We’ve often written about the American Council on Science and Health,
even urging donations. Now we owe a hat tip to the Council for sending along this study by researchers at the University of Arizona and Loma Linda University.
The study is titled, Assessment of the Potential for Cross Contamination of Food Products by Reusable Shopping Bags, and here is the researcher’s summary:
Most foodborne illnesses are believed to originate in the home. Reuse of bags creates an opportunity for cross contamination of foods. The purpose of this study was to assess the potential for cross contamination of food products from reusable bags used to carry groceries. Reusable bags were collected at random from consumers as they entered grocery stores in California and Arizona.
In interviews it was found that reusable bags are seldom if ever washed and often used for multiple purposes. Large numbers of bacteria were found in almost all bags and coliform bacteria in half. Escherichia coli were identified in 12% of the bags and a wide range of enteric bacteria, including several opportunistic pathogens.
When meat juices were added to bags and stored in the trunks of cars for two hours, the number of bacteria increased 10-fold indicating the potential for bacterial growth in the bags. Hand or machine washing was found to reduce the bacteria in bags by >99.9%. These results indicate that reusable bags can play a significant role in the cross contamination of foods if not properly washed on a regular basis. It is recommended that the public needs to be educated about the proper care of reusable bags by printed instructions on the bags or through public service announcement.
Of course, there was already some doubt about the environmental benefit of these reusable bags. Other studies
If consumers start running washing machines, perhaps as an extra run as they don’t want to wash something like this with their clothes, the additional water and detergent used might turn the whole environmental argument on its head.
We doubt it is a big food safety issue as most bulk produce is put in plastic bags before being put into a consumer’s take-home bag, but still, most prepackaged produce is not airtight — clamshells routinely have air holes, and some items such as melons are put in loose. Some salmonella-laced chicken juice could drip down into some berries or be transferred to the flesh of a melon by a knife.
To us the issue demonstrates how difficult it is to make things better. We consciously will an environmental improvement by urging reusable bags and, inadvertently, increase food safety risks by creating another environment for pathogens to grow.
Who is to say we won’t improve food safety, but in so doing raise the cost of fresh produce and lead people to switch to processed foods — and maybe that will cost more in lives due to obesity than will be saved with better food safety?
One thing is for sure: Good intentions are not a sufficient vector for evaluating such things. As they say, the road to Hell is paved with good intentions.