In an article published on January 18, 2022, in the journal Chemosphere, Joanke van Dijk from Utrecht University, Netherlands, and co-authors presented an in silico approach for designing safe and sustainable alternatives to chemicals with known human or environmental health hazards.
The authors outline how to identify chemicals suitable for redesign based on aspects mentioned in the EU’s Chemicals Strategy for Sustainability (FPF reported), especially the essential-use concept (FPF reported and here). After confirming the essentiality of the chemical’s function, they recommend redesign for recycling when emission into the environment can be excluded, and if not, redesign for degradation.
Van Dijk et al. used the organophosphate triisobutylphosphate (TiBP, CAS 126-71-6), a persistent flame retardant prone to enter the environment, as a case study to apply their computer-aided redesign approach. They first created 6.3 million alternative structures of TiBP in silico followed by quantitative structure-activity relationships (QSARs, FPF reported) to identify and then filter out structures that are potentially not biodegradable. QSAR models use chemical structures and molecular characteristics to make predictions on a substance’s physio-chemical and environmental properties. Using a multi-criteria analysis based on the predicted properties and the ability to synthesize the compounds, the set of suitable chemicals was broken down, and the compound di-n-butyl (2-hydroxyethyl) 28 phosphate was manually selected for synthesis. When further investigating the selected alternative, the scientists reported that it shows “favorable characteristics compared to TiBP, while first experimental results do not confirm enhanced biodegradability.” As one potential reason, the authors cited the current limitations of QSARs. To reliably predict biodegradability, the QSAR models will need further development.
Dijk et al. discussed other limitations of their current process for identifying chemical replacements and suggested multiple options to improve their approach. The researchers stressed the importance of improving the understanding of biodegradation mechanisms, which would lead to more accurate testing and prediction methods. The authors concluded that the presented approach “can be expanded and further verified to reach its full potential in the mitigation of chemical pollution and to help enable a safe circular economy.”
This latest approach includes elements of alternative assessment, as well as green and circular chemistry (FPF reported and here). The Organization for Economic Co-operation and Development (OECD) previously reviewed approaches to support alternatives assessment (FPF reported). In a commentary article published on January 25, 2022, in the journal Nature Review Materials, Vânia G. Zuin and Klaus Kümmerer from Leuphana University Lüneburg, Germany, emphasized that the design of new and better materials and improved circularity are not enough. Along with improved design, they suggest that “more sustainable systems” have to be created to overcome problems associated with plastic use. In particular, Zuen and Kümmerer suggest a focus on chemistry and material science is key to the improvement process. Their article further discusses “challenges and limitations of plastics,” including their chemical diversity, recoverability, and abundance and “the need for chemical and non-chemical approaches to overcome them.”
References
Van Dirk, J. et al. (2022). “Safe and sustainable by design: A computer-based approach to redesign chemicals for reduced environmental hazards.” Chemosphere. DOI: 10.1038/s41578-022-00415-2
Zuin, V., G. and Kümmerer, K. (2022). “Chemistry and materials science for a sustainable circular polymeric economy.” Nature Review Materials. DOI: 10.1016/j.chemosphere.2022.134050
