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Ozone depletion
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  Ozone depletion: Uncovering the hidden hazard of hairspray
by the Understanding Science team

A usual morning routine might include a spritz of hairspray, a spurt of shaving cream, or a spray of deodorant. We do these things almost automatically, not really even thinking about it. Aerosols are common, convenient, and harmless, right? It's hard to imagine that these everyday activities could be affecting the atmosphere ten miles above Earth's surface for the next hundred years, but in the 1970s, chemists Mario Molina and F. Sherwood Rowland discovered just that.

Mario Molina F. Sherwood Rowland
At left, Mario Molina addresses the Mexican Senate in 2008. At right, F. Sherwood Rowland during a 2007 interview.

At the time, many normal household items contained CFCs — a class of chemicals that are made up of combinations of chlorine (C), fluorine (F), and carbon atoms (C). Developed in the 1930s under the trade name Freon, they were thought to be wonder chemicals. They are nontoxic, nonflammable, don't react with any common chemicals, and thus were assumed to be safe for the environment. When Molina and Rowland began their work, CFCs were used in all kinds of things — refrigerators, Styrofoam, and aerosols (like hairspray or cleaning supplies), to name a few. Rather than assume, as others had, that CFCs had no effect on the environment, Rowland and Molina decided to scientifically examine the question of what happens to CFCs released into the atmosphere. What they found would not only alter the contents of hairspray, but would also earn them a Nobel Prize and change environmental policy the world over.

Examples of household items that used to contain CFCs.
Examples of household items that used to contain CFCs.

This case study highlights these aspects of the nature of science:

  • Science is a community endeavor that benefits from a diverse and broad range of perspectives, practices, and technologies.
  • Science helps us understand how our actions today are likely to affect future outcomes.
  • Science affects our day-to-day lives.
  • Data require analysis and interpretation. Different scientists can interpret the same data in different ways.
  • Scientific ideas evolve with new evidence; however, well-supported scientific ideas are not tenuous.
This entire section is available as a PDF download.

take a sidetrip
Throughout this story, we'll trace the path through the process of science that scientists took in this investigation. To review this process, visit How science works.

key points
Use this story to introduce your high school students to the Science Flowchart with this activity.

Mario Molina photo courtesy of the Senado de la República de México; F. Sherwood Rowland photo by William J. Cooper, UC Irvine; spray can photo provided by Thomas Hawk's flickr photostream under this Creative Commons license; refrigerator photo provided by SuziJane's flickr photostream under this Creative Commons license; foam packing peanuts photo provided by ThrasherDave's flickr photostream under this Creative Commons license

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