Childhood lead exposure in the United States is ubiquitous and lots greater regarding than previous estimates have suggested, consistent with a new study.
When the researchers analyzed lead gas use since the 1940s and combined it with data on blood lead levels from the mid-1970s, they found that more than 54% of Americans alive in 2015 had exposure to dangerous levels lead as children.
That’s more than 170 million adults who are now at increased risk for neurodegenerative diseases, mental illness and cardiovascular problems because of lead they breathed, ingested or ingested as children.
No exposure to lead is safe at any point in a person’s life, but this highly toxic metal can be particularly harmful to children as it can impede brain development, leading to lifelong learning disabilities and behavioural problems.
Overall, the researchers estimate that lead gas lowered the nation’s cumulative IQ by 824 million points, or nearly three points per person.
And that’s only the average. Those born in the 1960s & 1970s, when lead gas use was at its peak, may have lost an average of six to seven IQ points. The cohort’s lead exposure was eight times higher than the current health limit.
For most people, these effects aren’t easy to notice, but for some with below-average cognitive abilities, it can lead to a diagnosis of intellectual disability.
“Honestly, I was shocked,” says sociologist Michael McFarland of Florida State University (FSU). “And when I look at the numbers, I’m still in shock, although I’m prepared for it.
Since the US government banned leaded gasoline from cars in 1996, exposure of children to lead has gradually decreased. However, many Americans are still alive today struggling with the fall-out of their upbringing.
Children born after 1996 usually have decrease blood-lead levels than their parents and grandparents, however in comparison to generations before the preindustrial era, their lead exposure remains much higher.
Additionally, there are thousands of communities across the United States, such as Flint Michigan, that continue to suffer from the national legacy of unlimited lead use and racial disparities are stark.
For example, black adults over the age of 45 were found to have significantly higher blood lead levels than their white counterparts, even those born after 1996.
The study authors are now investigating the long-term consequences of this exposure and whether it can explain racial differences in health outcomes such as kidney disease, coronary heart disease and dementia.
“Millions of us walk around with a history of lead exposure,” says FSU clinical psychologist Aaron Reuben.
“It’s not like you get into a car accident and you had a rotator cuff tear that heals and then you are fine. It seems like an insult that is happening in the body in different ways that we are still trying to understand, but it can have life implications.
Lead poisoning by nature is insidious. Historically, the invisible, odorless pollutant has been used in paint, pipe and gasoline, and when restrictions are better than before, huge amounts of lead have already seeped into our drinking water, our airways and our homes, at least in the US.
Leaded gas from car exhaust may now not be the hazard it as soon as was, however different sources of lead pollution, like hunting ammunition, plumbing and industrial waste, nonetheless pose a danger to human beings and the wider environment.
In 2021, for example, a study of more than a million American children found detectable blood lead levels in half of the cohort. Children living in zip codes with predominantly black populations were more likely to fall into this group.
Lead pollution is considered by some researchers to be the nation’s “longest-running epidemic,” and calculating IQ points lost from lead exposure is a commonly used proxy of its detrimental health effects.
Last year, researchers found that lead exposure between 1999 & 2010 was connected with “astonishing high” and “alarming losses” in IQ.
The new estimates have looked further into the past, only to find even higher blood lead levels in older adults.
“By providing more comprehensive estimates of the number of people exposed to lead at a young age, this study takes a significant step towards understanding the full extent of the damage being done to the US population in one specific domain: cognitive ability,” the study authors conclude.
