give a hoot, don’t pollute!

In Autism Spectrum Disorders on Tuesday, 27 November 2012 at 15:26

High Levels of Pollution May Boost Autism Risk

By: Pam Harrison

Exposure to the highest levels of traffic-related air pollution during pregnancy and the first year of life increases the risk for autism, a case-control study shows.

Heather Volk, PhD, MPH, and colleagues from the Keck School of Medicine at the University of Southern California, in Los Angeles, found that children exposed to the highest levels of both particulate matter and nitrogen dioxide during pregnancy and the first year of life were 3 times more likely to have autism than children with the lowest levels of exposure.

“Previously, we looked at how far an individual lived away from a freeway or a busy road as a proxy for pollution exposure,” Dr. Volk told Medscape Medical News.

“In this study, we looked at modeled traffic-related pollution exposure and data from a regional air quality monitoring system so we could look at the actual amount of pollution to which the mother was exposed.

“Based on our data, it does seem to be the estimated level of exposure that increases the risk of autism, as there wasn’t any effect on autism risk from any of the other risk factors we analyzed.”

The study was published online November 26 in the Archives of General Psychiatry.

Hazardous to the Brain

In 2010, Dr. Volk and colleagues published an article reporting an association between the risk for autism in the Childhood Autism Risks from Genetics and the Environment (CHARGE) study cohort and living within 1000 feet of a freeway.

In this study, 279 children with autism and 245 control children with typical development from the same CHARGE study were analyzed.

Eight-four percent of the children in the study were boys.

Investigators used regional air quality data for exposure to particulate matter less than 2.5 μm (PM 2.5) and less than 10 μm (PM 10) in diameter as well as exposure to ozone and nitrogen dioxide.

The data were derived from the US Environmental Protection Agency’s Air Quality System data.

Unlike exposure to the highest levels of traffic-related air pollutants, exposure to the second and third quartiles of traffic pollutants was not associated with an increased risk for autism.

On the other hand, exposure to the highest quartiles of traffic-related air pollutants during pregnancy increased the risk for autism almost 2-fold compared with exposure to the lowest quartiles of air pollutants.

The authors also found that during all 3 trimesters of pregnancy, there were associations with the highest quartile of exposure to air pollutants and autism risk compared with the lowest quartile of air pollutants.

High levels of exposure to PM 2.5, PM 10, and nitrogen dioxide were also associated with an increased risk for autism.

In contrast, investigators did not find any association between exposure to regional ozone and autism.

Table: Risk for Autism for 524 Children, by Quartile of Traffic-Related Air Pollution

  4th Quartile 3rd Quartile 2nd Quartile
1st year of life (adjusted odds ratio) 3.10 1.00 0.91
All pregnancy (adjusted odds ratio) 1.98 1.09 1.26


“From studies conducted in the lab, we know that we can breathe in tiny particles, and they can produce inflammation,” said Dr. Volk. “Particles have varied composition, and there are many chemicals that can bind to them. The components of these particles could be hazardous to the brain.”

Highly Prevalent Disorder

In an accompanying editorial, Geraldine Dawson, PhD, University of North Carolina, Chapel Hill, points out that the prevalence of autism spectrum disorder (ASD) has increased by 78% in the past 6 years alone.

“The alarming rise in prevalence has led to more scrutiny of environmental risk factors, such as the study on air pollution as a risk factor for autism,” she added.

Although the study by Dr. Volk and colleagues was not the first to report an association between air pollution and autism risk, “the study is notable for its regional measurement of nitrogen dioxide and particulate matter,” Dr. Dawson states.

Moreover, results from the current study could not be attributed to ethnicity, parental education, smoking during pregnancy, or living in a densely populated region, she also notes.

According to Dr. Dawson, more research on risk factors and ASD is needed to develop strategies for preventing or reducing the disabling symptoms associated with this “highly prevalent and costly neurodevelopmental disorder.”

The study was supported by a grant from the National Institute of Environmental Health Sciences and by the MIND Institute. Dr. Volk reports receiving support from Autism Speaks to present research findings at the International Society for Environmental Epidemiology Meeting in 2012. Dr. Dawson has disclosed no relevant financial relationships.

Arch Gen Psychiatry. Published online November 26, 2012. AbstractEditorial

Retrieved from: http://www.medscape.com/viewarticle/775077?src=nl_topic


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