Surprisingly, cell phones and beer pong balls were among the least germy items

NSF International’s Applied Research Center (ARC) has completed its third germ study, this time with a new focus: college off-campus housing. NSF International studied germs in these homes to determine which germs are present and what areas of the home are the germiest.

Imagine the typical college student’s home—dirty dishes in the sink, molding food left spoiling on the counters or forgotten in the fridge, and mildewed showers. Often living on their own for the first time, many of these students, age 18-25, admit they don’t clean. As a result, many are at risk of being exposed to the sort of pathogens that could keep them out of the classroom.

NSF International scientists tested the homes of college-aged students in the Ann Arbor, Michigan area, looking for the presence of four major germ groups including E. coli, MRSA, coliforms, and yeast and mold. To their surprise, items that would seem most likely to contain germs, such as the beer pong ball or cell phones, were nearly free of them. This may not make sense to some, but the findings support what we know about the way germs spread.

“This study yet again shows that smooth, non-porous surfaces with a lack of moisture have far fewer germs because the germs do not have the proper environment to grow,” says NSF International scientist Dr. Jesse Miller, Director of the Applied Research Center at NSF International. “Germs like textured, moist surfaces. The wetter an area stays, the more the germs will persist and multiply, which is exactly what NSF International found in previous germ studies.”

Germs Can Lead to Health Issues

The germs found by NSF International in the study can cause a variety of health problems, from pneumonia to respiratory illness, and exacerbate underlying health conditions. Students with compromised immune systems from such diseases as diabetes, asthma or the flu can be sickened further by these germs.

The study tested for and found the presence of the following germs in college housing:

  • E. coli: Associated with food poisoning, this bacteria can cause vomiting, fever and in rare cases death.
  • Coliforms: These bacterial colonies can harbor disease-causing pathogens of fecal origin.
  • MRSA: Methicillin-resistant Staphylococcus aureus causes infections and resists antibiotics.
  • Yeast and mold: These can cause respiratory disease or magnify allergies.

Students Earn a “D” for Disgusting

Before testing homes, NSF International scientists asked the students to rank items in their home in the order of how germy they thought items would be. Students were only able to correctly identify four of the top six actual germiest areas of their home, a score that could be considered a “D” in the classroom. They had the right idea about some of the germiest spots in their homes, but they were completely wrong about others. Where did they go wrong?

What Students Thought:

  1. Dish sponge
  2. Kitchen sink drain
  3. Cell phone
  4. Shower/tub drain
  5. Bathroom doorknob
  6. Kitchen faucet handle

Actual Germiest Areas:

  1. Dish sponge
  2. Shower/tub drain
  3. Kitchen sink drain
  4. Shower head
  5. Kitchen faucet handle
  6. Coffee maker

“What we found particularly interesting is that students perceived that their high-touch items like their cell phone and beer pong ball would be germy. In fact, these were among the least germy items in their homes,” said Dr. Miller, who led the NSF International study.

Scientists at NSF International found elevated levels of germs, including E. coli, in the kitchen. “Students did not make the connection between moisture and germs, and they didn’t always realize that germs could be in these areas,” says Dr. Miller. “Areas like the shower and coffee maker were also gross.”

Good Cleaning Habits Help Students Make the Grade

Students can improve their cleaning grade to an “A” by paying attention to wet, textured surfaces that may hide germs. By following a few simple cleaning tips, they can reduce the risk of becoming sick and missing class or that important upcoming party. NSF International conducted similar studies in 2011 and 2013, and found household areas and items like the dish sponge, sink drain and faucet handle were the perfect environment for germs.

Dish sponge: Microwave for two minutes once per day and replace every week or two.
Kitchen sink: Apply disinfecting cleaner to the sink sides and bottom one or twice a week.
Faucet handles: Clean daily with disinfecting cleaner or disinfecting wipes.
Shower drain: Disinfect with a bathroom cleaner at least once a week.
Coffee maker: Clean with soap and hot water after every use. Once a week, run the machine with equal parts water and white vinegar or cleaning solution.

Learn more about how to keep the dirtiest areas of the home clean: NSF Germ Study Cleaning Tips

NSF International’s previous studies include the 2011 Household Germ Study and the 2013 Kitchen Study.

Editor’s Note: To learn more about NSF International, contact Thomas Frey, APR, at or call +1 734 214 6242.

About NSF International: NSF International is an independent global organization that writes standards, and tests and certifies products for the construction, food, water, health sciences and consumer goods industries to minimize adverse health effects and protect the environment ( NSF’s Applied Research Center provides custom research and development services for all major industries including contract method development; testing and consulting services in chemistry, microbiology, genomics and toxicology; product claim verification; lab quality/management; methods training; and human health risk assessment.