Brain, Environment and Toxic Chemicals

Researchers from the Harvard School of Public Health suggested in 2006 that fetal and early childhood exposures to chemicals in the environment can damage the developing brain and can lead to neurodevelopmental disorders, but warned that there is insufficient research to identify and avoid individual chemicals that cause brain injury. They described 202 chemicals that have the capacity to damage the human brain and concluded that chemical pollution may have harmed the brains of millions of children worldwide. 

Concern about disease-causing effects of agricultural chemicals has been expressed for several decades. In 1982, for example, Alan Anderson   reviewed the importance of nervous system toxins from the environment in causing mental malfunction. He stated:  "Of the 100,000 or so chemicals used by American industry, 575 are deemed dangerous in large doses and many of these are known to be associated with catastrophic illness, from cancer to respiratory disease. Perhaps no class of chemicals is more subtle and treacherous in its effects, however, than neurotoxins, which can damage the nervous system even in modest doses and cause a variety of behavioral and emotional symptoms - among them, hallucinations, loss of memory, confusion, depression and psychosis."

There are several groups of pesticides used to control insects, weeds, and fungi. The chemicals are classified by target organisms as insecticides, herbicides, fungicides, or fumigants. Insecticides are classified by chemical type as organophosphates (OPs), organochlorines, carbamates, and pyrethroids. Direct exposure to these chemicals when they are spayed on crops, forests, residential area, and used in and around the home are more obvious and more toxic that indirect exposure to low concentrations by drinking contaminated water and eating contaminated food. The effect of agricultural chemical contamination of the food supply is not clearly known. Individual sensitivity to contaminant chemicals varies and is interactive with other chemical stressors. Some pesticides are longer-lasting than other and can be generally distributed in the environment. DDT use, for example, is banned in North America, still shows up, carried on air currents from distant countries who continue to use it. Organochlorines have a long half-life, and serum levels can be used as a general marker of exposure to pesticides.

The biological effects of low levels of agricultural chemicals in the human body are uncertain. No authority can assure you that all is well.   Chronic exposure to low but cumulative doses of chemicals may lead to chronic illness, and sooner or later, avalanche into catastrophic illness. People who use pesticides on regular basis risk toxicity and should reconsider this use. Individuals are frequently exposed to many different pesticides or mixtures of pesticides repeatedly over many years.

Common pesticides (Malathion, Parathion, EPN, Schradan) are related to "nerve gases" (Saran, Soman), which all block the breakdown of acetylcholine in synapses, so that it accumulates and blocks receptors.  The result of a large dose is respiratory failure and convulsions, quickly fatal if the dose is high enough. Acute poisoning would only occur in people exposed to high concentrations of these chemicals in agriculture and industry. Kamel and Hopping summarized the problem: “Pesticides are used extensively throughout the world. In the United States, more than 18,000 products are licensed for use, and each year more than 2 billion pounds of pesticides are applied to crops, homes, schools, parks, and forests.  Such widespread use results in pervasive human exposure. Evidence continues to accumulate that pesticide exposure is associated with impaired health. Occupational exposure is known to result in an annual incidence of 18 cases of pesticide-related illness for every 100,000 workers in the United States. The best-documented health effects involve the nervous system. The neurotoxic consequences of acute high-level pesticide exposure are well established: Exposure is associated with a range of symptoms as well as deficits in neurobehavioral performance and abnormalities in nerve function. Whether exposure to more moderate levels of pesticides is also neurotoxic is more controversial. Pesticide exposure may also be associated with increased risk of neurodegenerative disease, particularly Parkinson disease.” 

Sixteen pesticides have been detected in eight brand-name baby foods In the USA, according to a study by the Environmental Working Group (EWG) and the National Campaign for Pesticide Policy Reform (1997). A random sampling of 76 jars of baby food from grocery store shelves in Denver, Philadelphia, and San Francisco revealed that 53% had traces of one pesticide, and 18% had two or more pesticides. Plums contained the highest amounts at 46 parts per billion and peaches contained 29 parts per billion. The EWG was concerned that pesticides are not “tested for safety in the way babies are exposed to them," and that babies and young children "react differently than adults to many drugs and toxic substances."

An investigation by the National Academy of Sciences (USA), published in 1993 in the report Pesticides in the Diets of Infants and Children, suggested that standards for food safety do not account for the special vulnerability of infants and growing children to chemical substances. The standards do not account for the total doses of pesticides that babies receive from other sources - fresh produce, drinking water, cow’s milk, human breast milk, or from the additive effects of these pesticides.

Lead, mercury compounds, pesticides, herbicides, fungicides, aluminum, styrene, tetrachlorobiphenyl, and dioxins are among the neurotoxins that may be airborne and contaminate the food supply. The Environmental Protection Agency in the USA reported that the magnitude of chemical contamination of the USA in 1987 was 9.7 billion pounds of chemicals into streams and 2.7 billion pounds into the air. The allowance of toxic chemicals for each citizen was about 50 pounds. Despite concern about chemical toxicity, little has changed in the last 3 decades except that more chemicals have been added to the environment. Individual sensitivity to contaminant chemicals varies and is interactive with other chemicals entering the body. The biological effects of agricultural chemicals in the human body at any level are not so well-known that any authority can assure you all is well.     You can argue that chronic exposure to low but cumulative doses of chemicals leads to chronic illness and sooner or later, avalanche into catastrophic illness. The effect of agricultural chemical contamination of the air, water and food supply is generally not known and seldom considered by physicians. Pesticides are generally distributed in the environment and need not be sprayed directly on crops to contaminate them.  Farmers who sprayed pesticides on their crops for many years have a higher incidence of Parkinson’s disease. Rats developed Parkinson's-like symptoms after receiving small but continuous doses of the pesticide, Rotenone.

About 100 different hormones have now been identified in the environment; they control growth, development and behavior in all vertebrates, including humans.    At least 50 synthetic industrial chemicals (detergents, plastics and pesticides) are known to interfere with hormones or have hormonal effects; they disrupt normal growth and development in birds, fish, mammals, reptiles, amphibians, and humans. The observed results are changes in sexual preference and behavior; small penises; diminished sperm count; cancers; nervous system disorders; birth defects and damage to the immune system.  

I recall going to a workshop on the impact of environmental chemicals at a meeting of the American College of Allergy and Immunology in 1992. The speaker came from the Centers for Disease Control and Prevention (USA).  His presentation was a surprise. He stated that the CDC had planned to measure environmental chemicals in the bodies of American subjects and then to follow these subjects to find out what diseases they developed. However, all such research was cancelled during the years of the Regan administration. He said come back in 10 years and with luck, I will have some data to report. About ten years later, the Centers for Disease Control and Prevention, National Center for Environmental Health Division of Laboratory Sciences issued the first “National Report on Human Exposure to Environmental Chemicals.”  The CDC plan was to provide an ongoing assessment of the U.S. population's exposure to environmental chemicals using biomonitoring. The first report was issued in March 2001.

A second report was released in January 2003 that presented biomonitoring exposure data for 116 environmental chemicals for the U.S. population over the 2-year period 1999-2000.    These reports are detailed and reveal worrisome body burdens of toxic chemicals but permit no conclusions about the adverse health effects of these chemicals. The first Report measured lead, mercury, cadmium, and other metals; the dialkyl phosphate metabolites of organo-phosphate pesticides; cotinine and phthalates. The second report added these chemicals:

Polycyclic aromatic hydrocarbons
Dioxins, furans, and polychlorinated biphenyls (PCBs)
Phytoestrogens
Organophosphate pesticides
Organochlorine pesticides
Carbamate pesticides
Herbicides
Pest repellents and disinfectants

US veterans returning from the Gulf War of 1990-1991 described a polysymptomatic disorder that included chemical sensitivity, chronic fatigue, fibromyalgia, neurocognitive deficits, irritable bowel syndrome, headaches, joint pains, fever, and a general malaise, referred to as Gulf War syndrome (GWS). I had been referring to this package of disturbances as type 3 or delayed pattern food allergy.  Some veterans believed they were ill because of exposure to chemicals.   Chemical suspects included low-level chemical and biological warfare agents, pyridostigmine bromide,   N,N-diethyl-m-toluamide, organophosphate pesticides, depleted uranium, combustion by-products of oil well fires, diesel exhaust, petroleum products, and infectious agents.  Later investigations revealed increased neurologic diseases, particularly an increased rate of amyotrophic lateral sclerosis (ALS).  

The investigation of the Gulf War Syndrome provided us with some useful statistics and a look at symptom clusters in a large population of Americans. In response to veterans' concerns about potential health effects resulting from service during Operations Desert Storm/Shield, the (US) Department of Defense (DOD) initiated the Comprehensive Clinical Evaluation Program (CCEP). The CCEP offered in-depth medical examinations to approximately 13,000 service and family members. Their report summarizes the diagnostic results of 10,020 participants who finished their medical evaluations. Symptoms and diagnoses seen in CCEP participants resemble those seen in the general population and in patients seeking primary medical care.   The most frequently reported chief complaints were fatigue (11%), joint pain (11%), headache (8%) and memory loss (4%). 

The most common symptoms were fatigue (47%), joint pain (47%), headache (39%), memory loss (33%), sleep disturbance (32%), and difficulty concentrating (27%). Vojani and Thrasher reported a series of immune abnormalities after they carried out detailed immunologic assays over several years on 100 symptomatic Gulf War veterans (patients) and 100 controls.  They described immune abnormalities associated with viral reactivation and induction of pro-inflammatory cytokines, resulting in symptoms similar to those of chronic fatigue and fibromyalgia.  They concluded: “We believe that GWS is a multifactor disease caused by exposure to a variety of environmental conditions, for example, xenobiotics, vaccinations, and other stressor-related conditions of the Gulf War environment. …The variation in individual susceptibility to environmental stresses and toxicants is a new discipline (toxicogenomics), initiated at the National Institute of Environmental Health Sciences, that studies the relationship between genes and environmental stressors. This new knowledge of toxicogenomics may enable us to answer why, upon exposure to these environmental factors, some soldiers developed GWS and others did not.

In many industries, workers are exposed to toxic chemicals. Some have short-acting effects and can be considered intoxicants. Other chemicals are toxic over a long-term leading to permanent injury to the brain, spinal cord and peripheral nerves. For example, exposure to vaporized bromopropane (1-BP), an industrial solvent widely used in the US and Japan is neurotoxic.  Majersik described six factory workers who glued foam cushions together and were exposed to 1-BP vapors from spray adhesives over several months. They developed lower extremity pain, sensory neuropathy and spastic muscle weakness.  Five had difficulty walking and two required assistance walking 15 months after exposure. Toxicology studies showed high serum bromide levels in all six. 

The US government supports an agency for toxic substances and a disease registry. They provide toxological profiles of 289 high priority chemicals and case studies for physician education.   Their emphasis is on the management of acute exposures from chemical dumping and spill incidents.

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The Human Brain in Health and Disease, 2010, is a Persona Digital Book. We encourage readers to quote and paraphrase topics from Human Brain in Health and Disease published online and expect proper citations to accompany all derivative writings. The author is Stephen Gislason and the publisher is Persona Digital Publications. The date of publication is 2010. The URL to the book description is Human Brain