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Hormones play a foundational role in the sex-specific organization of the brain and, consequently, the complex behaviors they coordinate. Our world and bodies are becoming increasingly polluted with chemicals capable of interfering with hormone action and thus, possibly, our neural and mental health. If and how these endocrine-disrupting compounds (EDCs) affect the development and function of the brain, and may be contributing to neural disorders that are rapidly rising in prevalence, are the central concerns of this book. This work also examines why even the concept of endocrine disruption is controversial in some circles; how differing definitions of endocrine disruption and “adverse” outcomes shape public policy; and where the current capacity to evaluate chemicals for safety in a regulatory context begins and ends. Fundamental concepts of the EDC hypothesis, including critical windows of exposure and sexually dimorphic effects, are explained. A historical perspective on how the endocrine disruption hypothesis emerged and a summary of how and to what degree prototypical EDCs affect human brain health are provided as a prelude to a critical evaluation of the evidence linking EDC exposures to human neurobehavioral disorders. The book concludes with suggestions for future research needs and a summary of emerging technology that might prove more capable of effectively evaluating existing and new chemicals for endocrine-disrupting properties. The impossibility of disentangling the “science” of EDC action on the brain and behavior from its public health policy implications and economic influence is comprehensively addressed throughout.

There is a global acceleration in the incidence of neurodevelopmental disorders. Numbers of children affected by an autism spectrum disorders (ASD) in the United States has reached 1 in 88 (1 in 56 boys), and even more have attention-deficit/hyperactivity disorder (ADHD). The cost of these disorders to the individual and society is enormous: ASD alone costs the United States a staggering 130 billion US dollars annually. Genetic causes cannot account for these increases. Surges in incidence must implicate environmental factors. Environmental chemicals interfering with thyroid hormone signaling are potential culprits. This argument is substantiated by four facts. First, thyroid hormone is essential for brain growth; second, lack of thyroid hormone causes intellectual deficiency; third, many chemicals found in the environment have thyroid hormone–disrupting properties; and finally, many women enter pregnancy with insufficient iodine. Chemical pollution and iodine deficiency can also decrease the overall IQ of the population. Just a 5% decrease in overall IQ can have serious socioeconomic consequences, decreasing the numbers of gifted people and increasing those with IQs below 70. The author provides an historical overview of cases documenting environmental pollution causing IQ losses across populations, explains the physiology of thyroid hormone action, the importance of iodine and selenium for thyroid hormone signaling and brain development, why thyroid hormone is such a sensitive target of environmental pollution, and the role of gene × environment interactions in neurodevelopmental disorders. What can and is to be done by individuals, associations, and decision makers to staunch these epidemics is also detailed.