As professors who work with undergraduate students, we’re familiar with beer pong—a drinking game in which players attempt to throw ping pong balls into cups of beer, and opponents drink from the cup in which a ball lands. The player who makes the most successful throws wins the game, forcing the loser to drink the beer left in the cups. Losing is no fun. This much, you probably know. But in addition to getting drunk, what other potentially bad things might be happening? Since we’re researchers who study food science and the spread of potentially harmful bacteria, that’s the question we set out to answer.
During a typical game, for instance, the ball can bounce on the table, or it can miss a cup and land on the ground. Some people rinse the ball between throws to clean it off—but wetting the ball might actually make it pick up more bacteria from people’s hands and wherever else it lands. Playing beer pong like this gives microorganisms lots of opportunities to transfer from various surfaces and onto the ball. Even if the balls are new, they’re not sterile when removed from the package—they just appear to be relatively clean.
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While most bacteria in the average home isn’t necessarily harmful, we do know that some bacteria and viruses cause disease. This means handling a ball exposed to non- sterile surfaces (including hands) likely increases the risk of exposure to such pathogens. Since beer pong involves drinking beer that has been exposed to a ping-pong ball, our research team wanted to determine if—and how much—bacteria are transferred to beer while playing beer pong. Our hypothesis was that bacteria do contaminate the balls, and that the bacteria on the balls are also transferred to the beer. Likewise, given what we now know about pathogens, the beer pong player who drinks the contaminated beer could have more to worry about than just losing the match.
To reach some answers, we first divided our objectives into two experiments: In one, we wanted to determine the overall number of bacteria found on balls used to play beer pong during a football homecoming weekend. In the second, we ran a controlled laboratory test to measure the number of bacteria transferred to beer from balls inoculated with a known number of bacteria.
To determine the numbers and types of bacteria found on balls used in actual beer pong games, our brave student researchers fanned out across the campus on homecoming weekend. Their goal was to infiltrate dens of beer pong activity to collect balls being used in beer pong games (in exchange for unused balls). What the participants in the beer pong games thought of this research was not recorded—and best not discussed.
In all, 63 beer pong balls were collected from games played on wooden porches (12), hardwood floors (4), vinyl flooring (17), carpet (6), and outdoors on dirt and grass (24). All balls collected had been dropped on the ground or floor more than once per game and rolled various distances on the ground, porch, carpet, vinyl, or hardwood floors. Each ball was also handled once per turn by each player and would often bounce or roll on the table or ground and—sometimes—would even land in the cup of beer.
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When our tests concluded, they revealed that numerous bacteria were indeed found on the surface of the balls. The bacterial populations varied widely according to where the game was being played. For instance, the average number of bacteria recovered from all balls—regardless of the environment—was 76,000. The good news? Balls from games played on carpet averaged only 600 bacteria per ball. The bad news: Most of the games were played outdoors on grass and dirt, where the bacterial count reached a whopping average of 201,165 bacteria per ball.
Keep in mind that this was an average count; the actual highest number of bacteria found on one ball was around three million cells. It’s the type of bacteria found on an individual ball that causes illness, however—not the average bacterial population. In other words, the threat of getting sick comes down to whether any of these bacteria are pathogenic. In most cases, that has less to do with bacteria on the ground than on the hands of your fellow players.
Furthermore, the infectious dosage of pathogens for each of us will vary based on your immunity. Just because balls that landed in the grass have more bacteria doesn’t necessarily mean they’re more likely to make you ill. It depends on the type of bacteria—and how much of it there is. Take E. coli, for instance—which can cause a wide range of gastrointestinal problems if you’re infected with a nasty strain.
In our controlled tests, nearly all E. coli bacteria inoculated on a ball—meaning we intentionally covered the ball with E. coli—were transferred to the beer within the 10 seconds the ball was left in the beer. But no E. coli cells were detected in beer after exposure to non-inoculated (in other words, what you might call new or “clean”) pong balls. Furthermore, no E. coli cells were recovered from the beer not exposed to any ping pong balls at all. This means beer pong balls do collect environmental bacteria from contaminated hands and surfaces and transmit that bacteria to beer.
So if you don’t think playing beer pong can spread disease, think again. In 2009, the Rensselaer Polytechnic Institute, a university in upstate New York, banned beer pong games due to concerns that the game had caused an unusually high number of cases of bird flu among college students. Furthermore, Billy Gaines, owner of BPONG, a company that organizes national beer pong championships, says that pong contestants have previously complained of coming down with “pong flu” at tournaments. (Gaines wasn’t sure, however, if the malaise was due to spreading of germs or to excessive beer consumption.)
Pong flu could possibly be some combination of both factors, but here’s something else to consider: The longer a beer pong game lasts, the tipsier the players become, and the more they need to relieve themselves. And the less likely they are to use good hygiene practices when visiting the bathroom before returning to the game, perhaps to throw a ball in your cup of beer with their unwashed hands. Now that you know about pathogens and bacteria transmission, isn’t that a nice thought to contemplate?
So is it wise to play beer pong? The answer depends on whether you are willing to risk getting sick. Keep in mind that the larger the population of bacterial contaminants on the ball’s surface, the greater the risk of transferring microorganisms to beer. Other factors to consider include the types of microorganisms present (that is, human pathogens or harmless microorganisms), the human infectious dose of the pathogen required to contract the disease, the general health status of the people playing the game (healthy versus immunocompromised), and whether the ethanol concentration in the beer and contact time with the ball are sufficient for the alcohol to kill any bacteria present. Ethanol has been shown to exert an antimicrobial effect on some microorganisms; however, the typical alcohol (ethanol) concentration of beer is too low to have much effect on microorganisms.
Essentially, the type of organism present and the general health status of the players are what determines the minimum population of bacteria/viruses required to make someone sick. These are factors to consider in determining the true risk associated with beer pong. Other things that affect bacterial transfer include surface properties (roughness, moistness), pressure applied during contact, contact time, and biofilms. We know there are differences in how bacteria adhere and transfer from these surfaces, but don’t start thinking it’s safer to play beer pong on a vinyl floor rather than outdoors. You are, after all, at the mercy of what gets on the ball and how sick it could make you. In other words, don’t hate the game—but understand that where the ball goes can create a problem.
Paul Dawson is a professor at Clemson University in the Food, Nutrition, and Packaging Sciences Department. Brian Sheldon is a professor emeritus at North Carolina State University in the departments of Food Science and Poultry Science.
This article is adapted from the new book Did You Just Eat That?: Two Scientists Explore Double-Dipping, the Five-Second Rule, and other Food Myths in the Lab, out today.
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