The focus on a mercury based preservative in some vaccines has taken public attention away from other commonly found toxic substances as possible causes, or contributing factors, in at least some of the increasingly large numbers of autism diagnoses being made today in the Canada, the US, the UK and elsewhere in the world. Yesterday CBC news carried a story Excessive lead found in water of 5 Toronto schools which as the title indicates, reports on five Toronto area schools in which testing showed the water supply exceeded the Ministry of the Environment standard of 10 micrograms of lead per litre. The school district is now supplying staff and students at the 5 schools with bottled water.
The article also notes in conclusion that "Childhood exposure to lead can cause learning problems and reduced intelligence." The CBC article also contains a link to the Ontario Ministry of the Environment web page which notes that, apart from lead pipes and drinking water there are many other sources of lead in our environment including some older lead paints. As we have learned recently lead is still being found in some popular children's toys. With respect to the health effects of drinking lead contaminated water the Ontario Environment Ministry page Lead and Drinking Water - Questions and Answers states that:
How does lead in water affect health?
Young children are more sensitive to the effects of lead because they are still developing and able to absorb ingested lead more easily than adults. Long-term exposure to lead above the standards may increase the risk of subtle impairment of learning capacity and intellectual development. Pregnant women need to limit their lead intake as much as possible to protect the fetus.
In Autism and Autistic Symptoms Associated with Childhood Lead Poisoning , published in the Journal of Applied Research, authors Theodore I. Lidsky, PhD , Department of Psychobiology, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York and Jay S. Schneider, PhD Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University College of Medicine, Philadelphia, Pennsylvania examined two case histories of children who, during periods of severe lead poisoning, developed autism or autistic symptoms.
In the abstract portion of the article the authors noted that "These cases underscore that there are multiple causes of autism and the importance of environmental influences in some cases." Both of these children emerged from their autism diagnoses (1 autism disorder, 1 PDD-NOS) with the passage of time but with no specialized treatment. Lidsky and Schneider concluded that:
The two case histories presented here, as well as the reports of autistic symptoms in children with disorders that produce brain lesions or encephalopa- thy, indicate that there are multiple causes of autism. Further, the ability of brain infections and lead poisoning to produce such symptoms highlights the importance of environmental factors in the etiology of *autism*.
The ability of *lead* *poisoning* to induce symptoms of *autism* is also relevant to cases of preexisting pervasive developmental disorders irrespective of etiology. Such individuals have a greater propensity to engage in pica and, as a result, are more likely to become *lead* poisoned.
In such cases, *lead* poisoning can be expected not only to negatively impact neurocognitive functioning, but also to potentially exacerbate the preexisting symptoms of *autism*. Indeed, one case report describes a decrease in hyperactivity and stereotypies in an autistic child with ablood *lead* of 42 µg/dL once this level was reduced by chelation with succimer.
In June of 2007 Dan Agin discussed the possibility of lead poisoning as a major environmental factor in autism on the Huffington Post in his article Autism and Our Passion For Simple Causes and Quick Fixes. Mr. Agin's Huffington biography states that he has a Ph.D. in Biological Psychology and thirty years laboratory research in Neurobiology. He's Emeritus Associate Professor of Molecular Genetics and Cell Biology at the University of Chicago, and for the past ten years he has been editor-in-chief of the journalScienceWeek(www.scienceweek.com), a science digest that focuses on explicating newresearch in the various sciences.
No one can credibly claim that autism is purely genetic or purely environmental. The unified autism theory seems to suggest that both types of factors are involved in the development of genetic mutations giving rise to autism. There is much research to be done, and much being done, on all sides in the search to understand what causes autism. We know there are major toxic substances, including mercury and lead, polluting our environment. It would be foolish to ignore them as possible causes of autism. It would also be foolish to pretend that the research on these issues is complete and that any of these toxic substances can be ruled out as causes of autism.