Exposure to phthalates during pregnancy can affect a newborn's brain development, study finds

Yahoo

02-04-2025

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Phthalates — the synthetic chemicals used in everyday products for food packaging, personal care, toys and more — have been linked to abnormal neurological development in infants.
Now, scientists may have discovered a biological pathway for how this phenomenon could occur. Researchers found that in utero exposure to phthalates is linked with altered metabolism of neurotransmitters and amino acids involved in brain maturation, according to a study published Wednesday in the journal Nature Communications.
The report is the first to use untargeted metabolomics — the study of all small molecules or metabolites in a biological system — to connect a mother's phthalate exposure to a newborn's metabolites, and those metabolites to neurological development, said senior study author Dr. Donghai Liang via email.
'This represents an important step forward in understanding how prenatal chemical exposures shape infant development at the molecular level,' added Liang, an associate professor of environmental health at Emory University's Rollins School of Public Health in Atlanta.
First introduced in the 1920s, phthalates are used to make plastics softer and more flexible, primarily in polyvinyl chloride (PVC) products such as vinyl flooring, medical devices, children's toys, food packaging or shower curtains. The chemicals also help lubricate substances and carry fragrances in various personal care products including deodorant; nail polish; perfumes; hair gels, sprays or shampoos; soaps; and body lotions.
Phthalates are also endocrine disruptors that have been linked to preterm birth, infant genital abnormalities, childhood obesity, asthma, cancer, cardiovascular issues, and low sperm count and testosterone in men.
'We conducted this study because phthalates are everywhere in our daily lives,' Liang said, hence their nickname 'everywhere chemicals.'
The findings are based on mother-newborn pairs enrolled in the Atlanta African American Maternal-Child Cohort between 2016 and 2018. In urine samples collected from 216 mothers between eight weeks and 14 weeks of gestation at visit one and 145 participants between 24 and 30 weeks' gestation at visit two, the authors measured eight phthalate metabolites. Participants were around age 24 on average, and their levels of some phthalate metabolites were higher than the average determined by the National Health and Nutrition Examination Survey.
Within a day or two of birth, the authors collected the babies' blood via a heel stick.
The team found prenatal phthalate levels were associated with lower levels of tyrosine, an amino acid and precursor to the thyroid hormone thyroxine. Thyroxine was also abnormally low in those with in utero phthalate exposure, and low thyroxine has been previously associated with greater vulnerability to illness and neurodevelopmental issues in newborns, the authors said. Tyrosine is also a precursor to the neurotransmitters dopamine, norepinephrine and epinephrine, all of which partly contribute to the body's fight-or-flight response. Low levels of these neurotransmitters can lead to various problems, including anxiety, depression and trouble focusing.
Prenatal phthalate exposure was also linked with lower levels of the essential amino acid tryptophan, which converts into 5-hydroxytryptophan (or 5-HTP), which then turns into serotonin. Both 5-HTP and serotonin were also low. Serotonin has several critical roles in the body, including mood regulation, sleep, learning, memory, digestion and the body's response to stress. Previous research has linked low serotonin with mood disorders such as depression and anxiety, sleep problems, and digestive issues.
These biological changes generally were also linked to lower scores on tests measuring attention and excitability, or the ability to respond to stimuli, in participants' newborns, according to the study.
Polyvinyl chloride plastic, a primary use for phthalates, 'continues to increase in use globally,' said Dr. Leonardo Trasande, director of the New York University Center for the Investigation of Environmental Hazards, who wasn't involved in the study. 'We know already — across not just brain development in babies, but a host of consequences that run from cradle to grave, and womb to tomb — that phthalates, in the form of (a) disease burden due to plastic, cost the US $250 billion annually.'
'This study just adds to a voluminous base of evidence that chemicals used in plastic materials harm human health,' Trasande added. 'It's not really something that we should be debating more actively. The more thoughtful approach would be to actually discuss what we need to do about the use of plastic.'
The American Chemistry Council, which represents chemical companies, said via email that its High Phthalates Panel is 'dedicated to promoting the benefits of high phthalates such as DIDP and DINP.' Phthalates with a high molecular weight have seven or more carbon atoms. The study did not measure DIDP (diisodecyl) and DINP (diisononyl phthalate), but some of phthalates identified in the study were high phthalates.
The study has a few important limitations, including the lack of information on participants' diets or whether their births were vaginal or caesarean, all of which can significantly affect both phthalate exposure and a newborn's metabolites, the authors said. Additionally, around 10% of participants reported using alcohol while pregnant, while 15% reported using tobacco and 40% reported using marijuana. There were no details collected on frequency, quantity or duration of use of those substances.
Adverse pregnancy outcomes related to environmental contaminants can also be influenced by psychological or social stressors, which the study couldn't account for.
'The sample size is small, of course, (but) it's a complicated and expensive study to conduct in the first place,' Trasande said. 'There may be multiple mechanisms by which phthalates disrupt brain development.'
For people to be able to avoid exposure to phthalates and other chemicals, experts are calling on manufacturers and policymakers to change.
'I'm part of the Scientists' Coalition for an Effective Plastics Treaty (and we) are actually suggesting banning phthalates as a group because of their demonstrated toxicity and that they can cause effects at very low doses,' said ecotoxicologist Dr. Susanne Brander, associate professor in the department of fisheries, wildlife and conservation sciences at Oregon State University. Brander wasn't involved in the study.
Some manufacturers are creating new plastic additives they hope are safer, but it's possible they could be as problematic as what we're using now, Trasande said. 'The burden needs to be on the manufacturers to prove that materials … are proven safe before they're used.'
In the meantime, people can reduce their exposure to phthalates by using glass, stainless steel or cast iron and not using nonstick cookware or microwaving or dishwashing plastic materials, Trasande said. 'Microwave safe' means the container will be OK, not your food — since it can absorb microscopic particles, he added.
When buying personal care products, look for those labeled 'phthalate-free' and check ingredient lists, Liang said. Phthalates may be listed as DEP (diethyl phthalate), DBP (dibutyl phthalate) or BBzP (butyl benzyl phthalate). You can use the Environmental Working Group's SkinDeep database to check which chemicals a product may contain.
'Since phthalates can be found in household dust, improving air circulation and regular cleaning with a damp cloth can help,' she added.