CANADA: Reusable grocery bags may pose a public health risk
Posted: May 20th, 2009 - 6:16pm
TORONTO -- While reusable shopping bags are being aggressively promoted by some grocery chains as an eco-friendly initiative, new evidence now suggests that these bags may not be so friendly to your health.
The evidence - "A Microbiological Study of Reusable Grocery Bags"
<http://www.cpia.ca/files/files/A_Microbiological_Study_of_Reuseable_Plastic_Grocery_Bags.pdf>) - is the first study of its kind in North America. It looked at whether reusable grocery bags become an active bacterial growth habitat and breeding ground for yeast and mold after persistent use and pose a public health risk.
Swab-testing of a scientifically-meaningful sample of both single-use and reusable grocery bags found unacceptably high levels of bacterial, yeast, mold and coliform counts in the reusable bags.
"The main risk is food poisoning", said Dr. Richard Summerbell, Director of Research at Toronto-based Sporometrics and former Chief of Medical Mycology for the Ontario Ministry of Health (1991-2000), who evaluated the study results."But other significant risks include skin infections such as bacterial boils, allergic reactions, triggering of asthma attacks, and ear infections."
The swab testing was conducted March 7-April 10th by two independent laboratories. The study found that 64% of the reusable bags were contaminated with some level of bacteria and close to 30% had elevated bacterial counts higher than the 500 CFU/mL considered safe for drinking water.
Further, 40% of the bags had yeast or mold, and some of the bags had an unacceptable presence of coliforms, faecal intestinal bacteria, when there should have been 0.
Some of the conclusions of the study are:
- The moist, dark, warm interior of a folded used reusable bag that has acquired a small amount of water and trace food contamination is an ideal incubator for bacteria. (See report
- The strong presence of yeasts in some bags indicates the presence of water and microbial growth substrate (food). The yeasts are thus a 'canary in the mine' confirming that microbes are growing in the bag.
- There is a potential for cross-contamination of food if the same reusable bags are used on successive trips; and
- Check-out staff in stores may be transferring these microbes from reusable bag to reusable bag as the contaminants get on their hands.
- In cases of food poisoning, experts are now going to have to test reusable bags in addition to food products as the possible sources of contamination.
"A growing problem", added Summerbell, "is possible exposure to the superbug called 'community-acquired MRSA' if the reusables are used to transport gym clothes or diapers in addition to groceries." MRSA (methycillin-resistant Staphylococcus aureus) is a highly antibiotic-resistant form of a common infectious bacterium. It first manifested in hospital settings and demonstrated an ability to spread on contaminated surfaces, such as unwashed hands and items they touched. The bacterium may enter grocery bags if they are re-used to carry athletic equipment. Over 50% of the reusables tested in this study were used as multi-purpose totes to carry gym equipment and groceries.
The research showed single-use bags and first-use reusables to be the most sanitary and safest options with no evidence of bacterial or other contaminants.
"The presence of faecal material in some of the reusable bags is particularly concerning," said Summerbell. "All meat products should be individually wrapped before being placed in a reusable bag to prevent against leakage. This should become a mandated safety standard across the entire grocery industry.”
The study has been sent to the federal Sub-Committee on Food Safety currently investigating the safety of Canada's food system, federal and provincial health ministers and medical organizations across the country with a request for immediate action.
The research was conducted by Guelph Chemical Laboratories and Bodycote Testing Group of Montreal. Oversight and evaluative commentary on the results was undertaken by Toronto-based Sporometrics, the foremost experts in many aspects of fungal and environmental bacterial testing in Canada. GCL tested 23 used reusables and Bodycote tested two older used bags (2 and 3 years old).
The Environment and Plastics Industry Council agreed to fund the testing.