C H I C A G O, May 23, 2001 -- The cash in your pocket may be contaminated with so much bacteria that it could make you sick.

Researchers from the Wright Patterson Medical Center in Dayton, Ohio, asked people standing in line at a grocery store checkout and at a high school concession stand to trade a $1 bill from their pocket for a new one. Then the doctors analyzed 68 of those old, worn bills.

Five of the bills contained bacteria that can cause an infection in perfectly healthy people, and 59 of them (that’s 87 percent) were contaminated with bacteria that could cause an infection in anyone with a compromised immune system, such as people with HIV or cancer.

Only four of the bills were relatively clean.

“One-dollar bills are widely used and each is exchanged many times,” said Dr. Peter Ender, one of the study’s authors. “If some are contaminated with bacteria, there is potential to spread these organisms from person to person.”

More Study Needed

So when you hand over the cash, are you giving more of yourself than you intend to? Not necessarily. The study only addresses how much and what kinds of bacteria live on paper money. Another study would be needed to determine whether the money can actually spread the bacteria.

Plus, since the authors only tested 68 bills — there are billions in circulation around the country — the study doesn’t go far enough to prove that as money moves across the country, so do diseases.

Ender says, though, the study does show that paper money is usually full of bacteria, and that a dollar bill could, theoretically, be the magic carpet it rides from one host to another.

But if, in fact, the bacteria can spread on paper money, there's nothing you can really do about it. You can try to keep your hands away from your eyes, nose and mouth — where the bacteria would get into your body — and try to wash your hands often.