Water pours under an overpass in Flint, MichiganShare on Pinterest
Flint, Michigan, is one of many towns in the United States that has had to deal with lead-tainted water. Sarah Rice/Getty Images
  • Researchers say people in the United States were exposed to large amounts of lead in the 1900s before it was banned in most products.
  • They say the exposure brought about a reduction in IQ scores and has caused heart health issues as well as cognition difficulties.
  • They say the problem is particularly acute in Communities of Color, which had more exposure and fewer resources to deal with the issues.

People in the United States have cumulatively lost more than 800 million points off their IQ scores from exposure to the lead added to gasoline for much of the 20th century.

That’s according to a new study by researchers at Florida State University and Duke University in North Carolina.

Researchers said cognitive ability was particularly affected among those born between 1951 and 1980.

The average American lost 2.6 points off their IQ due to exposure to lead, a developmental neurotoxin known to affect mental and physical development.

People born in the mid-to-late 1960s may have been most profoundly affected since that’s when the use of leaded gasoline peaked.

Lead was added to gasoline to improve engine performance as early as 1923 and had become the primary source of lead contamination in the United States by 1940.

“We estimated blood-lead levels arising from leaded gasoline use because… it was the dominate source of lead exposure for most Americans over the past 80 years,” Aaron Reuben, a study author and PhD candidate at Duke University, told Healthline. “Other sources, such as lead service lines or exfoliating paint from pre-1978, have no doubt contributed to individual American’s exposures in that time frame and should be estimated in the future as well.”

Reuben said most lead poisoning from leaded gasoline came from inhaling exhaust fumes or dust contaminated with lead from automobile exhaust, Reuben said.

The Environmental Protection Agency began phasing out lead use in gasoline in 1973, but it wasn’t completely banned until 1996.

From the 1960s until the early 1980s, average blood lead levels in the United States were three to five times higher than they are currently, researchers reported.

Jun Wu, PhD, a professor of environmental and occupational health at the University of California, Irvine’s Program in Public Health and co-director of the school’s Center for Environmental Health Disparities Research, told Healthline leaded gasoline continues to be one of the most significant sources of environmental toxicity in the United States.

“Definitely it’s on the top of the list for long-term impact on IQ and children’s cognitive ability and future success and achievement,” she said. “Lead paint and lead pipes are relatively localized, but leaded gasoline really brought the issue to a regional and national scale.”

According to the study, more than 170 million U.S. people alive today were exposed to high lead levels during their childhood. That includes millions exposed to at least five times the currently allowable limit of lead exposure.

Researchers drew their conclusions from estimates of blood lead levels (BLL) taken from the National Health and Nutrition Examination Survey, which examined children ages 1 to 5 between 1976 and 1980 and from 2015 to 2016. Estimates of lead exposure between 1940 and 1975 were calculated based on leaded gasoline consumption during those years.

Wu said the findings demonstrate contamination from leaded gasoline’s “significant impact on society as a whole as well as on individuals.”

“This is a very important environmental justice issue because a lot of [lead contamination] occurred in Communities of Color,” she said. “In addition to having higher exposure, these communities have less resources for coping with the harmful impact of IQ loss.”

“The levels are lower than before, but there is no fixed threshold for lead safety,” Wu said. “There’s been substantial effort to remove lead from paint, but little has been done to remove lead contamination from gasoline’s impact, probably because it’s too difficult. It’s everywhere.”

The water contamination crisis in Flint, Michigan, shows the problem of lead contamination, while greatly diminished, has not yet been solved.

Wu’s own research shows high levels of lead contamination persist in soil samples taken in urban areas and near highways decades after leaded gasoline was banned.

Michael McFarland, PhD, a professor in the Florida State University’s sociology department and a study author, noted that leaded gasoline is still used in propeller-driven aircraft.

“While the risk of exposure to lead is not nearly as high now, it’s still highly problematic. For instance, our most recent estimates from representative samples show that over 1 percent of young children have elevated blood lead levels,” McFarland told Healthline.

“This percentage may not sound high, but it equates to hundreds of thousands of children exposed children per year… Thousands of locales across the country have persistent legacy lead problems, many as bad as those seen in Flint during the water crisis,” he said.

Study authors said a full accounting of the impact of past lead contamination is needed not only to support abatement efforts but also to understand the disease burden of lead exposure and to improve cognitive, cardiovascular, and aging outcomes among those exposed to lead in the past.

“Every IQ point matters for important life outcomes such as educational and occupational attainment,” said Reuben.

“Economists have estimated that a single IQ point is worth about $10,000 in lifetime earnings… At the level of society, 2 to 6 IQ points per person is extraordinarily meaningful, as it lowers overall productivity… and increases the number of folks with cognitive impairment who require greater social support,” he said.

Researchers plan to use the same data to examine the impact of early lead exposure on brain health in old age and how racial disparities correlate with the brain damage from being exposed to lead in early life.