There is a roaring battle these days over whether a chemical called Bisphenol A is dangerous to humans. The chemical is ubiquitous - used to harden plastic in consumer products including baby bottles, food containers, cling wrap, toys, CDs, sunglasses, and thousands of other products.
A number of independent researchers say tests on animals and other research indicates that Bisphenol A can be toxic at very low doses.
But a review committee created by the National Institutes of Health's National Toxicology Program has yet to find significant danger from the drug. Last month the panel released a preliminary report finding that Bisphenol A is of some concern for fetuses and small children. But it found that adults have almost nothing to worry about.
Still, many researchers say that Bisphenol A, known as BPA, may cause a wide range of health problems, including breast and prostate cancer, infertility, diabetes, brain damage, even obesity. And they warn that the chemical is especially toxic to babies and children.
These scientists point to hundreds of studies showing that Bisphenol A harms animals. They say problems occur at exposure levels equivalent to those commonly seen in humans.
Several state legislatures, including those of California and Minnesota, have considered, but not passed, bills limiting use of BPA. This year, Prince Georges County Del. James W. Hubbard, a Democrat, introduced a bill outlawing use of BPA in baby products, including toys and bottles. The bill was voted down; Hubbard will try again in the January legislative session.
The controversy is part of a larger debate over how to measure the risks posed by the thousands of industrial chemicals that have become part of our lives over the past century - everything from plastics to Teflon to formaldehyde. Many activists and researchers say government rules allow industry to use potentially dangerous compounds without first ensuring the chemicals' safety.
In the U.S., industrial chemicals are regulated under the Toxic Substances Control Act (TSCA). Passed in 1976, the law requires companies to ask the U.S. Environmental Protection Agency for permission to use new chemicals. But companies do not have to test for potential health hazards, or provide any proof that the compound isn't hazardous.
Since the law passed, more than 82,000 chemicals have been registered with the EPA; environmental health scientist Michael Wilson says only a few thousand have received careful vetting. "The great majority of chemicals in common use have not been adequately studied for their effects on human health," says Wilson, executive director of the Center for Occupational and Environmental Health at the University of California, Berkeley. "The big picture is that there's a complete lack of basic public health information."
But the chemical industry says the law is effective. "It's absolutely clear that the EPA has the necessary regulatory authority to ensure that chemicals are safe," says Michael Walls, managing director of the American Chemistry Council, the industry's trade group. "TSCA is a strong statutory framework for chemical regulation."
But critics of TSCA say hundreds of chemicals - compounds commonly used in detergents, cleaning supplies, cosmetics, sunscreens, food packaging, and many other products - may pose serious human health risks. They say this is particularly true of chemicals, including BPA, introduced before TSCA took effect in 1979. Such compounds received a waiver, and are automatically assumed to be safe.
"There's a presumption that a chemical is safe because we know nothing about it," says Lynn Goldman, a pediatrician and a professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health. Dr. Goldman was a high-ranking EPA offical in the Clinton administration. "That's a perverse disincentive for industry to find out more about their chemicals."
BPA belongs to a class of chemicals that disrupt the hormonal system, mimicking the effects of hormones such as estrogen and testosterone. There are hundreds of such compounds, including common pesticides, fungicides and flame retardants, as well as other plastic components besides BPA. While dozens may cause human health problems, many researchers and activists have focused on BPA because it is so widespread, and may be more toxic.
Everyone agrees that BPA mimics estrogen. The disagreement is over how much effect the compound has, and at what doses. The question is crucial, because estrogen is a biological workhorse: It plays a role in a wide range of physiological processes, from sexual maturation to brain cell formation.