Exploring the Environmental Causes of Autism and Learning Disabilities, Part 1

By guest blogger and Rodalenews.com advisor Philip J. Landrigan, MD

Dr. Landrigan has been a member of the faculty of Mount Sinai School of Medicine in New York City since 1985, and Chair of the Department of Preventive Medicine since 1990. He was named Dean for Global Health in 2010. Dr. Landrigan is also the director of the Children’s Environmental Health Center.

Each year, biologically based disorders of brain development—autism, attention deficient/hyperactivity disorder (ADHD), mental retardation, dyslexia, and subclinical neurodevelopmental disabilities—affect between 200,000 and 400,000 of the 4 million babies born in the United States. That’s between 5 and 10 percent of all American children.

There is great concern about the rising rates of autism spectrum disorder (ASD). The Centers for Disease Control and Prevention (CDC) report that the prevalence of ASD increased by 57 percent between 2002 and 2006, and is now affecting one of every 110 babies born in the U.S.


Beyond Genetic Research


Until recently, most research into the causes of ASD had focused on genetic factors. This elegant research has linked a series of genetic factors to autism—including specific gene mutations, recurrent chromosomal microduplications, microdeletions, and copy number variations.

However, none of these genetic factors accounts for more than 2 to 3 percent of cases of autism. And taken together, the identified genetic causes account for no more than 20 to 25 percent of cases. Moreover, genetic inheritance alone fails to account for important clinical and epidemiological features of autism. For example, some families have children who exhibit fully developed cases of autism, side by side with other family members who manifest only certain “autistic traits.” Sporadic cases of autism also occur in families who have no prior history of ASD. Ultimately, a purely genetic theory has difficulty explaining discordant development of autism in identical twins, variations in expression within families, and the rise in incidence of autism.

The shortcomings of genetic research—coupled with emerging research on the developing brain’s vulnerability to external exposures—suggest that environmental factors also contribute to autism and learning disabilities. In many instances, it is quite possible that environmental exposures interact with individually inherited genetic susceptibilities. In fact, the U.S. National Academy of Sciences has reported that 28 percent of developmental disabilities in children may be caused by environmental exposures, concluding that environmental factors are solely responsible for causation in 3 percent of cases, and that they act in concert with genetic factors in 25 percent of cases.

The Case for an Environmental Contribution

We know that the brains of infants and children are extremely sensitive to toxic exposures in the environment. New research has identified “critical windows of vulnerability” in fetal life and early childhood when exposures to toxic chemicals can cause devastating injury to the brain and nervous system. Research has also found that toxic chemicals can damage the developing brains of infants and children at extremely low doses. Thus, there are no safe exposure “thresholds” in early brain development, as even low-level chemical exposures have been shown to cause lost intelligence, shortened attention, and disrupted behavior.

We are now learning that these chemical exposures can damage the brains of infants and children to cause autism and learning disabilities. For example, lead, methylmercury, PCBs, manganese, organophosphate pesticides, DDT, and ethyl alcohol have all been identified as causes of childhood brain damage.

Of grave concern is that this list of chemicals may be only the tip of a much larger problem. Currently, 200 synthetic chemicals are identified as neurotoxic in adult humans. Another 1,000 chemicals have been identified as neurotoxic in experimental models. Likelihood is high that among these 1,200 neurotoxic chemicals, there are some with the potential to cause childhood brain injury that could result in autism and learning disabilities. As these diseases continue to rise, there is a dire need to investigate which chemicals contribute to the causes of autism and learning disabilities. Now is the time to take action in discovering the environmental contribution.

Exploring the Environmental Causes of Autism and Learning Disabilities

To address these research questions, the Children’s Environmental Health Center (CEHC), which I direct at the Mount Sinai School of Medicine, convened at an all-day workshop on December 8, 2010. This meeting, titled Exploring the Environmental Causes of Autism and Learning Disabilities, was cosponsored by advocacy leaders Autism Speaks, and was held at the New York Academy of Medicine in New York City.

By bringing together international autism-research leaders, the workshop allowed us to review current research and create a dialogue about the environmental contribution to autism and learning disabilities. Ultimately, the conclusions from this workshop will help refine our future research strategy, guiding our understanding of which chemicals to investigate further as potential environmental causes of autism and learning disabilities.

Currently, we believe that autism may result from a combination of genetic susceptibility and external exposure: “the wrong chemical at the wrong time.” At the workshop, we identified several environmental exposures that have been linked to ASD:

  1. Thalidomide: A medication taken by women in early pregnancy during the 1950s.
  2. Misoprostol: A medication used in other parts of the world to induce abortion in the first trimester.
  3. Prenatal rubella infection: Timing of the infection during pregnancy determines the severity of neurodevelopmental effects.
  4. Valproic acid: A medication used to control epilepsy.
  5. Organophosphate insecticide chlorpyrifos: A pesticide once widely used in the U.S., it is now banned and used only in agricultural settings.

While these chemicals don’t account for the current rises in autism, as none—except the organophosphate pesticides—are commonly used in the United States, their proven links to autism establish proof of principle for an environmental contribution.

Read more about the workshop, and the research presented there, in part 2 of Dr. Landrigan’s post, coming soon.




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12 Responses to Exploring the Environmental Causes of Autism and Learning Disabilities, Part 1

  1. Kim March 8, 2011 at 5:20 pm #

    As a parent of a child with severe ADHD, I’ve struggled to find ways to educate my child, to determine what foods to give him, and to provide him with enough awareness of his own limitations as well as an awareness of the many people, places and things available to assist him with his disability. Unlike a physical disability, his disability is not visible. However, it has changed the trajectory of his future. I appreciate this research tremendously. Thank you for your work.

  2. Deb March 8, 2011 at 10:20 pm #

    My daughter was born 21 years ago with brain damage. We lived on a golf course when I was pregnant that was sprayed regularly with pesticides. Over the years I often thought that the pesticides may have had something to do with her disabilities.

  3. Vincent Do March 9, 2011 at 12:52 am #

    I have been saying ASD is not genetic but epigenetic and therefore can be successfully treated. ASD is treatable and in many cases I have seen kids recover. Please don’t give up parents. Find doctors that know how to heal your children.

  4. Lori Butler March 9, 2011 at 6:51 am #

    In addition to genetic and environmental factors, Dr. Gabor Mate describes in several very accessible books the likely sources of rising incident of brain development disorders that have mystified parents and doctors–ADHD, autism and the connection to drug addiction and chronic diseases. Very much worth reading to fully understand approaches to healing that will be effective.

  5. Andrea March 9, 2011 at 9:25 am #

    There is zero new here.
    The list of ASD causes is ridiculously out of date.
    Thalidomide? Please- maybe 30 yrs ago
    Rubella? Again 30 yrs ago.
    This epidemic is now
    This conference allowed now involvement from parents/ families until the last hr of a 9 hr meeting. Start listening more, talking less.

  6. Stacy March 9, 2011 at 8:17 pm #

    Is anyone familiar with Dr. Dietrich Klinghardt? I found him while researching Lyme’s Disease. But he has also apparently done considerable research on autism, declares it is an infectious disease and treats patients accordingly. I was very impressed with his approach to curing Lyme’s which most MDs can barely diagnose, much less treat, and will be seeing an MD in his network soon. For the Lyme’s and I believe also for autism (altho I did not read up on this as much as Lyme’s), an early stage of his treatment is detoxing you from heavy metals in the body, most and maybe all, from the environment. If I had an autistic child I would certainly consult him.

  7. Tammy March 11, 2011 at 7:28 pm #

    Another environmental cause of autism spectrum is Accutane/Isotretinoin which come on the US market in 1982. Research on children (babies) exposed to this drug is very limited. As a parent I can vouch that a large percentage of our children have sensory integration disorder, and other “autistic-like” behaviors.

  8. jameshyloton143 March 28, 2011 at 7:36 am #

    Some time due to the genetic disorders and toxic exposures the child was in autism. In these case the brain of the child was not growth as per compare to a normal child.For more information i suggest http://www.makehealtheasy.com

  9. Truman April 20, 2011 at 4:54 pm #

    My son tis very autistic, he just screams at me all the damn time, I just want to shove my face in a little jar, soundproof jar, actually. That is a fantastic ideal. I do believe autism is not curable I’ve everything! I tried to make him eat olive oil and eggs, and no problems were solved. I tired shoving avacado and pickles in his cereal and he just ate that up real fast like, but he never did want to get fixed for his problem. Damn children these days… I love autistic kids just not mine. peace love and last but not least, chicky grease. Aheheha.

  10. Ke$ha April 20, 2011 at 4:58 pm #

    Dear truman I suggest throwing glitter and alcohol at your kid. That is the best lifestyle at you ask me. Cause this place about to BLOW OW OW OW OW OW!!

  11. Candy April 20, 2011 at 5:02 pm #

    Yeah Truman me and you have some amazing times together with all them sexual times and all, but we need to talk. You forgot to talk about when you stuck our son Tatter in the oven ’cause I wanted some Tatter tots. That didn’t end quite so well. He was normal before than, that poor child. Why did I marry YOU!!! YOU SELFISH SON OF A BITCH!!!!! And get rid of all that chicky grease that you left all over the house. In the summer I fry up like an egg. YOU BASTARD!!!!
    <3 Your not so loving wife.

  12. tatter April 20, 2011 at 5:11 pm #

    i wuv you mapa even thoughe you roll me in sommme chickee greasse and stuck’d me in the oven……..ughh ehhh….dotsdotsdots

    <3 wuv tatter

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