AUTISM: Bad air, genetics add up to higher risk

Posted on Dec 7, 2013

AUTISM: Bad air, genetics add up to higher risk

Air pollution and a common genetic makeup may interact to significantly increase a baby’s risk for autism, USC scientists found.

The researchers at USC’s Keck School of Medicine cautioned in an interview that they need to do more studies to replicate their findings.

The study, to be published in the January 2014 edition of the journal Epidemiology, found that children with the specific gene who spent their in-utero months and their first year after birth in polluted areas of California had three-fold higher risks for autism disorders.

“We need to do more studies, but the genetic disposition and air pollution appear to work together to increase the risk of autism more than the risk of each one alone,” said the study’s lead author, Heather E. Volk, an assistant professor of research in preventive medicine at the medical school.

Volk’s earlier work found that children had twice the risk of developing autism if their mothers lived within 1,000 feet of a busy freeway during pregnancy.

For this research, Volk collaborated with genetics expert Daniel B. Campbell, an assistant professor in psychiatry and behavioral science at the USC medical school.

Campbell explained by telephone that roughly half the population has what geneticists call the “MET receptor tyrosine kinase gene.” The gene is found in about 60 percent of people who have autism, indicating that those with the gene have a higher risk, he said.


To probe the potential interplay between the gene and air quality, Volk, Campbell and their colleagues analyzed the genetics and air pollution exposures of 408 children in the Sacramento, San Francisco and Los Angeles areas; the children’s cases already were being tracked for research purposes. Of those children, 252 met the diagnostic criteria for the spectrum of autism disorders.

Using regional air quality readings and traffic proximity data, the research team determined each child’s air pollution exposure while they were fetuses and in their first year after birth — a critical period in the development of the brain and other organs. The scientists used a blood test to determine each child’s genetics.

The team found no increase in the autism risk among the children who had the gene but breathed relatively clean air. But those who had the gene and were exposed to air pollution were three times more likely to have the disease, Volk said.

Beth Burt, president of the Autism Society Inland Empire, said she appreciates the research.

“It is fascinating and important work,” said Burt, a Corona resident who has an autistic son who is 20.

“It is not an either/or situation — genetics or the environment,” she said. “But it may be the combination of a genetic predisposition with an environmental trigger.”

Lillian Vasquez, who also has a 20-year-old son with autism, said she was not surprised by USC’s findings.

She said she has always thought autism was the result of genetics and some sort of trigger, such as a vaccination or an artificial sweetener.

“Air pollution as a trigger seems quite plausible,” she said.

Vasquez, vice president of the Inland autism society, has lived in Colton since before her pregnancy. Colton, like most of the Inland area, has long had unhealthful levels of air pollution.


Autism disorders are incurable, lifelong brain disabilities characterized by problems with social interaction, communication and repetitive behaviors. The Centers for Disease Control and Prevention estimates that one in 88 children in the United States has an autism disorder.

Thousands of studies have linked air pollution to lung, heart and circulatory disorders.

The work by Volk and her colleagues, however, is part of a newer body of work linking air pollution to brain ailments. Other research has found that such pollution may play a role in Alzheimer’s and Parkinson’s diseases, learning problems and depression.

Other research also has probed the potential for harmful connections between air pollution and genetics.

In one recent study, rats exposed to freeway pollution in Riverside showed early signs of brain tumors — the brains cells of the animals started producing genes associated with tumors. The research, however, did not show whether the tumors actually developed.

Air pollution science is particularly important to Inland Southern California.

In 2012, the annual averages for fine-particle pollution, a category that includes diesel soot, exceeded the federal clean air standards at monitoring stations in Mira Loma and Rubidoux areas of Jurupa Valley in northwest Riverside County. The standard was also exceeded in Fontana and Ontario in western San Bernardino County.

Ozone, a corrosive gas, exceeded the federal standard 111 times somewhere within Southern California’s sea-to-mountains air basin in 2012; most violations were in Riverside and San Bernardino counties.

“As a mother and a member of society,” Burt said, “I think we are kidding ourselves if we think air pollution is not affecting our health.”