Could Utah's high autism rates be related to Salt Lake County's large number of toxic chemical releases?
University of Utah researchers say the question deserves more study after their preliminary review shows children with autism spectrum disorders and other intellectual disabilities are more likely to have been born near industries that emit toxic chemicals or heavy metals.
"If you take this combined with the other studies [showing links between pollution and autism], it's pointing to something that we need to seriously look at," said Judith Pinborough-Zimmerman, research assistant professor in the U.'s Department of Psychiatry.
She and researchers from the Rocky Mountain Center for Occupational and Environmental Health and the Utah Department of Health presented their findings at The International Society for Autism Research conference last month in San Diego.
They examined the maternal addresses found on birth certificates of children born in 1993 and 1994 in Davis, Salt Lake and Utah counties who were later diagnosed with autism or other mental disabilities. They also mapped the addresses of children without a known neurodevelopmental disorder.
They found that children born to mothers who lived within a mile of what are called Toxic Release Inventory sites that emit certain chemicals and heavy metals were more likely to have those problems. TRI facilities release or dispose toxic chemicals regulated by the Environmental Protection Agency. The EPA maintains a database of all such facilities and the type and amount of chemicals they release.
• The risk of having an autism spectrum disorder was 3.5 times greater for children born within a mile of a site releasing between 5,000 and 10,000 pounds of halogenated chemicals (dioxins, polychlorinated biphenyls and trichloroethylene). There were five such TRI sites emitting at those levels in the mid-1990s.
• The risk of having an autism spectrum disorder was twice as big when living within a mile of one of six TRI sites emitting up to 5,000 pounds of the heavy metals arsenic, cadmium, lead, nickel and mercury.
• The risk for developing an intellectual disability was similarly high within a mile of those sites.
• Oddly, the odds of developing a speech-language impairment was less for children born closer to a TRI site.
Those particular chemicals and heavy metals were chosen because they are suspected endocrine disrupters, which may cause developmental and neurological problems, said Rod Larson, with the Rocky Mountain Center. Most of the chemicals and metals are also known to affect the neurological system, according to the Agency for Toxic Substances and Disease Registry.
Salt Lake County has the second-highest amount of toxic chemical releases in the country, according to the EPA's TRI database. Tooele is ranked 64th.
Earlier in May, Pinborough-Zimmerman released a separate study showing Utah's autism rate among 8-year-olds doubled from 2002 to 2008. The latest report shows 1 in 77 have the disorder, which is marked by difficulties communicating and interacting socially. Children with autism also often engage in repetitive behavior. Many suffer from sleep disorders, anxiety, depression and other medical problems.
But it's too soon to say that living next to TRI sites contribute to the development of autism, cautioned Amanda Bakian, one of the researchers of the TRI study and epidemiologist for the Utah Registry of Autism and Developmental Disabilities.
She said the team plans a more rigorous study that would include controlling for other risk factors, such as maternal age and socioeconomic status. In addition, they want to include air dispersion models to know whether children with the disabilities were downwind and exposed to the chemicals.
The current review didn't include length of exposure to chemicals and heavy metals, or other sources of chemical exposures in the home or workplace.
It also couldn't account for whether the women were potentially exposed to the chemicals during the first trimester of pregnancy, a critical period of development.
"We need to take this study to the next step and have it peer-reviewed and published," Bakian said.
Other recent studies have also shown a link between autism and environmental exposures, such as living near a freeway or living among higher concentrations of some of the metals and chemicals the Utah researchers included.
Brian Moench, president of the Utah Physicians for a Healthy Environment, said the U. pilot study, along with the others, should serve as a wake-up call. "We need to start paying attention to the kinds of exposures we're allowing our families to be subjected to."
He points to one place to draw the line: Kennecott's planned expansion at the Bingham Canyon Mine. While the company maintains it will reduce air pollution with improved technology, Moench and other environmental and health groups are skeptical.
Because heavy metals don't break down, "the impact on public health increases every single year," he said. "It's time we looked at this and said, 'Can we afford the community [to be] continually exposed to these kinds of emissions?' "
Tracking toxic releases
The University of Utah study looked at sites that, in the mid-1990s, were releasing between 5,000 and 10,000 pounds of halogenated chemicals (dioxins, polychlorinated biphenyls and trichloroethylene) or up to 5,000 pounds of the heavy metals arsenic, cadmium, lead, nickel and mercury.
To find out about toxic releases in your neighborhood, go to http://www.epa.gov/tri/.