CURWOOD: Just ahead, keeping trouble from going down the drain. Seattle tests the powers of bio-remediation. First, this Environmental Health Note from Diane Toomey.

TOOMEY: The use of a drug derived from vitamin A may help protect former smokers against lung cancer by restoring production of a crucial protein. Although smokers reduce their risk of developing lung cancer when they quit, whatever cell damage they’ve done up to that point doesn’t disappear right away. Half of all lung cancers occur in former smokers. So researchers hope to find a way to repair this cell damage before it turns cancerous.

The drug used in this study belongs to a class of compounds known as retinoids. Retinoids play an important role in regulating the epithelial cells that line the lung. To do that, these retinoids must first latch on to their matching protein receptors. But smoking reduces the number of these receptors, making lungs vulnerable to cancer. It’s known that retinoids can restore the production of this protein receptor.

So, in this study, a few dozen former smokers were given an oral dose of retinoids for three months. Another group of former smokers was given a placebo. Researchers performed lung biopsies on the patients before and after the treatment. They found that in patients who receive the drug, the percentage of biopsies that showed the presence of the important protein receptor rose seven points. But in the placebo group, this percentage dropped six points. Although this study doesn’t prove the drug turned pre-cancerous cells into healthy ones, researchers say it demonstrates that so-called chemo-prevention of lung cancer may be possible.

And that’s this week’s Health Note. I’m Diane Toomey.

CURWOOD: And you’re listening to Living on Earth.