A team of scientists demonstrated that plastics release chemical additives not only as they break down in the natural environment, but from the moment they are discarded in fields or oceans. Although physical degradation into tiny fragments takes years, the additives begin leaching into water right away.
Lisbet Sørensen, a research scientist at SINTEF Ocean, notes that the study centers on effects in the marine environment, examining two groups of microorganisms: bacteria and microalgae, also known as phytoplankton.
“The research then shifted to cod eggs and larvae, a key natural resource,” Sørensen explains. “Like humans, immature fish are more susceptible to pollution’s health effects,” she adds.
Among the 50 plastic products tested were supermarket bags, disposable cups, dishwashing gloves, car tire granules, various children’s toys, and balloons. Some rubber materials were included later in the study.
What happens when plastic breaks down?
“We were surprised by the diversity of chemicals detected across products,” says Sørensen, who leads a cross-border team of biologists and chemists. “Only about 30 percent of the identified compounds appeared in two or more products. Many chemicals are not listed on standard substance inventories, so we cannot identify them with certainty. This reveals how little is known about the composition of everyday items around us.”
The project aimed to determine how toxic these chemicals are to living organisms once plastics enter the sea. When plastics fragment physically or chemically under environmental stress, microplastic particles form. Yet long before that step is reached, additives in plastics can leak into the ecosystem.
Natural rubber is far from harmless
The team investigated how leached chemicals from microplastics and rubber particles affect marine life.
SINTEF principal investigator Andy Booth commented, “Products with higher rubber content caused the strongest effects on the microorganisms studied. It was surprising, given that natural rubber is often viewed as benign. Yet it proved among the most toxic materials in the experiments.”
Chemical compounds released from rubber gloves proved particularly harmful. According to Booth, “Additives used in natural rubber for dishwashing gloves ranked as the most toxic to the microorganisms tested. The four products among the 50 analyzed here include dishwashing gloves, car tires, rubber balloons, and disposable gloves.”
Deformed fish larvae
Another set of tests exposed cod embryos and newborn larvae to microplastic particles and the chemicals found in plastics, including combinations of both to reflect real-world conditions. Findings appeared in the Journal of Hazardous Materials, Marine Pollution Bulletin, and Total Environmental Science. The team identified and isolated toxic chemicals from different plastics and studied their impact on cod larvae.
“Some chemicals directly prevented eggs from hatching, while others caused notable physical effects in larvae,” notes Stefania Piarulli, a SINTEF biologist. “Vertebral deformities resembling scoliosis were observed in the larvae.”
Which is worse, microplastics or chemicals?
Is the danger driven by the physical form of microplastics, or by the chemicals they carry? To clarify, the researchers compared the effects of particles and chemicals separately and found that chemicals were required to produce toxicity.
“A new method was developed to study clean microplastics free of any chemicals,” explains Piarulli. “This is the only way to determine the true impact of microplastic particles.” In short, no toxic effects were detected if the physical particles contained no chemicals.
Elastic plastics are one of a kind
The study shows that not all plastics are equally toxic. The level of harm depends on the mix of plastics involved, with elastic materials showing notably higher toxicity in several tests.
“The takeaway is that reducing toxicity is possible by choosing alternative polymer combinations during production,” says Booth. “Chemical additives in natural rubber used for dishwashing gloves were among the most toxic to microorganisms.”
What about mammals and humans?
Researchers also considered potential effects on humans and other animals. The team notes that both wild and farmed animals, including fish, poultry, and livestock, encounter macro and microplastics with various chemical additives. “Humans are also exposed to plastic-related chemicals through the foods we consume,” explains Stefania Piarulli. “More research is needed to determine how much comes from meat products versus packaging, and other everyday exposures linked to food processing and cooking.”
Lisbeth Sørensen adds that many food-related plastic products are among the least problematic. Food contact materials are strictly regulated to limit defined and undefined additives. “Even so, daily-use plastics, especially those designed for children, did not perform as well in the experiments as food-contact materials,” she notes. The team emphasizes that this project did not test direct human health effects but highlights the broader environmental and ecological implications.
“Never before have we faced pollution at current levels,” says Piarulli. “We should strive to reduce plastic use and their presence in ecosystems. Plastics serve many useful purposes—medical supplies and packaging among them—but they also appear in settings where they are unnecessary, such as in the textile industry and excessive packaging. The key is to minimize usage and influence purchase choices as consumers.”
Reference work: DOI: 10.1016/j.jhazmat.2023.131810
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