Endocrine-Disrupting Chemicals: Brain–Behavior Effects on Thyroid and Sexual Differentiation

2020 ◽  
pp. 426-448
Author(s):  
R. Thomas Zoeller ◽  
Frederick S. vom Saal
Keyword(s):  
Thyroid Hormone ◽  
Human Brain ◽  
Brain Development ◽  
Endocrine Disrupting Chemicals ◽  
Convincing Evidence ◽  
Industrial Chemicals ◽  
Safety Testing ◽  
Endocrine Disrupting ◽  
Estrogenic Chemicals ◽  
And Gender

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.

Endocrine Disruptors in the Environment

2014 ◽  
Author(s):  
Nancy Langston
Keyword(s):  
World War Ii ◽  
New Technologies ◽  
Endocrine Disrupting Chemicals ◽  
Environmental Chemicals ◽  
Pharmaceutical Drugs ◽  
Industrial Chemicals ◽  
World War ◽  
Synthetic Chemicals ◽  
Endocrine Disrupting ◽  
Post War

Since World War II, the production of synthetic chemicals has increased more than 30-fold due to the post-war boom in petrochemical exploration, manufacture, and marketing. The modern chemical industry, now a global enterprise of $2 trillion annually, is central to the world economy, as it generates millions of jobs and consumes vast quantities of energy and raw materials. Today, more than 70,000 different industrial chemicals are synthesized and sold each year (Chandler 2005; McCoy et al. 2006). New technologies and methods for the detection of these synthetic chemicals have drawn increasing attention to the pervasive and persistent presence of hormone-disrupting chemicals in our lives. Hormones—the chemicals that deliver messages throughout the body in order to coordinate physical processes—are deeply sensitive to external interference, and the consequences of such interference are becoming ever more apparent. In July 2005, the Centers for Disease Control (2005) released its Third National Report on Human Exposure to Environmental Chemicals, revealing that industrial chemicals now permeate bodies and ecosystems. Many of these chemicals can interfere with the body’s hormonal signaling system (called the endocrine system), and many persistently resist the metabolic processes that bind and break down natural hormones. More than 358 industrial chemicals and pesticides have been detected in the cord blood of minority American infants (Environmental Working Group 2009). Accumulating data suggests that reproductive problems are also increasing across a broad range of animals, from Great Lakes fish to people. Many researchers suspect that the culprits are environmental exposures to synthetic chemicals that disrupt hormonal signals, particularly in the developing fetus. Endocrine-disrupting chemicals are not rare; they include the most common synthetic chemicals in production, such as many pesticides, plastics, and pharmaceutical drugs. Since World War II, synthetic endocrine-disrupting chemicals have permeated bodies and ecosystems throughout the globe, potentially with profound health and ecological effects (Krimsky 2000). Hormones are chemical signals that regulate communication among cells and organs, thus orchestrating a complex process of fetal development that relies on precise dosage and timing.

scholarly journals Mixtures of endocrine-disrupting contaminants induce adverse developmental effects in preweaning rats

Reproduction ◽  
2014 ◽  
Vol 147 (4) ◽  
pp. 489-501 ◽  
Author(s):  
Marta Axelstad ◽  
Sofie Christiansen ◽  
Julie Boberg ◽  
Martin Scholze ◽  
Pernille Rosenskjold Jacobsen ◽  
...  
Keyword(s):  
Human Exposure ◽  
Endocrine Disrupting Chemicals ◽  
Reproductive Toxicity ◽  
Safety Margin ◽  
Levator Ani ◽  
Ventral Prostate ◽  
High Dose ◽  
Reproductive Effects ◽  
Endocrine Disrupting ◽  
Estrogenic Chemicals

Reproductive toxicity was investigated in rats after developmental exposure to a mixture of 13 endocrine-disrupting contaminants, including pesticides, plastic and cosmetic ingredients, and paracetamol. The mixture was composed on the basis of information about high-end human exposures, and the dose levels reflecting 100, 200, and 450 times this exposure were tested. The compounds were also grouped according to their estrogenicity or anti-androgenicity, and their joint effects were tested at two different doses, with each group reflecting 200 or 450 times human exposure. In addition, a single paracetamol dose was tested (350 mg/kg per day). All exposures and a vehicle were administered by oral gavage to time-mated Wistar dams rats throughout gestation and lactation, and their offspring were assessed for reproductive effects at birth and in prepuberty. The mixture doses, which included the anti-androgenic compounds, affected the male offspring by causing decreased anogenital distance, increased nipple retention (NR), and reduced ventral prostate weights, at both medium and high doses. In addition, the weights of the levator ani/bulbocavernosus muscle (LABC) were decreased at the high dose of anti-androgen mixture. No effects were seen after exposure to the estrogenic chemicals alone, whereas males exposed solely to paracetamol showed decreased LABC weights and increased NR. Thus adverse reproductive effects were observed at mixtures reflecting 200 times high-end human exposure, which is relatively close to the safety margin covered by the regulatory uncertainty factor of 100. This suggests that highly exposed human population groups may not be sufficiently protected against mixtures of endocrine-disrupting chemicals.

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