Tuesday, April 15, 2008

Possible Environmental Causes of Autism and Other Neurodevelopmental Disorders

Autism rates have changed significantly since my son was diagnosed 10 years ago. At that time it was common to read estimates ranging from 1 in 500 to 1 in 1000. But the estimates started changing to 1 in 250, then 1 in 166 and now 1 in 150. In the UK the figure currently used is 1 in 100. There are many today who believe that changes in the definition of autism introduced in the DSM-IV combined with diagnostic substitution explain the dramatic increases in autism disorder diagnoses. But the advocates of this theory really have no solid studies providing precise measurements to substantiate the belief that the autism increases are all largely changes in how we view autism rather than actual increases in incidents of autism.

The definition change believers seem to be on solid ground to the extent that they argue that such change is a substantial contributing factor to the increases in autism diagnoses. They seem to stretch their belief beyond reason though when they assert dogmatically that the increases are due entirely to these social factors and rule out any environmental increases. The well known identical twins studies show that, in some cases, one identical twin will receive an autism diagnosis but the other will not, suggesting a role for environmental factors in autism causation.

In Neurodevelopmental Disorders in ChildrenAutism and ADHD Mona Sethi Gupta, Ph.D. examines environmental factors that may disrupt neurological development including lead, mercury, PCBs, dioxins, arsenic and toluene. Dr. Gupta discusses some studies suggesting environmental contributors to increasing neurodevelopment problems among children who are more sensitive to environmental toxins than adults and reminds us of the thalidomide tragedy. Dr. Gupta notes emphasizes the importance of taking action to protect children from environmental toxins:

"The impact of environmental toxins on children’s health has become a major focus in the federal government resulting in establishment of eight new research centers in children’s environmental health with joint funding from EPA and the National Institute of Environmental Health Sciences (NIEHS). "The brains of our children are our most precious economic resource, and we haven't recognized how vulnerable they are," says Philippe Grandjean, adjunct professor at Harvard School of Public Health and the lead author of the study published in The Lancet . "We must make protection of the young brain a paramount goal of public health protection. You have only one chance to develop a brain.""

There are those who argue dogmatically that environmental factors are not involved in causing autism and that the startling autism increases are due entirely to definition change and diagnostic substitution. They may honestly believe their assertions or they may be tied to promotion of book royalties or blog site advertising but modern history, thalidomide, tobacco and cancer, suggest greater caution in ruling out all environmental contributors to autism and other developmental disorders. Our children deserve better than for society to rely on the faith and belief of dogmatists on such important issues.



1. An arrogantly assertive person.
2. One who expresses or sets forth dogma.

Noun1.dogmatist - a stubborn person of arbitrary or arrogant opinions

drumbeater, partisan, zealot - a fervent and even militant proponent of something


Maya M said...

It seems that on your 2nd row you mean "1 in 1000" instead of "1 in 100".
To the subject of the post: It is quite possible for a condition with a constant or almost constant prevalence to be partly or wholly caused by an environmental factor. E.g. the neural tube defects caused by folic acid deficiency.
However, if the growing autism prevalence is caused by environmental factor(s), we have to look for one that is not only present in recent decades, but also increasing with time.
I guess that prevalence of ASD diagnosis will soon reach a plateau. This will NOT be indicative of how much of it is genetic and how much environmental.
Personally, I believe that a factor is causing a condition when it is shown to do so in an animal model. Because of the technical and ethical limitations of humans as study objects, human studies tend to be murky. As my friend says, "Cucumbers are important for cancer mortality. More than 99% of cancer victims have eaten cucumbers."

Unknown said...

Yes I did drop a 0 and have changed it to 1000. Thank you Maya.

The point of my comment is that it is premature to rule out environmental causes of autism not to suggest that any one factor mercury, lead or cucumbers should be accepted as being causal factors. We are continuing to dump known toxins into our environment though and it seems to me foolish to assert that these substances will have no effect on our vulnerable children. More study? Absolutely.

Anonymous said...

The comment was great. It's getting a little late for the dogmatic sketpics with the latest legal and medical news but they keep at it.


That's a standard quackwatch and industry marketing technique - talk around the problem and pretend that there is uncertainty, then add in a nifty analogy to confuse the issue. Do you actually believe that your cucumber analogy applies to anything in particular, with regards to things like lead, pesticides and mercury? Inject an ape with ethyl mercury - watch it go into the brain - end of story.

It's all nice to be skeptical of toxicology and want more studies done on different chemicals, but come on now, cucumbers? You've been reading too much from Dr. Barrett.

There will be no way to please some people with regards to individual chemicals, so the tactic being used right now is to identify the part of the body actually causing an affliction like autism (mitochondria, glutamate receptors, etc) and then find the types of pollutants that are all known to affect that part. Smoking was easy to solve : lungs - smoke damaging lungs - easy, yet the marketing techniques of obfuscation helped keep the proper conclusions from being drawn for years.

Maya M said...

Anonymous, could you please give a link to the study showing that ethyl mercury causes an autism-like condition in a monkey model?
"That's a standard quackwatch and industry marketing technique - talk around the problem and pretend that there is uncertainty..."
So you claim that there is certainty regarding the environmental causation of autism? Any links, please?
There is some certainty regarding some of them. Valproic acid, thalidomide, rubella during pregnancy. Premature delivery. Not treating PKU.
There is NO certainty yet regarding common environmental polutants.
In fact, there is more certainty about the cucumber and cancer issue. Overdosing nitrogen-containing fertilizers can lead to nitrates accumulation in cucumbers and other vegetables. Inside our body, these nitrates turn into nitrites, and the latter are carcinogenic.
It is quite legitimate to study the impact of toxins and carcinogens derived from food (such as cucumbers), to impose safety limitations, to improve fertilization methods etc.
It is NOT legitimate to say, "We have found the cause! It is cucumbers! Why are you denying it? You are a paid agent of cucumber growers who are naturally opposing the much needed ban on cucumbers!" This is an exact analogy of what some people are doing.
And you know what "types of pollutants are all known" to affect mitochondria and glutamate receptors? Such erudition makes me stay silent in awe.

Maya M said...

Minimizing environmental pollution is beyond doubt a good thing. Moreover, it is our duty to the future generations. I am happy that lead was removed from car fuel and household dyes, that thimerosal was taken away from mandatory vaccines and that an increasing proportion of thermometers are mercury-free.
However, I am not at all happy when practitioners of alternative medicine scare parents into applying on their children "detoxifying" protocols of unproven efficiency and even safety.
Recently, a mother of an autistic child blogged about some guy who had a theory that a particular type of cosmetics could cause autism, and admitted she had used this very cosmetics during her pregnancy. I advised her not to feel any guilt before the know-all manages to grow autistic pups by doing make-up on pregnant mice.
Being autism parent is hard enough without people making you crazy.

Anonymous said...

Hey Autism Reality NB,
Great suff pal!!
My son is suffering from autism from 2 months.Is cure of autism possible?

Tom said...


Autism is treatable with biomedical intervention combined with behavioral therapy (ABA, Greenspan, and RDI being the main three). Speech and OT are also effective.

Biomedical treatment information is available at www.generationrescue.com.

I stand behind biomedical intervention because it helped my own son to recover (about 80% to 90%) from his symptoms. We also used behavioral therapy (Greenspan, then RDI) for about 3 1/2 years.

Terri Lewis

Anonymous said...

Maya, you know precisely the type of chemicals that affect mitochondria the same as everyone else who has been keeping up with the news. I shouldn't have to explain it to you. If you want to deny that mercury is one of them, go ahead. The paper that details mercury's affect on glutamate receptors has been around for years, since 2000. Ever wonder why genetic research into autism has been focusing on genes controlling glutamate.

The ape/ethyl mercury deal is well known also, and I can see you probably have heard of it. No, the apes did not get autism. They got ethyl mercury in the brain, precisely where kids would get it deposited once it left the blood quickly, as shown by the recent Pichinchero "kids excrete mercury quickly" paper. Of course, he concluded the mercury went from the blood and all got excreted, like magic.

Way too much quackwatch-style skepticism. Pollutants are not innocent until proven guility. One should prove their safety first, or at least figure out which people are more succeptible to injury. Are you at least in agreement with that.

Anonymous said...


Those "scare-happy" alternative doctors are now working with the AAP, even though they are probably loathe to admit it and the press release has been modified.

It's over. It really is. Just give up the quackwatch arguments.