According to a recent pilot study, bacteria can reside on unused paper towels and can transfer to hands after washing. The study, which was published in the American Journal of Infection Control, found that the types of bacteria on unused towels can make people sick, but has yet to cause any reported illnesses.

According to WebMD Health News reporting, experts say the findings are probably most important for people in hospital isolation units and those with weakened immune function who need to be extra cautious about contact with germs.

That said, researchers at Laval University in Canada tested six brands of commercial paper towels that are often found in public bathrooms. They found bacteria in each sample and noted that the towels made from recycled fibers were the most heavily contaminated.

Reports indicate that the concentration of bacteria in the recycled paper was between 100- to 1,000-fold higher than the virgin wood pulp brand. Researchers suspect that the bacterial slime known to be a problem at recycled paper mills, corrodes machines and may damage finished paper sheets. Bacteria may also thrive in recycled paper because it contains binding ingredients like starches and fillers that serve as food.

According to the reports, most of the bacteria found in paper towels were Bacillus bacteria, many of which can produce toxins that cause food poisoning. One brand of paper towel contained Bacillus cereus bacteria, which can cause food poisoning, but also has been associated with infections of the eyes, lungs, blood, and central nervous system.

Researchers stress that the amounts of bacteria found would likely have little to no affect on healthy people, but they may be problematic to individuals with weakened immune systems. Even so, until more is known, experts agree that this one study shouldn’t be a reason to avoid the use of paper towels.