(USA Today)-- PALM SPRINGS, Calif. - Jamie Norton considered himself an early adopter of reusable shopping bag, keeping them in the trunk of his car so they're on hand whenever he stops for groceries.
But washing the bags wasn't part of the routine.
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"If it gets too dirty, I just toss it out," Norton, 61, said as he walked out of Jensen's grocery store here with one of his bags full of food. "I have never washed a reusable bag."
Research shows the vast majority of shoppers are like Norton. A 2011 study from scientists at the University of Arizona and Loma Linda University found only 3% of shoppers with multi-use bags said they regularly washed them. The same study found bacteria in 99% of bags tested; half carried coliform bacteria while 8% carried E. coli, an indicator of fecal contamination.
"I classify them as pretty dirty things, like the bottom of your shoes," said Ryan Sinclair of the Loma Linda University School of Public Health, a co-author of the study.
He is finalizing another study he hopes to publish soon looking at how pathogens spread through grocery stores with the help of reusable bags. The study, conducted at a central California grocery store in early 2013, involved spraying bags with a bacteria not harmful to humans but transported in a similar way to norovirus, a leading cause of gastrointestinal disease linked to more than 19 million illnesses each year in the United States.
The tracer bacteria was detected in high concentrations on shopping carts, at the checkout counter and on food items shoppers had touched but kept on the shelf.
Sinclair said the contamination cycle often began right after shoppers entered the store and placed their bags in the bottom or the baby carrier of a shopping cart, two places notorious for germs.
"The baby carrier portion of the grocery cart is the most contaminated public surface you ever come in contact with," he said.
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Reusable bags, often given away as event swag or sold for around $1 at grocery stores, are becoming more common, and 69 local bans on the thin, single-use plastic alternatives, have passed in California.
But Sinclair doesn't think habits about washing the bags are changing much in the years since the study he helped create was published.
The researchers found that bacteria thrived and multiplied on bags stored in the trunks of cars and that machine or hand washing reduced bacteria on bags by more than 99.9%. A separate study published in 2012 traced a norovirus outbreak among a girls' soccer team from Oregon to a reusable bag stored in a hotel bathroom used by an ill team member.
Norton, a Palm Springs resident, said the flimsy plastic bags come in handy, especially for cleaning up after his dog, but he supports bans.
"I really do think plastic bags are a blight," he said.
A proposed ban here would prohibit most stores from giving out thin plastic shopping bags and instead require them to charge 10 cents for a recycled paper bag. Plastic bags for meat, produce and takeout food still would be allowed, as would heavier plastic bags such as ones often given out at clothing retailers.
A similar ban took effect in Los Angeles on New Year's Day. San Franciso passed its ban in 2007, the first city in the nation to do so.
For their study, Sinclair and other scientists collected bags from shoppers in California and Arizona, offering them a replacement bag or money as compensation and swabbed the bags for any contamination. Shoppers also were questioned about how often they use and wash their bags.
Sinclair recommended that the bags be treated like the dirtiest laundry and washed in hot water with a detergent and disinfectant. He said he puts his own bags in the washer with socks and underwear, and that even the polyurethane bags can be washed five or six times before they start to fall apart.
Putting the bags in the washing machine and dryer about once a week is a good strategy, Sinclair said. Washing with a spray cleaner and cloth isn't effective, he said, because it tends to miss dirt deep in corners and creases.
The study recommended more public awareness efforts about washing reusable bags and that manufacturers print laundering directions on the bags.
Sinclair and other authors faced some criticism after the study was published because the American Chemical Council partially paid for the research. The trade organization has advocated against reusable shopping bags on behalf of its members who manufacture the thinner, petroleum-based plastic bags.
Sinclair said he wasn't aware of the association's support until after the study was published and that the money doesn't discount the finding or recommendations.
"Personally, my recommendation is to use reusable bags, but just wash them. It's not a big deal," he said.
At the grocery store, Sinclair recommends that shoppers use cleaning wipes if the store has them available for carts and that foods be washed before going into storage at home. Separate bags also should be used for meats and vegetables.
Betsy Hammes of Palm Springs grabbed a shopping cart outside Jensen's and placed her reusable bag in the bottom. She said she's diligent about washing the bags with a spray cleaner and then throwing them away after a few washings.
Before entering the store, Hammes pulled a disinfectant wipe from the dispenser and cleaned the shopping cart handle.
"I always do that," she said. "You never know who was using it before."
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