Health experts say the effects of leaded gasoline in cars, although banned since 1996, still linger today after a new study found Americans exposed to the highly toxic metal may have a lower IQ.
Researchers at Duke University and Florida State University analyzed publicly available data on U.S. childhood blood-lead levels, leaded-gas use and population statistics and determined the likely lifelong burden of lead exposure carried by every American alive in 2015.
They found 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, according to the study published Monday in Proceedings of the National Academy of Sciences.
They estimated this level of lead exposure may have lowered a person’s IQ by an average of three points, which is a total of about 824 million points among all Americans exposed to lead.
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“I frankly was shocked,” said co-author Michael McFarland, professor of sociology at Florida State University. “And when I look at the numbers, I’m still shocked even though I’m prepared for it.”
Lead is a neurotoxic metal that can erode brain cells after entering the body, health experts say. There’s no safe level of exposure to lead and children are especially vulnerable to impaired brain development.
The current blood-lead value that would trigger clinical concern and case management is 3.5 micrograms per deciliter, said study lead author Aaron Reuben, a PhD candidate in clinical psychology at Duke University.
“We found over 4.5 million Americans had levels over 30 – 10 times what’s considered alarming,” he said.
Previous studies have found a strong association between blood-lead levels and IQ, study authors said, but few have tried to measure that impact.
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Researchers say anyone born before leaded gas was banned in 1996 may have suffered the cognitive consequences of lead exposure. At its worst, people born during the peak use of leaded gas in the 1960s and 70s may have lost up to seven IQ points.
“The tricky thing about health is that it often takes very long for health to show exposure,” said Hannes Schwandt, an expert in human development and social policy, and professor at Northwestern University, who was not involved with the study. “It’s not like you have lead exposure and the next day the problem shows up. It comes to the surface over people’s entire lifetimes.”
While the study demonstrates the impacts of average exposure, he said, not every American is exposed to the same level of lead. Children in vulnerable communities who live near busy streets and highways are more likely to be exposed and impacted by the toxic metal. Schwandt hopes future studies on lead and other pollutants take a closer look at this population.
Reuben argues it’s important for patients and their physicians to understand the potential consequences of lead exposure, seeing as it may affect half of the country.
“It’s hard to know if you’re one of those Americans but if you grew up near lead emitting, you might just take a proactive approach,” he said. “Let your primary care physician know that it’s a concern and it could motivate additional surveillance of conditions that could arise later in life.”
Cars haven’t used leaded gas for more than 26 years, but health experts say today’s children still face harm from lead exposure.
Lead is still used in aviation fuel for certain aircrafts, Reuben said, and children also can be exposed to lead paint and contaminated water.
“We document a history of problems but by no means is this a historical issue. It’s very much current,” he said.
“It’s not cheap to replace lead service lines, it’s not easy to provide requirements for fuel switching. But studies like ours add to the weight of evidence that says whatever the cost of removing lead from our communities … the benefits are far in excess.”
Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT.
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