Baby teeth from children with autism contain more
toxic lead and less of the essential nutrients zinc
and manganese, compared to teeth from children
Cross-section of tooth showing laser removal of the
dentine layer, in tan, for analysis of metal
content. Mount Sinai Health System.
According to an innovative study funded by the
National Institute of Environmental Health Sciences
(NIEHS), part of the National Institutes of Health,
researchers studied twins to control genetic
influences and focus on possible environmental
contributors to the disease.
The findings suggest that differences in early-life
exposure to metals, or more importantly how a
child’s body processes them, may affect the risk of
The differences in metal uptake between children
with and without autism were especially notable
during the months just before and after the children
The scientists determined this by using lasers to
map the growth rings in baby teeth generated during
different developmental periods.
The researchers observed higher levels of lead in
children with autism throughout development, with
the greatest disparity observed during the period
They also observed lower uptake of manganese in
children with autism, both before and after birth.
The pattern was more complex for zinc.
Children with autism had lower zinc levels earlier
in the womb, but these levels then increased after
birth, compared to children without autism.
The researchers note that replication in larger
studies is needed to confirm the connection between
metal uptake and autism.
“We think autism begins very early, most likely in
the womb, and research suggests that our environment
can increase a child’s risk.
But by the time children are diagnosed at age 3 or
4, it’s hard to go back and know what the moms were
exposed to,” said Cindy Lawler, Ph.D., head of the
NIEHS Genes, Environment, and Health Branch. “With
baby teeth, we can actually do that.”
Patterns of metal uptake were compared using teeth
from 32 pairs of twins and 12 individual twins.
The researchers compared patterns in twins where
only one had autism, as well as in twins where both
or neither had autism.
Smaller differences in the patterns of metal uptake
occurred when both twins had autism.
Larger differences occurred in twins where only one
sibling had autism.
The findings build on prior research showing that
exposure to toxic metals, such as lead, and
deficiencies of essential nutrients, like manganese,
may harm brain development while in the womb or
during early childhood.
Although manganese is an essential nutrient, it can
also be toxic at high doses.
Exposure to both lead and high levels of manganese
has been associated with autism traits and severity.
The study was led by Manish Arora, Ph.D., an
environmental scientist and dentist at the Icahn
School of Medicine at Mount Sinai in New York.
With support from NIEHS, Arora and colleagues had
previously developed a method that used naturally
shed baby teeth to measure children’s exposure to
lead and other metals while in the womb and during
The researchers use lasers to extract precise layers
of dentine, the hard substance beneath tooth enamel,
for metal analysis.
The team previously showed that the amount of lead
in different layers of dentine corresponds to lead
exposure during different developmental periods.
Arora said that autism is a condition where both
genes and environment play a role, but figuring out
which environmental exposures may increase risk has
“What is needed is a window into our fetal life,” he
said. “Unlike genes, our environment is constantly
changing, and our body’s response to environmental
stressors not only depends on just how much we were
exposed to, but at what age we experienced that
The method of using baby teeth to measure past
exposure to metals also holds promise for other
disorders, such as attention deficit hyperactivity
For more information
Fetal and postnatal metal dysregulation in autism
Arora M, Reichenberg A, Willfors C, Austin C,
Gennings C, Berggren S, Lichtenstein P, Anckarsater
H, Tammimies K, Bolte S. 2017.