For more Body & Brain stories,
leaves its mark
Metal affects brain size,
risk of violent behavior
By Rachel Ehrenberg
The effects of lead weigh heavy on the
minds of people exposed to the metal during childhood. Two new studies of adults
who lived in lead-contaminated housing
as kids find that higher lead levels in the
blood during childhood are associated with
smaller brains and with an increased risk
for violent criminal behavior.
“Lead has special status as a risk factor because we can prevent it,” comments
David C. Bellinger, an epidemiologist at
Harvard Medical School in Boston and
an expert in environmental and public
health. Bellinger, who was not involved
in the research, wrote a commentary that
appears with the two studies in the May 27
PLo S Medicine. “There are a lot of risk factors for these kids and lead was one among
many. It’s hard to prevent poverty,” he says.
“But with lead, we know the pathways to
exposure and we can prevent it.”
Mothers of the studies’ participants
were recruited from 1979 to 1984 from
neighborhoods in Cincinnati with a lot of
old, lead-contaminated houses and historically high rates of childhood lead poisoning. Blood lead levels were measured in the
pregnant moms and then in the children
at several intervals after birth, until they
were at least 6 years old. Of the children,
now 19 to 24 years old, 250 participated in
the study examining the association with
criminal behavior and 157 participated in
the brain imaging study.
MRI scans of the young adults’ brains
revealed that the more lead the participants were exposed to as children, the
smaller their adult brains were, the
researchers report. The anterior cingulate cortex — a brain region associated
with mood regulation, decision making
and impulse control — was particularly
In the ’50s, children were exposed to lead where they lived and played, including this Ohio building.
affected, says Kim Dietrich of the University of Cincinnati College of Medicine’s
epidemiology and biostatistics division.
Male brains were significantly more
affected than female brains, he notes.
Childhood lead exposure has been
linked to lower IQ scores and to attention
and hyperactivity problems, but the brain
imaging work is the first to look beyond
performance to how lead affects the underlying neural substrate, Bellinger says. The
study’s results “are red flags,” he says.
The second study looked at the participants’ current arrest records and compared
them with the participants’ childhood levels of lead in the blood. Total arrests and
arrests for violent crimes increased with
each 5 microgram per deciliter increase in
blood lead level, the researchers report.
“This is a real problem for this generation,” Dietrich says. “We’re not doing a very
good job right now for these kids.”
Dietrich says the average childhood
blood lead level in the brain imaging study
was about 13 µg/dl (almost everyone has
background levels of 1 to 2 µg/dl). The Centers for Disease Control and Prevention
“action level” for lead — the blood level that
is supposed to prompt an investigation of
environmental exposure — is 10 µg/dl.
“Ten is no bright line,” he says. “The
real problems remain where there is still
lead paint in older homes.”
The good news, says Bellinger, is that
levels of lead in the blood have gone down a
lot since the early 1980s. CDC surveillance
data show that by 2006 only 2. 3 percent
of children in Ohio had blood lead levels
of more than 10 µg/dl, compared with
16. 6 percent in 1997.
“Lead is difficult,” says Bellinger.
“People refer to it as a multimedia pollutant because there are so many ways
that people get exposed. There’s gasoline,
paint, fallout in air. It gets into the soil and
tracked into homes. It’s in interior paint,
which deteriorates and gets into dust. It
was used in can solder.… It’s a ubiquitous
and useful metal — I suppose that’s why it
is still around.” s