The human population is exposed to literally hundreds of industrial chemicals. Studies show that, on average, there are well over 100 industrial chemicals in cord blood samples taken from babies born in the United States. This observation may be disregarded if it were not for solid—and growing—evidence that many of these chemicals interfere with hormone systems that play important roles in human brain development. For example, thyroid hormone is known to be essential for normal brain development and the human brain is much more sensitive to thyroid hormone insufficiency than believed 50 years ago. Chemicals such as perchlorate, polychlorinated biphenyls, and polybrominated flame retardants are associated with cognitive deficits in humans, and the experimental literature reveals a complex interaction with the thyroid system that can account for these effects. Likewise, estrogenic chemicals like bisphenol A (BPA) can affect the development of many organ systems, including sexually dimorphic regions of the brain. There is now convincing evidence that even slight perturbations in hormonal systems caused by endocrine-disrupting chemicals can impact brain development, reducing cognitive function and gender-specific behaviors throughout the remainder of life. The consequences of such chronic exposures at low doses typical of human exposures had, until relatively recently, not been appreciated due to safety testing strategies that are designed to identify overt toxicities, not endocrine disruption and its consequences.
Prenatal exposure to endocrine disrupting chemicals in relation to thyroid hormone levels in infants – a Dutch prospective cohort study
