30 January, 2000

During yesterday's hike to Castle Rock, I managed to get a little sunburned. I was sure to put on sunscreen before the hike, but probably should have re applied it during the day. When out on the ice, the already strong rays are reflected back at exposed skin, making the amount of exposure to Ultra Violet light parcticularly stong.

In Antarctica, the UV light is much stronger than in other pearts of the world. This is due to the presence of the well publicized "Ozone Hole". This hole in our protective ozone layer was first discovered by scientists working in Antarctica in the 1980s. It has been detected every year since and this past season it was the largest on record. Unfortunately, the ozone hole does not appear to be going away anytime soon. In fact, the ozone depleting chemicals (mostly CFC's) that were released in the 60s, 70s and 80s, will continue to destroy ozone in the upper atmosphere for at least the next 50 years to come. Fortunately, as a result of the scientific knowledge gained by Antarctic research, many nations around the world have agreed to eliminate the use of CFCs. To find out more about the ozonbe hole do a web search or visit:

http://www.atm.ch.cam.ac.uk/tour/index.html

For a hands on activity to learn more about UV radiation, try this:

Antarctic UV Radiation and the Effectiveness of Sunscreen.

Andre Wille Basalt High School

awille@rof.net

The ozone hole was first observed over Antarctica during the southern winter. There, the cold conditions in the upper atmosphere promote a chemical reaction between man made chemicals known as CFC¹s and ozone molecules. Ozone molecules, which are composed of three atoms of oxygen, have the vital role of shielding life on Earth from dangerous Ultraviolet radiation (UV). This UV radiation is known to damage the DNA in cells and is a cause of skin cancer. In this lab we ask the question:

What conditions effect the strength of UV radiation and can sunscreen protect us from these harmful rays ?

To answer, I invite you to join in an online experiment with me while I travel to Antarctica. I will conduct part A of this activity so that you can compare your results with me. To obtain my results , and to follow my journals, contact me at:

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Materials

Light sensitive ³Nature Print Paper² Contact Mark Duff at BHS. He has a supply of the light sensitive paper or for later purchasing: Nature Print Paper PO Box 314 Moraga Ca. 94556

Various sunscreen samples

Timer (watch with seconds)

Water tray to develop paper

Part A: Strength of UV radiation

To test Ultraviolet radiation strength and to make comparisons between different locations, several considerations must be made including:

Time of day. The most intense UV radiation will be at noon, so valid comparisons should be at the same time of day in each location.

Latitude- depending on the season, the directness of the suns rays will vary depending on the latitude. An experiment done in Antarctica during the astral summer will have much more direct radiation than a test done in the northern latitudes.

Altitude-Higher altitudes have thinner atmospheres and thus less protection from UV radiation.

Exposure time-

Each of these variables presents a number of problems to the design of a good experiment. They also provide a number of different experiments that can be compared to one another. What is the effect of the time of day ? How does altitude effect UV strength ?

To compare the results of experiments from different locations, experimental results must be compared to a control paper with a variety of shades. The control paper was made by dividing the paper into 5 to 10 strips and exposing the strips for varying lengths of time. If two or more groups have control papers made at the same time and place, fair comparisons can be made. I will carry one of these control papers with me to Antarctica when I conduct the experiment so that I can compare the shade of color with that produced by your experiment. The control paper provided here was made on December 23 (winter solstice) at 12 noon.

To make your own control paper for other experiments or to compare to the control provided, Label each strip from 1 to 5. Now cover all but the strip numbered 5 and expose for 5 seconds. Count 1 one thousand, 2 one thousand to five. Next slide the cover back to expose strip number 4 for another 5 seconds. Continue and expose strips 5,4, & 3, for 5 seconds. When done, Strip 5 will have been exposed 25 seconds, strip one for five seconds.

Part B. How effective is your sunscreen ?

Sunscreen can be tested by covering part of the paper with an even coating of sunscreen and exposed for a controlled time period. Compare different brands, or different SPF factors from the same brand. ( a good experiment only tests one variable at a time) Is a sample really waterproof like the advertising may claim ?

Design and conduct your own experiment to answer one or all of these questions.

-Be sure to keep track of each experiment in an organized data table .

Do an internet search on the ozone hole.

1. What causes this problem ?

2. Why does it occur over Antarctica ?

3. Is there an ozone hole anywhere else ?