Environment Health World — 10 November 2011

Researchers collected reusable polypropylene bags from and found coliform bacteria in over half of them.

Cities and local governments around the country are banning plastic grocery bags with little awareness that they may be trading an environmental problem for a potential public health threat.

Reusable shopping bags, which are replacing single use bags, are a breeding ground for E. coli and other bacteria, according to a recent study by the University of Arizona and Loma Linda University in California.

Researchers collected reusable polypropylene bags from consumers in Los Angeles, San Francisco and Tucson and found coliform bacteria in over half of them. Escherichia coli, a potentially dangerous pathogen that can cause food poisoning, was detected in 12% of the bags. Contamination rates were higher in California, particularly in Los Angeles, where E. coli was found in nearly 25% of the bags sampled. Researchers believe the rate of contamination was higher in Los Angeles because its weather is warmer and more humid, conditions that are more conducive to bacterial growth. No bacteria were found in newly purchased reusable bags.

“Our findings suggest a serious threat to public health,” said Charles Gerba, a University of Arizona professor of environmental science and co-author of the study. “Furthermore, consumers are alarmingly unaware of these risks and the critical need to sanitize their bags on a weekly basis.”

97% of the consumers interviewed for the study never washed their reusable bags. Many said they used the bags to transport other items besides food, such as gym clothing and books, creating the potential for cross contamination of food with additional pathogens. Washing bags is effective at reducing or eliminating all types of bacteria.

The study warned of “significant adverse public health impacts” if reusable bags become more widely used and called for public education campaigns. Recommendations include printed instructions on bags that they be cleaned regularly, as well as public service announcements on risk and prevention.

14 cities in California have plastic bag bans, including Long Beach, Oakland, San Francisco, San Jose and Santa Monica. Los Angeles county has also banned plastic grocery bags in unincorporated areas. In the public debate leading up to the bans, there has been almost no discussion about the importance of sanitizing reusable bags.

A recent sampling of reusable bags sold in southern California supermarkets found little or no information about cleaning them. Reusable bags sold by Trader Joe’s and Vons came with no instructions about cleaning. Reusable bags sold by Ralphs have tags that say “wipe clean” or “machine wash cold” but no guidelines about how often the bags should be washed. All of the bags were manufactured in China.

More info: http://uanews.org/pdfs/GerbaWilliamsSinclair_BagContamination.pdf

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Pat Anson, Editor

Pat is Editor in Chief of American News Report. He is a veteran journalist and a former correspondent and producer for HealthWeek (PBS), Nightly Business Report (PBS) and other nationally syndicated shows. Pat has won numerous journalism awards, including a Golden Mike award for investigative reporting.

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