Researcher finds proximity to freeway associated with autism

Dec 17, 2010
This is Dr. Volk of the Community, Health Outcomes & Intervention Research Program at The Saban Research Institute of Children’s Hospital Los Angeles, the Zilkha Neurogenetic Institute and the Department of Preventative Medicine at USC. Credit: photo courtesy of Heather Volk

Living near a freeway may be associated with increased risk of autism, according to a study published by a team of researchers from Children's Hospital Los Angeles, the Keck School of Medicine of the University of Southern California (USC) and the UC Davis MIND Institute.

The paper will appear online in the journal this week.

"Children born to mothers living within 309 meters of a freeway appeared to be twice as likely to have autism," said Heather Volk, PhD, MPH, and first author on the study. Dr. Volk holds a joint appointment at the Community, & Intervention Research Program at The Saban Research Institute of Children's Hospital Los Angeles, the Zilkha Neurogenetic Institute and the Department of Preventative Medicine at USC.

Autism is a developmental disorder that has long been ascribed to genetic factors. While changes in diagnostic criteria and increased awareness have been thought to contribute to the rising incidence of the disorder, these factors alone cannot explain the dramatic increase in the number of children affected. The Centers for Disease Control reported a 57 percent increase between 2002 and 2006. This study supports the theory that environmental factors, in conjunction with a strong genetic risk, may be one possible explanation for the increase.

While little is known about the role of environmental pollutants on autism, air pollution exposure during pregnancy has been seen to have physical and developmental effects on the fetus in other studies. Exposure to air pollution during the first months of life has also been linked to cognitive developmental delay. However, the authors said that this study is the first to link exposure to vehicular pollutants with autism risk, though direct measurements of pollutants were not made.

Data from children with autism and typically developing children, who served as controls, were drawn from the Childhood Autism Risks from Genetics and the Environment (CHARGE) study, a population-based case-control study of preschool children. Children were between the ages of 24 and 60 months at the start of the study and lived in communities around Los Angeles, San Francisco and Sacramento. Population-based controls were recruited from state of California birth files, and were frequency matched to the autism cases by age, gender, and broad geographic area. Each participating family was evaluated in person. All children were assessed; assessment of autism was done using well-validated instruments.

The study examined the locations where the children's families' lived during the first, second and third trimesters of their mothers' pregnancies, and at the time of the baby's birth and looked at the proximity of these homes to a major road or freeway. The participants' gestational ages were determined using ultrasound measurements and prenatal records.

Dr. Volk and her colleagues found that living within 309 meters of a freeway (or just over 1000 feet) at birth was associated with a two-fold increase in autism risk. This association was not altered by adjustment for child gender or ethnicity, maximum education in the home, maternal age, or prenatal smoking. The researchers found no consistent pattern of association of autism with proximity to a major road.

Traffic-related air pollutants have been observed to induce inflammation and oxidative stress in toxicological and human studies. The emerging evidence that oxidative stress and inflammation are involved in the pathogenesis of autism supports the findings of this study.

"We expect to find many, perhaps dozens, of environmental factors over the next few years, with each of them probably contributing to a fraction of cases. It is highly likely that most of them operate in conjunction with other exposures and/or with genes," said Irva Hertz-Picciotto, PhD, chief of the division of environmental and occupational health in the Department of Public Health Sciences at UC Davis, and principal investigator on the CHARGE study.

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Provided by Children's Hospital Los Angeles

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User comments : 15

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mileyshadglands
5 / 5 (3) Dec 17, 2010
Let us not forget, correlation != causation
Skeptic_Heretic
2.8 / 5 (6) Dec 17, 2010
"Children born to mothers living within 309 meters of a freeway appeared to be twice as likely to have autism,"
What an arbitrary number.

This already smacks of "data forced to fit supposition".
The researchers found no consistent pattern of association of autism with proximity to a major road.
Then what does the headline have to do with the article?
"We expect to find many, perhaps dozens, of environmental factors over the next few years, with each of them probably contributing to a fraction of autism cases.
Expect to be wrong.
geokstr
3 / 5 (4) Dec 17, 2010
And no mention at all of the fact that the very definition of "autism" itself has been expanded to obscene levels, just like that of ADHD, to where the majority of the population could probably be called "sufferers".

But hey, we do need lots of useless "projects" and "studies" and "analyses" to soak up all the earmarks Congress uses to buy votes with. I mean, after all, what would all the graduates of the Marxist "Studies" and "-ism" departments do if they didn't get major funds with which to properly deconstruct and vilify America with.

Get a job flipping burgers, maybe.
Sinister181
3 / 5 (2) Dec 17, 2010
They'll say anything to make it look like they have an explanation.
erikreinertsen
5 / 5 (3) Dec 17, 2010
This already smacks of "data forced to fit supposition".


They said "appears", it was an observation. The hypothesis was generalized, this isn't a penetration analysis or diffusion study.

The researchers found no consistent pattern of association of autism with proximity to a major road.


It's either worded ridiculously poorly (typo?), or they mean that freeways are different than "major roads". We'd expect a slight, but lesser correlation when the scale of the road decreases, assuming car-produced pollution was a contributing factor.
MatthiasF
5 / 5 (5) Dec 17, 2010
Homes close to freeways are also generally cheaper. Have they looked at family incomes?
trekgeek1
5 / 5 (2) Dec 17, 2010
Homes close to freeways are also generally cheaper. Have they looked at family incomes?


Exactly what I was thinking.
bmcghie
1 / 5 (1) Dec 18, 2010
Homes close to freeways are also generally cheaper. Have they looked at family incomes?


Exactly what I was thinking.


I didn't want to say it. :) I'm sure the people who can afford to live further away from a noisy road can also afford a balanced and nutritious diet for their developing child... just sayin'.

I hate these bullshit studies.
Mayday
5 / 5 (1) Dec 18, 2010
And now the houses close to freeways are going to be REALLY cheap!
mysticfree
5 / 5 (1) Dec 18, 2010
Given the millions of highway miles in American, should there be a lot more autistic children than there is?
Skeptic_Heretic
5 / 5 (2) Dec 18, 2010
Given the millions of highway miles in American, should there be a lot more autistic children than there is?

You'd expect to see more incidences of autism in Europe seeing as they are far more densely populated than the US.
Quantum_Conundrum
not rated yet Dec 19, 2010
Homes close to freeways are also generally cheaper. Have they looked at family incomes?


By implication, yes.

The paragraph about 3/4 of the way down says that adjusting for various factors like education does not change the results.

arbitrary number


It's a statistical number. If they had given a perfectly round number like 300, then it would be slightly suspect.

If you are calculating means, modes, medians, and standard deviations from real world data sets, expect to get odd-ball numbers, not perfectly round numbers.

---

I am, however, curious as to how exactly they distinguish a "freeway" from a "major road", and why there should be no correlation to proximity a "major road," but strong correlation to proximity to a "freeway".

A major road would have lots of traffick of all types too.

Is a "freeway" made out of an aggregate or structural component, something toxic, that a "major road" isn't made out of?
Quantum_Conundrum
not rated yet Dec 19, 2010
Ok, everyone in the south just calls a "free way" the "interstate". Nobody ever uses the ter "free way" around here. Only time I ever hear it is sometimes on internet, and in the Roger Rabbit movie long time ago.

Well then, "free ways" most certainly have many components that "major roads" may or may not have

Concrete instead asphault
Steel re-bar and/or wire
lime added to soil in road foundation
overhead lighting which may or may not have toxic bulbs
metallic expansion joints

more traffick density, on average
slightly more trucking accidents (chemical, gases, etc)*

*note that if there is a chemical spill following an accident, traces of the chemical would spread along the interstate at 70mph in both directions, not counting speeders.

So if someone spilled, or had a trace leak, involving dioxin, chlorine, or any other terratogen or poison it could spread both ways at 70mph, and that would be sufficient to cause enormouse spike in birth defect occurence.
Quantum_Conundrum
not rated yet Dec 19, 2010
If truck A and truck B both have trace chemical leaks, then even if neither truck is leaking something harmful, the chemicals may or may not be able to combine to make something else harmful.

Now consider the way freeways work, and people are driving adjacent to one another for potentially hours on end for trucks. They could be leaving a trail for dozens or even hundreds of miles, having a trace amount of chemicals, that in some instances combines to make a trace amount of terratogenic compound. That's all it would take to do this sort of thing statistically, even if such a scenario happened just once in a long time per any given road.
suntraider
not rated yet Dec 19, 2010
freeway?? How about more trucks and more use use of air brakes? As an extra...people having the need to express their community services in the underpasses using paint spray. then the theatre and hairspray.

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