Prenatal exposure to air pollution related to autism risk, according to a study

"Not only did we have access to rich data, which allowed us to develop one of the largest studies to date, but we were also able to conduct this study in a city where pollution atmospheric is relatively less important, "he said.

More than 100,000 children studied

Pagalan and his colleagues analyzed the records of 129,436 children born in Vancouver from 2004 to 2009.

"We analyzed the air pollution data in Vancouver during the same period to assess the exposure to air pollution in pregnant women," he said. "Their children were followed for at least 5 years to see if they had been diagnosed with Autism Spectrum Disorder."

The researchers found that, overall, about 1% of children had been diagnosed with autism at the age of 5 years. They compared autism rates among the children of women who had been exposed to the slightest air pollution during pregnancy and rates among the children of the most exposed women.

The three measures of air pollution (particulate matter, nitrogen dioxide and nitric oxide) showed a similar association with autism.

The odds of developing autism in children exposed before birth to higher levels of PM2.5 (particles less than 2.5 micrometers in diameter) were 1.04%, the odds of autism in children exposed to higher levels of nitrogen dioxide were 1.06%. autism in children exposed to higher levels of nitric oxide were 1.07%. This final increase in risk turned out to be "statistically significant", meaning it crossed the straight line of chance and revealed a true relationship.

Pagalan said that the causes of autism are not completely known. "They are complicated and have many factors, but researchers recognize that both genetics and environmental factors play a role," he said.

Experts say that any association between air pollution and autism is at best small.

Autism exists in families and its causes remain unknown

Nevertheless, she believes that the authors have "well addressed" some shortcomings of previous studies on the same subject. For example, the criteria for children with autism included only those who had received a "standard" diagnosis, according to data from the British Columbia Autism Assessment Network.

However, other important factors were not included in the analysis, she added, such as the socio-economic status, which turned out to be related to the # 39; autism.

"In addition, the focus has been on the place of residence of mothers and it is possible that mothers' workplaces have a different environmental composition that it might be important to take into account," he said. she wrote in an email. "It is possible that these pollutants and / or other exposures have an influence on fathers and on the quality of their sperm."

"Autism is highly genetic – we know it because it's practiced in families," said Cusack, who did not participate in the study. He added that the researchers had found that a "very small increase" in the likelihood of having an autistic child in women exposed to increased air pollution, particularly at home. nitric oxide. "Other differences that have not been measured, such as genetic differences, may explain this increase.This study provides no evidence that air pollution causes autism. "

"In general terms, the results of the study were essentially the same for all three pollutants," said McConway, who has played no role in the new research. However, only nitric oxide went "beyond the conventional limit of statistical significance," he said, "and has just passed."

"In studies like this, it's not really possible to really determine what causes what," he said. "Maybe the air pollution really affects [autism] risk, or maybe not. "Although the study" adds more evidence, "he concluded," we are very far from knowing. "

Pagalan said that since there is no curative treatment for autism, "the identification of environmental risk factors helps identify prevention opportunities".