"There are many unknowns about the impacts of nanomaterials on living organisms and ecosystems, but a great deal is known about the properties of the materials that are used to create nanomaterials," said Mark Wiesner of Rice University. "Our goal was to produce an early estimate of the environmental footprint for nanomaterials fabrication."
Wiesner and colleagues assessed single-walled carbon nanotubes made by a HiPco process, fullerenes (C60 molecules), zinc selenide quantum dots, alumoxane nanoparticles and titanium dioxide nanoparticles. They assigned the processes levels of risk according to properties of the raw materials, such as toxicity, volatility, carcinogenicity, flammability and environmental persistence, and process parameters, such as temperature and pressure.
The researchers also used an actuarial protocol developed by the insurance industry to provide risk ratings for incident risk, i.e. the impact of an in-process accident that leads to accidental exposure, normal operations risk, namely the risk from substances emitted during the fabrication process, and latent contamination risk - the potential for long-term contamination of the operations site.
"This type of risk assessment, although not inclusive of all environmental impacts or life-cycle considerations, is representative of the type of risk assessment nanomaterials manufacturers will encounter as insurers grapple with qualifying the relative risk of these new processes," the researchers said in a paper in Environmental Science and Technology.
The team compared their results for nanomaterials with those for manufacturing silicon wafers, wine, high-density plastic, lead-acid car batteries, refined petroleum and aspirin. For nanotubes and alumoxane nanoparticles, the normal operations risks were comparable to those of making wine or aspirin. Producing zinc selenide quantum dots, fullerenes and nano-titanium dioxide were generally higher risk
"We can't anticipate all of the details of how nanomaterials fabrication will evolve, but based on what we do know, the fabrication of the nanomaterials we considered appears to present lower risks than current industrial activities like petrochemical refining, polyethylene production and synthetic pharmaceutical production," said Wiesner. "That doesn't imply that the non-nano processes present an acceptable level of risk, or that there is no room for improvement across the board, but the study does suggest that the risks of making these new materials will not be drastically different from those we encounter in current industries."
Wiesner and colleagues suggest that nanomaterials manufacturers could reduce the normal operations risks by using rigorous processes that recycle and recapture materials.
The scientists also state in their paper that "the production of significant quantities of anthropogenically derived nanomaterials will inevitably result in the introduction of these materials to the atmosphere, hydrosphere and biosphere".
The researchers reported their work in Environmental Science and Technology.