The problem is that you may not even notice that your shopping bag is making you ill. There are reports that researchers found the lethal toxins in re-usable bags. There are reports in media that tests were conducted on the bags and it was found that bags contained the traces of E.coli which can cause the food poisoning and the other tests also established that bags may contain salmonella as well. If you keep on carrying the same bag to the shopping for very long time, there are fair chances that your bag will contain other bacteria as well. It is always good to get the items packed in the material which has been sterilized and is considered safer. You must dispose off your bags after the use is over. The high level of bacteria in the existing bags is certainly a concern. There are more questions and lesser answers to most of the issues. There is no word on the bags that which one are the safest. You would get to read the news about the unsafe bags but someone also needs to tell us about the safe bags as well