Nowhere is the issue of trade-off more obvious than with flame retardants, which today are found in virtually every U.S. resident at levels that are far and away the world's highest. They're commonly found in the air and water, and they've been measured in lake sediments and in wildlife worldwide.

Animal studies have shown that at high enough levels, the chemicals harm the nervous system and cause reproductive problems, including spontaneous abortions.

They also save lives.

"Certainly there would be a much higher fire risk without flame retardants," said Ron Hites, a chemist in the school of public and environmental affairs at Indiana University who has studied the spread of flame retardants in the environment.

The problem is that not enough research has been done to know whether the levels of flame retardants and other persistent toxic chemicals found in people are safe.

But health officials do know that once those chemicals get into the body, no pill or treatment can remove them. They can be passed to a fetus in the womb through the placenta and to a baby through the mother's breast milk.

They also know that levels of flame retardants and nonstick chemicals measured in people, though low, are rising so quickly that they are now nearing concentrations shown to cause harm in animals.

Many medical researchers and health experts are asking whether the U.S. regulates toxic chemicals in a way that adequately protects people.

Companies are not required to test new chemicals for health effects, unless evidence already exists of potential harm. All that companies have to do is apply to an overworked corner of the EPA that handles an average of 142 applications a month.

It's then up to the EPA to do the costly research to determine whether a chemical poses a risk. But it only has 90 days to review the application and make the determination.

If problems are discovered after a chemical is in widespread use, it's up to the agency to prove the chemical is to blame.

As a result, very little meaningful information exists on the potential health effects of many of the nearly 82,000 chemicals in commercial use.

"We have lots of products that are still being sold every day that we really don't know enough about to be confident that they're safe," said Dan Esty, a senior EPA administrator in the first Bush administration who now directs the Yale Center for Environmental Law and Policy at Yale Law School.

In a July report, the Government Accountability Office criticized federal law for placing the burden of testing new chemicals for human risks on the EPA. In August, the Senate Environment & Public Works Committee held hearings to determine whether to amend the law to better protect human health and the environment.

The committee declined to act.

Others say that the U.S. has adequate safeguards.