Since 1940, Americans' IQ may have been lowered due to lead exposure.

New research discovered that childhood lead exposure in the United States is widespread and far more alarming than prior estimates. 

After merging data on leaded gas consumption from 1940 with data on blood-lead levels from the mid-1970s, researchers determined that more than 54 per cent of Americans alive in 2015 had been exposed to hazardous amounts of lead as children. 

More than 170 million people are now at risk of neurological disease, mental illness, and cardiovascular difficulties due to the lead they breathed in, ingested, or absorbed as kids. 

There is no such thing as a safe level of lead exposure at any age. Still, it is highly damaging to children's brain development, resulting in long-term learning disabilities and behavioral issues. 

According to research, lead gas reduced the nation's cumulative IQ score by 824 million points or around three points per person. 

This is just the standard deviation. Those born during the 1960s and 1970s, when lead gas was at its peak, may have lost six to seven IQ points on average. Most individuals are not aware of these consequences. Still, some people with lower-than-average cognitive ability may be diagnosed with intellectual disability due to their exposure to eight times the current lead health limits. 

Michael McFarland, a sociologist at Florida State University, acknowledges, "I was shocked" (FSU). "And even though I expected it, the statistics still surprise me." 

Since the United States banned leaded gasoline in autos in 1996, childhood lead exposure has reduced. However, many Americans are still dealing with the ramifications of their upbringing. 

Children who are born after 1996 have lower lead levels than their grandparents generation, but their exposure to lead is still substantially higher than generations prior to the preindustrial era. 

Moreover, hundreds of communities around the United States, including Flint, Michigan, continue to be affected by the country's legacy of unrestrained lead use, with striking racial disparities. 

For example, researchers showed Black adults over 45 to have much higher blood lead levels than White adults, even if they were born after 1996. 

The study's authors are now investigating the long-term effects of such exposure to see if they might explain racial differences in health outcomes, including kidney disease, coronary heart disease, and dementia. 

"Millions of us are wandering around with a history of lead exposure," says FSU clinical psychologist Aaron Reuben. 

"It's not like you were in a car accident and tore your rotator cuff, which healed, and you were fine; it appears to be a life-threatening insult transported throughout the body in numerous ways that we're still trying to figure out." 

Poisoning with lead is an insidious disease. Even though the odorless and invisible contaminant has long been used in paints, pipes, and gasoline, massive levels of lead have already gotten into our drinking water, airways, and houses, at least in the United States. However, restrictions are better than they once were; enormous amounts of lead have already seeped into our drinking water, airways, and homes. 

While lead pollution from automotive exhaust is no longer a concern, other sources of lead contamination, such as hunting ammunition, plumbing, and industrial waste, continue to endanger people and the environment. 

In 2021, for example, researchers determined that half a million American children had detectable levels of lead in their blood. This category was more likely to include children who resided in mostly Black zip codes. 

According to some research, lead poisoning is the country's "longest-running epidemic," and calculating the number of IQ points lost due to lead exposure is a standard indicator of its adverse health effects. 

Researchers discovered that lead exposure was linked to "astonishingly large" and "alarming" IQ declines between 1999 and 2010. 

The new data goes even further, demonstrating significantly higher blood-lead levels among the elderly. 

"By giving more complete estimates of the number of people exposed to lead in early childhood, our study takes a critical step toward determining the full amount of the damage done to the American population in one single domain: cognitive capacity," the authors write. 

study was published at PNAS.ORG