This January, a study by the University of California San Francisco confirmed that pregnant women carry multiple chemicals in their bodies that can be passed on to their fetus. Published in Environmental Health Perspectives, the study evaluated data collected by the U.S. Centers for Disease Control and Prevention in 2003-2004. Overall, 43 banned and currently used chemicals — including PCBs, organochlorine pesticides, PFCs, phenols, PBDE flame retardants, phthalates — were detected in 99-100 percent of more than 250 pregnant women.

Though we have known for years that humans are contaminated with dozens of chemicals from birth until late in life, this study marks the first time the number of chemicals in pregnant women has been counted. Many of the 163 chemicals studied are known to be transferred to the fetus and have been linked to poor health outcomes, placing them at risk for birth defects or chronic illnesses later in life. Some of the chemicals detected, such as PCBs, have been banned for more than 30 years. 

This study adds to the weight of evidence that fetuses are exposed to a soup of chemicals during vulnerable periods of development. Furthermore, because the women in the study were tested for exposure to only a fraction of chemicals on the market, it also suggests that pregnant women are likely carrying and passing onto their fetuses many more chemicals than have been reported here. Catherine Zandonella spoke with NRDC senior scientist Dr. Sarah Janssen about the implications for women and their children.

SimpleSteps: What are the possible harmful health effects to a child who was exposed in the womb to these chemicals during pregnancy?

Dr. Sarah Janssen: Over the past several decades, scientists have discovered that exposures occurring early in life, either in the womb or during early stages of childhood development, can cause harm that doesn’t occur when the exposure happens later in life. This is because during fetal, neonatal and early childhood, the body is rapidly growing and developing under a carefully orchestrated process that is dependent on stepwise events.

When one of those events is interrupted, the next event is disrupted and so on until permanent and irreversible changes can result. This could result in a very subtle effect — like an alteration in how the brain develops resulting in changes in attention span, learning ability or behavioral changes. Or it could result in other impacts like altering where fat cells are deposited in the body or modifying the development of an organ predisposing it to cancer later in life.

Many of these types of studies have been done in laboratory animals, but we do have some evidence gestational exposures are causing human harm. For example, lead, mercury and PCBs have all been shown to harm the developing brain resulting in a loss of IQ points, impaired learning and memory, and behavioral changes.

Can nursing infants be exposed to these chemicals. If so, and what harm might result from breastfeeding?

Yes, some of these chemicals are found in breast milk. It is frustrating and maddening that a baby’s first food is contaminated with industrial chemicals, but breast milk remains the best form of nutrition for infants.

The benefits of breast feeding outweigh any of the risks — including exposure to chemicals. We have information about the benefits to mom and baby on our website.

In addition, there have been some studies that have shown breast feeding can counter some of the harmful effects often seen after exposure to PCBs in the womb. Bottom line is that while we work to eliminate the most harmful chemicals from our breast milk — breast remains best!

Can fetal exposure to chemicals in the womb cause problems with fertility and reproduction later in life?

Yes, it is likely. Because gametes — the cells that form sperm and eggs — are formed in fetal life and reproductive organs are also forming throughout gestation, exposures to chemicals during this time can permanently alter these structures and result in infertility that isn’t manifest until several decades later.

For example, from animal studies we know that exposure to phthalates during fetal development can result in malformed genitals, poor sperm quality and even testicular cancer. Preliminary studies in humans have linked phthalate exposure during fetal development to a feminization of the genitals, though it isn’t yet known whether this results in reproductive harm.

So you are telling me that these chemicals can harm the children of exposed pregnant women. Do these chemicals harm the women also? How?

For most industrial chemicals, we have very limited information on their effect on adults. There are some studies that have shown that bisphenol A (or BPA) may promote the growth of aggressive breast tumors and also may interfere with chemotherapy treatments. Recently published research has found women with polycystic ovarian syndrome also have higher levels of BPA. Phthalates have been linked to poor sperm quality in adult men.

By far, the most information we have is on exposures during early development but we must remember that there are other life stages that are also vulnerable, including puberty, pregnancy, lactation and menopause. Most research has focused on earlier life stages. We need more research on the other vulnerable periods of development.

Aren't the levels of the chemicals detected in the study very small? How do we know that these tiny amounts can cause harm to a developing fetus?

Yes, the levels of chemicals found in the bodies of these pregnant women were very small. Many of them are in the parts-per-billion range, which is analogous to a teaspoon of water in an Olympic size swimming pool. This may not seem like a very large amount, but it is important to remember that the profound physical, emotional and behavioral changes that occur during puberty are the result of a spike in sex hormone levels in the parts-per-billion or even parts-per-trillion range. So small amounts of a chemical exposure could be significant, especially if they interfere with your body’s hormones.

I don’t agree with the view that, unless EPA or the public can prove that hundreds of chemicals in our bodies cause harm, we can safely assume they are not a problem. Toxic chemicals — carcinogens, endocrine disrupters, neurotoxicants like those found in the bodies of pregnant women in this study — are a problem, which is why we should be reducing exposure and identifying safer substitutes as much as possible.

SimpleSteps: Aren’t people living longer and rates of cancer going down?

Overall deaths from cancer are going down, largely due to the decrease in smoking, and because early cancer detection and treatment has improved. We have more cancer survivors and that is a great accomplishment, but the incidence of a number of cancers have continued to rise or have remained steady, including thyroid, liver, kidney and children’s brain cancer and children’s leukemia. Many of these cancers have been linked to chemical exposures.

Do these chemicals stay in bodies forever, or at least for long periods of time?

Chemicals like BPA and phthalates are broken down by the body relatively rapidly, within a couple of days, and excreted. However, the fact that we can so consistently measure these chemicals in humans means that we are taking them in as fast as our bodies can get rid of them, so there is a more or less constant level of exposure.

Other chemicals that are more persistent, accumulate in fat and resist breakdown are more long-lived in our bodies. These are chemicals like PCBs, flame retardants like PBDEs, and heavy metals like mercury and lead. Some of these chemicals can reside in our bodies for decades, which is why this study found so many chemicals that have been banned for many years.

How are people exposed? Through dust? Ingesting leaching chemicals? Direct contact?

The route of exposure really is chemical- and situation-specific. For example, for most people BPA exposure occurs from food. However, BPA is used in many other places including thermal paper receipts, and cashiers who handle these receipts have been found to have higher BPA exposures, presumably because it is absorbed across their skin.

BPA is also used in medical devices and other studies have found that infants in the neonatal ICU have high levels of exposure, presumably because BPA is leaching from the devices into their bodies.

Many other chemicals have been found in dust, which can be ingested or inhaled especially by infants and toddlers who spend most of their time on the floor picking up things and putting them in their mouths. Flame retardants and phthalates are examples of two groups of chemicals that have been found to accumulate in dust.

What is the evidence that exposure to mixtures of chemicals could pose greater risks in combination than they would individually?

Mixtures of phthalates and other hormone-disrupting chemicals including some pesticides have been found to have additive effects such that exposures to the individual chemicals at doses shown to cause no harm have been found to cause harm when combined in a mixture.

Furthermore, there are a number of environmental chemicals which mimic thyroid hormone and also can be expected to exert additive or synergistic effects when combined in a mixture. Chemicals that interfere with normal development and function of the brain such as lead, mercury and PCBs -- which were all detected in this study of pregnant women -- could act together to collectively result in a greater decline in mental capacity than any one chemical alone.

The National Academy of Sciences (NAS) recently issued a report underscoring the importance of evaluating groups of chemicals that cause the same adverse outcome, such as neurodevelopmental harm caused by thyroid hormone disrupting chemicals. The NAS stated that basing chemical safety evaluations on just one chemical at a time or ignoring other modes of action that contribute to the same outcome “may lead to considerable underestimation of risks to the developing fetus.”

If these chemicals are so bad for us, then why do our federal laws allow pregnant women to be exposed to them?

Unfortunately, the federal law that governs exposure to most industrial chemicals is broken. Unlike the other landmark environmental laws passed in the mid-1970s, the Toxic Substances Control Act (TSCA) has never been updated and is long overdue for reform.

The law covers some 60,000-plus chemicals that are not pesticides or pharmaceuticals and has been so ineffective that it hasn’t allowed for a full ban of asbestos and has allowed other known toxic chemicals like formaldehyde, phthalates, and heavy metals like lead and mercury to be prevalent in so many of our consumer products.

On top of all that, the flaws in the law have resulted in most chemicals being introduced into the marketplace with little to no information about whether or not they are safe.  This unchecked and unregulated use of chemicals has resulted in widespread contamination of our environment and our bodies.

For pregnant women and women who are thinking about becoming pregnant, there are many different pieces of advice on things to avoid in order to have a safe and healthy pregnancy. How do you rank this study in terms of how worried women should be about chemical exposures in light of other worries like what foods to avoid, not drinking alcohol or smoking, how much exercise to get, what dietary supplements to take, etc.?

Certainly the amount of information women are bombarded with about what to do and what not to do when getting trying to get pregnant is overwhelming and confusing. There are a lot of things that are in your control -- like avoiding alcohol or limiting caffeine intake -- and things that may seem out of your control, like avoiding exposure to chemicals that were banned over 30 years ago. It might not seem obvious but there are a lot of overlaps in the sources of exposure to many of these "don'ts" and simple adjustments in behavior can mean that you don't have to decide which is more important because you can being doing multiple good things with one action. For example, many of the now banned chemicals which were found in the pregnant women in this study are found in animal fat. So eating a low fat diet is not only a healthy nutrition choice but also reduces exposure to these toxic chemicals.

Here are six easy and important ways to reduce exposures:

1. Leave your shoes at the door — pesticides and other outdoor contaminants can find their way into your home by being tracked in on your shoes.
2. Avoid “antibacterial” products — plain soap and water does the job of getting rid of “germs” and use of chemicals like triclosan or triclocarban in your soap, toothpaste or other personal care products leads to unnecessary exposure to these hormone-disrupting chemicals. Waterless hand sanitizers that contain alcohol are a good and safe alternative when you are away from a sink (see our fact sheet on these chemicals, PDF).
3. Use a damp mop or cloth to dust and use a HEPA filter on your vacuum cleaner — dry dusting, sweeping or using a filterless vacuum cleaner will kick up contaminant laden dust in your home making it easier to breathe in. If you use something damp or a microfiber cloth with a static charge to collect the dust particles you can avoid this.
4. Wash your hands frequently (with plain soap and water). Be sure to wash your hands after dusting or cleaning and after using electronics to wash away any contaminants that might have accumulated on your hands.
5. As much as possible, eat fresh or frozen fruits and vegetables instead of processed or canned food — fresh or frozen fruits and vegetables are less likely to be contaminated with chemicals found in food packaging.
6. Limit your use of strongly fragranced products — cleaning, personal care or other household products. The fragrance often harbors dozens of chemicals that have been linked to harmful health effects.

And for more ways to can minimize exposure, see "9 Steps  to a Safer Pregnancy."

How can the public use the information from this study? What can individuals and retailers do? Should this be a call for government action?

Of course, the tips above don't just apply to pregnant women. But retailers and members of the public should work towards stronger laws that limit the use of chemicals that have never been proven to be safe.

Learn more about the need for TSCA reform at our website: and take action by asking the President to act on the recommendations of the 2010 President’s Cancer Panel report, which called for chemical policy reform.

Join the Safer Chemicals Health Family coalition, of which NRDC is a founding member. You can follow us on Facebook. 

This article was reprinted with permission from

Toxic chemicals in pregnant women: A Q&A with Sarah Janssen
NRDC scientist Sarah Janssen discusses how at least 163 chemicals can be found in pregnant women and why everyone should care about the implications.