21 January 2015. The industrial chemicals known to interfere with brain development in children include the PCBs (polychlorinated biphenyls). But PCB is a mixture of compounds, and some of them resemble the extremely toxic dioxin, known from the Seveso explosion in Italy and its presence in Agent Orange. Could it be that PCB is a brain drainer due to dioxin-like effects? A new study from Germany suggests that prenatal exposure to dioxins is associated with increased distractability and deficient attention at age 9. Even though human milk contains dioxins, the exposure from breast-feeding had no clear effect. So dioxin’s main interference with brain development seemed to happen in the mother’s womb.
The results also suggested that PCB exposure by itself can cause adverse effects. So PCB is likely a drain drainer in its own right, and not just because some of the PCBs resemble dioxin. That would make sense in light of all that we know about PCB neurotoxicity. Also, several possible neurotoxic mechanisms are known, and some of them are not triggered by dioxin.
But this is just a single study of 117 children. Although the findings are in agreement with a previous report from The Netherlands, the findings would need to be confirmed. Or is that necessary? Additional studies should not be anticipated right away. For one, the analysis of a single blood sample for its dioxin content can easily cost more than $1,000, thus making studies extremely costly. In addition, such studies take time. Even if further documentation appears, some uncertainties will likely remain. After all, it took more than 20 years for the U.S.Environmental Protection Agency to finalize a risk assessment for dioxins. Given the plausibility that dioxin is in fact a brain drainer, should weighting of the evidence take into account how hard it is to document the brain toxicity in children? Public health logic would say yes, any doubt should not prevent recognition that dioxin is also poisonous to developing brains. So that would add one more unwanted compound to the list of known brain drainers. However, the good news in this case is that dioxin exposures are decreasing, and in most parts of the world, they are now lower than the levels that the German kids were exposed to prenatally about 15 years ago.