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 well-being.
In a new study from Duke University, researchers found 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 finding suggests 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.
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.
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.
In the study, the team used publicly available data to determine 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.
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, the team 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).
The team’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.
If you care about brain health, please read studies about bottom blood pressure number that can tell your dementia risk, and antibiotic drug that could treat common dementia.
For more information about brain health, please see recent studies about diet that leads to fewer blood clots in the brain, and results showing that brain parasite spread by cats affect 30 million Americans.
The study is published in the journal Proceedings of the National Academy of Sciences and was conducted by Aaron Reuben et al.
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