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What Role Do Chemicals Play?

“Science suggests that exposure to toxic chemicals may contribute substantially to the incidence of learning and developmental disabilities in this society,” said Larry Silver, MD, Clinical Professor of Psychiatry at Georgetown University Medical Center; former Acting Director of the National Institute of Mental Health (NIMH); past president of the Learning Disabilities Association of America; and Mind, Disrupted project participant, who has Attention Deficit and Hyperactivity Disorder (ADHD). “This concerns me deeply.”

The effects of chemicals on the nervous system have been recognized since ancient times. Most early reports were the results of high exposures in workers that led to debilitating conditions or even death. For example, over 2000 years ago, the Greek physician Dioscorides wrote that lead exposure “makes the mind give way.”

As science progressed, it was recognized that even small doses of some chemicals result in subtle nervous system impacts that affect an individual’s performance. Chemicals with the capacity to sabotage the development of our brains and nervous systems are termed “developmental neurotoxicants,” while chemicals that interfere with the functioning of our brains are termed “neurotoxic chemicals.”

Many factors influence how vulnerable a person is to the health effects of chemical exposures, among them socioeconomic status, gender, gene expression, nutrition, stress, exposure to infectious agents, and timing of exposure. Still, a growing body of peer-reviewed scientific research shows that, for those who are most vulnerable, exposure to even minute doses of neurotoxic chemicals can tip the balance toward learning and developmental disabilities.

According to an article published in the Lancet in 2006, “A few industrial chemicals (e.g., lead, methylmercury, polychlorinated biphenyls [PCBs], arsenic, and toluene) are recognised causes of neurodevelopmental disorders and subclinical brain dysfunction” and “another 200 chemicals are known to cause clinical neurotoxic effects in adults.”12 Another review article, linking violent behaviors to chemical exposures, stated that, “A number of environmental exposures are documented to result in a common pattern of neurobehavioral effects, including lowered IQ, shortened attention span, and increased frequency of antisocial behavior.”13 In a study conducted by researchers at the Columbia Center for Children’s Environmental Health, children with higher concentrations of PBDEs (flame retardants) in their umbilical cord blood at birth scored lower on tests of mental and physical development at 1 to 4 and 6 years of age.14 In addition, exposure to mercury from a variety of sources, such as prenatal maternal consumption of seafood high in methylmercury, has been shown to reduce IQ in children.12,15

One intriguing research study that was published in 2009 in the journal NeuroToxicology noted an association between polyvinyl chloride (PVC) flooring and incidence of autism. While this has not been substantiated, it raises the question about how a range of chemicals — ones we may not even have considered to date — may impact neurological health and how little we truly know about chemical exposure and safety when it comes to human health.16 Another study evaluating “the hypothesis that maternal residence near agricultural pesticide applications during key periods of gestation could be associated with the development of autism spectrum disorders in children,” found that “ASD risk increased with the poundage of organochlorine [pesticides] applied and decreased with distance from field sites.”17 A study of household pesticide use found that “compared with mothers of typically developing children, mothers of children with autism spectrum disorders were twice as likely to report that they had shampooed their pets with pyrethrin-containing antiflea/antitick shampoos around the time of their pregnancy.”18 Yet for the majority of chemicals in use there is a lack of data on potential neurodevelopment effects from exposure.

For those who already have learning or developmental disabilities, minimizing exposure to neurotoxic chemicals may mitigate the severity of their condition and improve their quality of life.19 And yet, chemicals known and suspected to be neurotoxic are present in our air, water, food consumer products, homes, and workplaces — and, as this project demonstrates, in our bodies.

“I have cerebral palsy,” responds Ann WingQuest. “I’m very sensitive to the fact that people with developmental disabilities have compromised systems, and introducing any kinds of toxins to their systems complicates everything. The current policy approach to dealing with our environment makes it clear that [when it comes to managing chemicals] we have no idea what we’re doing. And that really concerns me.”

Our nation’s primary law concerning toxic chemicals, the Toxic Substances Control Act (TSCA), became law in 1976. Since its passage, evidence has been accumulating that chemicals such as lead, mercury, bisphenol A (BPA) and PBDEs may harm the developing brain at levels much lower than those previously considered safe. TSCA has not been updated to reflect our better understanding of toxic chemicals.

Meanwhile, many chemicals in common use remain untested. A U.S. Environmental Protection Agency (EPA) analysis revealed that, of the roughly 3,000 chemicals produced or imported in the U.S. in quantities over 1 million pounds a year, only 43% have been tested for basic toxicity, and a scant 7% have been subjected to the six tests considered “necessary for a minimum understanding of a chemical’s toxicity” (among which is a test for basic developmental and reproductive toxicity).20

“These chemicals are not supposed to end up in our bodies,” says project participant Cathy Ficker Terrill, President and CEO of the Ray Graham Association for People with Disabilities. Cathy’s daughter, Beth Terrill, a self-advocate, has a developmental disability and chemical sensitivities, and is also a participant in Mind, Disrupted.