Chlorofluorocarbons and Ozone Depletion: How we came together to solve a global problem

Written by Kathlyn Piga

 

Chlorofluorocarbons (CFCs) presented a well known global environmental predicament that brought together global policy change in the 1980s. But first, what are CFCs and how did banning them present a solution that we can all get behind as consumers?

CFCs had their start in the 1920s when refrigeration and conditioning systems used ammonia, chloromethane, propane and sulfur dioxide as refrigerants. These compounds were highly effective, but were toxic and flammable and exposure could result in serious injury or death. Scientists therefore sought to develop nontoxic, non-flammable alternatives to the refrigerants. One of the earlier CFCs replacements, dichlorodifluoromethane, CCl2F2, or “Freon” was volatile and chemically inert. . Years passed and by the early 1970s CFCs were widely used and were produced worldwide at nearly one million tons per year.

Despite the worldwide success of CFCs, the adverse impact of CFCs in the atmosphere was later discovered. To understand better the harsh effect of CFCs on the ozone layer, we must understand the different layers in the atmosphere and their roles in protecting the Earth. For example, in the troposphere, from the Earth’s surface up to 6 miles, ozone is considered a pollutant and a component of photochemical smog. However, in the stratosphere, from 6 to 31 miles above the Earth’s surface, ozone is crucial for absorbing damaging ultraviolet (UV) radiation.

The impact of CFCs in the atmosphere can then be understood as a difference in where CFCs end up. CFCs are inert in the lower troposphere. However, they can be broken down by UV radiation as they drift into the stratosphere. Research determined that CFCs produced near the surface of the Earth would, over time, end up in the stratosphere. UV radiation would split off the chlorine atoms and the chlorine atoms would then react with an ozone molecule. This results in a chain reaction that destroys thousands of ozone molecules. It was estimated that a ban of CFCs would still result in ozone loss for years, but ozone loss would be even greater if CFCs were produced at a normal rate.

A call to action was needed and in 1976, the National Academies of Science produced a report on the effects of CFCs on the stratospheric ozone. Similar conclusions were made in congressional hearings, and states and the federal government in the United States started to explore the ban of CFCs in aerosol cans. The road to banning CFCs was not paved well, however, as many critics argued that it did not make sense to ban highly useful chemicals as, at the time, relatively little evidence supported the scientists’ theory. Scientists faced two main challenges. Firstly, only trace amounts of the chemical species of CFCs interacted with ozone in the stratosphere and this data to understand was difficult to replicate in the laboratory and secondly, determining ozone concentrations in the stratosphere, through balloons, aircraft, and satellites, was difficult in the mid-1970s and their concentrations fluctuated depending on the geography. These methodology difficulties fueled critics to halt the ban of CFCs on a government level.

Despite these difficulties, scientists were able to show crucial evidence that eventually spurred lawmakers and the public to change policies and our ways. In 1984, it was determined that stratospheric ozone decreased greatly since the 1960s; an article published in Nature stated that stratospheric ozone over Antarctica reduced by 40% in September, 1984. Most significantly, the prediction demonstrated an estimated increase in skin cancer incidence that would result from continued use of CFCs. This encouraged international action and in 1987, 56 countries agreed under the Montreal Protocol to cut CFC production and use in half. Eventually, it would lead to a worldwide phaseout of CFCs and other ozone depleting chemicals.

Today, our efforts to band together to help fix the ozone layer can be seen, albeit slowly. The 2019 Antarctic ozone hole was one of the smallest recorded since the hole was first discovered in the 1980s. It was determined that the 2019 ozone hole was not caused by the reduction of ozone depleting substances, but by meteorological and atmospheric conditions. Despite this, there is still a lot of work to be done and areas for improvement. Scientists believe that the ozone layer is healing, and there is hope that by 2060 ozone layers may return to pre-1980 levels. 

Ultimately, however, the story of CFCs and the ozone layer presents an important lesson for how humanity deals with global climate change, and how we can all band together to enact change at an international level.

 

References:

  1. https://www.acs.org/content/acs/en/education/whatischemistry/landmarks/cfcs-ozone.html
  2. https://www.independent.co.uk/climate-change/news/arctic-ozone-hole-closes-size-a9487961.html
  3. https://atmosphere.copernicus.eu/2019s-ozone-hole-context
  4. https://www.nature.com/articles/315207a0