In today’s society, contributions from the field of chemistry are evident all around us. Advancements in chemistry have led to the production of medicines to alleviate our pain, polyester to keep us warm, fertilizers to provide our crops with nutrients, cooking oil to add flavor to our food, and many other things. These same advancements have also generated numerous toxic chemicals, from the insecticides sprayed on our crops to the compounds found in water-based paints. Not only are these toxins harmful to our health, they are also damaging to the environment. For example, the release of chlorofluorocarbons (CFCs) and related compounds generated during chemical processes contributes to the depletion of the ozone layer, which in turn increases the amount of harmful solar radiation that makes it to the Earth’s surface [1]. In the year 2000, 7 billion pounds of toxic materials were released by the U.S. alone [2].   

Green chemistry is an approach that aims to eliminate the usage and generation of hazardous substances by designing better manufacturing processes for chemical products. Specifically, the goal of making the finished product and by-products less toxic directs the decisions made during chemical production. Aspects of the manufacturing process considered include the initial selection of chemicals, the mechanism of chemical synthesis, the end products of the process, and the management of toxic products generated during production. By limiting the hazard intrinsic to the chemical products, the risk introduced by the product is consequently reduced [2]. In addition to protecting the environment, green chemistry has the potential to benefit the large and diverse group of people whose job or residence places them at risk for exposure to toxic chemicals produced by manufacturing [4].   

Governmental promotion of green chemistry

In an attempt to eliminate the risks presented by chemical processes, the U.S. Environmental Protection Agency (EPA) was formed in 1970. By the 1980s, the EPA had passed more than 100 environmental laws [5]. With the passage of the Pollution Prevention Act of 1990, the green chemistry movement was initiated. The 1990 Act was unique because it prioritized reducing the amount of pollution generated [6]. In contrast, a “command and control” approach was taken pre-1990 to regulate pollution, where the priority was to limit risks by reducing exposure to environmental toxins through regulation of the use, handling, treatment, and disposal of chemicals. Consequently, in the pre-1990 years, the laws regulating pollution restricted the amount of pollution that could be released into the atmosphere and presented timetables for reducing pollution that often overlooked practical considerations like feasibility and cost [7].   

Shortly after the formation of the EPA, the first research initiative for green chemistry, the “Alternative Synthetic Pathways for Pollution Prevention” (eventually renamed the “U.S. Green Chemistry Program”), was launched. This initiative provided generous financial support for research conducted with the intention of preventing pollution through the innovative design and synthesis of chemicals. Because there was not yet enough technology for measuring the toxicity of chemicals or understanding their negative effects, green chemistry led to collaborative research efforts across many disciplines in the industrial, academic, and government sectors.   

Current trajectory of green chemistry

One component of the U.S. Green Chemistry Program was the adoption of the Presidential Green Chemistry Challenge, which recognizes the innovative ideas and accomplishments made to advance green chemistry. The awardees must create either less toxic methods for making chemicals, or make less toxic chemicals to replace existing harmful chemicals [5]. The aims of the Challenge are in-line with the guiding principles of green chemistry. The 12 principles provide a framework for designing new materials, products, processes, and systems that may lead to a greener chemical manufacturing process.   

1. Prevention. It is easier to prevent waste formation than to treat waste after it is generated [3].   

2. Atom economy. Design of synthetic methods that aim to maximally incorporate as much as possible of the materials used to generate the final product(s) [3].   

3. Less hazardous chemical syntheses. Where feasible, the substances used and created in the manufacturing process should pose little or no toxicity to human health and the environment [3].   

4. Designing safer chemicals. Chemical products are designed to have the lowest levels of toxicity. [3]   

5. Safer solvents. Solvents, which are used to dissolve other substances into a solution during the production of chemicals, should be of minimal toxicity. [3] As many solvents are toxic, flammable, or cause pollution, current research is focused on making chemicals without using solvents or using non-toxic solvents to reduce the damage to the environment caused by current solvents. One candidate replacement is carbon dioxide, as it is inexpensive, renewable, non-toxic, and has many desirable chemical properties [8].   

6. Design for energy efficiency. The impact of the energy requirements in chemical production on the environment and economy should be recognized and lessened when feasible [3].   

7. Reduce derivatives. Unnecessary steps that produce by-products should be avoided where practical, for they increase the total waste generated [3].   

8. Use of renewable raw material. The raw materials used should be renewable and not depleting whenever technically and economically feasible [3]. Currently, many of the chemicals that are manufactured industrially are created by chemically modifying petroleum. These modifications often require the use of toxic chemicals such as heavy metals. An attractive alternative is the development of chemicals derived from living matter such as plants. These bio-based materials are renewable and could reduce or eliminate the need to use toxic compounds. However, there is currently only one bio-based material source available in the large quantities required for industrial-scale manufacturing [8].   

9. Catalysts. Selective catalytic agents, which can make a chemical reaction proceed faster, are preferred because they reduce the amount of chemicals required in a chemical reaction [3].   

10. Design for degradation. The products used should be biodegradable to reduce their effect on the environment.   

11. Real-time analysis for pollution prevention. Real-time monitoring methods need to be created to control the formation of toxic chemicals.   

12. Inherently safer chemistry for accident prevention. The substances used in chemical processes should be chosen based on minimizing the potential to cause chemical accidents, such as explosions, fires, and releases into the environment [3].   

A video presentation of the 12 Principles of Green Chemistry.   

Green chemistry has influenced many areas of chemical production, including the choice of materials used, the methods used for making chemicals, and the design of safer chemicals [8]. Nevertheless, as discussed above, much remains to be done before the green chemical approach can be deemed a success.   

Future direction

Green chemistry is an innovative approach introduced in the early 1990s to reduce the release of toxic chemicals into our environment. While advances have been made in the fields of research and engineering, many barriers to the implementation of green chemistry still exist. For example, the cost of cleaner technology is extremely high and tax incentives are not offered by the government to alleviate this cost. Furthermore, innovative technology is often patented, which rewards the inventors but may prevent the widespread adoption of cleaner technology at low-cost. Lastly, the research advancements made in the different sectors of academia, industry, and government are often not shared among each other because of a lack of communication. Regardless of these limitations, green chemistry is advancing and is transforming the status quo in chemical production to one that is less toxic and more environmentally conscious. The changes instituted by green chemistry will thereby lead to safer work environments and safer products for consumers.   

Jessica W. Chen is a PhD student in Biological and Biomedical Sciences at Harvard Medical School.  

 

(Image by Jessica Chen. Modified from http://cordis.europa.eu/esprit/src/melari.htm and http://upstrm.wordpress.com/2010/12/07/green-chemistry/)

References:   

[1] 2010. Air Pollution. (U.S. Environmental Protection Agency) http://www.epa.gov/apti/course422/ap.html   

[2] Poliakoff, M., Fitzpatrick, J.M., Farren, T.R., & Anastas, P.T. (2002) Green chemistry: science and politics of change. Science 297:807-810.   

[3] Anastas, P. T., & Warner, J. C. Green Chemistry: Theory and Practice. Oxford University Press: New York, 1998, p.30.   

[4] 2011. Green Chemistry. (Clean Production Action) http://www.cleanproduction.org/Green.php   

[5] Cann, M.C. Greening Across the Chemistry Curriculum. (University of Scranton) http://academic.scranton.edu/faculty/cannm1/dreyfusmodules.html   

[6] 2010. Green Chemistry Program at EPA. (U.S. Environmental Protection Agency) http://www.epa.gov/gcc/pubs/epa_gc.html   

[7] Anastas, P.T., & Kirchhoff, M.M. (2002) Origins, current status, and future challenges of green chemistry. Acc. Chem. Res. 35: 686-694.   

[8] Kirchhoff, M.M. (2003) Promoting green engineering through green chemistry. Environ. Sci. Technol. 37: 5349-5353.   

   

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