Jul 11, 2008 5:55 pm US/Pacific
Good Question: How Does Sunscreen Work?
(CBS13)
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Mom applies sunscreen to child. (file)
AP
Sunscreen made headlines recently. Critics said some of the best selling brands just don't work. That's disputed -- but it lead to a good question: How does sunscreen work?
We visited a chemistry lab at UC Davis to get a lesson in "Sunscreen 101" from one of our favorite professors Dr. Matt Augustine.
"Sunscreen works much like common sunglasses. What it does is shield your body from harmful ultraviolet light," Dr. Augustine.
We're not wearing sunglasses but safety goggles to protect our eyes from his demonstration that involves a laser and a rock with uranium, which the professor promises is not radioactive.
"But what's interesting about the rock is that the uranium when hit with ultraviolet light glows red and green," said Dr. Augustine.
When he puts a quartz slide with nothing on it, you can see the ultraviolet light shines straight through. "However, if I take some sunscreen and put it on the surface of this quartz slide and now put that in between the laser and the rock you see that the light disappears," said Dr. Augustine. "That's because the carbon containing molecules in the sunscreen absorbs the ultraviolet light and in essence protects your skin from harmful ultraviolet light," he added.
So the question is: What are the chemicals in the sunscreen that are blocking the ultraviolet light? Typically these chemicals are the aromatic compounds that have carbon carbon double bonds.
Now you don't have to know what carbon carbon double bonds are but at least now you know how sunscreen works and that there's science behind it.
Carbon carbon double bonds change the structure of the molecules, and that allows them to absorb ultraviolet light and turn it into heat! The problem is, some of those chemicals are carcinogens, as recent critics pointed out and can cause cancer.
(© MMIX, CBS Broadcasting Inc. All Rights Reserved.)
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