Despite the Food & Drug Administration assertion last month that products such as polycarbonate baby bottles that contain bisphenol A are safe, a scientific review by another federal agency says the possibility that BPA may affect human development cannot be dismissed.
In releasing the final version of a preliminary report it issued in April, the National Toxicology Program Sept. 3 reiterated that it has ``some concern'' about the effects of BPA on the development of the prostate gland and brain, and for behavioral effects in fetuses, infants and children.
In a statement, Michael Shelby, director of the NTP Center for the Evaluation of Risks to Human Reproduction, said it was difficult to offer advice to consumers.
``More research is clearly needed to understand exactly how these findings relate to human health and development, but at this point we can't dismiss the possibility that the effects we're seeing in animals may occur in humans. If parents are concerned, they can make the personal choice to reduce exposures of their infants and children to BPA,'' Shelby said
NTP retreated, however, from its previous stance that BPA could accelerate puberty in girls, saying it now believes that poses ``minimal concern.''
Richard Wiles, executive director of the Environmental Working Group in Washington, applauded NTP's statement.
``Unlike the FDA, NTP has … concluded that the BPA threat to the brains, bodies and behavior of our children must be taken seriously,'' Wiles said in a statement. ``The FDA has no credibility when it comes to BPA safety.''
NTP's report was issued one day after researchers at the Yale School of Medicine published a study that said BPA can cause the loss of connections between brain cells, which could cause memory loss and learning impairments, as well as depression.
The Yale study acknowledged that daily human BPA exposure usually does not reach the level used in its tests, but noted that human exposure is not limited to a single month, but is continuous over a lifetime.
FDA did not comment on the Yale study, which was based on injecting primates for 28 days with an amount of BPA considered safe by the Environmental Protection Agency. But FDA's report last month questioned the relevancy of BPA assessments when the chemical is injected.
``Safety assessments … should be based on laboratory animal studies using oral routes of exposure since this is the most relevant route of human exposure for food contact materials,'' said the FDA report, which will have a public hearing Sept. 16 in Rockville, Md. ``Studies based on other routes of exposure, such as injections, are likely not comparable to typical human exposures to food-contact materials and will not produce results relevant to safety assessments of food-contact materials.''
There is ``no direct evidence'' that exposure to BPA adversely affects human development or reproduction, said Steve Hentges, executive director of the polycarbonate/PBA global group of the plastics division of the American Chemistry Council in Arlington, Va.
``As several recent government reviews of bisphenol A concluded, studies with nonoral routes of exposure [such as the Yale study] are of little relevance to human health, since people are exposed by the oral route of exposure,'' Hengtes said in a telephone interview. ``The efficient metabolism of bisphenol A that occurs after oral exposure is bypassed by nonoral exposures, which is why studies with nonoral exposures are of little relevance to people.''
In its report last month, FDA said it was not recommending that anyone discontinue using products that contain BPA.
``There is a large body of evidence that indicates that FDA-regulated products containing BPA currently on the market are safe, and that exposure levels to BPA from food-contact materials, including for infants and children, are below those that may cause health effects,'' FDA said.
NTP reviewed more than 500 scientific studies before issuing its report. NTP's associate director, John Bucher, said more research is needed.
In making its conclusions, NTP also relied on low-dose animal tests where BPA is injected, because some studies have suggested BPA is metabolized at the same rate regardless of whether it is injected or delivered orally.
``There are so many levels of uncertainty'' regarding the information on BPA, that NTP finds it difficult to make overall recommendations as to how people should view the chemical at this point, Bucher said.
But because of developmental and behavioral effects in the offspring of pregnant animals given ``very, very low levels of BPA,'' there is a need for more research to reduce some of those uncertainties, he said.
``The fact that we are seeing these [effects] at levels of bisphenol A exposures that are not particularly far different from those that are experienced by humans would indicate to us that effects cannot be completely dismissed at this point,'' Bucher said.
``Our evaluation of bisphenol A is the most difficult and challenging evaluation that we have ever undertaken,'' Shelby added.
``The problem that kept repeating itself was having a body of information of literature on a specific topic that was in disagreement, that reported conflicting results [and] that conducted experiments using protocols that prevented us from making valid comparisons of results from one experiment to another,'' he said.
Health Canada is considering a ban on PC baby bottles. In April, Wal-Mart Stores Inc. stopped selling baby bottles, sippy cups, pacifiers, food containers and water bottles containing BPA in Canada.
Both Wal-Mart and Toys R Us have said they will stop selling baby bottles that contain BPA in the U.S. sometime next year.