When I read that there are 100s of toxic chemicals in human cord blood (including BPA), I feel a little sick. And when I read that there are 100s of toxic chemicals in pregnant women's blood, I feel a little sicker.

Especially since many of the chemicals identified in the cord blood samples cause irreversible changes in the brains, reproductive systems and other vital organs of fetal and newborn test animals. Among the worst actors:

• ** Bisphenol A, a hormone-disrupting plastic chemical now under federal scrutiny for a possible ban in baby bottles, infant formula cans and other food packaging;
• ** Perchlorate, a rocket fuel component and ubiquitous water pollutant that undermines thyroid function crucial to brain development;
• ** Polychlorinated biphenyls (PCBs), probable human carcinogens and endocrine disruptors effectively banned during the Carter administration, yet still showing up in human and animal tissue worldwide;
• ** Lead, found in older pipes and paint, toxic to the brain and nervous system;
• ** Mercury, another neurotoxin, commonly ingested in contaminated seafood like tuna.

Some of the questions news like this often raises are addressed in the Environmental Working Group's recent report on the chemicals in human cord blood (it has an excellent FAQ):

Why are in utero chemical exposures so significant?
During pregnancy, the placenta transfers nutrients from the mother to the fetus and moves fetal waste to the mother, who excretes them. Numerous studies show that the placenta does not, as once thought, shield the developing fetus from the hundreds of industrial chemicals and pesticides with which the mother comes in contact.

In-utero contamination is particularly worrisome because of the unique vulnerabilities of the developing fetus:

• ** The blood-brain barrier, a protective mechanism that prevents many harmful chemicals from entering the human brain, is not fully developed until after birth.
• ** The developing fetus cannot detoxify and excrete many chemicals as completely as a mature body.
• ** The fetus undergoes rapid cellular division, proliferation and differentiation, during which processes its cells are particularly susceptible to chemical exposures
• ** Exposure to toxic industrial chemicals during critical windows of development can result in permanent and irreversible brain and organ damage.

How and when is the mother exposed to these chemicals?
More than 80,000 commercial chemicals are approved for use in the U.S., a number that grows by 2,500 new chemicals yearly. U.S. industries produce or import 3,000 of these substances in quantities of greater than one million pounds per year.

Many pesticides banned in the U.S. for decades persist in the environment, build up in the food chain and continue to contribute to daily exposures (PCBs and DDT, for example). Government sources detail more than 3,000 chemicals used as food additives, an estimated 10,500 ingredients in personal care products, and more than 500 chemicals approved as active ingredients in pesticides.

Many of these chemicals, whether used purposefully or unwanted impurities, can contribute to a person's body burden through exposures from food, air, water, dust, soil and consumer products.

What are the implications of chemical exposures for human health?
For many chemicals in our bodies, the health consequences are unknown. Studies aren't required under federal law and in most cases haven't been done.

What steps can women who are pregnant or planning to be pregnant take to reduce any adverse effects on their children?
Some exposure to pesticides, industrial chemicals and environmentally persistent pollutants aren't avoidable. But some are. Read EWG's Tips for a Healthy Pregnancy here.

Because their chemicals don't belong in YOUR womb.