Thanks for asking this question. I had never even considered this until you asked, especially since from an environmental viewpoint it has been recommended for years that we reuse plastic food continers as many times as possible because they don't biodegrade.
Yet, apparently you are right. Delicious Organics, a local organic food delivery service in South Florida has put together a great page with all kinds of information on plastic food containers and avoiding plastic with regard to food. Here are some excerpts that specifically address your question.
Plastics #s 1, 2, 4, and 5 are safer and are not known to leach chemicals.
#1 polyethylene terephthalate (PET or PETE) - usually for soft drinks, water bottles, ketchup and salad dressing, peanut butter, pickle, jelly and jam jars
#2 high density polyethylene (HDPE) - used mostly for milk, water and juice bottles, yogurt and margarine tubs, cereal box liners, and grocery, trash and retail bags
#4 low density polyethylene (LDPE) - bread and frozen food bags and squeezable bottles
#5 polypropylene (PP) - margarine tubs
Dr Weil says:
You may have heard about results of two studies, one from Canada and another done recently at the University of Idaho. The Canadian study found that reused water bottles carried by youngsters at an elementary school were contaminated with bacteria, including fecal coliforms. Researchers speculated that the bacteria came from the hands and mouths of the children and speculated that the kids probably didn't wash their hands very often and that the bottles weren't being washed at home frequently. Results of the study were published in the Canadian Journal of Public Health and school officials in the Calgary town where the study was conducted advised parents to make sure that the bottles were brought home and washed properly and frequently. The other study looked at what could happen if you do wash plastic water bottles well enough to kill bacteria. Here, researchers found that frequent washing might accelerate the break-down of the plastic, possibly causing harmful chemicals to leach into the water or other beverages in the bottles. One of the chemicals the researchers identified was the carcinogen DEHA, suspected of causing cancer in humans. The water and soft drink bottles studied are made of a plastic called polyethelene terephthalate (PET) and are intended for single use, but researchers said that reuse is widespread and that some people hold onto the bottles for months, sometimes until they begin to leak. The Canadian Bottled Water Association has advised against reuse and urged that plastic bottles be recycled after a single use.
You may think it is environmentally irresponsible to throw out so many plastic bottles (as a nation, we toss 150 million daily), but given these results it may be healthier to do so. If you routinely re-use plastic water bottles, you may want to replace them after a few washings, or better yet, use the heavier clear plastic bottles made for camping. Avoid the softer opaque bottles for any liquid, as they may shed chemicals even before washing.
Annie Side Note: There is also information that freezing a water bottle may cause the plastic to leach into the water.
A newsletter on food safety from the University of Nebraska also addresses the health effects of reusing plastic containers. They say:
While some items should not be used with foods, others should be used only ONCE, and then for their intended purpose. For example, USDA states:
"Plastic wrap, foam meat trays, convenience food dishes, and egg cartons have been approved for a specific use and should be considered one-time-use packaging. Bacteria from foods that these packages once contained may remain on the packaging and thus be able to contaminate foods or even hands if reused." www.fsis.usda.gov/OA/pubs/meatpack.htm
Other items that were developed with the intention of single use include these four articles:
Single-use plastic water bottles
It is better to buy a reusable water bottle and use that instead of reusing a bottle in which water is sold. The plastic water bottles in which water is sold are intended for single service. They are hard to clean and dry and are not meant for multiple cleanings. They may not hold up under the hot water and cleansing needed to remove lipstick, etc.
Disposable plastic utensils, cups and containers
This category includes plastic forks, spoons and knives; plastic cups; and containers from cottage cheese, sour cream, chip dip, margarine, milk, etc. These items are not made of materials designed for repeated use or repeated cleaning with hot soap and water. Cups and containers may have edges that curl over and collect bacteria that cannot be cleaned out. These containers are developed for specific types/temperatures of foods and may not stand up to all foods, such as high acid and/or hot foods.
Single-use wooden items
Some wooden food-related items, such as popsicle sticks and shish kabob skewers, are intended for one-time use. If you want to reuse shish kabob sticks, buy the metal ones. Rather than reuse popsicle sticks, purchase one of the containers for making popsicles that comes with reusable handles. Or, use a new purchased popsicle stick every time.
Lids with non-cleanable liners
Glass jars can be cleaned and reused; however you must be careful of reusing the lids. Lids with a non-cleanable liner,such as a waxed cardboard liner, should not be re-used.
As good of an idea reuse of these plastic containers is for the environment, from a health perspective, it's a better idea to use glass to store leftovers. The Container Store carries a large selection of glass food storage containers in many sizes and styles (type "glass food storage" in their search box). Also see greenfeet.com.