More Evidence Environment Is Impacting Autism



Evidence continues to mount that environmental exposures prior to pregnancy are contributing to rising autism rates. Most recently researchers submitted the results of three studies at the International Society for Autism Research conference in Spain, tying increased autism risk to pregnant mothers’ exposure to air pollutants and to insecticides used in the home. Iron supplementation prior to and during early pregnancy was found to reduce autism risk. Autism rates have jumped to one in 50 kids according to the latest findings from the Centers for Disease Control and Prevention, with boys still four times as likely as girls to be diagnosed with the disorder. Autism spectrum disorder, or ASD, is defined by the CDC as “mild to severe impairments in social interaction and communication along with restricted, repetitive, and stereotyped patterns of behavior, interests, and activities.”

While increases in diagnoses and better diagnoses of milder forms of autism have contributed somewhat to this increase, there is a real rise in autism cases over the past two decades that cannot be accounted for by genetics alone. In fact, a 2011 study by researchers at Stanford University reversed the notion that genes, not environmental factors, account for most autism cases. The researchers studied 192 pairs of twins, 54 identical and 138 fraternal, in which at least one child from each pair had been diagnosed with autism. They found that genes accounted for 38% of autism risk while environmental factors were responsible for 62%. “Our work suggests that the role of environmental factors has been underestimated,” said lead researcher Dr. Joachim Hallmayer at the time the findings were published in the Archives of General Psychiatry.

In one recent study, researchers from the Harvard School of Public Health zeroed in on traffic-related air pollutants including ground-level ozone, nitrogen dioxide and particulate matter to see how they impacted autism outcomes for children of Los Angeles mothers born between 1995 and 2006. They were able to identify more than 7,000 children with autism who met the study criteria. They found that a mother’s exposure to high levels of certain air pollutants—such as diesel particles—increased the risk of having a baby with autism by 30% to 50%. The strongest associations were seen with ozone and fine particulate matter.

Dr. Beate Ritz of UCLA, the study’s senior author, noted that these pollutants are ubiquitous, particularly in congested cities, and could only advise expectant moms to avoid sitting in traffic where possible. It is not the first study to link autism risk to air pollutants. “At this stage it does seem there’s something related to air pollution,” said Dr. Weisskopf, a professor of environmental health and epidemiology.

Irva Hertz-Picciotto, an environmental epidemiologist at the University of California, Davis, who presented the study on insecticides, said: “The exciting thing about looking at environment, or environment and genes in conjunction with each other, is this provides the possibility of intervention.”

Hertz-Picciotto is one of many researchers involved in the CHARGE Study (Childhood Autism Risks from Genetics and the Environment) at UC Davis which is looking at the way genes and environmental factors contribute to rising autism rates, including lack of prenatal vitamins and supplementation. During the autism conference, CHARGE revealed the results of a study comparing 510 kids with an ASD to 341 without autism. They found that mothers who reported having taken iron supplements before or during early pregnancy had a 40% decrease in risk of having a child with autism.

While researchers cautioned that pregnant mothers should seek a physician’s advice before boosting their iron supplementation, researcher Rebecca Schmidt noted that “It’s much easier to change your diet or supplemental intake than it is to change your exposure to many other toxins.”

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