Here's the latest news: " Reusable grocery bags may cause food poisoning". It's all over the news -- see, e.g., http://network.nationalpost.com/np/blogs/theappetizer/archive/2009/05/20/back-to-plastic-reusable-grocery-bags-may-pose-public-health-risk.aspx, http://thetvrealist.com/gossip/Health-risks-soar-with-reusable-bags-4801552.html.
Where do they get this claptrap? One says it's "Researchers at the University of Arizona." But guess what? "According to a study funded by the Canadian Plastics Industry Association (CPIA), our reusable bags make a nice breeding ground for a variety of culprits like bacteria, yeast, mold and coliforms (intestinal bacteria) that we'd rather not know about let alone touch our food. "
You can bet that this little piece of news is dispassionate and scientifically accurate when it comes to you, thanks to the people who want you to you use plastic until you flood the planet.
Who do they think they're fooling? Most of the food we bring home is already swathed in plastic (i.e., meat products), is in cartons (milk; ceram; yogurt), or you can put into plastic at the counter (fresh fruits and vegetables). Plus you should be washing those fruits and veggies anyway -- they were growing in manure! How much more is your bag going to add to the risk?
If you're really paranoid, wash your bag as well as what you buy.
Housewives in France have been using thin mesh tote bags for decades. Carry your canned and frozen foods in one bag, packaged meats in another, and use the mesh bags for the veggies and fruit. Using a mesh bag isn't perfect, but there's less surface for bad stuff to catch on and they're a snap to wash out and dry.