Study reveals reusable shopping bags could harbor bacteria

Study reveals reusable shopping bags could harbor bacteria

University of Arizona Microbiologist Dr. Charles Gerba found bacteria present in almost all bags tested and recommends washing reusable bags to reduce exposure to bacteria that can cause illness.

The International Association for Food Protection's Food Protection Trends published a study in its latest issue revealing that most consumers surveyed never wash their reusable bags between uses, permitting bacteria to grow. The peer-reviewed study, completed by University of Arizona Microbiologist Dr. Charles Gerba, found that large numbers of bacteria were found in almost all bags and that coliform bacteria were found in half of those tested.  Eight percent of bags contained E. coli.

The study tested 87 reusable bags obtained at random from grocery shoppers in California and Arizona during the early summer of 2010.  Each bag was swabbed for bacteria and laboratory tested.  

"I was surprised to learn through this study that only three percent of shoppers surveyed actually said they washed their reusable bags between uses.  More surprising were the numbers of people who stated they used the bags not only for food shopping, but also to transport clothing and other products to and from work and the gym," said Dr. Gerba.  "There has been a growing movement to use reusable bags when we shop, but without proper washing, these bags can expose our families to bacteria that can cause illness."

Reusable bags are particularly susceptible to contamination since remnants of meats and dairy products which may seep out of packaging remain in bags unless washed out, resulting in bacterial growth.  Once subjected to the heat of a car trunk, these bacteria quickly multiple.

"Washing bags is the only way to protect your family. It will remove 99.9 percent of germs.  Although it may be a nuisance, washing must be done to ensure your food is safe to eat," added Gerba. "I'd recommend washing it with hot, soapy water after each use."

Dr. Gerba added, "If you choose to use a reusable bag for grocery shopping, it's important to keep your meats in separate plastic bags, use separate reusable bags for food items, and wash them between uses."

An abstract of the study can be found here.

About Dr. Charles Gerba

Chuck Gerba is a professor in the Departments of Soil, Water and Environmental Science (College of Agriculture), and Epidemiology and Environmental Health (College of Public Health) at the University of Arizona. He obtained his Ph.D. in Microbiology from the University of Miami, Florida and was a faculty member in the Department of Virology and Epidemiology at Baylor College of Medicine from 1974 to 1981. He conducts research the transmission of pathogens through the environment. Dr. Gerba serves as an advisor to Hilex Poly, the world's largest bag-to-bag recycler of plastic grocery bags. Hilex also manufacturers reusable bags. His recent research encompasses the transmission of pathogens by water, food and fomites; fate of pathogens in land applied wastes; development of new disinfectants; domestic microbiology and microbial risk assessment. He has been an author on more than 500 articles including several books on environmental microbiology and pollution science. He is a fellow of the American Academy of Microbiology, American Association for the Advancement of Science, and the International Water Association. In 1998 he received the A. P. Black Award from the American Water Works Association for outstanding contributions to water science and in 1996 he received the McKee medal from the Water Environment Federation for outstanding contributions to groundwater protection. He received the 1999 Award of Excellence in Environmental Health from National Association of County and City Health Officials. 

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