Narrator: This is Science Today. Millions of people take cholesterol-lowering drugs. Dr. Thomas Newman of the University of California, San Francisco says doctors should be more cautious in prescribing them, especially for young people and children. The reason is the drugs cause cancer in mice and rats -- which in itself doesn't necessarily mean much.

Newman: And for some of the industrial chemicals or pesticides I think people have been worried inappropriately, because the amount that causes cancer in a mouse or rat is a million or thousand times as much as a human is likely to be exposed to. It's different with drugs in general and particularly with the cholesterol lowering drugs, because you're taking them intentionally for a possible benefit, and so the amount that a person is exposed to is much closer to the amount that causes cancer in the mice and rats.

Narrator: Newman believes the drugs shouldn't be prescribed except when the benefit of lowered cholesterol outweighs the potential risk of cancer -- usually in adults at immediate high risk of heart disease.

Newman: Probably still in children the benefits the benefits of the drugs don't exceed the risks, except in very exceptional circumstances.

Narrator: For Science Today, I'm Steve Tokar.