Name: _______________
Case Study
Ozone Destruction and Health
The ozone layer is a region in the lower stratosphere, about 20 to
30 km above Earth. Here, ozone is destroyed as it absorbs UV
radiation. As a result, the ozone layer naturally prevents UV
radiation from reaching organisms on Earth. While some UV does
reach the surface, specific wavelengths known as UV-B are largely
screened out. UV-B is harmful to most living things and is the main
cause of sunburn. It can also damage eyes and cause skin
cancers—in humans as well as in other animals such as sheep, cows, and surfacing ocean mammals
such as orcas.
Some substances that humans release into the atmosphere destroy ozone. Those that contain
chlorine (Cl) and bromine (Br) are two of the most destructive. Human-made compounds called
halocarbons increase atmospheric concentrations of Cl and Br. Halocarbons rise to the
stratosphere, where UV radiation breaks them down to yield Cl or Br atoms. Because these
atoms persist for a long time in the stratosphere, each atom can break down over 100 000
ozone molecules.
In the late 1970s, scientists began to observe a decrease in stratospheric ozone levels of about
4% per decade. As the density of the ozone layer decreases, more UV-B radiation gets through.
Above the poles, especially Antarctica, there is so much seasonal decline that an ozone hole is
often created. The first hole was discovered over Antarctica in 1985. Holes have also occurred
over the Arctic.
Government Initiatives to Combat Ozone Depletion
In 1978, CFCs in aerosol sprays were banned in Canada, the United States, and Scandinavia. As
research revealed the severity of the damage to the ozone layer, many other countries acted to
limit CFCs. As a result, the atmospheric concentration of chlorine has been declining since it
peaked in 1994. A 2005 study showed that, on average, global ozone depletion has stabilized.
Threats to the ozone layer still exist, however. CFCs and other ozone-depleting substances
continue to be used in countries where bans are not yet in place. These substances are
sometimes smuggled into Canada and the United States. In addition, many of the substances
invented to replace CFCs are greenhouse gases and contribute to climate change.
Research and Analyze
1. Research Canada's regulations for CFCs and other ozone-depleting substances under the
Canadian Environmental Protection Act (CEPA). How are regulations enforced and how are
alternative technologies encouraged? Assess the success these regulations have had in
reducing damage to the ozone layer. (4 marks)
2. Since CFCs have been banned in North America, some people consider the ozone hole to
be “old news.” Why is this view not supported by the scientific community? (Hint: Find out
how long it would take the ozone hole over Antarctica to be restored if all CFCs were
immediately banned.) (3 marks)
3. Find out more about the dangerous effects of UV radiation to plants, microscopic
organisms, humans, and other animals. (3 marks)
4. Create a plan to protect yourself against UV rays. How could you limit your exposure and
minimize risk when you are exposed? Communicate at least two ways to the class via your
infographic. (2 marks)
Communicate:
a. Share the answers to the above questions in an infographic!
Infographic: a visual image such as a chart or diagram used to
represent information or data.
Example of infographic 
You can use Microsoft Publisher, PhotoShop, or there are many
online infographic “DIY” websites.
Marking:
Information
Graphics/images
Effort
WOW Factor
Sources
-
12 marks
6 marks
4 marks
2 marks
2 marks
Total
- 26 marks
DUE: Tuesday, March 24, 2015