Many people have been misled to think that using a reusable shopping bag is an environmentally friendly solution to using plastic bags. Proponents of plastic bag bans, like the proverbial used car salesman, point out the advantages of the reusable bag and never talk about the disadvantages. For example, they will never tell you about the health hazards associated with the reusable bag.
First, reusable bags can become contaminated by meat juices, moisture, and traces of nutrients from food items and become a perfect breeding ground for bacteria, yeast, mold, and coliforms including E. Coli. Bacteria are known to increase by 10-fold if bags are stored in the trunk for as little as two hours. Bacteria can be transferred to packaged food items during the transport home, and ultimately to your hands and to your mouth when packages are opened and food items are ingested.
Second, the reusable bag can act as a carrier to transmit viruses to other people who by touching the bag can become sick. This happened to an Oregon girls Soccer team where a contaminated reusable bag transmitted the norovirus from one girl to an entire team who became ill with gastroenteritis. It was only after a concerned mother contacted the Department of Public Health that a team of investigators identified the reusable bag as the culprit.
There are two lessons we learn from this incident. First, without the involvement of public health officials to identify the reusable bag as the source of a food borne illness, incidents involving reusable bags will be under reported. Second, if the norovirus can be transmitted to others via the reusable bag, so can other viruses, bacteria, and parasites. Some of these are: the common cold, strep, cold sores, conjunctivitis, croup, E. Coli, Giardia, influenza, lice, meningitis, rotavirus, and RSV.
The solution to both of these health issues is very simple. Wash and sanitize your reusable bags at a regular interval such as between uses, weekly, or monthly. Washing bags will kill 99.9% of bacteria and viruses. Remember, bacteria and viruses are invisible to the naked eye, so wash your bags at a regular interval.
Washing reusable bags once per month is more than likely to be sufficient for most people; however, people with compromised immune systems or who take medications that suppress the immune system might want wash their bags more frequently as a precaution.
So what has all this to do with reusable bags being unfriendly to the environment? Every time you wash your bags you consume soap, bleach, water, electricity, natural gas, and generate greenhouse gases. Since this is done on a recurring basis, the cumulative consumption of water and energy and generation of greenhouse gases is large enough such that the reusable bag on a per use basis no longer has the lowest impact to the environment. In other words, a reusable bag has a larger negative environmental impact than the use of plastic or paper bags.
Many reusable bags can only be hand washed. Reusable bags that can be machine washed and dried are more convenient. In the long run people will gravitate to using reusable bags that can be machine washed and dried. Depending upon the type of appliances you have, machine washing and drying your bags just once per month would add an additional $9 to $18 per year to household utility bills; if weekly, the increase will be from $37 to $76 per year. Of course, using water and energy to sanitize reusable shopping bags is a waste of resources when sanitary plastic or paper bags are available off-the-shelf.