Lead exposure in last century shrank IQ scores of half of Americans,
study finds
Leaded gasoline calculated to have stolen more than 800 million
cumulative IQ points since the 1940s

Date:
March 7, 2022
Source:
Duke University
Summary:
Researchers calculate that exposure to car exhaust from leaded
gas during childhood stole a collective 824 million IQ points
from over 170 million Americans alive today, more than half of
the population of the United States.



FULL STORY ==========================================================================
In 1923, lead was first added to gasoline to help keep car engines
healthy.

However, automotive health came at the great expense of our own health
and well-being.


==========================================================================
A new study calculates that exposure to car exhaust from leaded gas
during childhood stole a collective 824 million IQ points from more
than 170 million Americans alive today, about half the population of
the United States.

The findings, from Aaron Reuben, a PhD candidate in clinical psychology at
Duke University, and colleagues at Florida State University, suggest that Americans born before 1996 may now be at greater risk for lead-related
health problems, such as faster aging of the brain. Leaded gas for cars
was banned in the U.S.

in 1996, but the researchers say that anyone born before the end of that
era, and especially those at the peak of its use in the 1960s and 1970s,
had concerningly high lead exposures as children.

The team's paper appeared the week of March 7 in the journal Proceedings
of the National Academy of Sciences.

Lead is neurotoxic and can erode brain cells after it enters the body. As
such, there is no safe level of exposure at any point in life, health
experts say.

Young children are especially vulnerable to lead's ability to impair
brain development and lower cognitive ability. Unfortunately, no matter
what age, our brains are ill-equipped for keeping it at bay.

"Lead is able to reach the bloodstream once it's inhaled as dust, or
ingested, or consumed in water," Reuben said. "In the bloodstream, it's
able to pass into the brain through the blood-brain barrier, which is
quite good at keeping a lot of toxicants and pathogens out of the brain,
but not all of them." One major way lead used to invade bloodstreams
was through automotive exhaust.



==========================================================================
To answer the complex question of how leaded gas use for more than
70 years may have left a permanent mark on human health, Reuben and
his co-authors Michael McFarland and Mathew Hauer, both professors of
sociology at Florida State University, opted for a fairly simple strategy.

Using publicly available data on U.S. childhood blood-lead levels,
leaded-gas use, and population statistics, they determined the likely
lifelong burden of lead exposure carried by every American alive in
2015. From this data, they estimated lead's assault on our intelligence
by calculating IQ points lost from leaded gas exposure as a proxy for
its harmful impact on public health.

The researchers were stunned by the results.

"I frankly was shocked," McFarland said. "And when I look at the numbers,
I'm still shocked even though I'm prepared for it." As of 2015, more
than 170 million Americans (more than half of the U.S.

population) had clinically concerning levels of lead in their blood when
they were children, likely resulting in lower IQs and putting them at
higher risk for other long-term health impairments, such as reduced brain
size, greater likelihood of mental illness, and increased cardiovascular disease in adulthood.



========================================================================== Leaded gasoline consumption rose rapidly in the early 1960s and peaked in
the 1970s. As a result, Reuben and his colleagues found that essentially everyone born during those two decades are all but guaranteed to have
been exposed to pernicious levels of lead from car exhaust.

Even more startling was lead's toll on intelligence: childhood lead
exposure may have blunted America's cumulative IQ score by an estimated
824 million points -- nearly three points per person on average. The researchers calculated that at its worst, people born in the mid-to-late
1960s may have lost up to six IQ points, and children registering the
highest levels of lead in their blood, eight times the current minimum
level to initiate clinical concern, fared even worse, potentially losing
more than seven IQ points on average.

Dropping a few IQ points may seem negligible, but the authors note
that these changes are dramatic enough to potentially shift people
with below-average cognitive ability (IQ score less than 85) to being classified as having an intellectual disability (IQ score below 70).

Moving forward, McFarland is analyzing the racial disparities of childhood
lead exposure, hoping to highlight the health inequities suffered by Black children, who were exposed more often to lead and in greater quantities
than white children.

Reuben's next step will be to examine the long-term consequences of past
lead exposure on brain health in old age, based on previous findings
that adults with high childhood lead exposure may experience accelerated
brain aging.

"Millions of us are walking around with a history of lead exposure,"
Reuben said. "It's not like you got into a car accident and had a
rotator cuff tear that heals and then you're fine. It appears to be an
insult carried in the body in different ways that we're still trying to understand but that can have implications for life."

========================================================================== Story Source: Materials provided by Duke_University. Original written
by Dan Vahaba. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Michael J. McFarland, Matt E. Hauer, Aaron Reuben. Half of US
population
exposed to adverse lead levels in early childhood. Proceedings
of the National Academy of Sciences, 2022; 119 (11) DOI:
10.1073/pnas.2118631119 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220307162011.htm

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