecane, or HBCD. This flame retardant is classified among persistent organic pollutants, substances that break down slowly in the environment.
Measuring only the quantity or size of waste does not fully describe what it carries. Two fragments of comparable dimensions may contain different substances depending on their material, origin, age, and journey through the marine environment.
The authors therefore propose giving greater consideration to the chemical content of plastics, the persistence of additives, and their transport when assessing risks. A next step will be to better track what happens to these substances, particularly during long journeys at sea.