National Environmental Indicator Series: Indicators

Ozone, a gas that is chemically related to oxygen, is primarily found in the stratosphere, a layer of the atmosphere located 15-35 km above the Earth's surface. This "layer" of ozone acts as a natural filter for harmful ultraviolet (UV) radiation. Since the late 1970s, a thinning of the ozone layer has been recorded over the entire globe, especially over the poles. The main cause of ozone depletion is the release of industrial chemicals that break down ozone in the stratosphere. These ozone depleting substances (ODS) are sometimes used in air conditioners, refrigeration equipment, aerosol sprays, foam plastics, fire extinguishers and pesticides. Some ODS are also powerful greenhouse gases.

What is happening?

Stratospheric ozone levels have generally declined since the late 1970s. The average ozone level was 2% lower than pre-1980 levels in 1998 and 6% lower in 2000. Even small reductions in ozone layer thickness can have significant effects. Much progress has been made in reducing ODS emissions worldwide, but ozone levels will continue to be affected for many years by ODS already in the atmosphere.

This line graph displays the fluctuation of average annual ozone level over Canada from 1957 to 2001 dobson units. It shows a decreasing trend from above 370 dobson, until the early 1990s, when approximately 325 dobson was attained. From this period onward, there has been an increase in annual average levels to around 350 dobson.

Canada's National Environmental Indicator Series 2003

In depth

Source: Meteorological Service of Canada, Environment Canada.¹

Why is it important?

Lower ozone levels allow more UV radiation to reach the Earth’s surface. UV exposure can lead to sunburn, skin cancer, eye damage, weakening of the immune system, reduced yields of some agricultural crops, and ecosystem damage.

What you can do

Purchase halon-free fire extinguishers.
When refrigerators, freezers and air conditioners are serviced, request that CFCs be recovered and recycled.
Watch for Environment Canada's UV Index in your daily weather forecast and be extra careful of sun exposure on high UV days.

What the Government of Canada is doing

Canada played a key role in developing the Montreal Protocol, an international agreement to protect the ozone layer, requiring the gradual phase-out of ODS. Canada has had much success in phasing out the use of ODS. In 2000, Canada's ODS production and consumption were 96% lower than the peak value in 1987. The Government of Canada's ozone research and monitoring programs have made major contributions to the global understanding of the ozone layer. In 1992, Canada developed the UV Index to describe the strength of the sun's UV rays, and became the first country to issue nation-wide daily UV forecasts.

Challenge

Recovery of the ozone layer could occur within the next 50 years, but recent research suggests such recovery could be delayed by the effects of climate change.²

Related indicators

Sources:
1. Environment Canada. 2002. Meteorological Service of Canada, Downsview, Ontario, Canada.
2. World Meteorological Organization. 1998. “Executive Summary”, Scientific Assesment of Ozone Depletion: 1998. Global Ozone Research and Monitoring Program, Report No. 44.

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Indicators

Stratospheric Ozone Layer

What is the issue?