The study, in which scientists from the Institute of Agrochemistry and Food Technology (IATA-CSIC), located at the University of Valencia Science Park (PCUV), have participated, has had the collaboration of the Institute of Environmental Diagnosis and Water Studies (IDAEA-CSIC) and the Susplast platform. The work, published in the Journal of Hazardous Materials, has analyzed the toxicity of compostable plastic bags, conventional plastic bags and other recycled plastic bags in zebrafish cells. The results show a high level of toxicity in compostable plastic bags, which increases with photodegradation, i.e., when ultraviolet rays hit them. Although the study is preliminary, with a small number of bags, these results are representative of the degradation processes of the bags.
During the investigation, the bags were extracted to analyze the toxic compounds that could be released into the environment. The toxicity of these compounds was evaluated with zebrafish cell lines in three different situations: directly, from the samples of the bags; after a simulation of aging of the bags with ultraviolet rays (photodegradation); and by means of the small fragments of the bags that remained after being converted into quality compost. Finally, the compost resulting from the bag composting process was analyzed.
"We were surprised that cells exposed to conventional plastic bags showed no traces of toxicity. However, we did detect it in the biodegradable ones, which decreased cell viability," explains Cinta Porte, lead author of the study and researcher at IDAEA-CSIC. She added that "our hypothesis is that manufacturers add chemical additives to biodegradable bags that could be particularly toxic." In addition, recycled plastic bags also showed higher levels of toxicity than conventional ones, as plastic additives would also be added for reuse.
"We were surprised that cells exposed to conventional plastic bags showed no traces of toxicity. However, we did detect it in the biodegradable ones, which decreased cell viability," Cinta Porte, lead author of the study and researcher at IDAEA-CSIC
The biodegradable plastic bags, which are currently available in the fruit and vegetable section of supermarkets, have the "OK compost" seal, which indicates that they comply with the characteristics and current legislation to be industrially compostable. The study shows that the toxicity observed in compostable bags is transferred to the compost during the biodegradation process, which has repercussions on the accumulation of contaminants, which can affect the environment and negatively impact the health of the population.
"The toxicity observed may derive both from the additives used during processing and from the fragments of biodegradable plastics produced during composting," says Amparo López Rubio, a researcher at IATA-CSIC, where they have a Unit for Certification of Compostability and Biodegradability of materials.
"It is necessary to thoroughly investigate the migration and ecotoxicity of these new materials and establish a good regulatory framework, based on scientific evidence, to ensure their safety before they reach the market. We need an open and transparent interaction with companies that will allow us to advance in the development of materials that, in addition to being more sustainable, are safe," adds López Rubio.
"It is necessary to thoroughly investigate the migration and ecotoxicity of these new materials and establish a good regulatory framework, based on scientific evidence, to ensure their safety before they reach the market. We need an open and transparent interaction with companies that allows us to advance in the development of materials that, in addition to being more sustainable, are safe", Amparo López Rubio, researcher at IATA-CSIC
Similar toxicity levels
The specific chemical compounds added to these compostable bags could not be identified in the study, as many additives are protected by patents. "Although each manufacturer may add different additives to their products, we have observed that all biodegradable bags have similar levels of toxicity," says Tiantian Wang, first author of the study and predoctoral researcher at IDAEA-CSIC.
The research team points out that this is a preliminary study and urges further research into the toxicity detected in biodegradable bags. In addition, they insist on the need to take measures to regulate the plastic additives that are added to these bags.
Reference:
Wang, T., Hosseinzadeh, M., Cuccagna, A., Alakenova, R., Casademunt, P., Reyes Rovatti, A., López Rubio, A., Porte, Cinta. Comparative toxicity of conventional versus compostable plastic consumer products: An in-vitro assessment. Journal of Hazardous Materials. DOI: 10.1016/j.jhazmat.2023.132123