How to Keep Your Reusable Bags Bacteria-Free

Now that South San Francisco has adopted a reusable bag ordinance, banning plastic bags and charging 10 cents per paper bag, what should you do to prevent bacteria from growing in your reusable bag? According to a recent study, reusable bags can play a significant role in the cross contamination of foods if not properly washed on a regular basis.

Patch spoke with Dr. Charles Gerba, a professor in the Departments of Soil, Water and Environmental Science and Epidemiology and Environmental Health at the University of Arizona, who conducted research on bacteria in reusable bags. He interviewed customers on their reusable bag use and took samples of the inside of their reusable bags. For the study, a total of 84 bags were collected (25 Los Angeles, 25, San Francisco and 34 from Tucson) from each location.

What did he find? Large numbers of bacteria were found in almost all bags, including fecal bacteria such as coliform and E. coli.   

Patch: What did your research show?

Gerba: We were looking at the issue of how contaminated the bags got with fecal bacteria and half the bags contained fecal bacteria. Eight to 10 percent contained E. coli and only three percent washed their bags on a regular basis. We found that when they put them in cars — which are warm — bacteria grew more. One third had used their bags for other things, too, which was the problem. There is that concern if you go grocery shopping with a contaminated bag, it could make you ill; we saw one outbreak. It’s about developing strategy to protect yourself and taking better care of the bags.

Patch: What is the best method of dealing with this?

Gerba: No. 1, use cloth bags that can be washed in the laundry (cheaper ones are only hand-washable, non-woven fabric fibers).

No. 2, separate raw produce from raw meat and wash bags that you use for meat on a weekly basis.

No. 3, don’t use them for other purposes except for food (like for dirty guy clothes or laundry).

View Dr. Gerba’s full study here. For more information on bacteria in your bags, visit this site and check out this infographic.

The following information was supplied by the San Mateo Sheriff’s office, and unless otherwise noted, an arrest does not indicate a conviction. Click the "Keep me posted" button for an alert when we publish this daily report.

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