Also, children born to mothers who lived near freeways in California were more likely to be autistic, according to a 2011 study by University of Southern California researchers.
“Diesel and these other air pollutants are something that a broad segment of the population is exposed to. It’s important to look at these things,” said Michael Maloney, executive director of the nonprofit Organization for Autism Research.
Maloney said parents “naturally want to know what causes autism.”
“Some parents have an absolute certainty that something specific caused the condition, such as vaccinations,” Maloney said, referring to ongoing controversy over whether child vaccines spur autism. “But most just want to know how to help their child.”
Certain genes are linked to the disorder, according to the National Institutes of Health. Studies suggest that defective genes, which can disrupt fetal brain development, could result in autism disorders. And researchers are increasingly looking at environmental pollutants, which could spur defective genes.
“There are a couple of things we do know – these things [pollutants] are neurotoxins and they can pass from mother to the fetus while it’s still developing,” Roberts said. “And some of these chemicals can cause genetic mutations – the type associated with autism.”
Kalkbrenner said it’s also possible that the pollutants are not allowing the nervous system to develop naturally or hampering the ability of immune cells to help neurons move efficiently.
Hertz-Picciotto, who was senior author on a 2011 study that found prenatal vitamins were associated with decreased autism risk, said the disorder is likely caused by a number of factors.
“Maybe air pollution is a problem, mother’s nutrition probably plays a role,” she said. “And then some children are more than likely just more susceptible.”
Roberts said a good next research step would be to take blood samples from pregnant women or from babies to measure some pollutants.
But not all pollutants end up in the blood so they are difficult to measure. And autism’s nature makes teasing out a definitive cause difficult.
“If you follow hundreds of children from birth, only a couple will have autism. You can enroll 100,000 children in a study, but it’s prohibitively expensive,” Kalkbrenner said. “Or you can follow them after they’re diagnosed – but it’s the exposures very early in life that we’re concerned about. So by the time they’re diagnosed, it’s too late.”
This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.