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 EDC Strategies Partnership webinar, Dr. Tom Zoeller discussed 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 presented 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 was moderated by Sharyle Patton, Director of the Biomonitoring Resource Center.
Featured Speaker
R. Thomas Zoeller, PhD is Professor Emeritus in the Department of Biology at the University of Massachusetts Amherst. His research focuses on effects of thyroid hormone on brain development and environmental disruption of thyroid hormone action.
This webinar was hosted by the EDC Strategies Partnership, which is co-chaired by Sharyle Patton (Commonweal Biomonitoring Resource Center), Jerry Heindel and Sarah Howard (Environmental Health Sciences' Healthy Environment and Endocrine Disruptor Strategies HEEDS), Génon Jensen (Health and Environment Alliance, HEAL), and Rachel Massey (CHE, Collaborative for Health and Environment). To see a full list of past calls and webinars related to EDCs and listen to or view recordings, please visit our partnership page.