In recent years, bioplastics have come onto the market as an alternative to conventional plastic products containing potentially toxic chemicals, and a potential solution to the problem of plastic pollution.
Bioplastic has some apparent advantages: it is usually made from recycled material or plant cellulose and it can be biodegradable - or both.
Food and beverage giants such as Nestle, Coca-Cola and PepsiCo have all made recent commitments to reduce plastic use, replacing it with paper or bioplastics.
Nestle, for example, is investing up to CHF2bn to lead the shift from virgin plastics to food-grade recycled plastics and develop innovative sustainable packaging as it aims to reduce its use of virgin plastics by one third by 2025. It also has a commitment to make 100% of its packaging recyclable or reusable by 2025.
But bioplastics are in fact just as toxic as other plastics, according to an article recently published in the journal Environment International.
"Bio-based and biodegradable plastic are not any safer than other plastics," said the lead author of the article, Lisa Zimmermann from Goethe Universität in Frankfurt.
Zimmermann pointed out that products based on cellulose and starch contained the most chemicals. They also triggered stronger toxic reactions under laboratory conditions.
"Three out of four of these plastic products contain substances that we know are dangerous under laboratory conditions, the same as for conventional plastic," added Martin Wagner, associate professor at the Norwegian University of Science and Technology's Department of Biology, and one of the collaborators for PlastX, a research group at the Institut für sozial-ökologische Forschung (ISOE) in Frankfurt.
This group led the work on the largest survey to date of chemicals in bioplastics and plastics made from plant-based materials.
They looked at toxic substances in these types of plastic; substances that can be directly toxic to cells in the laboratory, or act as hormones that in turn can disturb the body's balance.
The study investigated 43 different plastic products, including disposable cutlery, chocolate packaging paper, drink bottles and wine corks.
"Eighty per cent of the products contained more than 1000 different chemicals. Some of them as many as 20000 chemicals," said Wagner.
The study concluded it is almost impossible to keep track of absolutely all the possible harmful effects of so many different materials.
“Even seemingly similar products have their own special chemical composition. A plastic bag made of bio-polyethylene can contain completely different substances than a wine cork made of the same material.
"Making general statements about certain materials becomes almost impossible," said Wagner.
“At present, the consequences this has for the environment and for people's health are still uncertain. We don't know to what extent the substances in plastic are transferable to humans.
"Nor do we know whether the alternatives to bioplastics and conventional plastics are better for us and the environment around us, since so many factors come into play. The alternatives may involve polluting production methods and limited opportunities for recycling, or food production has to give way to obtain the materials for the alternative products. More research is needed.”
Wagner stressed that the food and beverage industry should continue its efforts to explore more environmentally-friendly packaging options.
"The key finding of our studies is that conventional and bioplastics as well as plant-based alternatives contain very complex mixtures of chemicals that can induce toxicity in vitro," he told FoodNavigator.
"While we do not draw conclusions on potential human health risks, our findings should create awareness within the food and food packaging sectors that their products can contain a large number of chemicals, most of which remain unknown and untested for chemical safety. The recent movement to make packaging more environmentally friendly creates opportunity for the industry to at the same time improve the chemical safety of their products."
He added, however, he was not aware of 'any industry initiatives to re-design their packaging to make it contain less toxic chemicals'.
"The solution to minimise the use of toxic chemicals in packaging is to redesign the materials," he said. "While this sounds like an immense task, our results indicate that there are products on the market that contain little or no toxicity. This is good news and shows that the use of toxic chemicals can be easily avoided. However, the fact that chemical formulation of those products is confidential makes it very challenging for other manufacturers to learn from that."
Are bioplastics and plant-based materials safer than conventional plastics? In vitro toxicity and chemical composition