Air pollutants linked to autism

A study finds that air pollutants, such as those from cars and trucks, may increase risk for autism development.

A researcher at the University of Wisconsin-Milwaukee (UWM) has added to a growing body of evidence that links autism to air pollutants such as those generated by cars and trucks.

Amy Kalkbrenner's study, published this week online at the journal Epidemiology, showed that pollution's impact on autism rates in North Carolina is similar to results of pollution-autism studies in California -- despite weather and climate differences between the two states.

In addition, the work of Kalkbrenner and her colleagues, building on previous studies, showed that women in the third trimester of pregnancy were more susceptible to the damaging effects of air pollution on their unborn child.

"It adds another piece supporting the hypothesis that environmental chemicals are part of the autism puzzle," says Kalkbrenner, an assistant professor in UWM's Joseph J. Zilber School of Public Health. Autism, a spectrum of disorders affecting interpersonal relations and work achievement, now affects some 1 in 68 children in the U.S.

Her research team focused on exposure to coarse and fine particulate matter, known as PM10, which arises in part from traffic-related air pollution. The study evaluated records in the two states, covering pre-conception through the first birthday for 87,000 children in North Carolina and 77,500 in California born in the mid-to-late 1990s. Key regions in each state were selected based on researchers' ability to simultaneously measure the level of particulate matter present, and know which children had autism in these regions.

Researchers used a new, more exact tool to measure the levels of particulate matter in smaller slices of time, based on pollution at the family's address during pregnancy. With this method, they were able to compare exposures during specific weeks of pregnancy. The approximately one thousand children who later developed some form of autism spectrum disorders were then compared to all other children.

Kalkbrenner says it was important to look at eastern states because of the differences in climate, seasonal weather patterns and the chemical make-up of the particulate matter that might impact brain development. "Evidence for a link between a chemical exposure and a health impact like autism is stronger when it can be shown in more than one region." The team found that the concentration of particulate matter was highest among children born in summer months in North Carolina and those born in fall and winter months in California.

Reasons for increased susceptibility in the third trimester of pregnancy are not known at this time. However, Kalkbrenner says this finding is consistent with theories that show links between autism and altered brain network development, specifically synaptic connections that are developing during the final months of pregnancy.

"We've now had three solid studies saying the same thing. The evidence is pretty compelling that something is going on with air pollution and autism," says Kalkbrenner, who adds that further study is needed to determine the neurodevelopmental impacts of specific chemical pollutants during precise developmental windows.

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Autism and the environment

A study discusses how environmental factors may increase a person's risk of developing autism.

A large U.S. study suggests environmental pollution might be contributing to autism risk, although the specific culprit toxins remain unknown.

Researchers analyzed medical records and found a correlation between U.S. counties' autism rates and their rates of genital birth defects in boys, which could be a sign of some common environmental contributors.

However, the findings, which were reported March 13 in the journal PLoS Computational Biology, do not prove that any particular environmental exposure directly raises the risk for the developmental disorder, experts said.

There's no "smoking gun," said Alycia Halladay, senior director of environmental and clinical sciences for the advocacy group Autism Speaks.

"This study was not designed to figure out what the [environmental] factors are," said Halladay, who was not involved in the research.

Still, she said, experts believe autism arises from a combination of genetic vulnerability and any number of environmental exposures. Some suspects include infections such as flu during pregnancy, certain prescription drugs taken during pregnancy and environmental toxins.

These latest findings support the "scientific agreement that it's a mix of genes and environment," Halladay said.

The lead researcher on the study agreed. "Both genes and environment are important," said Andrey Rzhetsky, a professor of genetic medicine at the University of Chicago.

The task ahead, Rzhetsky said, is to figure out which environmental exposures matter.

Autism refers to a collection of disorders, usually diagnosed during childhood, that affect language and social skills.

For the study, Rzhetsky's team analyzed nearly 100 million U.S. health insurance claims for a county-by-county look at rates of autism and intellectual disability. They also examined rates of genital malformations in boys -- such as micropenis, undescended testicles and hypospadias (in which the urethral opening is on the underside of the penis).

Those genital malformations were used as an indicator of parents' exposure to environmental pollutants, Rzhetsky said. The exact causes of those birth defects are not clear, but some studies have suggested that certain environmental toxins -- including pesticides and lead -- might play a role, he said.

In this study, county rates of genital birth defects ranged from none to just over 2 percent. Overall, the researchers found, for every 1 percent increase in those birth defects, the rate of autism rose by close to 300 percent.

Even accounting for county demographics, a strong link existed between rates of genital defects and autism, Rzhetsky said.

But the reasons for the correlation aren't clear. Genes could play some role, Rzhetsky said, and so could environmental factors other than pollutants.

Halladay said endocrine disruptors -- chemicals found in plastics, food cans and other everyday products -- have been linked to genital birth defects. But so far, researchers haven't found a connection to autism risk.

On the other hand, some studies have found a link between high exposure to air pollution during pregnancy and an increased autism risk, Halladay said.

Researchers continue to look for the environmental players in autism, Halladay said. Autism Speaks has a program that funds research on the environmental factors -- including toxic exposures and nutrition during pregnancy -- that might affect autism risk.

Rzhetsky said he hopes his team's findings help fuel the interest in that type of research. "There is a lot of research focused on the genetics," he said. "But environment plays a big role."

But chemicals in the environment are only one potential reason autism rates vary across the United States.

Rzhetsky's team also found lower rates of autism in states where regulations require a doctor's diagnosis of autism before kids can qualify for special education.

Halladay said the finding is consistent with past studies suggesting that differences in diagnosis help explain regional differences in autism rates.

A 2012 study from the U.S. Centers for Disease Control and Prevention found that one in 88 U.S. children had an autism spectrum disorder -- up almost 25 percent from just a few years before. But the rate varied widely, from one in 47 in Utah to one in 210 in Alabama.

Experts speculated that the national increase had a lot to do with better detection, and that differences in awareness and autism services might explain the regional differences.

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Study claims heavy metal removal does not help autism symptoms

Let's ring in the new year by dispelling some "neuro flapdoodle"! -  A study shows that removing heavy metals from the blood through a process called chelation does not help children who have autism. JR

Removing heavy metals from the body through a process traditionally used to treat mercury and lead poisoning doesn't help relieve autism symptoms, a new analysis suggests.

During chelation therapy, patients are given injections of a chemical that binds to heavy metals, lowering their concentration in the blood and ultimately allowing the metals to be excreted through urine.

Chelation gained traction as an alternative treatment for autism due to a theory that mercury poisoning might play a role in the developmental disorder. However, evidence hasn't supported that idea and it's been essentially discarded in the scientific community, researchers said.

The procedure also carries safety concerns, including risks of kidney damage and gastrointestinal problems.

Lead researcher Tonya Davis from Baylor University in Waco, Texas, said the study team's goal was not to tell parents which treatments they should or shouldn't seek for their children.

"I see that they want to try everything, and they are well intentioned," she told Reuters Health.

"But there are risks involved with any treatment choice, and some of those risks are very serious. So far science does not support (chelation) as being an effective treatment, and that's a big risk to take when you have limited resources and limited time."

The Centers for Disease Control and Prevention estimates that one in 88 kids in the U.S. has an autism spectrum disorder.

Davis and her colleagues found five studies that tested the effects of chelation in kids with autism. Those studies each had between one and 41 children, from age three to 14.

Researchers had given the kids chelation therapy - sometimes along with vitamin supplements or other treatments - between one and 12 times a week for up to seven months. They used tests and questionnaires or anecdotal reports from parents to see how symptoms changed over time.

The study with only one child, a four-year-old boy, found chelation had positive effects on autism symptoms based on a parent report. The other four studies all showed mixed results, with some kids improving on some symptom measures.

However, none of the studies provided any certainty that those benefits were due to chelation itself, and not another treatment or just kids getting older, the researchers wrote in the journal Research in Autism Spectrum Disorders.

Davis said she and her colleagues were surprised to find so few studies measuring the effects of chelation, given how many families they each knew that were using it. That lack of evidence was a concern, she said, along with the questionable study designs and conclusions.

"I just hope that parents get as much information as they can" before trying a new treatment, Davis said.

A typical package of chelation treatments runs for about $2,000 to $5,000. In addition to treating lead poisoning, chelation has also been used for cancer and heart disease.

But when it comes to autism, even calling chelation an alternative therapy is a stretch, said one autism researcher not involved in the new study.

"There's really no evidence that mercury causes autism or has a place in causing autism, and also we know that chelation can be dangerous as well. Even the underlying theories don't make sense," said Dr. Joyce Mauk, head of the Child Study Center, an organization that treats kids with developmental disabilities in Fort Worth, Texas.

"Most children with developmental disabilities, what gets them better is a really skilled therapist and lots of work," Mauk told Reuters Health.

"If you hear about something when all you do is inject something or take a pill, it's unlikely to work."

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Study: Autism Risk for Developing Children Exposed to Air Pollution

This study discusses a possible link between exposure to air pollution during pregnancy or while an infant and the development of autism in the child. Is this another epigenetic factor? JR

Research conducted by University of Southern California (USC) and Children's Hospital Los Angeles scientists demonstrates that polluted air -- whether regional pollution or coming from local traffic sources -- is associated with autism.

The study titled "Traffic Related Air Pollution, Particulate Matter, and Autism," shows that exposure to traffic-related air pollution during pregnancy and the first year of life is associated with a more than two-fold risk of autism. In addition, exposure to regional pollution consisting of nitrogen dioxide (NO₂) and small particles -- particulate matter less than 2.5 and 10 microns in diameter (PM2.5 and PM10) -- is also associated with autism even if the mother did not live near a busy road. The study is published in theArchives of General Psychiatry, a sister publication of the Journal of the American Medical Association.

"This work has broad potential public health implications," said the study's principal investigator, Heather Volk, Ph.D., assistant professor of preventive medicine at the Keck School of Medicine of USC and investigator in the Division of Research on Children, Youth and Families at Keck School-affiliated Children's Hospital Los Angeles. "We've known for a long time that air pollution is bad for our lungs, and especially for children. We're now beginning to understand how air pollution may affect the brain."

The research is the first to look at the amount of near-roadway traffic pollution individuals were exposed to and combine that with measures of regional air quality. The study builds on previous research by Volk and colleagues that examined how close subjects lived to a freeway, said Volk, who also has appointments at the Keck School's Zilkha Neurogenetic Institute and Department of Pediatrics.

"We took into account how far away people lived from roads, meteorology such as which way the wind was blowing, how busy the road was, and other factors to study traffic-related pollution," she said. "We also examined data from air quality monitors, which measure pollution over a larger region that could come from traffic, industry, rail yards, or many other sources."

In the 2012 study, Volk and colleagues from USC and the University of California, Davis examined data on 279 autism cases and 245 control subjects enrolled in the California-based Childhood Autism Risks from Genetics and the Environment (CHARGE) study. Mothers' addresses from birth certificates and addresses reported from a residential history were used to estimate exposure during each trimester of pregnancy and the first year of life. The researchers used air pollution levels derived from the Environmental Protection Agency's Air Quality System to determine exposure to NO2, PM2.5, and PM10. They also applied dispersion models to estimate the amount of traffic the mothers and children were exposed to.

Particularly interesting was the effect of mothers' and children's exposure to particles, both PM10 and PM2.5. PM10 includes both coarse and fine particles, while PM2.5 includes only the smaller (fine) particles, which are most likely to have deleterious effects on the human body.

"From studies conducted in the lab, we know that we can breathe in tiny particles and they can produce inflammation," said Volk. "Particles have varied composition, and there are many chemicals that can bind to them. The components of these particles could be hazardous to the brain."

Other researchers who participated in the study include Irva Hertz-Picciotto, University of California, Davis; Rob McConnell from USC; and Fred Lurmann and Bryan Penfold from Sonoma Technology, Inc.

The research was funded by the National Institute of Environmental Health Sciences (grant 1 R21 ES019002-01).

Volk and colleagues are now at work on a study of how genes related to autism may be affected by environmental exposures to try to identify if there are factors that make people are genetically more vulnerable to particular pollutants.

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