Source: Global Pesticide Campaigner (Volume 13, Number 2), August 2003.
The Collaborative on Health and the Environment (CHE) a new and important U.S. network working on environmental health issues, recently launched a nationwide Learning and Developmental Disabilities Initiative to raise awareness about the role of neuro-toxicants in the sharp increase in learning and developmental disabilities (LDDs) in children in the U.S. An estimated 12 million U.S. children (17% of youth under 18) are now affected by deafness, blindness, epilepsy, speech deficits, cerebral palsy, delays in growth and development, emotional or behavioral problems, or learning disabilities.(1)
Learning disabilities alone affect 5-10% of children in public schools.(1) Attention deficit hyperactivity disorder (ADHD) conservatively affects 3-6% of all U.S. school children.(2) Within the state of California, the number of children entered into the autism registry increased by 210% between 1987 and 1998. A few studies have suggested that the increase in autism over the past 10-12 years may be as much as tenfold.(3)
Some argue these increases reflect improved diagnostic techniques for conditions which scientists are still attempting to understand. For example, Asperger's Syndrome, one of the conditions considered an "autism spectrum disorder," was added to the Diagnostic Statistical Manual as recently as the early 1990s. In addition, LDDs and autism often manifest as complex sets of behaviors and symptoms, adding to difficulty of their diagnoses and the clinical response.
Research has shown that exposures to certain neurotoxicants such as pesticides (particularly organophosphates and pyrethroids), lead, mercury, polychlorinated biphenyls (PCBs) and solvents can disrupt neurological development and can lead to learning disabilities. Even a relatively small exposure to a toxic chemical during a window of vulnerability can have a permanent impact, one that might not occur if the same exposure happened at another time.(4)
The vast majority of chemicals in use today have never been examined for their impacts on the developing brain. Given the vulnerability of the developing brain to chemical exposures, scientists have raised concerns that this lack of information may be affecting many children and preventing us from recognizing the true magnitude of the public health threat.(5)
For example, despite the fact that organophosphate and pyrethoid pesticides are common and 90% of U.S. children have detectable residues of at least one organophosphate pesticide in their bodies,(6) little is known about their effects on the developing brain. In the laboratory, a single low-level exposure to an organophosphate pesticide or a pyrethroid at day 10 of life causes permanent changes in the brain and hyperactivity of rodents.(7) The effects of combined multiple and cumulative exposures experienced by children in the course of their daily lives remains virtually unstudied.
Neuro-developmental toxicants that have been studied, including lead, mercury, polychlorinated biphenyls, alcohol, and nicotine, have demonstrated the vulnerability of the developing brain to environmental agents at exposure levels much lower than those having a similar affect on an adult. Scientific understanding of the effects of these toxicants has emerged slowly, and the regulatory response has lagged even further. Meanwhile generations of children have been exposed to these chemicals at levels that may have caused irreversible damage. Evidence of this is the U.S. Centers for Disease Control (CDC) recent consideration of lowering even further the screening threshold of lead, from 10 microgm/dl blood to 5 microgm/dl blood, since impacts have now been documented at these lower levels.(8)
Most support groups for learning and developmental disabilities focus on filling the need for diagnosis and services. The Learning and Developmental Disabilities Initiative (LDDI ) bring a coordinated focus on preventing exposure to neurotoxicants to the ongoing work of national learning and disabilities groups. Together with scientists and health groups, LDDI works to raise public awareness, inform lawmakers and support specific legislation to eliminate dangerous neurotoxicants from our environment.
The American Association of Mental Retardation, the Arc of the United States, the Autism Society, Developmental Delay Resources, the National Institute for Literacy, the Epilepsy Foundation, the Asperger Syndrome Coaltion, Pesticide Action Network North America (PANNA), and U.S. Public Interest Research Groups (PIRGs), along with almost forty other groups and individuals have already joined LDDI.
LDDI has also formed a small group to focus on Criminal Justice, and will examine the role of environmental contaminants-recognized as risk factors for learning and developmental disabilities-found in disproportionate number in those in the juvenile and criminal justice system. This subgroup has been joined by Communities Against Violence Network, the National Association of Women Judges, and others.
Individuals and groups can sign on to the LDDI Resolution on Environmental Contributors to LDDs and read a summary of the neurotoxicants highlighted in the recent biomonitoring reports released by the CDC and the Environmental Working Group, on the CHE website, http://www.cheforhealth.org.
Parrill M. 1996. Research implications for health and human services. In: Learning Disabilities, Lifelong Issues (Cramer S, Ellis W, eds). Baltimore, MD: Paul W. Brookes Publishing.
Goldman L, Genel M, Bezman R, Slanetz P. 1998. Diagnosis and treatment of attention deficit hyperactivity disorder in children and adolescents. J Am Med Assoc 279(14):1100-1107.
Schettler, T, J Stein, F Reich, and M Valenti. 2000. In Harm--s Way: Toxic threats to child development, Greater Boston Physicians for Social Responsibility.
CHE Partnership Call Notes, Autism, April 23, 2003, http://www.cheforhealth.org/update/Apr2303Notes.html.
Schettler, Ted, Developmental disabilities--impairment of children--s brain development and function: the role of environmental factors, on CHE science website http://www.protectingourhealth.org/newscience/learning/2003-02peerreviewlearningbehavior.htm, adapted from Schettler T. Toxic threats to neurologic development of children. Environ Health Perspectives, 2001 Dec; 109 Suppl 6:813-6.
Ahlbom J, Fredriksson A, Eriksson P. 1995. Exposure to an organophosphate (DFP) during a defined period in neonatal life indusces permanent changes in brain muscarinic receptors and behaviour in adult mice. Brain Res 677:13-19.
Lanphear BP, Dietrich K, Auinger P, Cox C. 2000. Cognitive deficits associated with blood lead concentrations <10 microg/dL in U.S. children and adolescents. Public Health Reports 115(6):521-9.