Scientists say chemicals could undercut global plastics treaty

Next week the United Nations intergovernmental negotiating committee will meet in Uruguay to develop an international legally binding instrument on plastic pollution. There is concern brewing among scientists that the negotiations will overlook the diversity and complexity of chemicals present in plastics. This would severely undermine the treaty's effectiveness, according to a new article published today in Environmental Science & Technology Letters.

Plastics are complex materials. A recent study has identified more than 10,000 chemical substances that may have been used in plastic production, resulting in plastics that may contain a wide range of chemical substances. Even though many of these chemicals may serve the same function, a general lack of coordination among manufacturers has resulted in plastics from different manufacturers often having different chemical compositions for the same applications.

Such diversity and complexity of plastic formulations comes along with various negative impacts and challenges. Among them, the concern about the adverse impacts on human and ecosystem health of many chemicals in plastics (which can leach out of the product during its lifetime) has been increasingly raised by scientists and civil society organizations. However, this is not all. Equally important but often overlooked: the diversity of chemicals in plastics can pose many challenges to the current and envisioned technological solutions to plastic pollution.

"This diversity of chemicals in different plastic products make[s] different waste streams incompatible. This incompatibility can significantly reduce the quality of recycling products, resulting in down-cycling, and leading to toxic waste that requires extra safe handling measures," says lead author Dr. Zhanyun Wang, a scientist from Empa-Swiss Federal Laboratories for Materials Science and Technology.

Dr. Antonia Praetorius, assistant professor at the University of Amsterdam, further adds, "A proposed solution to counteract plastic waste caused by single-use plastics is the increased use of more durable plastics, e.g., to allow for multiple reuse cycles of plastic takeaway food containers. The more complex the chemical makeup of these durable plastics, the more difficult it is to ensure their integrity and safety over extended product lifetimes."

Nevertheless, there is now room for optimism for advancing global solutions to plastic pollution. The authors strongly recommend that policymakers and business leaders use the unique opportunity provided by the plastic treaty negotiations to join forces and redesign plastics. By identifying a common set of safe chemical additives serving certain key functions, simpler and more standardized plastic formulations can be achieved.

In particular, the authors make concrete actionable recommendations on how the treaty can include mechanisms to reduce the diversity and complexity of chemicals in plastic production. This will not only allow for phasing-out hazardous chemicals from plastic production, but also enable the societal transition to a circular plastic economy.