New method uncovers hidden chemicals in pregnant women

Did you know that there are more than 80,000 chemicals registered for commercial use in the US, with an estimated 2,000 new ones being introduced each year?  More than 30,000 pounds of chemicals are manufactured and imported for every American, nearly 15 times of the amount of food that one would eat annually.

blog infographic.jpgBelieve it or not, for most of these chemicals, we have no idea whether they can enter the human body—but studies that measure chemicals in people (called biomonitoring), which currently can measure about 350 chemicals, have found numerous chemical exposures in different populations. For example, a study found at least 43 different chemicals of a representative sample of U.S. pregnant women. And sadly, our new study suggests this is just the tip of the iceberg.

We used an innovative approach to identify novel chemicals never measured before in pregnant women’s blood, suggesting that moms-to-be are exposed to more chemicals than we previously knew. This raises concern for both women and children’s health, because chemicals can cross the placenta, and the developing fetus can be more sensitive to the adverse effects of these chemicals. Scientific evidence finds that in utero exposures to environmental chemicals can have health implications for the individual over the lifespan.

To uncover what hidden chemicals might be in pregnant women, we used high-resolution mass spectrometry technology to screen for a broad array of chemicals from maternal blood samples collected from 75 pregnant women. Still, screening for chemicals in a person is like finding needles in a haystack as blood contains thousands of chemicals and break-down products derived from not only environmental chemicals but also food, drugs and supplements etc. Thus, we used a novel approach called “suspect screening”, where we compiled a chemical database including ~700 chemicals found in pesticides, consumer products and industrial uses. This database served as a “road map” to guide our search in the novel environmental compounds, i.e., we are looking for the known unknowns (“suspect” compounds that have the same molecular weight as the chemical in our database). Then, we selected suspect chemicals for identity confirmation by comparing their mass profile to the corresponding reference standards (see figure below).

blog post

We found an average of 56 suspect chemicals in each sample and confirmed the presence of six novel chemicals (see table below). Two of these six chemicals – 2,4-Di-tert-butylphenol and pyrocatecholhave a production volumes of 10 million to 50 million pounds/year in the U.S. We have limited information on the uses and health hazards for many of these chemicals. In addition, our suspect screening method was limited to the chemicals covered in our database, which represents a small fraction of the full universe of chemicals in current use.  In reality, pregnant women are likely exposed to many more chemicals than we could screen for.

Chemical Name

Selected Chemical Uses from EPA’s CPCat Database

Health Hazard



Toys; Personal care
products; Manufacturing

Estrogenic effects

acid (19715-19-6)

Not available

No information



Pesticides; Pharmaceuticals; Coloring agents

Cataract formation;
Causing genetic defects;
Damaging fertility and the fetus



Cosmetics; Food additives; Pesticides;
Pharmaceuticals; Manufacturing

Possible human (Group 2B)



Fragrances; Food additives; Pesticides;
Pharmaceuticals; Manufacturing

No information




No information

CPCat: Chemical and Product Categories

Chemicals can get into a women’s body when they use products, breathe in contaminated air, drink contaminated water, or eat contaminated food. As a next step, we are developing a method to measure the level of these previously unidentified chemicals in pregnant women and evaluate their impact on health.

A lot of us assume that the government carefully reviews the safety of chemicals before they enter the market, but unfortunately this is not the case. We actually have little information on most of the chemicals in commerce. It’s a daunting task to figure out which ones of the thousands of chemicals may pose health hazards to humans, especially to vulnerable populations like pregnant women and children. Our study offers a new approach to more efficiently screen for these chemicals and help prioritize certain ones for further research including toxicity testing and health effect studies.

While we are finding answers to important questions about the unknowns, we already have enough scientific evidence to take action now to reduce our body’s chemical burden. For practical tips on how to prevent chemical exposures at home, at work, and in your community, check out PRHE’s All That Matters brochure series in both English and Spanish.

You can also view this blog post in Chinese.

My co-authors on this study were: Roy Gerona, Jackie Schwartz, Thomas Lin, Marina Sirota, Rachel Morello-Frosch (UC Berkeley), and Tracey Woodruff (senior author). I would also like to thank the clinicians, clinical research coordinators, and all Chemicals in Our Bodies 2 (CiOB2) study participants for their contribution to the study.


Pollution and gene interactions may raise birth defect risks

About 1 in 33 babies are born with a birth defect. Spina bifida, a neural tube defect, which is one of the most common birth defects, affects about 4 in 10,000 – 1,500 babies are born with spina bifida each year in the U.S. Spina bifida occurs when the neural tube does not close completely during development and can have a significant effect on the physical and neurologic well-being of a child. Because of this, it is a leading cause of disability in children.

To help women have healthy pregnancies and babies, I investigate what causes birth defects like spina bifida. Evidence indicates multiple factors can increase the risk of spina bifida including the environment, genetics and nutrition. Spina bifida tends to run in families – after having one child with the condition or if one of the parents has the condition, there is a 4% chance that the next child will also be affected, suggesting that genes play a role. Studies also find that cigarette smoking, obesity and folic acid deficiency may make a woman more likely to have a baby with spina bifida, revealing the environment is also important. I am investigating how environmental exposures such as air pollution, in combination with additional factors like genes, may make a woman more likely to have a baby with a birth defect.

Since cigarette smoke and outdoor air pollution have similar components, it is possible that exposure to air pollution affects pregnant women the same way as cigarettes. Women are particularly vulnerable to the effects of air pollution when they are pregnant because of the changes that occur to carry and develop the fetus.


Indeed, my previous research found a link between air pollution and spina bifida– women exposed to high levels of outdoor air pollution (the chemicals carbon monoxide and nitrogen dioxide) were at higher risk of having a baby with spina bifida. Next, I wondered how mom’s genetic makeup might affect this risk. My recent paper was one of the first to investigate this question—how the combination of a mother’s genetic differences and air pollution exposure during early pregnancy may contribute to her risk of having a baby with spina bifida. We found that genetic differences could increase the risk– women exposed to high levels of air pollution (especially particulate matter) during early pregnancy and who had certain genetic differences had a higher likelihood of having a baby with spina bifida. Some of the genetic differences involved how the body reacts to environmental chemicals—suggesting that some people are more susceptible to the toxic effects of air pollutants because their body processes chemicals differently. My research has also found that chemicals are not the only stressors that can increase risks. My previous study found that women who were exposed to high levels of air pollution and lived in neighborhoods with more poverty (a socio-economic stressor) were more likely to have a baby with spina bifida.

Although we are at the early stages of investigating gene-environment combinations and socioeconomic factors, it is clear that the causes of birth defects may involve multiple factors. It is also apparent that air pollution and other environmental stressors contribute to risks, and that certain people may be more susceptible to these exposures. I plan to expand our research on gene-environment combinations and focus on additional environmental exposures including drinking water contaminants and specific air pollutants that are produced from traffic and fires. My research shows that we need to consider multiple factors, including genetics, that can put women and their babies more at risk from exposure to air pollution when we develop interventions and policies to reduce risks to debilitating birth defects. Policies need to incorporate the most current science on susceptibility to limit harmful environmental exposures and protect women and children’s health.

PadulaAmy Padula, PhD, is an Assistant Professor with the Program for Reproductive Health and the Environment in the Department of Obstetrics, Gynecology and Reproductive Sciences at the University of California, San Francisco. Her doctorate is in Epidemiology from the University of California Berkeley and her postdoctoral training was at Stanford University.  Her research has been on the effects of ambient air pollution during pregnancy on adverse birth outcomes including preterm birth, low birth weight and birth defects. The projects have expanded to evaluate social factors, comorbidities during pregnancy and gene-environment interactions. Dr. Padula has an K99/R00 Transition to Independence Award from the National Institute of Environmental Health Science and las year was named one of the 20 Pioneers under 40 in Environmental Public Health by the Collaborative on Health and the Environment.
Dr. Padula’s co-authors on the papers referenced in the post above include: Gary Shaw, Wei Yang, Suzan Carmichael, Fred Lurmann, Ira Tager, Katharine Hammond and Kathleen Schulz.