All bioplastics are edible

Bioplastics can be toxic

Because of eco: bioplastics are by no means more non-toxic than conventional plastic - on the contrary, as laboratory tests have now revealed. 80 percent of the materials examined contained cell-toxic or otherwise harmful chemicals. Surprisingly, this was especially true for starch- and cellulose-based plastics. In addition, most bioplastic objects contained more than 1,000 different chemicals, some even a good 20,000.

In view of the flood of plastic waste, bioplastics are seen as the more sustainable alternative. Because many of these materials are made from vegetable raw materials, others are biodegradable or even both - at least that's what they say. In practice, however, the main problem is with the degradability of many of these materials, as studies show. Scientists also fear that the increasing demand for vegetable raw materials could lead to increased deforestation.

Are Bioplastics Healthier?

Are the bioplastics then at least less harmful to health? After all, in addition to its basic components, conventional plastic contains a lot of plasticizers and other additives, some of which have considerable harmful effects. Lisa Zimmermann from the Goethe University in Frankfurt and her colleagues have now examined what it looks like with the biological alternatives in the most comprehensive study to date.

To do this, the researchers analyzed 43 everyday objects made of nine different bioplastic materials - from drinking cups made of polylactic acid to chocolate foil or cigarette filters made of cellulose derivatives to plastic bags made of bio-polyethylene. All samples were chemically analyzed for their components, and the scientists also tested the biological effect on cell cultures.

Three quarters are toxic to cells

The result: "Three quarters of all products examined contained harmful chemicals," reports Zimmermann. “In this case, harmful means that substances have a toxic effect on cells or cause hormone-like effects.” Specifically, 67 percent of the samples showed a toxic effect on cells, 42 percent caused oxidative cell stress and 23 percent disrupted the effect of male sex hormones.

"These results show that the bio-based and biodegradable materials are by no means less of a concern," says Zimmermann. Because for everyday objects made of normal plastics, an earlier test came up with similar values. The only difference: the proportion of cell-toxic samples was greater in the case of bioplastics, whereas conventional plastics more often contained substances with a hormone-like effect.

Starch and cellulosic plastics are the most toxic

Surprisingly, however: Paradoxically, bioplastics made from starch- and cellulose-based materials, such as those used in disposable tableware, food bags or cigarette filters, have proven to be particularly harmful. "All starch and cellulose products were toxic to cells and many of them contained compounds that acted like hormones," the scientists report. "The chemicals in these materials are therefore more toxic in vitro than others."

And the analyzes revealed something else: the bioplastics contain an unexpectedly large number of chemical components. Zimmermann and her team detected more than 1,000 individual chemicals in 80 percent of the samples. In the case of bioplastics made from starch or cellulose, there were even up to 20,000 components. The researchers suspect that most of these chemicals are added or formed during the preparation and processing of the raw materials. Because in their tests there were clear differences even with products made from the same raw material.

"That makes it almost impossible to make general statements about the safety of certain materials," explains co-author Martin Wagner from the University of Trondheim. "A food-safe bag made of bio-polyethylene can contain toxic substances, a wine cork made of the same material does not necessarily have to and vice versa."

“Organic” does not mean harmless

According to the researchers, their results demonstrate that “organic” does not automatically mean harmless when it comes to plastics. The test on cell cultures does not say anything about how harmful these materials are in everyday use. Nevertheless, the results show that even bioplastics made from plant-based raw materials need not be harmless per se.

Further studies in the course of risk research on plastic and its alternatives are therefore urgently needed. "Precisely because there is a trend towards biomaterials, it is now important to put the chemical safety of conventional plastics as well as bio-based and biodegradable alternatives on the political agenda," says co-author Carolin Völker from the Institute for Social-Ecological Research (ISOE) in Frankfurt. (Environment International, 2020; doi: 10.1016 / j.envint.2020.106066)

Source: ISOE - Institute for Social-Ecological Research

September 18, 2020

- Nadja Podbregar