According to a new study, lead exposure among children in the United States is pervasive and far more concerning than previous estimates suggested.

When researchers analyzed lead gas use from the 1940s and combined it with data on blood lead levels from the mid-1970s, they found that more than 54 percent of Americans living in 2015 had been exposed to dangerous levels of lead as children.

It is more than 170 million adults who are now more at risk of neurodegenerative diseasemental illnesses and cardiovascular problems, because of the lead they breathed in, ingested or absorbed as children.

No level of exposure to lead is safe at any time in a person’s life, but this highly toxic metal can be particularly harmful to children because it can hinder brain developmentleading to permanent learning difficulties and behavioral problems.

In total, the researchers estimate that leaded gasoline reduced the country’s cumulative IQ score by 824 million points, or almost three points per person.

And that’s just the average. People born in the 1960s and 1970s, when the use of leaded gasoline peaked, could have lost an average of six to seven IQ points. The cohort’s lead exposure was eight times higher than current health limits.

For most people, these effects are not easily noticeable, but for some who have below average cognitive abilities, it can lead to a diagnosis of intellectual disability.

“I was frankly shocked” said Florida State University (FSU) sociologist Michael McFarland. “And when I look at the numbers, I’m still shocked even though I’m preparing for it.”

Since the US government banned leaded gasoline for cars in 1996, children’s exposure to lead has gradually declined. Yet there are still many Americans alive today who are dealing with the fallout from their upbringing.

Children born after 1996 generally have lower blood lead levels than their parents and grandparents, but compared to pre-industrial generations, their exposure to lead is still much higher.

Also there are thousands of communities in the United States, like Flint Michigan, which continues to suffer from the national legacy of unlimited lead use, and the racial disparities are stark.

Black adults over the age of 45, for example, had significantly higher blood lead levels than their white counterparts, and this was true even for those born after 1996.

The study authors are now examining the long-term consequences of this exposure and whether it can explain racial disparities in health outcomes, such as kidney disease, coronary heart disease and dementia.

“Millions of us are walking around with a history of lead exposure,” said clinical psychologist Aaron Reuben of FSU.

“It’s not like you’ve been in a car accident and you have a rotator cuff tear that heals and then you’re fine. It seems like an insult carried through the body in different ways that we’re still trying. to understand, but it can have repercussions on life.”

Lead poisoning is insidious in nature. The invisible, odorless pollutant has historically been used in paints, pipes and gasoline, and while restrictions are better than they once were, at least in the United States, huge amounts of lead are have already seeped into our drinking water, our respiratory tracts and our homes.

Lead gas from car exhaust may no longer be the threat it once was, but other sources of lead pollution, like hunting ammunitionplumbing and industrial waste, still pose a threat to humans and the wider environment.

In 2021, for example, a study of more than one million American children found detectable levels of lead in the blood of half of the cohort. Children who live in ZIP codes with predominantly black populations were more likely to be in this group.

Some researchers regard lead pollution as “oldest epidemicin the country, and the calculation of IQ points lost to lead exposure is a commonly used indicator of its adverse health effects.

Last year, researchers found lead exposure was linked to “surprisingly high” and “alarming” losses in IQ from 1999 to 2010.

The new estimates go back further in time, only to find even higher blood lead levels in older people.

“By providing more comprehensive estimates of the number of people exposed to lead in early life, this study takes a significant step toward understanding the extent of harm to the U.S. population in one specific area: cognitive abilities,” the authors said. conclude.

The study was published in PNAS.