New Insights on How Plastics Release Chemicals to Marine Life
A team of scientists demonstrated that certain plastics shed chemical additives not only as they degrade in the environment but from the moment they are discarded into land or sea. Although physical breakdown into small fragments takes time, the chemicals inside start leaching as soon as plastics enter water.
SinTEF Ocean research scientist Lisbet Sørensen explains that the study centers on marine life, looking at two groups of microorganisms: bacteria and microalgae, or phytoplankton.
“The focus then shifted to cod eggs and larvae, one of our most vital natural resources,” Sørensen notes. “We recognize that juvenile fish, like humans, are more vulnerable to pollution’s health effects,” she adds.
Across the project, fifty plastic products were tested, including supermarket bags, disposable cups, dishwashing gloves, tire granules, various children’s toys, and balloons. Some items, such as rubber materials, were added later in the research.
What happens when plastic breaks down?
“We were surprised by the variety of chemicals detected in these products,” says Sørensen, who leads a multinational team of biologists and chemists. “Only about 30 percent of identified compounds appeared in two or more products. There are many chemicals that cannot be identified with certainty because they are not listed on standard substance inventories. This reveals how little we know about the composition of everyday products around us.”
The project aimed to determine how toxic these chemicals are to living organisms exposed to plastics in the marine environment. When plastics break down, they form microplastic particles, yet chemical additives can leak out long before this process completes.
Natural rubber is far from harmless
The research team studied how chemicals leached from microplastics and rubber particles affect marine life.
SinTEF principal investigator Andy Booth notes, “Products with high rubber content showed the strongest adverse effects on the microorganisms tested. This was surprising, given that natural rubber is often considered a benign material.” He adds that rubber emerged among the most toxic substances in the experiments.
Chemicals migrating from rubber gloves were particularly harmful. “Additives used in natural rubber and common in dishwashing gloves proved to be the most toxic to the microorganisms we studied,” Booth states. “Four of the fifty products analyzed included these ingredients: dishwashing gloves, car tires, rubber balloons, and disposable gloves.”
Deformed fish larvae
Another part of the project exposed cod embryos and larvae to microplastic particles and the chemical compounds found in plastics. Eggs and larvae were also exposed to a combination of both, mirroring real-world exposure. The team published results in journals including the Journal of Hazardous Materials and Marine Pollution Bulletin, with findings summarized in Total Environmental Science.
The researchers first identified and isolated toxic chemicals from different plastics and studied their effects on cod larvae.
Some chemicals were observed to prevent eggs from hatching, while others caused notable physical changes in the larvae. Biologist Stefania Piarulli describes vertebral deformities resembling scoliosis in the developing fish, underscoring the range of harm chemicals can cause.
Which is worse, microplastics or chemicals?
Is the danger from physical microplastic particles due to their size, or from the chemicals they release? The researchers compared the effects of particles and chemicals separately and found that the toxic impact arises from the chemicals themselves. The study also introduced a new method to separate microplastics from residual chemicals, enabling a clearer understanding of particle-only effects. In the end, toxic effects did not appear when clean microplastics were free of chemical additives.
Elastic plastics stand out
The team found that not all plastics are equally harmful. The toxicity depends on the combination of polymers present, with elastic plastics showing among the strongest effects in tests.
Booth emphasizes, “Reducing toxicity can come from selecting alternative polymer blends during production.” He also notes that the additives found in natural rubber used in dishwashing gloves were among the most dangerous to microorganisms.
What about mammals and humans?
Researchers also considered potential effects on humans. Do animals raised for food or people ingest these chemicals via meat, dairy, or packaging? Stefania Piarulli explains that both humans and wildlife are continually exposed to macro and microplastics along with chemical additives. More research is needed to quantify how much comes from meat products versus packaging, and to understand the broader exposure pathways from food processing and cooking. He stresses that while plastic in daily life is essential in many contexts, it should be used thoughtfully and where alternatives are feasible.
Sørensen adds that items used for food storage and consumption tend to be less problematic, but food-contact materials are regulated to limit chemical additives. She cautions that everyday consumer products, especially those designed for children, may not have been as thoroughly evaluated in these experiments. While this project did not directly measure human health effects, it highlights the need to curb plastic use and to choose safer materials when possible.
“Never before has the pollution level been as high as it is today,” Piarulli remarks. “Reducing plastic use remains a key goal, and there are tangible steps consumers can take to influence demand for safer products.” He also points to the essential role plastics play in medicine and certain packaging, while urging awareness of unnecessary uses in textiles and over-packaged items. Consumer choices can help shift production toward safer, lower-toxicity materials.
The researchers reference a DOI for further details: 10.1016/j.jhazmat.2023.131810
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Environmental department contact information was provided as part of the study materials but is not included here.