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Harvard study links high air pollution with increased risk of babies born with autism

SALT LAKE CITY — The first national study of its kind links air pollution to a greater risk of having a baby born with autism, with some pollutants doubling that chance, results that could have significant impact in Utah.

The Harvard School of Public Health looked at the U.S. Environmental Protection Agency's modeling data for pollution, building on two regional studies that examined pregnant women's exposure to multiple pollutants, their baby's delivery date and the location.

Results showed that women who lived in the areas with the highest levels of diesel particulates or airborne mercury were twice as likely to have a child with autism, compared with those who lived in the areas with the lowest levels of air pollution.

For other pollutants such as lead, manganese and methylene chloride, exposure to high levels resulted in a rate 1 ½ times that of women who were not exposed.

"I think this study adds a lot of weight to the evidence that there may be something in pollution that is causing the risk of autism to increase," said Andrea Roberts, the study's lead author and a research associate at Harvard.

The study, published online in Environmental Health Perspectives, is likely to propel even more focus on Utah's air quality problem and give rise to questions given a Centers for Disease Control and Prevention study that said Utah has the highest incidence of autism among its children — 1 in 47 compared with 1 in 88 nationally.

"I would like to see even more research done," said Jon Owen, president of the Utah Autism Coalition. "I think we have the perfect population here to study the effects of air pollution on autism. We have certain months with really bad air and then months with good air. … It seems like a good thing to study."

While pollution may be at its lowest levels across the country since the 1970s, Roberts said that does not mean it isn't a risk factor for autism.

"Even though air pollution has been decreasing, there is exposure to other pollutants, such as what is in plastic," she said. "There are a lot of reasons to have found what we found."

Other risk factors, too, are factored into escalating rates of autism, such as the man's age at fatherhood, Roberts said.

"People are marrying later, having children later," she said.

The study examined data from the Nurses Health Study II, a long-term study at Brigham and Women's Hospital that involved 116,430 nurses. From that group, the study authors looked at 325 women who had a child with autism and 22,000 women who had a child without the disorder.

Roberts said the study had its limitations, such as relying only on the pregnant woman's home address and not factoring in travel to work, school or for other reasons. The study is also a mathematical computation based on EPA data and not based on "actual" exposure.

Still, she said the guiding statistical principle to remember is that a flawed study will show an absence of any link or correlation.

"One thing to keep in mind is when you don't measure things well, you tend to get no association at all, even if there is one. What is more likely in this case is that the relationship is stronger because we did not measure the pollutant exposure as well," Roberts said.

Ideally, it would have been more revealing to equip all the study women with individual air pollution monitors, she said.

"By no means is this study definitive," she said. "I think this opens the way to explore this more."

Owen hopes so.

"My son is 6, and he was born in May," he said. "That means my wife was pregnant during the inversion here in Salt Lake City."


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