The latest study was conducted on larval zebra fish, an animal whose brain development proceeds similarly to that of human fetuses. Newly hatched zebra fish exposed to very low levels of the neuroendocrine-disrupting chemical BPA displayed bursts in activity -- an anxiety-like behavior -- that were nearly threefold the level seen in normally developing zebra fish larvae.
While low-level exposure to BPA prompted a 180% increase in the production of neurons in the hypothalamus of zebrafish, exposure to BPS boosted neurogenesis during a key window by 240%.
The new research and nearly a dozen studies of BPA's physiological and behavioral effects in humans "begin to point to the prenatal period as a period of BPA vulnerability" and "suggest that pregnant mothers limit exposure to plastics and receipts" -- two classes of products in which BPA continues to be widely used.
It may be most important to avoid exposure to such industrial chemicals in the second trimester of pregnancy, a formative period for the brain in which neurons are born, specialized brain regions emerge, and synapses begin to lash together the resulting community of cells. Hormones play key roles in all of those processes, and the signals they provide often dictate the duration and sequence of neuronal development.
The study, published online Monday in the journal Proceedings of the National Academy of Sciences, also calls into serious question the safety of the chemical most widely used in products labeled "BPA-free," and therefore marketed as a safer alternative to BPA. A recent analysis of Americans' and Asians' urine samples confirmed previous work in finding that, while 93% had detectable levels of BPA, 81% had detectable levels of BPS.