Here’s something to add to your list of travel concerns: Those plastic bins that send your phone, shoes, and wallet through airport X-rays are teeming with potentially health-threatening germs, according to a new study spotted by Sky News.

Finnish and British researchers swabbed trays at the Helsinki Airport and discovered that half of the samples were contaminated with rhinovirus or adenovirus—two categories of common viruses that can trigger cold-like symptoms. In addition, they also took samples of various airport surfaces, and 10 percent of those tested positive for viruses. However, plastic security bins reportedly pose the greatest health threat.

Researchers suggested that hand sanitizer be offered at the end of the security line to help reduce the risk of infection. “To our knowledge, security trays are not routinely disinfected,” they wrote in their study, published in the journal BioMed Central Infectious Diseases. “Although this would not eliminate all viruses on hands, (e.g. alcohol gels have been found to be less effective than hand-washing for rhinovirus), it is effective for many viruses, including influenza.”

While this discovery may seem alarming, it must be noted that the sample size for this study—eight bins, plus swabs from 12 other surfaces around the airport—was small. The samples were also taken three times during Finland's "peak period of seasonal influenza" from 2015 to 2016, and different airports with different degrees of cleanliness could potentially yield different results.

It doesn’t hurt to play it safe and bring your own hand sanitizer along for the journey, though. The tray tables on airplanes are also known to be incredibly dirty—despite the fact that travelers eat off them—so you may want to make room in your carry-on for sanitizing wipes, too.

[h/t Sky News]