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Forty-five years ago the US Surgeon General reported that smoking is bad for your health. The message has sunk in: over 40 percent of Americans smoked then but now only about 20 percent do.

But new research says just how addictive smoking is for you depends on the color of your skin. "Living on Earth's" Ike Sriskandarajah filed this report.

Dr. Gary King from Pennsylvania State University studied nicotine -- the highly addictive stimulant that makes people crave cigarettes -- and melanin, a compound your body makes that determines how dark you are. And he found a connection.

According to Dr. King, the melanin is strongly attracted to nicotine, and the way it works is when you light up a cigarette, the tobacco and all the chemicals created when it burns into your mouth, into your lungs and the rest of your organs, including your biggest organ ... skin.

"Skin does react like every other organ in the body unto nicotine and the other 4,000 chemicals that are consumed when one actually smokes," said Dr. King. "And that binding process in and of itself may lead to greater dependence."

Inhaling thousands of chemicals is not a good idea. But it is especially bad for people with dark, melanin-rich skin. That's because melanin grabs and hangs onto the nicotine.

Greater dependence means it's much harder for darker skinned people to kick the habit. In fact white smokers on average are 15 percent better at quitting than blacks. Even though whites typically smoke about five more cigarettes a day.

"Nicotine doesn't remain in the body for an extended period of time, which is one reason why smokers continually have to replenish their supply," said Dr. King. "The suggestion is that it does remain in their body much longer for African Americans than white Americans. African Americans typically smoke fewer cigarettes than Caucasian Americans and some other groups but yet still the dependence rate is much higher."

But that doesn't mean white people are off the nicotine hook he adds. Their lighter skin still makes the type of melanin we all accumulate from being in the sun, "Then this very well could affect populations that are more likely to perhaps to work in outdoor environments where there's sun and, interestingly enough, may have implications for persons who live closer to the equator.

Which is why Dr. King's next step is to survey dark and light skinned people all over the world. His findings are based on a pretty small sample -- 150 subjects, all of whom are African American. The study targeted African Americans for several reasons: for one, black people have the widest range of melanin concentration.

Also, by focusing on African American communities, Dr. King says he was better able to control for the non-biological factors that influence smoking habits:

"Yes. Clearly we could not just look at two different variables and that is nicotine exposure and melanin but we had an array of other sociological factors such as one's education, the amount of stress that a person was experiencing. We also looked at ... we had a scale to measure racial discrimination. However, after controlling for all of these other factors including age and gender we did not find that they reduce the significance of our association between melanin and nicotine."

Hosted by Steve Curwood, "Living on Earth" is an award-winning environmental news program that delves into the leading issues affecting the world we inhabit. More "Living on Earth."

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