A new Clemson study found that the popular college game of “beer pong” may be hazardous to your health—- and not just because it involves alcohol.

The Associated Press first reported that a group of Clemson University students tested Ping-Pong balls used in games across the Upstate campus one weekend last fall. They discovered the balls were teeming with millions of bacteria, including some strains that could be dangerous.

Food science professor Paul Dawson said students collected the balls used in the games and brought them into the lab. There, they measured the level of bacteria on the balls, before dipping them in sampled cups of water and beer to see how much bacteria would transfer to the liquid. They found that almost 90 percent of the bacteria transferred to the water.

Dawson said students were only able to identify the types of bacteria and not particular strains. “One of the categories was listeria. That doesn’t mean it was listeria, but that it could have been listeria,” he told South Carolina Radio Network, ”Then there was staphylococcus. Some staphs can make you sick. Salmonella. Certainly, E.coli‘s present in nature.”

The purpose of beer pong is for players to toss balls into glasses of beer. When one player “scores,” the opponent must chug the beer inside the glass where the ball landed. The study found beer pong played outdoors had much higher amounts of bacteria— to the tune of over 2 million bacteria on one ball. But even indoor games played on vinyl floors recorded 5,000 bacteria on one of the balls.

“That it happened at some level didn’t surprise me,” Dawson said, “But the fact that it was at that high of a level did surprise me.”

Dawson said he submitted the findings to the International Journal of Food Safety, Nutrition, & Public Health.

The research is part of Clemson’s Creative Inquiry program, in which students are told to pose common-sense scientific questions, then plan research to find the answers.