Recently I had someone e-mail my office with the following concern: "I’ve heard that it could cause cancer if you froze water repeatedly in a water bottle."

In order to give the best researched-based answer I immediately contacted Dr. Elizabeth L. Andress, professor and extension food safety specialist at the University of Georgia Cooperative Extension. Following is a portion of the information Dr. Andress provided. For her complete report, please call or e-mail me.

"There actually have been several issues over the past few years related to water bottle use and re-use. (It’s one of those food safety topics that resurface due to a new finding, a new student research project, etc.)

"Sometimes the issue is about microbiological concerns, while other times it is about chemicals in the plastics.

"The referenced studies in each report have to be analyzed for just which type of plastic bottle was studied, as usually it is only one type of plastic.

"The current issue, as I have heard and read about it, is more about bottles that you buy as empty bottles, not the ones already holding water for daily use.

"What has been in the most recent news is about hard plastic bottles, made from the clear polycarbonate plastic (clear as in transparent, but still may be colored).

"And this issue about unsafe chemicals migrating from polycarbonate has been around making news occasionally since at least 2004. There still has not been enough evidence to disallow its use.

"If chemicals are going to leach or migrate into the water, heat actually increases the possibility in most packaging; we would not automatically expect freezing to cause a problem unless the plastic itself goes through some breakdown in structure from the temperature changes.

"It seems reasonable that repeated freezing and thawing of a plastic not intended to be used that way could also lead to structural breakdown. Prolonged, repeated use also receives some attention as a possible concern in breakdown of the plastic.

"It is important to remember, however, that even studies trying to document the impact of these processes are not yet conclusive and consistent as to whether there is a health risk.

"If buying a water bottle, one choice at this time if you are concerned is to not use polycarbonate bottles until the answers are more clear; the concern is not the same with all plastic bottles.

"For example, use polyethylene versions (more "milky" or cloudy plastic that is also more flexible). HDPE (high density polyethylene) means there will be a recycling number 2 in a triangle on the bottle. Polycarbonates will have a 7, but not all 7’s are polycarbonate.

"The manufacturers of some plastic bottles as well as plastics manufacturers (both with vested interest of course) believe the polycarbonate to be safe and that if leaching occurs, it is not at harmful levels. The more independent sources seem to vary as to what the risk is.

"Another option is to trust that FDA will remove polycarbonate bottles from the marketplace when more studies are done and enough data show there is a concern. Until then, in this option you would not worry until there is more evidence of a problem.

"And an important piece of advice, no matter which kind of plastic bottle you use, is to only use the bottles as described for their intended purpose. If the manufacturer does not say you can freeze (or heat) water in it, don’t. If the bottles are sold for freezing, they are supposed to have been tested for safety when frozen.

"There is also the issue of microbial safety in reusing water bottles, even though that is not the current concern raising questions.

"Remember, the commercial bottles that come filled with drinking water are made with plastic designed and intended for one-time use even though it is not for chemical plastic safety. But they are not intended to last structurally through prolonged re-use partly because economically the price of water can’t use too-expensive packaging.

"The water bottles sold as bottles only, such as in sporting good stores, are made from a more durable plastic. They are a better alternative and are designed to be used over and over.

"The opening of the bottle is wider making it easier to clean. Because of the narrow neck of most commercial water bottles, sanitizing your water bottle in the dishwasher is not the best option because water probably can not get up into the bottle for a thorough cleaning.

"If you refill a commercial water bottle or any container for that matter, washing it every day is critical to prevent bacteria from contaminating this healthy beverage.

"Wash the bottle with hot soapy water, and rinse well. Use a clean bottlebrush to clean in and around the neck of the bottle. Scrub the lids with a brush. Allow the water bottle and cap to air dry completely between uses.

"This is my take at this time," Andress said.