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).

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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.

About the Author

Aolin Wang, PhD is a former Postdoctoral Scholar for PRHE and for the UCSF Bakar Computational Health Sciences Institute. Prior to joining UCSF, she obtained her PhD in epidemiology and has extensive training in statistical modeling at University of California, Los Angeles.

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