09
Sep
Endocrine (Hormone) Disrupting Chemicals, Including Pesticides, Also Affect the Nervous System
(Beyond Pesticides, September 9, 2021) A new study published in Toxicology Reports finds the same chemicals that disrupt the endocrine (hormone) system also disrupt the nervous system. Endocrine disruptors are xenobiotics (i.e., chemical substances like toxic pesticides foreign to an organism or ecosystem) present in nearly all organisms and ecosystems. The World Health Organization (WHO), European Union (EU), and endocrine disruptor expert (deceased) Theo Colborn, Ph.D., classify over 55 to 177 chemical compounds as endocrine disruptors, including various household products like detergents, disinfectants, plastics, and pesticides. Past research shows exposure to endocrine-disrupting pesticides adversely affects human health, from reproductive function to cancer development, and effects can span generations. However, this study is one of the few to evaluate associations between endocrine-disrupting chemicals and neurological function. Although the etiology (cause) of many sporadic (non-heritable) neurological diseases are unknown, scientists suggest exposure to environmental toxicants plays a role in disease development. Therefore, government and health officials have been urged to consider how exposure to endocrine-disrupting chemicals can impact bodily function and development apart from hormone disruption.
In the body, cells communicate through electrical or chemical signals transmitted within the nervous or endocrine system. Studies find exposure to endocrine-disrupting chemicals has a direct and indirect impact on hormone function and development. However, researchers investigated whether the chemicals play a similar role in neurological development and functionality: Do endocrine-disrupting chemicals impact the nervous system via neuroendocrine or general mechanisms? These mechanisms include direct effects on the neurons/nervous system or indirect effects on the nervous system via thyroid regulation. Using scientific studies based on neurotoxicity, cognition, and behavior from PubMed and Google scholar, researchers assessed 176, WHO classified, endocrine-disrupting compounds, in addition to Roundup (177), for neurological effects.
The results demonstrate that all classifiable endocrine-disrupting chemicals, including Roundup/glyphosate, negatively affect the nervous system, causing neurological disruption (neurodisruption). Although previous research notes the primary mechanism of endocrine disruption is through the thyroid, only 20 percent of endocrine disruptors in this study operate via the thyroid to cause nervous system impacts. The remaining 80 percent of endocrine disruptors function via other general mechanisms to produce adverse nervous system effects. Therefore, the researchers establish the novel concept that endocrine disruptors are neurological disruptors (neurodisruptors) and collectively refer to these chemicals as endocrine and nervous disruptors (ENDs).
Past research shows exposures to endocrine-disrupting chemicals can adversely impact human, animal—and thus environmental—health, by altering the natural hormones in the body responsible for conventional fertile, physical, and mental development. Research demonstrates that endocrine disruption is prevalent among many pesticide products like herbicides, fungicides, insecticides, and even pesticide manufacturing by-products like dioxin (TCDD). These chemical ingredients can enter the body, disrupting hormones and causing adverse developmental, disease, and reproductive problems. The endocrine system consists of glands (thyroid, gonads, adrenal, and pituitary) and the hormones they produce (thyroxine, estrogen, testosterone, and adrenaline). These glands and their respective hormones guide the development, growth, reproduction, and behavior of animals, including humans. Endocrine disruption is an ever-present, growing issue that plagues the global population. Hence, advocates maintain that policies should enforce stricter pesticide regulations and increase research on the long-term impacts of pesticide exposure.
The nervous system is an integral part of the human body and includes the brain, spinal cord, a vast network of nerves and neurons, all of which are responsible for many of our bodily functions—from what we sense to how we move. However, exposure to chemical toxicants, like pesticides, can cause neurotoxic effects or exacerbate preexisting chemical damage to the nervous system. The impacts of pesticides on the nervous system, including the brain, are hazardous, especially for chronically exposed individuals (e.g., farm workers) or during critical windows of vulnerability and development (e.g., childhood, pregnancy). Mounting evidence over the past years shows that chronic exposure to sublethal (low) levels of pesticides adversely affects the central nervous system (CNS). Specifically, researchers identify agricultural chemical exposure as a cause of many adverse CNS impacts. In addition to CNS effects, pesticide exposure can impact a plethora of neurological diseases. These diseases include amyotrophic lateral sclerosis (ALS) and Parkinson’s disease, dementia-like diseases such as Alzheimer’s, and other effects on cognitive function. Overall, endocrine disruption can negatively impact reproductive function, nervous system function, metabolic/immune function, hormone-related cancers, and fetal/body development. Therefore, advocates say it is essential to avoid toxic chemical exposure to lessen potential acute and chronic health risks.
Not only do researchers find exposure to sublethal doses of endocrine-disrupting chemicals affect hormone receptors, but neural receptors such as connections between nerves, the brain, enzymes, and DNA, as well. This study adds to the growing body of research surrounding pesticide neurotoxicity. In addition to this research, several studies demonstrate autism, mood disorders (e.g., depression), and degenerative neurological conditions (e.g., ALS, Alzheimer’s, Parkinson’s) among aquatic and terrestrial animals, including humans, exposed to pesticides. Pesticides themselves, mixtures of chemicals such as Agent Orange or dioxins, and therapeutic hormones or pharmaceutical products are endocrine disruptors that possess the ability to disrupt neurological function. Furthermore, studies suggest pesticides formulants (adjuvants) such as POEA (polyoxyethylene tallow amine) have both neurological and endocrine-disrupting activity. POEA is present in some glyphosate-based herbicides like Roundup and has higher nervous system toxicity than the active ingredient (glyphosate). Although the biological function and cause/effect of neurotoxicity related to endocrine and nervous disruptors is unclear, scientists note synchronized communication within and between cells. Many of these endocrine compounds are petroleum derivatives that have a mechanism of action of “spamming” communication signals.
The U.S. Environmental Protection Agency lacks comprehensive pesticide testing protocol and fails to evaluate the full impact of pesticide products, severely limiting real-world exposure concerns. The Office of the Inspector General (OIG) reports EPA’s Endocrine Disruptor Screening Program fails to adequately assess endocrine-disrupting pesticides and protect the general population from exposure. The OIG report concludes, “Without the required testing and an effective system of internal controls, the EPA cannot make measurable progress toward compliance with statutory requirements or safeguard human health and the environment against risk from endocrine-disrupting chemicals.” (See Beyond Pesticides report.)
The endocrine and nervous systems are integral to everyday human activities and the body’s ability to function normally. There is a lack of understanding of the etiology of pesticide-induced diseases, including predictable lag time between chemical exposure, health impacts, and epidemiological data. Exposure to pesticides can increase the risk of developing chronic illnesses, and studies related to pesticides and endocrine disruption can help scientists understand the underlying mechanisms that indirectly or directly cause neurotoxicity. Therefore, advocates are calling for policies that enforce stricter pesticide regulations and increase research on the long-term impacts of pesticide exposure.
There are several limitations in defining real-world poisoning as captured by epidemiologic studies in Beyond Pesticides’ Pesticide-Induced Diseases Database (PIDD). The adverse health effects of pesticides, exposure, and the aggregate risk of pesticides showcase a need for more extensive research on occupational and non-occupational pesticide exposure, especially in agriculture. However, the PIDD database supports the clear need for strategic action to shift away from pesticide dependency. For more information on the multiple harms of pesticides exposure on human health, see PIDD pages on endocrine disruption, brain and nervous system disorders, cancer, and other diseases.
Beyond Pesticides advocates for a precautionary approach to pest management in land management and agriculture by transitioning to organic practices. Buying, growing, and supporting organic can help eliminate the extensive use of pesticides in the environment and from your diet. For more information on why organic is the right choice for consumers and the farmworkers who grow our food, see Beyond Pesticides webpage, Health Benefits of Organic Agriculture.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: GM Watch, Toxicology Reports
