Ozone Layer

The ozone layer is a region in the Stratosphere where ozone is highly concentrated.

Why do I care?  The ozone layer protects us from excessive UV rays that contribute to skin cancer and other health problems.

I should already be familiar withStructure of the AtmosphereGreenhouse Gases

Layers of the atmosphere (not to scale)
Figure A. Ozone layer within stratosphere contains highest concentration of ozone.

The ozone layer is defined by meteorologists as an area/region of concentrated ozone just above the troposphere/lower layer of the stratosphere. It is important to note that ozone is not only confined to the stratosphere (about 90% of the atmosphere’s ozone is in the stratosphere), but across the whole atmosphere. In big cities during the summertime, air quality at the surface can be an issue when ozone and other gases increase to dangerous levels.

Ozone gas is like a double edged sword. When ozone is at the earth’s surface, it can be dangerous as it is corrosive and harmful to breathe in. However, when it is concentrated in the lower stratosphere, it actually protects us from the sun’s harmful UV rays. Without ozone in the atmosphere, it would be too dangerous to walk outside without having to wear some sort of special suit. 

Note: Figure A not drawn to scale...the troposphere and stratosphere make up an extremely small layer above the earth's surface

Ozone "hole" over the South Pole
Figure B. Ozone hole. (Image from NASA).

During the mid 1980s, concerns grew over what appeared to be a ‘hole’ in the ozone layer over Antarctica in spring. Scientists determined that the ‘hole’ was caused by humans due to man-made chemicals such as CFCs (chlorofluorocarbons). The CFCs and other chemicals were interacting with the ozone and destroying the layer over Antarctica. A smaller hole was also seen over the Northern Hemisphere.  Initially, it seemed impossible that CFCs could reach the stratosphere as they were heavier than air. However, weather phenomena like thunderstorms can produce updrafts and carry air (and other) particles to the top of the troposphere and even into the parts of the stratosphere. In 1987, the Montreal Protocol was put together by several nations with the goal of reducing and completely stopping the production of CFCs. While CFCs are still being produced today by smaller nations, the ozone ‘hole’ has begun to fill in, although it may be decades before it completely recovers.


How does this relate to public health?

Exposure to ultraviolet (UV) rays from the sun (shortwave radiation) is said to cause 65% to 90% of melanoma of the skin, which accounts for three-fourths of all skin cancer deaths.1,2 Additionally, the sun’s UV rays can also cause cataracts and other damage to the eye.3 On the other hand, exposure to UV rays impacts vitamin D circulation, which is said to be a protective factor against colon or rectum cancer.4

1Centers for Disease Control and Prevention. Basic information about skin cancer. April 24, 2012. <http://www.cdc.gov/cancer/skin/basic_info/> Accessed November 17, 2012.

2National Cancer Institute. Skin cancer. (n.d.) <http://www.cancer.gov/cancertopics/types/skin> Accessed January 27, 2012.

3World Health Organization. Ultraviolet radiation and human health. December 2009. <http://www.who.int/mediacentre/factsheets/fs305/en/index.html> Accessed November 17, 2012.

4Portier CJ, et al. 2010. A human health perspective on climate change: a report outlining the research needs on the human health effects of climate change. Research Triangle Park, NC: Environmental Health Perspectives/National Institute of Environmental Health Sciences. doi:10.1289/ehp.1002272 <www.niehs.nih.gov/climatereport> Accessed November 17, 2012.


Want to learn more?

Global Warming vs. Climate ChangeHalocarbons


Activities to accompany the information above:

Activity: Ground-level Ozone: Your Vehicle (pdf version of original activity.)

Description: This activity will assist students in understanding the role of vehicles on greenhouse gas levels. Students will use their vehicle or their parent's vehicle to calculate the emissions levels for nitrogen oxides and hydrocarbons and compare the values to a hybrid vehicle. This activity is focused more toward an AP Environmental Science class.

Relationships to topics: Greenhouse GasesOzone LayerCauses of Climate Change


Activity: The Atmosphere: Ozone Depletion (pdf version of original activity.)

Description: This activity looks at data from 4 different satellite that have been monitoring ozone levels for students to examine ozone thickness and changes in the ozone layer over 20 years.

Relationships to topics: Ozone LayerSolar Cycles