Medical News Today: Chemicals in plastic stunt brain growth in rats

Phthalates are commonly added to plastics, and their impact on human health has been debated for years. A new study finds that exposure to these compounds reduces the number of neurons in rat brains.
Plastic water bottles
Could plastic chemicals harm the developing brain?

In modern society, there are few human-made compounds more ubiquitous than plastic.

Aside from plastic’s devastating environmental impact, researchers have wondered for years about the potential health effects of some plastic-related chemicals.

More specifically, questions have been asked about phthalates, which are used in a host of products, including cosmetics, shampoos, adhesives, and building materials.

Phthalates are primarily used to make plastics more flexible, transparent, durable, and long-lasting.

Phthalate exposure on trial

Scientists have demonstrated that phthalate exposure is widespread in the United States, and that exposure can interfere with hormones in some laboratory animals.

Phthalates can travel across the placenta to the unborn child as well as pass into breast milk. And, as the developing brain is dependent on a highly orchestrated symphony of hormones, questions have been asked as to how these compounds might impact a human nervous system under construction.

Some studies have found links between exposure to the chemicals and developmental issues, but the details are still murky, and not all studies have measured negative effects.

Most recently, researchers from the University of Illinois at Urbana-Champaign set out to assess whether phthalates could alter the developing brain and impact cognitive ability in rats. Their results are published in the The Journal of Neuroscience.

In order to investigate, they fed rats a cookie laced with phthalates at quantities that mimicked those found in humans, based on data from pregnant women.

The animals were divided into three experimental groups: a control group that received no phthalates, a low-dose group, and a high-dose group.

The rats received a cookie daily during pregnancy and for 10 days while lactating.

Specific deficits measured

When the offspring of the phthalate-fed rats were born, their brains were investigated. The team, led by Prof. Janice Juraska, found a significant lack of both neurons and synapses in the rats’ medial prefrontal cortex (mPFC). This was the case for both of the phthalate groups when compared with the control rats.

The mPFC is involved in many high-level cognitive functions, including memory, decision-making, error detection, conflict monitoring, and cognitive flexibility.

It has also been implicated in conditions including autism, depression, and schizophrenia. The authors write:

These results may have serious implications for humans given the mPFC is involved in executive functions and is implicated in the pathology of many neuropsychiatric disorders.”

Once the rats had reached adulthood, their cognitive flexibility was tested using an attentional set-shifting task. As expected, the scientists found measurable deficits.

The debate over phthalates and their impact on the human population will, no doubt, continue on. Because these chemicals are so incredibly prevalent in our environment, it is essential that we understand exactly what influence they have on our bodies.

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