"What that told me is that no matter what I tried to do, the plumes of chemicals that we are passing in and out of everyday give us exposure," said Baltz, who works for Commonweal, an environmental group in Bolinas, Calif. Commonweal and the Washington-based Environmental Working Group funded tests for Baltz and eight others at $5,000 apiece.

For decades, researchers have sampled the air, land and sea to measure pollution from power plants, factories and automobiles. More recently, they have expressed concern about mounting "e-waste" — discarded tech gadgets that contain flame retardants, lead and other toxins.

But there's been trouble determining precisely how much pollution gets absorbed by humans.

Now, in a process called biomonitoring, scientists are sampling urine, blood and mother's milk to catalogue the pollutants accumulating in humans. They call the results "body burden."

Though the tests are yielding scary lists of contaminants found in the body, their links to disease are less clear. Nonetheless, proponents say such testing will help researchers learn what role the environment plays in causing disease and how to treat it.

Many chemicals such as PCB and DDT, both banned decades ago, remain in the environment for years and build up in the body over a lifetime.

It's not a new phenomenon. Rachel Carson wrote about the poisons in her 1962 book "Silent Spring," which is widely credited for jump-starting the environmental movement.

But until now, researchers were left mostly to guess about exactly how much and how many of the toxins lingered in our bodies.

Few of the estimated 75,000 chemicals found in the United States have been tested for their health effects, Baltz and other biomonitoring proponents say. By looking directly in the human body, they hope to catalogue the environmental influences that may cause disease.

Already, several studies have been completed:

• In March, California researchers reported that San Francisco-area women have three to 10 times as much chemical flame retardant in their breast tissue as European or Japanese women.
• Indiana University researchers reported at the same time that levels in Indiana and California women and infants were 20 times higher than those in Sweden and Norway, which recently banned flame retardant.
• The Centers for Disease Control and Prevention earlier this year released data from 2,500 volunteers tested for 116 pollutants and found such chemicals as mercury, uranium and cotinine, a chemical broken down from nicotine.

The CDC also found that black children have twice the level of cotinine than other children, implying they were exposed to more secondhand smoke than their peers of other races.

Meanwhile, Mexican-American children were found to have three times the amount of a chemical derived from DDT compared with other children. Scientists suspect that Mexico and Latin America countries may still be using the banned chemical.

Next month, state Sen. Deborah Ortiz plans to renew calls for California's polluters to finance testing of contaminants in mother's milk.

"This will allow women to better make informed decision about their health," said Ortiz, a Democrat. "And the information will help researchers and public health officials."

But some fear that biomonitoring results could be misinterpreted and frighten new mothers from breast feeding their babies.

"We are clearly concerned about what effects the stories of biomonitoring will have," said Barbara Brenner, executive director of the San Francisco-based Breast Cancer Action nonprofit advocacy group. "Any rational woman will say to herself, `Should I be breast feeding?'"

Others see political motives behind some of the tests.

"Everyone's exposed to substances and there's no evidence that the low levels people are exposed to are harming anybody," said Steven Milloy, author of "Junk Science Judo: Self Defense Against Health Scares and Scams." "It's a waste of time and money that only serves to scare people."

Milloy noted that despite all the chemicals, the overall U.S. population is living longer and healthier.

Although the tests conducted on Baltz and other Commonweal volunteers, including public television journalist Bill Moyers, are too expensive for most people, proponents believe costs will go down as technology advances. Moyers' body had traces of 84 toxins, including lead and a byproduct of mercury.

There's still a debate among advocates over which of the 75,000 chemicals to specifically look for when biomonitoring. And even when chemicals are found, there's little an individual can do.

But Baltz said the knowledge can at least help consumers make more informed choices over what they eat.