A highly diverse group of pregnant individuals in the United States were exposed to a number of potentially harmful chemicals from plastics, pesticides, and other sources, according to the largest study of its kind.
Some chemicals were replacements for others that are banned or are being phased out due to their potential toxicity. Many individuals in the study were exposed to neonicotinoid insecticides, which are also implicated in the decline of bee populations.
Pregnant individuals can be exposed to chemicals in food, water, air, dust, and through the use of personal care and other consumer products. Many of these chemicals can pass to the developing fetus.
“This study helps further identify which — and how much — specific chemicals humans are exposed to,” said study author John Meeker, ScD, a professor of environmental health sciences and global public health at the University of Michigan’s School of Public Health.
He said this information could focus research efforts on the chemicals that pregnant individuals are most exposed to. This includes gaining a better understanding of the negative health effects of the chemicals and how people are exposed to them.
It’s important to note that not everyone assigned female at birth identifies with the label “woman.” While we aim to create content that includes and reflects the diversity of our readers, specificity is key when reporting on research participants and clinical findings. The study referenced in this article did not include data on participants who are transgender, nonbinary, gender nonconforming, genderqueer, agender, or genderless.
The study included 171 pregnant women from five states — California, Georgia, Illinois, New Hampshire, New York — and Puerto Rico. About 60 percent of the group identified as Black or Hispanic about 34 percent were non-Hispanic white.
Women were participating in the National Institutes of Health Environmental influences on Child Health Outcomes (ECHO) program.
The study was published May 10 in the journal Environmental Science & Technology.
Urine samples collected from 2017 to 2020 were used to measure women’s exposure to 103 chemicals from pesticides and plastics, including replacement chemicals for BPA and phthalates.
Urine samples collected from 2017 to 2020 were used to measure women’s exposure to 89 analytes or chemical substances representing 103 chemicals. These included chemicals from pesticides and plastics and replacement chemicals for BPA and phthalates.
Researchers looked for certain biomarkers of those chemicals in the urine — either the chemicals themselves or products that occur when the chemicals break down in the body.
Over 80 percent of those biomarkers were detected in at least one woman in the study. In addition, 40 percent were found in over half of the women.
Barbara Cohn, PhD, MPH, researcher, and director of Public Health Institute’s Child Health and Development Studies, said this is the “most comprehensive assessment of chemical exposures in pregnant women.”
Importantly, she said researchers focused their efforts on the chemicals that are most likely to be potentially harmful.
“This is not a random list of chemicals but is instead a targeted list where concern is based on legitimate science,” she said, including work done in population science, epidemiology, experimental toxicology, environmental science, and engineering.
For example, one group of analytes that the researchers investigated were phthalates and phthalate alternatives. These chemicals make plastics more durable and can be founding vinyl flooring and personal-care products like soaps and shampoos. Phthalates have been found to affect the reproductive health of animals, and their effects, in low doses, on human health are not fully understood, according to the Centers for Disease Control and Prevention.
Some of the biomarkers that were found in the majority of women are not currently monitored as part of the National Health and Nutrition Examination Survey (NHANES), a long-term study on the health of adults and children in the United States.
In fact, the vast majority of the thousands of chemicals used in the country are not monitored by NHANES. This includes chemicals suspected of being toxic and replacements for chemicals being phased out.
“When this [lack of monitoring] is combined with the current stance in this country — which tends to be ‘innocent until proven guilty’ when it comes to regulating chemicals — it results in the potential for overexposure to many chemicals that could be harmful,” said Meeker.
Cohn agreed, saying, “If you do not measure toxic chemicals in humans, you cannot know the extent of their presence. … Ignorance is a dangerous public policy.”
Chemical exposure is a concern to anyone, but especially to pregnant people and the developing fetus.
“Pregnant women are vulnerable themselves during the dramatic changes that accompany pregnancy,” said Cohn, but they “are also carrying the future generation during a highly vulnerable window of susceptibility to toxic exposures.”
In the new study, Black and Hispanic women had higher concentrations of potentially harmful chemicals, as did women with a lower education level and those who were single or had been exposed to tobacco.
In particular, Hispanic women had higher levels of exposure to parabens, which are commonly used as preservatives in cosmetic products, and phthalates and bisphenols, which are used in plastics.
This and other research shows “that there are important disparities in exposure to chemicals,” said Meeker, “which may very well contribute to known disparities in adverse pregnancy and child development outcomes.”
Cohn said it is critical for studies such as this to include a diverse group of participants in order to understand whether certain groups are more impacted by chemical exposure.
“There is evidence that exposures to toxic chemicals in pregnancy can have lifelong health consequences for mothers, their offspring and for generations to come,” she said.
Cohn has spent decades researching the health effects of toxic chemicals during pregnancy for mothers, their children, and their granddaughters.
“Notably, the granddaughters of women who were exposed to [the banned pesticide] DDT during pregnancy are at risk of significant health threats, [including] higher rates of obesity and menstrual periods that start before age 11,” she said.
This can increase the granddaughters’ risk of breast cancer, high blood pressure, diabetes and other diseases, she added. DDT has been banned for use in the U.S. since 1972.
Meeker said there are some things women can do to reduce their risk of overexposure to chemicals while pregnant.
This includes limiting their use of personal care and other products that contain potentially harmful chemicals and limiting their use of or exposure to pesticides.
“However, we need to be careful to recognize that many of these strategies may not be equally accessible to all women, which may further increase disparities in exposure and adverse health,” he said.
This makes it important to move away from expecting individuals to be solely responsible for reducing their own risks from chemicals.
“While individuals can make some choices to reduce their exposures, many exposures are not in their control and can only be addressed by public policy and also advocacy efforts from consumers,” said Cohn.
She also said that because people are exposed to a wide range of chemicals at different levels, it is impractical to expect science to be able to know the exact harms of chemicals and which levels are unsafe.
But this doesn’t mean we shouldn’t take steps to protect people’s health.
“The evidence here seems to support the concept of precaution, meaning that individuals, industry, and our society could commit to reduce these exposures even before harm can be completely documented or fully understood,” said Cohn.