How phthalates may impact the baby's brain - not for the faint of heart

Not usually prone to catastrophic thinking, I found myself wondering why mental health issues and neurodiversity have become so widespread in our children's generation.

So pronounced across the world and in every culture, I’ve started to think it might be linked to something our generation was exposed to in the environment —something that not only affected our fertility but also the development of our babies' brains before they were born.

This new study suggests it might have and it’s not easy reading.

About phthalates
Phthalates are man-made chemicals that have been used in consumer products for over a century. Omnipresent in plastics, cosmetics, shampoo, soap, vinyl flooring, and even food packaging, they help soften materials and preserve scent, color, or texture.

Because they are so widely used, almost everyone is exposed to them. We take them in by eating food that has touched plastic, through the skin by using personal care items, or even just by breathing in indoor dust.

Once inside the body, phthalates break down into smaller compounds and are excreted through urine, making it possible to measure recent exposure.

Previous studies show that most Americans have detectable levels in their systems, with higher concentrations seen in women and in Black populations. This difference is likely influenced by systemic factors like targeted marketing and access to safer products, especially in personal care.

Disruption of hormones in early development
Phthalates are known as hormone disruptors, meaning they can interfere with the body's natural hormone systems.

Although daily exposure levels are low, these chemicals can still mimic or block hormone signals, which is especially risky during sensitive stages like pregnancy.

Some phthalates can cross the placenta and may affect how the fetus develops. Research has connected prenatal exposure to changes in infant development, including nervous system function.

For example, studies have found that exposure to certain phthalates during pregnancy is linked to lower scores on neurobehavioral tests in newborns. These tests evaluate reflexes, attention, and arousal, which are early indicators of brain function.

Importantly, these effects may not be seen right away but could influence long-term cognitive and behavioral outcomes.

The study
A new study focused on understanding how phthalates might influence the chemistry of newborns at the molecular level.

Researchers examined pregnant black women and their babies in Atlanta. A total of 216 women were tested between weeks 8 and 14 of pregnancy, and 145 were tested again between weeks 24 and 30. A smaller group of participants also provided data used to study newborn metabolism and early neurodevelopment.

They collected urine samples from the women during early and late pregnancy and measured phthalate levels. Every single urine sample contained these metabolites from phthalates...

After giving birth, they analyzed blood from newborns to study their metabolome - that is the complete set of small molecules produced during the babies metabolism.

To look for a link between phthalate exposure to early signs of altered brain development - the scientists compared the mother's exposure to phthalates (levels in urine) during pregnancy with changes in chemical pathways of the baby's blood sample.

They found that certain metabolites in the babies were affected by phthalate levels during pregnancy. These included molecules related to our stress response, inflammation, and brain signaling.

Notably, the timing of exposure mattered: early pregnancy exposure had a stronger effect on pathways involved in inflammation. This timing is critical because early development includes the formation of the brain, eyes, and other major organs.

The results suggest that exposure during this early window may interfere with foundational processes.

Brain chemistry and baby behavior
Further analysis revealed that several of the altered metabolites are some really important ones for brain development.

Among the most affected ones were Tyrosine and tryptophan, Those two amino acids serve as building blocks for neurotransmitters like dopamine and serotonin.

Dopamine and serotonin are brain chemicals that regulate mood, motivation, and behavior. Dopamine drives reward, movement, and focus, while serotonin helps control mood, sleep, and appetite.

Disruption of dopamine and serotonin levels during fetal development may interfere with brain circuit formation. This may increase the risk of emotional, behavioral, and cognitive disorders later in life, such as attention problems, anxiety, or autism-related traits, due to altered signaling in mood and reward pathways.

But thats not all. In particular, the level of thyroxine, a thyroid hormone needed for brain growth, was reduced in the babies in response to higher levels of one common phthalate. Fatty acids that are critical for brain cell membranes were also affected. These molecular shifts offer clues about how even low-dose chemical exposure could subtly alter the shape of the early nervous system.

Infants were these metabolites was downregulated by phthalates, scored lower in attention and arousal on neurobehavioral assessments. These effects were most noticeable in infants whose mothers had higher levels of exposure.

Interestingly, these findings were not isolated to newborns. The same metabolic pathways were disrupted in both mother and child, suggesting a shared response to environmental chemicals that could influence maternal health and fetal development alike.

More than one exposure, more than one effect
The study uncovered other environmental chemicals in both mothers and infants, including pesticides, fungicides, and tobacco-related compounds.

The researchers emphasized that when people are exposed to mixtures of pollutants, it's hard to separate the effect of one chemical from another. Many pollutants are correlated, and their combined effect may be greater than the sum of their parts.

In summary, this research highlights a potential molecular link between phthalate exposure and early brain development.

By connecting real-world chemical exposure to changes in the newborn’s metabolome and behavior, the study provides clues into how everyday environmental factors might shape our brain function and our mental health from the very beginning of life.

About the scientific paper:

First author: Susan S. Hoffman, USA
Published: Nature Communications February 2025
Link to paper: https://www.nature.com/articles/s41467-025-57273-z