By Catherine Clabby

Autism researchers have a big problem that tiny baby teeth might help solve.

Evidence is rising that environmental exposures in the womb and after birth may explain some of the rise in autism diagnoses nationally, a count that now includes close to one out of every 68 kids.

shows a baby tooth in a small container, about twice the size of a quarter, which is also pictured
Baby teeth, increasingly valued biological samples, are being packed up in small containers by researchers at UNC and other collaborating campuses for shipment to Mt. Sinai in New York for analysis. Photo Courtesy of Chad Chappell, Carolina Institute for Developmental Disabilities, UNC-Chapel Hill

But what toxins could be causing the trouble? When might exposure be most risky? To answer that, University of North Carolina, Chapel Hill researchers and others around the country are expanding their research to study milk teeth to find out.

Once valued only to lure Tooth Fairy “visits” to a child’s bedroom, deciduous teeth are actually biobanks. Because they begin forming during the embryonic stage of development, the structures absorb and store traces of many compounds — good and bad — that a fetus and later a newborn has contact with.

Technology developed at the Icahn School of Medicine at Mt. Sinai in New York uses a mix of lasers and chemical sensors to read what’s stored within layers of dentine, a hard substance shielded by tooth enamel. Just as tree rings do, new layers formed within these teeth every week or so place what was absorbed in chronological order.

That tool made possible a study published early this month revealing that the teeth of children with autism contain more toxic lead and lower levels of the essential nutrients zinc and manganese when compared to teeth lost by children without autism.

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Using baby teeth as a novel biomarker of early life environmental exposure, researchers from the Lautenberg Environmental Health Science Lab and the Seaver Autism Center for Research and Treatment at Mount Sinai in New York City found ways to discover clues to the development of autism.

The differences detected in the study, funded by the National Institute of Environmental Health Sciences, were most pronounced in the layers of teeth formed before the children were born.

“This can really give you timing as well as amount of exposure,” said

Joseph Piven, director of the Carolina Institute for Developmental Disabilities

at UNC-Chapel Hill, whose research team is now collecting baby teeth from families enrolled in its studies of the younger siblings of children with autism.

A complicated puzzle

The cause of autism is a tough nut to crack because the disorder is really a group of disorders. Some people diagnosed with autism are brilliant, with bear-trap memories and rare talents. Others can be severely cognitively and developmentally impaired.

But no matter where they dwell along the spectrum, people with autism usually share three traits.

They have trouble communicating, whether that be speaking or understanding language. They miss social cues—including facial expressions—that most people read effortlessly. And they partake in repetitive behaviors, such as talking about just one topic or repeating gestures other people consider odd.

It’s certain that genetics contribute significantly to the abnormal brain development suspected to spur autism. If one identical twin has autism, for instance, the second almost always does.

But environmental exposures are also in play, with higher risk of developing autism now tied to exposure to auto exhaust, pesticides and even inflammation experienced by a pregnant woman during pregnancy.

Information, box, courtesy: National Institute of Environmental Health Science

Further complicating things, genetic variation can influence the scale of danger posed by some toxins. Children whose genetic makeup causes them to be more susceptible to the health effects of high levels of air pollution, for instance, are at greater risk for having the disorder.

Looking closer

Piven’s UNC team and its collaborators in the Infant Brain Imaging Study (IBIS) track how physical differences in the brains of children with autism relate to autistic-like behavior.

Technology developed byManish Arora, director of exposure biology at Icahn School of Medicine at Mount Sina in New York uses lasers to probe contents stored in tiny layers that accumulate within baby teeth. Image courtesy of Mount Sinai Health System
Technology developed by Manish Arora, director of exposure biology at Icahn School of Medicine at Mount Sina in New York uses lasers to probe contents stored in tiny layers that accumulate within baby teeth. Image courtesy of Mount Sinai Health System

To try to capture both as they unfold, the team has scanned the brains and recorded the behavior of younger brothers and sisters of kids with autism for years. These siblings are at increased risk of having autism too, with one in five nationally likely to be diagnosed.

The UNC studies have documented that abnormal growth and other qualities in the brains of the siblings frequently predict by ages six and 12 months which of the children will be diagnosed with autism by age two. Early diagnosis of kids with autism is favored because even though children can’t be cured, many benefit from early treatment.

Studies of the siblings’ teeth, possible due to a collaboration with the Mt. Sinai researchers, will contribute more insight into those children’s environments, within and without the womb. “The idea is to collect the baby teeth of these kids to look at environmental exposures,” Piven said.

While teeth studies can’t convey all that children at risk have been exposed to, they can document a good bit, particularly metals, said Heather Volk, a public health scientist at Johns Hopkins University collaborating with Piven.

“It’s not just measuring exposures to metals that can be bad. They also look at exposures that are necessary for brain development that are lacking,” said Volk, whose research has linked exposure to vehicle air pollution during the first year of life to higher rates of autism.

“That’s the sort of information that can potentially open new avenues for prenatal care that promote healthy  brains,” she said.

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Catherine Clabby (senior environmental reporter) is a writer and editor. A former senior editor at American Scientist magazine, Clabby won multiple awards reporting on science, medicine and higher education...

4 replies on “Autism Researchers Extract Precious Data from Baby Teeth”

  1. Great to see this getting replicated:
    J Toxicol Environ Health A. 2007 Jun;70(12):1046-51.
    Mercury, lead, and zinc in baby teeth of children with autism versus controls.

    Adams JB1, Romdalvik J, Ramanujam VM, Legator MS.
    Author information
    This study determined the level of mercury, lead, and zinc in baby teeth of children with autism spectrum disorder (n = 15, age 6.1 +/- 2.2 yr) and typically developing children (n = 11, age = 7 +/- 1.7 yr). Children with autism had significantly (2.1-fold) higher levels of mercury but similar levels of lead and similar levels of zinc. Children with autism also had significantly higher usage of oral antibiotics during their first 12 mo of life, and possibly higher usage of oral antibiotics during their first 36 mo of life. Baby teeth are a good measure of cumulative exposure to toxic metals during fetal development and early infancy, so this study suggests that children with autism had a higher body burden of mercury during fetal/infant development. Antibiotic use is known to almost completely inhibit excretion of mercury in rats due to alteration of gut flora. Thus, higher use of oral antibiotics in the children with autism may have reduced their ability to excrete mercury, and hence may partially explain the higher level in baby teeth. Higher usage of oral antibiotics in infancy may also partially explain the high incidence of chronic gastrointestinal problems in individuals with autism.
    PMID: 17497416 DOI: 10.1080/15287390601172080
    [Indexed for MEDLINE]

    Ted Fogarty, MD
    Chair of Radiology at the University of North Dakota
    Metals Imaging Researcher (Lead in Venison)

  2. This is not a new kind of study. Baby teeth have been studied for a decade to test for overall toxins. However, the N.C. study seems to be concentrated on everything environmental besides what really causes autism. Autism is mainly a man made illness caused by vaccines. Vaccines that have never been tested properly for dangers, that have so many toxins in them besides the antigens themselves, that have never been tested for the synergistic effect of giving so many at the same time. Just imagine-74 vaccines by the time kids are 18. Unheard of anywhere but the US. Mandated vaccines without informed consent (not giving the parents the vaccine inserts first). Injecting mercury, aluminum, and a bag full of other toxins into an infant should be a crime. End the maiming and killing of babies and children with vaccines. End direct advertising of drugs on tv and all media. End “no liability” for vaccine makers. Save our children. It’s already too late for millions of them.

  3. As National Institutes of Health director Francis Collins has written, evidence is strong that vaccines do not cause autism. Arguments linking the two sometimes cite one research study published in 1998 that was proven to be a deliberate fraud. Shunning childhood immunizations is contributing to a resurgence of measles and other potentially fatal infectious diseases in the United States, public health officials say, including a measles outbreak active now in Minnesota.

  4. Great story! I was familiar with Dr. Arora’s work at Mt. Sinai School of Medicine but not the UNC collaboration.

    The benefit of Arora’s technique, compared to the 2007 article mentioned in an earlier comment, is a more precise extraction of the tooth layers so that metal uptake can be mapped out over time. Arora and co-authors then determined the time periods where differences in metal uptake were especially influential on autism risk, which tended to be just before and after birth.

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