By Susanne Rust
SAFETY TIPS [/b]Polycarbonates can be identified by the recycling No. 7, which often appears with arrows in the shape of a triangle on the bottom of containers. Bottles that show wear, are cracked, or are cloudy should be discarded. Exposing these products to high temperatures should be avoided.
Although its name may not be familiar, bisphenol-A is everywhere. It's in the lining of your soup can, the clear plastic of your baby's bottle and the sealants covering your teeth.
But it might be harmful to your health.
An expert panel of endocrinologists, statisticians and biologists was called together last week by a federal agency to review a report on this ubiquitous chemical. The final review, which was supposed to be announced earlier this month, was postponed.
For several years, scientists have been concerned about bisphenol-A. Hundreds of papers have shown that it can be toxic in extremely low doses.
Traces of bisphenol-A have been found in nearly every American tested for it. The chemical mimics estrogen and binds to estrogen receptors on cells. In more than 100 experiments conducted on lab animals, it has been shown to cause genetic changes leading to prostate cancer, as well as decreased testosterone, low sperm counts and signs of early female puberty.
Work also has been done on human tissue, with results showing that exposure can cause changes in prostate and breast tissue.
The National Institutes of Health's Center for the Evaluation of Risks to Human Reproduction, which was charged with drafting the report, may be compromised, critics say. The environmental organization Environmental Working Group has evidence showing that a private consulting firm with close ties to the chemical industry did much of the work on this report, as well as for the center itself.
The firm, Sciences International, has had clients including BASF and Dow Chemical â€” companies that manufacture bisphenol-A â€” as well as DuPont, Chevron, Exxon Mobil, 3M, Union Carbide, the American Petroleum Institute and the American Chemistry Council.
Since allegations were made public earlier this month, Sciences International has been removed from the review. But questions remain about its role within the federal center and in the report it compiled for the expert panel's review.
However, the reason for the delay in the expert panel's conclusions was not any association with Sciences International, said Allen Dearry, the interim associate director of the NIH's National Toxicology Program, which is also associated with the reproductive-health center.
The delay, he said, is the result of the enormous volume of material required for the panel to review.
"They are reviewing 600 studies," said Christine Bruske-Flowers, spokeswoman for the federal National Institutes of Environmental Health Science, which is also involved with the center. "They haven't been able to get through them all."
The panel will reconvene in two or three months, officials said.
Sciences International referred all questions to the center.
Bisphenol-A is the raw material of polycarbonate plastic and epoxy resins. Plastic manufacturers value this polymer for its ability to withstand high temperatures, its durability and its transparency. It is because of these characteristics that manufacturers use it for making drinking vessels such as water and baby bottles. Epoxy resins are used on the inside of tin and aluminum cans to prevent corrosion.
According to Rudolph Deanin, a professor of plastics engineering at the University of Massachusetts-Lowell, bisphenol-A will leach from polycarbonate if exposed to hot liquids or alkaline material.
Other studies have suggested it can leach into water at lower temperatures.
The chemical has been highly controversial. Industry groups have claimed that human exposure levels are too low to cause harm. Indeed, they have provided about a dozen of their own studies to support this contention.
But researchers, including Patricia Hunt, a reproductive biologist at Washington State University, beg to differ.
Hunt became interested in bisphenol-A research after all of her laboratory mice started showing high levels of genetic abnormalities in 2003. She discovered the animals had been exposed to bisphenol-A that was leaching from their polycarbonate cages â€” and it was this chemical that had caused the abnormalities.
Since then, she has conducted experiments showing that at low doses, the chemical can cause problems. In a recent study, she demonstrated that bisphenol-A, when exposed to pregnant female mice, affected not only the pregnant mice, but the egg production of the female pups.
That's an effect that spans three generations â€” the pregnant mouse, the fetal mouse and the eggs of the fetal mouse. "I fell into this by accident," she said. "But I'm pretty committed because I'm horrified by what I see."
Hunt said the chemical is more likely to leach as the product ages. Bottles that show wear or are cracked or cloudy should be discarded. And exposing these products to high temperatures should be avoided.
Polycarbonates can be identified by the recycling No. 7, which often appears with arrows in the shape of a triangle at the bottom of a bottle or container. Baby-bottle manufacturers are not required to label their bottles.
"I'm trying to walk a fine line," Hunt said, "between making consumers aware and freaking parents out and making them unable to sleep at night." But she's concerned enough that she now stores her food in glass containers and never microwaves plastic.
WHAT IT'S IN
Products that might contain bisphenol-A:
â€¢ Hard, clear plastic baby bottles
â€¢ Hard, clear, sometimes tinted plastic water bottles
â€¢ Hard, clear plastic bowls, tableware and storage containers
â€¢ Liners inside food and drink cans
â€¢ Dental sealant to prevent cavities
â€¢ Electronic equipment
â€¢ Sports-safety equipment
â€¢ Medical devices
â€¢ Pet carriers
â€¢ Spray-on flame retardants
Source: American Plastics Council
Polycarbonates can be identified by the recycling No. 7, which often appears with arrows in the shape of a triangle on the bottom of containers. Bottles that show wear, are cracked, or are cloudy should be discarded. Exposing these products to high temperatures should be avoided.