Neuroendocrine disruptors and brain development: Lessons from PCBs

December 12, 2023 , 1:00 pm 2:00 pm EST

Polychlorinated biphenyls (PCBs) are acutely toxic at high concentrations. At lower concentrations they are endocrine-disrupting chemicals (EDCs), with multiple effects on human health. In this webinar, Dr. Tom Zoeller will discuss how the endocrine disrupting effects of PCBs can affect human brain development. Lessons from PCBs can also help us to understand the effects of other EDCs on the developing brain and nervous system. 

There are 209 theoretical PCB “congeners,” although just over 100 of them occur in industrial systems. These chemicals were used in a wide variety of products from electrical, heat transfer and hydraulic systems, to paints and dyes and other construction applications. 

Dr. Zoeller will present findings from a recent review of the evidence on how PCBs cause neuroendocrine effects. PCB congeners can be very roughly divided into “dioxin-like” and “non-dioxin-like” PCBs. But among the non-dioxin-like PCBs, health effects can vary widely. For example, at very low concentrations, PCB 95 (2,2’,3,5’,6-Pentachlorobiphenyl) can activate the ryanodine receptor. This receptor is critical in brain development and brain function. Other PCB congeners, such as PCBs 105 and 118 among others, can affect the thyroid hormone system. Thyroid hormone is essential for normal brain development.

An important observation in this field is that dioxin-like PCBs can induce the expression of an enzyme that modifies (hydroxylates) two specific non-dioxin-like PCBs that then activate thyroid hormone receptors. This work explains why a chemical exposure can have tissue-specific, or even cell-specific, effects on hormone signaling. It is also a warning about how in vitro assays — so-called New Approach Methodologies (NAMs) — are interpreted.

The story of PCBs also provides lessons about chemical regulations to protect human health and the environment. Commercial production of PCBs was banned in the 1970s, but humans are still contaminated with PCBs — including those that are residual as well as those that are inadvertently produced. PCBs were banned as a class, yet PFAS are still being examined in a one-by-one manner. 

This webinar will be moderated by Sharyle Patton, Director of the Biomonitoring Resource Center.