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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Pediatric migraines may be caused by environment

Different environmental factors, such as sleep deprivation, diet, and school, could play a role in pediatric migraines.

Environmental stressors play a large role in triggering migraines in children, according to Dr. Eric Pearlman.

"Migraine is definitely a pediatric disorder. It peaks in young adulthood, but it definitely occurs in kids," Dr. Pearlman, chair of the department of pediatrics at Mercer University in Savannah, Ga., said at the annual meeting of the American Academy of Pediatrics.

Epidemiologic data suggest that migraine occurs in 10.5% of 10- to 15-year-old children and 3% of 7-year-olds, and that headaches – possibly including migraines – occur in 4% of 3-year-olds. By about 13 years of age, the prevalence of migraines starts reaching adult levels of about 6% in males, and 18% in females.

Environmental factors such as sleep deprivation, dehydration, dietary factors, school stressors, hidden stressors (like peers), and hormonal fluctuations represent triggers that can be particularly pronounced in children, he noted.

With International Classification of Headache Disorders, third edition (ICHD-III) criteria, migraines can be differentiated from acute, acute recurrent, and chronic progressive or chronic nonprogressive headaches if a child has experienced at least five attacks lasting up to 72 hours (whether untreated or unsuccessfully treated), if nausea and/or vomiting or photophobia and phonophobia are present, and if the child has at least two of four characteristics, including unilateral location, pulsating quality, moderate to severe intensity, and a tendency to be aggravated by – or avoid – routine physical activity.

In children, photophobia and phonophobia can be inferred (if they report having to lie down in a dark, quiet room, for example), as many have difficulty describing or understanding these symptoms

Unilateral headaches are rare in children, Dr. Pearlman noted.

If a diagnosis of migraine is established, it is important to make the diagnosis known to the child, and to educate the child about the condition and treatments.

Consider providing handouts and referring to websites (such as theAmerican Headache Society or the National Headache Foundationsites), to help educate patients and to manage their expectations, as they need to understand you cannot cure their migraine, he advised.

Involving both the patient and their parents in decision making can improve compliance with treatment recommendations, he said.

Pharmacologic interventions can include nonspecific short-term therapies, migraine-specific therapies, and preventive treatment.

Nonspecific short-term therapies may include acetaminophen, nonsteroidal anti-inflammatory drugs, or combination drugs. Migraine-specific therapies include ergotamine and dihydroergotamine, and the "triptans."

Seven triptans are available, including two that are approved for use in children; rizitriptan (Maxalt) is approved for children older than age 6 years, and almitriptan (Axert) is approved for those aged 12-17 years.

Maxalt comes in both an oral and orally disintegrating form, and is available as a generic drug. Generic sumitriptan (Imitrex) also is available.

"There are good data for most of the triptans for adolescents aged 12 and older," Dr. Pearlman said.

Rescue medications for those who have an inadequate response to short-term therapy can include a combination of an analgesic like a nonsteroidal and an antiemetic, or an opiate and an antiemetic if the patient used a nonsteroidal initially. Rescue medications may be needed "because nothing is going to work 100% of the time," he said.

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