The Principles of Green Chemistry

Green chemistry, which focuses in part on manufacturing, designing or using products and processes to reduce or eliminate threats to human health or the environment, can have an important impact on the emerging field of nanotechnology.

“The golden opportunity with nanotechnology is the opportunity to have influence over those products and processes at the front end instead of trying to deal with an existing process that’s already got capital in the ground and a long product history,” Hutchison said.

The Principles

Hutchison explained that both product- and process-based principles of green chemistry can help create a safer nanotechnology environment. Product-based principles include considering the toxicity or health and ecological impacts of the material; determining if the material is explosive or flammable; and designing the product so it can either degrade into harmless substances or easily be recycled at the end of its life.

Process-based principles, meanwhile, include developing processes that don’t use hazardous agents or substances; using substitutions for overly reaction reagents; reducing the amount of solvents used or even eliminating solvents; considering energy costs and redesigning processes so that extremes of heating and cooling are avoided.

The principles of green chemistry, as listed in the Green Chemistry Theory and Practice by Paul T. Anastas and John C. Warner, include:

• Making efforts to prevent waste rather than treat or clean up waste after it is formed;
• Designing synthetic materials to incorporate all materials used in the process in the final product;
• Designing synthetic methodologies to use and generate substances that possess little or no toxicity to human health and the environment;
• Designing chemical products the preserve the function’s efficacy while reducing toxicity;
• Making the use of auxiliary substances, such as solvents or separation agents, unnecessary when possible or innocuous when used;
• Minimizing the environmental and economic impact of energy requirements and conducting synthetic methods at ambient temperature and pressure;
• Using renewable raw material feedstock whenever possible;
• Avoiding unnecessary derivatization (blocking group, protection/depletion, temporary modification of physical or chemical processes) when possible;
• Maintaining that catalytic reagents are superior to stoichiometric reagents;
• Designing chemical products so that at the end of their function they do not persist in the environment and break down into innocuous degradation products;
• Further developing analytical methodologies to allow for real-time in-process monitoring and control prior to the formation of hazardous substances; and
• Choosing substances for chemical processes to minimize the potential for chemical accidents, such as releases, explosions and fires.

Protecting Workers

“Whenever one can reduce hazards, either in the product or the process, that’s good for everybody – for the people who work directly in producing the material all the way through the life cycle,” Hutchison said.

He pointed out that in occupational settings, people tend to heavily rely on environmental controls to protect workers. Those controls, Hutchison said, are most effective when all the hazards are known. But that might not always be possible.

“In nanotechnology, we don’t know as much about the hazards,” he said. One option is to take a precautionary approach and to wait for more information about potential hazards before acting. But being on the cutting edge of technology, such as with nanotechnology, doesn’t always make that option feasible, Hutchison said.

“A better approach would be to think about all that we do know about material safety and then see how that can be extrapolated to product design,” he explained.

Elemental composition and dimensional bracketing, meanwhile, are two design rules that currently can be implemented to help assure safety. If heavy metals are found while examining a material’s elemental composition, for example, the high surface area of nanomaterials results in an increased probability of those metals being released or leached. And by examining both large- and molecular-scale materials and finding that they both exhibit a hazard, it is likely that the nanoscale material will include the same hazard.

“With respect to process safety, the green chemistry principles really relate well to reducing hazards for the occupational setting,” Hutchison said.

For a related article addressing nanotechnology developments, read Managing Nanotech Hazards with Green Chemistry.

To learn more about green chemistry and its occupational safety implications, sign up for Occupational Hazards’ live Safety WebExpo and Conference, where keynote speakers from UC-Berkeley will offer a cutting-edge presentation on green chemistry, toxics policy and occupational health.