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Lesson One: The Essentials of Green Chemistry

Module Three: Green Chemistry Focuses on Inherent Hazards


Video Lecture

Click the Video Lecture window to explore the details necessary to understanding this module's key ideas.

Learning Objectives

At the end of this module, students will be able to:

  • Define the two key elements of risk, and determine that green chemistry focuses on hazard
  • Examine how risk frames sustainability
  • Discuss how green chemists must learn how to deal with hazard

In 1991, Chemist Paul Anastas defined the field of green chemistry this way:

"Green chemistry is the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances."

The goal of green chemistry is to design products and processes that do no harm to humans or the environment. That's a formidable ambition, and, as laid out by Paul Anastas and his co-author John Warner in their seminal 1998 book Green Chemistry: Theory and Practice, it is also a significant departure from the way chemistry has traditionally been practiced. This module defines and explores green chemistry and contrasts it with traditional chemistry.

For most of the past 150 years we have developed commercial chemicals without sufficient understanding of their associated hazards. As the field of chemistry and the industries and markets it serves have become increasingly complex, we have been releasing a growing number of hazardous chemicals into the environment.

When that happens, the long-term costs can be very high. Superfund sites in the United States represent dramatic efforts to remediate hazardous sites, and cost can exceed hundreds of millions of dollars. We design masks, leak proof reactors and air scrubbers to protect people and the environment from the hazardous substances our technologies create, all at a cost. But rather than pay these costs after the fact, green chemists ask, "Wouldn't it be better to replace those products and processes that contain hazardous substances with more benign alternatives in the first place?"

Anastas and Warner suggested framing the challenge with this simple concept equation:

Risk = f [Exposure, Hazard]

which specifies that the risk of any chemical product or process is a function of both the exposure of humans (and/or the environment) and the inherent hazard.

Designing for Safety

The need to design safer chemicals is one of the most important of the Twelve Principles of Green Chemistry that Anastas and Warner laid out in their book (see Assignments). (Modules three and four in this lesson owe a great deal to the insights outlined in Green Chemistry: Theory and Practice  by Paul Anastas and John Warner.) As society gains a better understanding of the dangers of hazardous chemicals, products that are free of them are also gaining popularity. This shift in demand presents myriad opportunities to chemists interested in developing products and processes that are safer, more efficient and less costly.

We will explore these issues in greater detail as we move more deeply into the course.

To explore this module's material in depth, view the lecture.

Key Points

  • In the early to mid-1990s, Paul Anastas coined the name "green chemistry" and defined it as "the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances."
  • Green chemistry marks a departure from traditional chemistry. Research and education in the field aims to understand why certain substances in commerce are hazardous, and then explores the design of safer alternatives.
  • The risks associated with chemical products are a function of two things: the level of exposure and the inherent hazard itself. Risk = f [Exposure, Hazard]
  • In Green Chemistry: Theory and Practice, Anastas and Warner laid out twelve principles of green chemistry that have helped guide the field. (See this module's lecture and the twelve principles at the EPA website.)
  • In the past, we have tried to reduce the risks associated with hazardous substances in products and processes by limiting how much people and the environment are exposed to them.
  • Green chemists aim to eliminate risks by designing hazardous substances out of chemical products and processes. When hazardous substances can't be eliminated, green chemists seek approaches that will reduce or eliminate the exposures before they are created.