The leaded generation
More than half of Americans alive today were exposed to dangerous levels of lead as kids
The average Gen Xer lost about 6 points of IQ due to early childhood lead exposure, according to a study recently published in the Proceedings of the National Academies of Science.
The era from roughly 1965 to 1980 — when Gen Xers were born — was also the period when leaded gasoline use peaked in the U.S. The lead in that gas got released into the atmosphere via automobile exhaust, and was subsequently inhaled by everyone living in the country at the time. That lead showed up in samples of children’s blood that were drawn as part of the National Health and Nutrition Examination Survey (NHANES), an ongoing CDC project tracking the health of the country.
For the study, the researchers compiled and plotted that data in order to answer a fundamental question: how many Americans alive today were exposed to dangerous levels of lead as children? The chart below tells the story.
This shows the distribution of childhood blood levels by age of the population in the year 2015. So, on the far left of the chart you’ve got a column for those who were just born that year, age 0. Nearly 100 percent of them fall into the dark blue category, indicating blood lead levels below the 2015 safety benchmark of 5 micrograms per deciliter of blood (that’s since been lowered to 3.5 micrograms, but I’m using the 2015 benchmark because that’s what the study authors used).
As you move rightward across the chart, increasing with age, the dark blue component of the columns start shrinking. Only about 75 percent of twenty-year-olds in 2015 had childhood blood levels below the safe benchmark. Among 30-year-olds the share is less than half. By the time we reach the 40-somethings the dark blue category has disappeared completely.
We’re in the heart of Generation X now. You can see that for people in their mid-40s in 2015, well over three-quarters had childhood blood lead levels surpassing three times the safe limit. Close to half were at four to five times the limit, with anywhere from ten to twenty percent of the cohort at somewhere north of five or six times above.
Then, the wave of lead recedes. By the time we hit the folks who were in their 70s in 2015 — those who had been born before the era of widespread leaded gas — more than half are back in the dark blue category for exposure.
The wave of lead in the chart corresponds almost exactly with the rise and fall of leaded gas use in the United States. Leaded gas consumption peaked around 1970 and started falling thereafter. The EPA began working to phase it out in earnest in 1973, although it wasn’t fully banned until 1996. Today, leaded gas is still used in some types of airplane fuel.
To put it mildly, lead is extremely, extremely bad for you. It damages the brain, slowing growth and causing developmental delays and cognitive problems, particularly in children. And American children born in the 60s and 70s were exposed to frankly insane levels of the stuff, thanks to the leaded gasoline used in cars at the time. Millions of them, for instance, had lab-confirmed blood lead levels approaching 10 times today’s safe limit.
The study authors estimate that all that childhood lead exposure has lowered our national average IQ by close to 3 points as of 2015. But that loss is distributed unevenly: people born in the 60s and 70s have lost closer to 5 or 6 IQ points due to lead. Kids born in more recent years, on the other hand, can expect to see less IQ loss due to led. But the authors note that even today, blood lead levels in kids are considerably higher than they were back in the preindustrial era.
“Even relatively small deficits in achieved IQ can have a meaningful impact on people’s lives, as cognitive ability, described by IQ, meaningfully predicts a person’s educational and occupational attainment, health, wealth, and happiness,” they write.
There’s a strong case to be made that the little Gen. Xers huffing leaded car exhaust as kids became the bigger Gen. Xers driving much of the elevated national crime rate 15 to 20 years later. “Lead exposure at young ages leaves children with problems like learning disabilities, ADHD, and impulse control problems; and those problems cause them to commit crime as adults — particularly violent crime,” as Brookings’ Jennifer Doleac explains it.
That leaded legacy remains with us today. “Pronounced exposure to lead in early childhood will remain a hallmark of the US population for the next several decades,” the authors write. There’s still a lot about childhood lead exposure we don’t know — how does it affect a person’s propensity to develop Alzheimer’s or other late-life cognitive issues, for instance? How will those kids’ kidneys, lungs or hearts be affected as seniors?
As the Gen. X population ages, we’re about to find out.