Carbon nanotubes have advanced toward energy and health applications, but misconceptions remain

The growing use of carbon nanotubes (CNTs) and a European Union proposal to ban the entire class of materials highlight the need for an updated, standardized approach to assessing the human and environmental impacts of CNTs and products that contain them, according to a new collaborative study co-authored by Rice University researchers.

More than 5,000 tons of CNTs are produced each year for use in research laboratories and commercial industries. Due to their unique properties, CNTs are used in various applications such as batteries, lightweight construction materials, functional textiles, wearable devices and, increasingly, in biomedical research.

“As we move toward a clean and diverse energy and materials revolution, the field of advanced materials needs a clearly defined scientific path for measurement, identification, classification and reporting throughout the material life cycle, from development to disposal, in order to fully scale CNTs across sectors and industries while also benefiting society and the environment,” said Rachel Meidl, energy and sustainability researcher at Rice’s Baker Institute for Public Policy and co-author of the study published in the journal Nature documents.

In 2019, a European Union (EU) non-governmental organization added carbon nanotubes to a list of chemicals that it said “should be restricted or banned in the EU”, citing concerns from some of the numerous published works studying toxicology. and the environmental persistence of carbon nanotubes.

The authors of the new study investigated how carbon nanotubes have been classified chemically, given their many and diverse forms and the ways they can be processed, modified or used. The results of toxicological and environmental studies varied widely, depending on these different forms of carbon nanotubes and how the studies were conducted.

“We realized that there were so many different forms of carbon nanotubes that it seemed strange that such diverse materials could even be classified under a single name,” said Daniel Heller, study co-author and head of the Cancer Nanomedicine Laboratory at Memorial. Sloan Kettering Cancer Center and Rice alumnus.

“We also found that the toxicological and environmental risks of carbon nanotubes depend heavily on these differences, as does how different forms of silicon dioxide can either cause silicosis, a lung disease, or help keep your teeth clean by as an ingredient in toothpaste.”

The authors suggest that the volume and prevalence of these materials and the nuanced and inconsistent picture of risks require that they be classified and defined more precisely in order to identify toxicological and environmental risks. Investigators should adopt more consistent classification methods and measurement standards and consider potential toxicological and environmental impacts throughout the life cycle of materials containing carbon nanotubes, including when they are used to replace more toxic or polluting materials, they said.

The authors recommend the construction of a comprehensive framework to classify, characterize and evaluate the potential impacts of CNTs on health, environment and safety, as this would have a positive impact on both research and industry. And these tasks will provide policymakers with data-driven tools to selectively regulate subsets of CNTs considered high risk, while ensuring that all restrictions on synthesis, production, manufacturing, Use, transport and disposal are based on scientific data and cause minimal disruption to operations. the emerging field of carbon nanomaterials.

Additionally, the transition to a circular carbon economy will mean that researchers will strive to design waste or use carbon valorization pathways that view end-of-use CNTs and CNT-based products as a resource.

“Carbon nanotubes may have significantly fewer energy and material requirements as well as fewer environmental and social consequences than other materials, making them ideal for the energy transition,” said co-author Matteo Pasquali, professor AJ Hartsook of Chemical and Biomolecular Engineering and Director. from Rice’s Carbon Hub. “For example, they are the only credible alternative to copper and aluminum for large-scale electrification and to steel for large-scale construction.

“Toxicological studies carried out at the beginning gave contrasting results and are no longer applicable to the new generation of materials, manufactured with much better control of structure, purity and macroscopic form,” he continued. . “Standardization of CNT classifications is necessary to sort the wheat from the chaff, so that policymakers are able to minimize risks to workers and consumers while creating regulatory certainty for the industry, researchers and the general public.”

The authors argue that addressing this problem from a systems perspective presents opportunities to expand the application of carbon materials in the industrial, commercial, and medical sectors; support a dynamic and competent workforce; ensure responsible development, use and end-of-life management, from laboratory to market; and help the world achieve global climate goals and sustainability goals.