Air Pollution And Autism: Moms' Exposure To Fine Particulate Matter During Pregnancy Ups Risk In Kids

Air Pollution
A new study supports previous research suggesting the environment plays a part in risk of autism. Moms exposed to certain types during pregnancy risk having kids with the disorder. Photo courtesy of Shutterstock

Autism rates in the U.S. have increased 10-fold over the past 40 years, accounting for one in every 68 children. It’s unclear why there are so many kids being diagnosed with the disorder, but scientists have been working tirelessly to find out. With the completion of the Human Genome Project, they’ve been able to analyze the genomes of children with autism spectrum disorder (ASD), and find some signs it’s inherited. But there’s more to it; some research suggests it’s caused by environmental factors, too. Now, a new study finds that mothers who are exposed to certain types of air pollution risk having a child with ASD.

The form of air pollution implicated: fine particulate matter (PM2.5). At only 2.5 micrometers or less in diameter, these particles have diameters 50 times smaller than a strand of human hair, and typically come from construction sites, unpaved roads, fires, power plants, and car and truck exhaust. They’re easily inhaled, which is when they go deep inside the lungs, causing particularly dangerous effects. Research from the Environmental Protection Agency (EPA) has linked PM2.5 to nonfatal heart attacks, irregular heartbeat, severe asthma, impaired lung function, respiratory disease, and premature death.

Researchers from Harvard University’s School of Public Health found that PM2.5 increased a woman’s chances of having a child with autism only if she was exposed to the pollution during pregnancy, especially during the third trimester. “The evidence base for a role for maternal exposure to air pollution increasing the risk of autism spectrum disorders is becoming quite strong,” said senior author Marc Weisskopf, associate professor of environmental and occupational epidemiology, in a press release. “This not only gives us important insight as we continue to pursue the origins of autism spectrum disorders, but as a modifiable exposure, opens the door to thinking about possible preventative measures.”

Although particulate matter can include many types of metals and other chemicals, a study from October found that children whose mothers were exposed to styrene, chromium, or cyanide during pregnancy were 65 percent more likely to develop ASD. In terms of environmental risks, another study from June found that children whose mothers lived near farms or any other land where pesticides were applied to crops had a 60 percent higher chance of developing autism.

For the current study, the researchers looked at the health of children whose mothers participated in the Nurses’ Health Study II, which began tracking 116,000 nurses throughout all 50 states in 1989. After analyzing data on the nurses’ pregnancies and air pollution reports from the EPA, they found that higher levels of pollution were linked to autism risk.

While environmental factors are certainly something to consider in the search for what causes autism, it is research in genetics that will truly discover solutions to preventing the disorder. That’s because environmental factors only tell us a person’s risk at an individual level, while genetic research can show us similarities among a large group of people, and therefore scientists will be able to target specific mutations or abnormalities. Autism Speaks, an advocacy group for people with autism, recently began an ambitious project, called MSSNG, to analyze the DNA sequences of 10,000 families affected by the condition. If it successfully finds correlations in the genome of these families, we’ll be one step closer to bring autism rates down to where they once were, and even further.

Source: Raz R, Roberts A, Lyall K, et al. Autism Spectrum Disorder and Particulate Matter Air Pollution before, during, and after Pregnancy: A Nested Case-Control Analysis within the Nurses' Health Study II Cohort. Environmental Health Perspectives. 2014. 

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