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A debate is raging over bisphenol A, which promises to dwarf the 1989 Alar scare. For those who do not remember, Alar (daminozide) is a pesticide that was used on apples and cherries to enhance ripening. A Canadian researcher found that daminozide can degrade during thermal processing to yield a chemical (unsymmetrical dimethylhydrazine), which is chemically similar to a potent carcinogen (symmetrical dimethylhydrazine).
The players in this affair included CBS TV’s 60 Minutes, Fenton Communications Inc., and the Natural Resources Defense Council. Following airing of the inflammatory episode, parents quickly removed apples from their children’s lunch pails. Years later, as the science finally caught up with the media hype, it was shown that the risks from daminozide and the breakdown chemical were minimal. This controversy hurt the Washington State apple industry, and removing daminozide from the marketplace and apples from lunches did not make consumers safer.
Bisphenol A or BPA (4,4’-iso-propylidene diphenol) has been used for over half a century as an additive to polycarbonate plastics to make them harder and give them glass-like clarity. Polycarbonate containers are sometimes labeled with a "PC" and are grouped with other types of plastics in the recycling category "7". PC products include hard plastic water bottles, baby bottles, and tableware. BPA is also incorporated into the epoxy lacquer that is used to coat the inside of metal cans and bottle tops. The coating prevents the contents of the can from corroding the metal and keeps the metal from contaminating the food.
BPA has been shown to migrate from containers and become an indirect food additive. Migration into foods is primarily influenced by coating type and thickness, food product, and processing temperature. Storage or food-to-package contact time appears to play a lesser role in the migration. An FDA scientist has confirmed that soda and beer products that were tested by FDA approximately 10 years ago did not contain detectable residues of BPA (Begley, 2008).
There is general agreement regarding the safe limit of exposure to BPA among regulatory bodies. The EPA (1993) established a Reference Dose (RfD) for BPA of 50 μg/ kg bw-d. The European Commission (2002) recommended a temporary-Tolerable Daily Intake (t-TDI) of 10 μg/kg bw-d. The European Food Safety Authority (EFSA, 2007) established a TDI of 50 μg/kg bw-d.
Most of our exposure to BPA is from dietary sources. CDC has measured BPA and its metabolites in 95% of urine samples tested (NHANES III). Remembering that the "dose makes the poison," it is also important to look at exposure estimates. The European Commission has estimated that the worst-case exposure levels for adults and infants are 0.48 and 1.6 μg/ kg bw-d, respectively. These levels are much lower than the established safety limits.
Based upon current exposure estimates and safety limits, BPA is a safe chemical for use in food packaging. In 2007, an FDA official stated, "An infant would have to ingest over 7,100 times more than the current daily exposure before there would be the potential for an adverse toxic effect" (GMA, 2008).
Some recommendations and projections follow:
• Since studies have found no detectable residues of BPA in canned carbonated beverages or canned beer, the use of BPA in the packaging of these products should continue.
• Techniques to further reduce the migration of BPA from food packages should be explored.
• BPA alternatives for infant bottles will likely be adopted due to public misperception. Health Canada is banning BPA in infant bottles although they acknowledge that these bottles are safe.
• More data are needed on BPA concentrations in U.S. food products and in the breast milk of U.S. women.
• The National Toxicology Program (NTP) recommends further research based upon findings using laboratory animals. NTP believes that the number of human studies is inadequate to reach conclusions on developmental or reproductive risks.
We must continue to evaluate the safety of chemicals used in food production and packaging. The U.S. is no longer a leader in food toxicology and, as a result, finds itself responding to food safety studies that were conducted in other parts of the world (e.g., daminozide, ethylene thiourea, acrylamide, brominated flame retardants).
We should resist the growing trend toward determining safety as preached by those that subscribe to the precautionary principle. This principle was shown to be seriously flawed during the safety evaluation of biotech crops. Adoption of a precautionary policy will waste valuable resources and cause us to miss important opportunities for protecting public health.
References are available from the author.
by Charles R. Santerre, Ph.D., a Professional Member of IFT, is Professor, Dept. of Foods and Nutrition, Purdue University, West Lafayette, IN 47907 ([email protected] edu). He is also a technical advisor for the American Beverage Association.