New processes in the laboratory can prevent the creation of industrial pollutants and produce more environmentally friendly products. This evolving technology is minimizing the use of hazardous materials in design and development, thus representing a fundamentally different way to reduce pollution.

Cheryl Pellerin is a science writer for the U.S. State Department in the Bureau of International Information Programs.

The term green chemistry refers to the design of chemical products and processes that reduce or eliminate the generation and use of hazardous substances. The practice began in the United States with the passage of the Pollution Prevention Act of 1990, which established a national policy to prevent or reduce pollution at its source whenever feasible.

The act also provided a way to move beyond traditional U.S. Environmental Protection Agency (EPA) programs and devise creative strategies for protecting human health and the environment. Reducing pollution at the source, according to the act, "is fundamentally different and more desirable than waste management and pollution control."

After the act's passage, the EPA Office of Pollution Prevention and Toxics (OPPT) began to explore the idea of developing or improving chemical products and processes to make them less hazardous. In 1991, OPPT launched a model program that for the first time provided grants for research projects that included pollution prevention in the synthesis of chemicals. Since then, the EPA Green Chemistry Program (http://www.epa.gov/greenchemistry) has built collaborations with academia, industry, other government agencies, and nongovernmental organizations to promote pollution prevention through green chemistry.

Green Chemistry at Work

Chemical manufacturing is the source of many useful products. These include antibiotics and other medicines, plastics, gasoline and other fuels, agricultural chemicals such as fertilizers and pesticides, and synthetic fabrics like nylon, rayon, and polyester. These products are important but some of the chemicals and processes used to make them harm the environment and human health. Green chemistry aims to reduce pollution by preventing its creation in the first place.

In designing a chemical reaction according to the principles of this discipline, chemists pay close attention to what is known about possible hazards a chemical presents to health or the environment before using the chemical in a reaction or creating it as a product. In other words, they treat the hazard a substance poses as a property that must be considered along with other chemical and physical properties, and they select substances that minimize harm.

In their 1998 book, Green Chemistry: Theory and Practice (Oxford University Press), Paul Anastas and John Warner developed 12 principles that give chemists a road map for implementing green chemistry. Four of the principles follow.

1. Get off to a safe start: Identify reactions that use nonhazardous starting materials to make a desired product.

This minimizes danger to workers in manufacturing plants when they handle chemicals and prevents accidental release of harmful chemicals from leaks or explosions. A new way to make an important industrial chemical, adipic acid, illustrates this principle.

Almost 2 billion kilograms of adipic acid are needed each year to make nylon, polyurethane, lubricants, and plasticizers. The standard way to make adipic acid uses benzene, which can cause cancer, as the starting material. In a newly developed process that uses genetically altered bacteria called biocatalysts, the simple sugar glucose is substituted for benzene.

Starting with a safe substance like glucose to make adipic acid means that the use of large quantities of a harmful chemical can be avoided if new processes like this one become widely used.

2. Use renewable resources: Put more emphasis on renewable starting materials, such as substances derived from growing plants, rather than irreplaceable materials like petroleum and natural gas supplies.

The glucose mentioned in the example above as a starting material can be derived from cornstarch or the cellulose found in plant materials. Even corncobs, stalks, and fallen leaves can yield glucose. In another example, cornstarch is used to produce the small, puffed packaging pellets that cushion materials shipped in containers. These pellets can replace plastic packing materials made from petroleum-based chemicals.

3. Find safer solvents: Eliminate the use of toxic solvents to dissolve the reacting materials.

Solvents are chemicals that can dissolve another substance. Many solvents used in large quantities in industry are harmful to health or can create other dangers like explosions or fires. Widely used solvents that carry health risks include carbon tetrachloride, chloroform, and perchloroethylene.

It is sometimes possible to substitute safer solvents like water or liquid carbon dioxide. For example, new dry-cleaning processes for clothing have recently been developed that dissolve grease and dirt using liquid carbon dioxide rather than the toxic chemical perchloroethylene.

4. Economize on atoms: Design reactions in which most or all of the atoms you start with end up in the product rather than in waste byproducts.

Stanford University chemist Barry Trost developed this concept, which he calls atom economy. An example of this principle is an improved process designed in 1991 to make the pain reliever ibuprofen, the active ingredient in the brand name drugs Motrin, Advil, Nuprin, and Medipren.

In the original six-step process developed in the 1960s, only 40 percent of the reactant atoms ended up in the product (ibuprofen) and 60 percent ended up in unwanted byproducts or waste. Trost's new process has three steps, and 77 percent of the reactant atoms end up in the ibuprofen. This green process eliminates hundreds of thousands of kilograms of chemical byproducts every year and reduces by hundreds of thousands of kilograms the amount of reactants needed to make ibuprofen.

Attention to these principles helps the environment and can save companies money in the long run by lowering the cost of pollution control and using less energy.

International Interest

Since the 1990s, many organizations around the world have embraced green chemistry.

The Green Chemistry Institute (CGI) (http://www.chemistry.org/portal/a/c/s/1/acsdisplay.html?DOC=greenchemistryinstitute%5cindex.html) is a nonprofit organization of the American Chemical Society, founded to promote green chemistry through research, education, information dissemination, conferences, symposia, and international collaboration. More than 20 international chapters are affiliated with the Green Chemistry Institute, including ones from Canada, India, Italy, China, South Africa, and Thailand.

In the United Kingdom, the Royal Society of Chemistry launched the Green Chemistry Network (GCN) (http://www.chemsoc.org/networks/gcn), based in the Department of Chemistry, University of York. The GCN promotes awareness and facilitates education, training, and the practice of green chemistry in industry, commerce, academia, and schools.

The CRYSTAL Faraday Partnership (http://www.crystalfaraday.org) in the United Kingdom is a virtual center of excellence in green chemical technology that accesses the resources of industrial and academic participants to promote lower-cost, sustainable manufacturing for the chemical industry. Its three core organizations are the Institution of Chemical Engineers, the Royal Society of Chemistry, and the Chemical Industries Association. Ten consortia and network technology organizations and 18 universities also participate.

In Japan, the Green & Sustainable Chemistry Network (GSCN) (http://www.gscn.net/indexE.html) promotes research and development on green and sustainable chemistry through collaboration, including international activities, information exchange, communication, education, and proposals to funding agencies. Members include 24 major societies, associations, and industry organizations.