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Chemical synthesis involves combining chemicals to make new ones that have useful properties.What is Green Chemistry?

Stated most simply, green chemistry is the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. Fewer hazardous substances means less hazardous waste and a healthier environment.

Chemical synthesis involves combining chemicals to make new ones that have useful properties. The 12 principles of green chemistry are:

  1. Prevent waste: Design chemical syntheses to prevent waste, leaving no waste to treat or clean up.

  2. Design safer chemicals and products: Design chemical products to be fully effective, yet have little or no toxicity.

  3. Design less hazardous chemical syntheses: Design syntheses to use and generate substances with little or no toxicity to humans and the environment.

  4. Use renewable feedstocks: Use raw materials and feedstocks that are renewable rather than depleting. Renewable feedstocks are often made from agricultural products or are the wastes of other processes; depleting feedstocks are made from fossil fuels (petroleum, natural gas, or coal) or are mined.

  5. Use catalysts, not stoichiometric reagents: Minimize waste by using catalytic reactions [1]. Catalysts are used in small amounts and can carry out a single reaction many times. They are preferable to stoichiometric [2] reagents, which are used in excess and work only once.

  6. Avoid chemical derivatives: Avoid using blocking or protecting groups [3] or any temporary modifications if possible. Derivatives use additional reagents and generate waste.

  7. Maximize atom economy: Design syntheses so that the final product contains the maximum proportion of the starting materials. There should be few, if any, wasted atoms.

  8. Use safer solvents and reaction conditions: Avoid using solvents, separation agents, or other auxiliary chemicals. If these chemicals are necessary, use less harmful or dangerous chemicals.

  9. Increase energy efficiency: Run chemical reactions at background or room temperature and pressure whenever possible.

  10. Design chemicals and products to degrade after use: Design chemical products to break down to innocuous substances after use so that they do not accumulate in the environment.

  11. Analyze in real time to prevent pollution: Include in-process real-time monitoring and control during syntheses to minimize or eliminate the formation of byproducts.

  12. Minimize the potential for accidents: Design chemicals and their forms (solid, liquid, or gas) to minimize the potential for chemical accidents including explosions, fires, and releases to the environment.

What can Green Chemistry do?

Green chemistry is not a particular set of technologies, but rather an emphasis on the design of chemical products and processes. Sometimes, green chemistry takes place at the molecular level to reduce or eliminate the use and generation of hazardous substances. This approach offers environmentally beneficial alternatives to more hazardous chemicals and processes, and thus promotes pollution prevention.

Green chemistry can lead to dramatic changes in how we interact with chemicals on a daily basis as in the case of the 2005 Nobel Prize in Chemistry for the development of the metathesis method in organic synthesis. "The word metathesis means 'change-places.' In metathesis reactions, double bonds are broken and made between carbon atoms in ways that cause atom groups to change places. This happens with the assistance of special catalyst molecules. Metathesis can be compared to a dance in which the couples change partners... Metathesis is used daily in the chemical industry, mainly in the development of pharmaceuticals and of advanced plastic materials. Thanks to the Laureates' contributions, synthesis methods have been developed that are

  • more efficient (fewer reaction steps, fewer resources required, less wastage),
  • simpler to use (stable in air, at normal temperatures and pressures), and
  • environmentally friendlier (non-injurious solvents, less hazardous waste products).

This represents a great step forward for 'green chemistry,' reducing potentially hazardous waste through smarter production. Metathesis is an example of how important basic science has been applied for the benefit of man, society and the environment."

The U.S EPA Presidential Green Chemistry Challenge promotes and recognizes outstanding chemical technologies that incorporate the principles of green chemistry into chemical design, manufacture, and use. It recognizes chemical development that has been or can be used by industry in achieving their pollution prevention goals. Past award winners' achievements have included the development of alternative coatings, surfactants [4] and fire extinguishing agents.

How is DTSC Promoting Green Chemistry?

DTSC and green chemistry share a common principle - preventing the generation of waste. California law directs DTSC to place the reduction of hazardous waste as its highest priority when developing new programs or carrying out the provisions of the Hazardous Waste Control Law.

DTSC also promotes the application of Green Chemistry through its source reduction programs. DTSC requires hazardous waste generators to prepare hazardous waste source reduction plans for their major waste streams and update them every four years. In these plans, generators examine their waste generating processes and identify source reduction opportunities.

Source reduction means one of the following:

  • Any action that causes a net reduction in the generation of hazardous waste.

  • Any action taken before the hazardous waste is generated that result in a reduction of the properties which cause it to be classified as a hazardous waste.

Source reduction involves reducing, avoiding, or eliminating the generation of hazardous waste. It can include such practices as:

  • Input change – changing raw materials or feedstocks used in a production process or operation.

  • Operational improvement – improving site management, also referred to as housekeeping practices.

  • Production process change – changing processes, methods, or techniques used to produce a product or a desired result, including returning materials or their components for reuse within the existing processes or operations.

  • Product reformulation – changing the design, composition, or specifications of end products, including creating a totally different, non-hazardous product.

As part of its source reduction mandate, DTSC also implements cooperative technical assistance and outreach programs with industry to promote multi-media pollution prevention.

DTSC is currently monitoring the European Commission efforts to implement legislation for the Registration, Evaluation and Authorisation of Chemicals (REACH). In REACH, the European Union is considering legislation to track and make publicly available information about all new chemicals.

Although DTSC does not regulate products made from or containing hazardous substances, those products create waste that is of interest and concern to DTSC. Thus, as part of its role in environmental protection, DTSC hosted technical symposia on a variety of emerging technologies and products such has nanotechnology and pharmaceuticals and personal care products.

Chemical/Product Prioritization Resources

Alternatives Assessment Resources

Other Resources

  • Assembly Bill 1879
    The California Environmental Protection Agency is given greater authority to regulate toxins in consumer products.

  • Senate Bill 509
    Authorizes the online Toxics Information Clearinghouse to provide Californians with information on hazardous chemicals encountered in their everyday lives.

[1] A reaction where a substance is used to increase the rate of a chemical reaction, without being consumed or produced by the reaction.

[2] Refers to compounds or reactions in which the components are in fixed, whole-number ratios.

[3] A removable chemical unit used by synthetic chemists to purposefully cover up certain regions of a molecule so they do not react with other compounds during a reaction.

[4] Surfactants are wetting agents that lower the surface tension of a liquid, allowing easier spreading, and lower the interfacial tension between two liquids.