Autism, attention deficit hyperactivity disorder (ADHD), dyslexia, mental retardation, lowered IQ and other learning and behavior disorders are very common in today’s American children. The occurrence of these learning and developmental disabilities (LDDs) appears to be rising with between 5 to 15 percent of all children under the age of 18 in the United States affected. In general, these disabilities have significantly increased over the past 40 years and now affect more than 12 million children in the United States.
On February 20, 2008 The Collaborative on Health and the Environment’s Learning and Developmental Disabilities Initiative published a Scientific Consensus Statement on Environmental Agents Associated with Neurodevelopmental Disorder. This statement signed by more than 50 national and international health professionals and scientists summarizes the most recent science about environmental contaminants associated with learning and developmental disabilities. The report that was drafted by this prestigious group contains over 200 scientific references.
“We know enough now to move on with taking steps to protect our children. This document pulls that knowledge together to further this vital effort," said reviewer Martha Herbert, PhD, MD, an assistant professor of neurology at Harvard Medical School and a pediatric neurologist with subspecialty certification in neurodevelopmental disabilities at the Massachusetts General Hospital in Boston.
Exposure to a wide variety of chemicals is now an unavoidable fact of modern life. Approximately 3,000 chemicals are manufactured in amounts over 1,000,000 pounds each year. The vast majority of these chemicals have little to no information on their potential to effect learning and development. According to the report, “there is good evidence that about 200 of these chemicals are adult neurotoxicants and another 1,000 are suspected of affecting the nervous system. Overall there has been a gross failure to require developmental neurotoxicity testing.”
Historically, of all the factors that contribute to learning and developmental problems, chemical contaminants have been the least studied, although ironically the most preventable. The report states that, “we now have solid scientific evidence that a variety of environmental agents can adversely affect the nervous system,” and that “a child’s developing nervous system is more sensitive to chemical exposure than the adult nervous system.”
Children that lack certain nutrients are more susceptible to these chemical toxicants. For instance, iron and/or calcium deficiencies can affect the absorption and toxicity of heavy metals such as lead and manganese. “The role of nutrition in mitigating exposure to environmental agents is an important public health issue.”
The following environmental contaminants have been “conclusively shown” to affect the developing nervous system and cause a range of performance deficits.
Alcohol – The effects of alcohol on the brain are well recognized. “Fetal Alcohol Syndrome (FAS), now considered part of the Fetal Alcohol Spectrum Disorder (FASD), is the most preventable form of behavioral and learning disabilities. Even low or moderate consumption of alcohol during pregnancy can cause subtle and permanent performance deficits.”
Mercury – There is no doubt that mercury causes learning and developmental disorders. “We are all exposed to some form of mercury. Inorganic mercury is the liquid silver form and is used in dental amalgams. Mercury is also present in coal, and coal-burning electric utilities facilities are a significant source of atmospheric environmental mercury.”
PCBs – Polychlorinated biphenyls (PCBs) are mixtures of chlorinated compounds that were once used as cooling and insulating fluids in electrical transformers and other electronic components. “Numerous studies have documented that PCB exposure can adversely affect motor skills, learning and memory as shown in lower full-scale and verbal IQ scores and reading ability.”
PBDEs – Polybrominated diphenyl ethers (PBDEs) have been used commonly as flame-retardant chemicals for years. “Recent studies have left little doubt that PBDEs are developmental neurotoxicants in animals and lead to changes in motor activity and reduced performance on learning and memory tests.”
Manganese – Manganese is a trace element which is essential in small quantities for normal growth and development. “Recent studies indicate that high levels of manganese exposure, either from inhalation or through drinking water, can damage the developing nervous system.”
Arsenic – Arsenic is frequently found in drinking water around the world. “Recent studies have found a dose-response relationship between exposure to arsenic and intellectual impairment. While additional studies assessing the impact of low levels of arsenic in drinking water are needed, it is clear that arsenic affects the neurodevelopment of children.
Solvents – Solvents include a broad array of different compounds including toluene, benzene, alcohol, turpentine, acetone and tetrachloroethylene. More than 50 million metric tons are used in the United States with more than 10 million people exposed in the workplace. “Several reports have documented that the adverse developmental effects of maternal toluene exposure include low birth weight, decreased head circumference and developmental delays.”
PAHs – Polycyclic aromatic hydrocarbons (PAHs) are widely dispersed air pollutants and well-recognized human mutagens and carcinogens. PAHs are generated during combustion of fuels from motor vehicles, coal-fired power plants, residential heating and cooking and are also present in tobacco smoke. “Recent studies have indicated that elevated exposure to PAHs results in lower birth weight and affects cognitive development.”
Pesticides – Pesticides are ubiquitous in our modern environment. Agricultural and residential application of pesticides totals more than 1 billion pounds each year in the United States. “There is now evidence that childhood exposure to pesticides, such as organophosphates, enhances the risk for developmental disorders including deficits in memory, poorer motor performance and an array of other conditions.”
Nicotine and environmental tobacco smoke (ETS) – Many studies link maternal smoking to behavior disorders in children. The developmental delays caused by ETS are costly and preventable. “Furthermore, new data indicates that childhood exposure to ETS is associated with neurobehavioral effects. There is growing recognition of subsequent behavioral disorders in young adults following exposures either prenatally or as children.”
Unfortunately, it is not possible to address all the chemicals that might be associated with LDDs. Again, it’s important to note that for the majority of chemicals “we do not have the data necessary to conclude there are no adverse developmental effects.” There are an estimated 200 chemicals that are known to cause neurotoxic effects in adults, but for many of these chemicals “developmental effects have not been examined.”
The following are number of agents that are of significant concern:
Endocrine disruptors – “Animal studies have documented that a wide range of chemicals have the ability to disrupt endocrine function in animals and affect cognitive function. Endocrine disruptors include phthalates, PCBs and polychlorinated dibenzodioxins, brominated flame retardants, dioxins, DDT, perfluorinated compounds (PFCs), organochlorine pesticides, bisphenol A and some metals. The controversy around the effects of endocrine disruptors is perhaps best illustrated by research on bisphenol A whose estrogenic activity was first reported in 1936. It was subsequently found to stabilize polycarbonates and resins and is now widely used in many products including food-can liners. There is a growing body of evidence related to the very low-dose effects of bisphenol A”
Fluoride – Fluoride is commonly added to drinking water across the United States in an effort to reduce dental decay. Fluoride is also found in a range of consumer products including toothpastes and mouthwashes. “Excessive fluoride ingestion is known to lower thyroid hormone levels, which is particularly critical for women with subclinical hypothyroidism: decreased maternal thyroid levels adversely affect fetal neurodevelopment. In addition, a study in China reported decreased child IQ levels associated with fluoride in drinking water. The primary concern is that multiple routes of exposure, from drinking water, food and dental care products, may result in a high enough cumulative exposure to fluoride to cause developmental effects.”
Food additives – Artificial food colors and additives are found throughout the modern food supply and have long been suspected as causing conduct disorders. Diets, such as the Feingold Diet removes food additives from the diets of individuals with ADHD. “Previous and recent carefully conducted double-blind human studies have confirmed that artificial food colorings such as sunset yellow, tartrazine, carmoisine and ponceau, as well as the preservative sodium benzoate, can cause conduct disorders. Recent studies using well-designed randomized, double-blind, placebo-controlled, crossover trials show that artificial food colors and additives cause increased hyperactivity in three-year-old children. This has the potential to become a serious issue given the large number of children diagnosed with ADHD.”
“Accepting childhood exposure to contaminants that result in compromised learning and behavioral abilities violates the basic tenets of biomedical ethics. The principle of beneficence (“do good”) requires that the benefits be maximized while the harm be minimized or eliminated. Respect for autonomy or personhood is violated when children are unnecessarily exposed to harmful substances. Respect of person also implies informed consent, and no child has given the informed consent for exposure to harmful chemicals. Finally, the principle of justice requires that burdens be shared equally, and because children are more vulnerable they endure a greater burden. It is wrong to allow the exposure of children to environmental agents that cause learning and developmental disorders.”
We are still dealing with the health effects of adding lead to paint and gasoline, even though at the time the toxic effects of lead were well known. “To protect children, a precautionary approach is required that shifts the burden of responsibility to producers or manufacturers to demonstrate safety prior to potential exposure.”
“We could cut the health costs of childhood disabilities and disease by billions of dollars every year by minimizing contaminants in the environment,” said Phil Landrigan, MD, MSc, of the Children’s Environmental Health Center at the Mount Sinai School of Medicine. “Investing in our children’s health is both cost-effective and the right thing to do.”
“The overwhelming evidence shows that certain environmental exposures can contribute to life-long learning and developmental disorders,” noted Ted Schettler, MD, MPH, with the Science and Environmental Health Network. “We should eliminate children’s exposures to substances that we know can have these impacts by implementing stronger health-based policies requiring safer alternatives. Further, we must urgently examine other environmental contaminants of concern for which safety data are lacking. ”
“The proportion of environmentally induced learning and developmental disabilities is a question of profound human, scientific and public policy significance,” said lead author Steven G. Gilbert, PhD, DABT, of the Institute of Neurotoxicology & Neurological Disorders, “and has implications for individuals, families, school systems, communities and the future of our society. The bottom line is it is our ethical responsibility to ensure all children have a healthy future.”
The authors of the study do not include all the hazards that affect the brains of our children. Nutritional deficiencies of omega-3 fatty acids, B vitamins, selenium, vitamin E, and others are documented in the medical literature as affecting brain health and development. The avoidance of dairy, wheat, and artificial sweeteners in the diet have been shown to positively change neurologic problems. Excessive television viewing has also been associated with behavior and attention problems. Thimerosal, found in vaccines and other products, has been shown that it “induces oxidative stress and apoptosis by activating mitochondrial cell death pathways” and to have “induced DNA strand breaks, caspase-3 activation, membrane damage and cell death” (NeuroToxicology, Vol. 26, 2005)
The authors conclude, “The scientific evidence we have reviewed indicates environmental contaminants are an important cause of learning and developmental disabilities. The proportion of environmentally induced LDDs is a question of profound human, scientific and public policy significance. Existing animal and human data suggest that a demonstrated with scientific certainty. The consequences of LDDs are most significant for the affected individual but also have profound implications for the family, school system, local community and greater society. Despite some uncertainty, there is sufficient knowledge to take preventive action to reduce fetal and childhood exposures to environmental contaminants. Given the serious consequences of LDDs, a precautionary approach is warranted to protect the most vulnerable of our society.”
The over 50 scientists of this report state they are developing a companion document outlining specific policy recommendations based on the current scientific knowledge that was used to assemble this report.
We as individuals can act now. We can avoid alcohol and tobacco smoke. We can get water and air filters to minimize exposure to lead, mercury, and other contaminants. We can avoid using pesticides on our lawns and by choosing to eat organic foods. We can avoid processed foods that contain artificial colors and ingredients. We can use fluoride free products. We can use natural cleaners that don’t contain harmful solvents in our homes. We can use products that don’t contain phthalates and other harmful chemicals. We can ensure we get enough nutrients by avoiding nutritionally deficient junk foods and focus on getting enough omega-3 fatty acids and key vitamins and minerals in our diets. We can minimize our exposure to television and instead focus on positive activities such as exercise, reading, playing, and creating.
We can make the changes that help our children and reverse course on an epidemic of neurologic problems. We can make a difference one life and one child at a time if we have the ethics and will to do so.
Source: Scientific Consensus Statement of Environmental Agents Associated with Neurodevelopmental Disorders