Image Credit: Obi Onyeador / Unsplash. This image has been modified.

Why You Don’t Want “Normal” Blood Lead Levels

“By the 1950s, lead—a dangerous neurotoxin that was once buried deep in the ground, far away from humans—had polluted the entire planet.” We have leaded gasoline to thank for this. It’s hard to imagine “a better strategy for maximizing population exposure to a poison than to have it emitted by a ubiquitous mobile source and to line the surfaces of dwellings” and our neighborhoods with it.

“Overall, about 5 million metric tons of lead was deposited in the environment as a result of the combustion of leaded gasoline” by our automobiles before it was regulated. A single busy street could receive more than a metric ton a year, and the lead just built up, decade after decade. Finally, thanks to regulations starting in the 1970s, we stopped spewing so much into the air. As you can see at 0:57 in my video “Normal” Blood Lead Levels Can Be Toxic, as lead use dropped, so did the levels of lead in our blood, resulting in a 98 percent reduction in the percentage of young children with elevated blood lead levels. Of course, the term “elevated” is relative.

“Prior to 1970, lead poisoning was defined by a blood lead concentration of 60 mg/dL or higher” but “since then, the blood lead concentration for defining lead toxicity gradually has been reduced” to 40 mg/dL, then 30 mg/dL, then 25 mg/dL, and then further down to 10mg/dL, as lead levels “previously thought to be safe or inconsequential for children have consistently been shown to be risk factors” for cognitive and behavioral problems.

Currently, an elevated blood lead level is considered to be more than 5 mg/dL. So, under 5 mg/dL, your lead level is considered to be non-elevated or normal. But what does having a “normal” lead level mean?

“Virtually all residents of industrialized countries have bone lead stores that are several orders of magnitude greater than those of our preindustrial ancestors.” If you go to a museum and test the lead levels of ancient skeletons buried a millennium ago, they are a thousand times lower compared to people today, “which indicates the probable existence within most Americans of dysfunctions caused by poisoning from chronic, excessive overexposures to industrial Pb lead.”

You can see a graphical representation of “body burdens of lead” in a preindustrial ancestor, a typical American citizen, and a person with overtly symptomatic lead poisoning, where he might be doubled over in pain, at 2:30 in my video. What the medical and research communities had failed to understand is that they had only concerned themselves with people with actual lead poisoning and those at “typical” lead levels, but “the new value for natural lead levels in [preindustrial] humans shows that typical levels of lead in humans are quite definitely not properly described by the term ‘very low levels’ at all, but instead constitute grossly excessive, 1000-fold over-exposure levels.”

 The bottom line? “No level of lead exposure appears to be ‘safe’ and even the current ‘low’ levels of exposure in children are associated with neurodevelopmental deficits,” including reduced IQ. It could have been a lot worse if we hadn’t started restricting leaded gas. Thanks to falling blood lead levels starting in the 1970s, preschoolers born in the 1990s were two to five IQ points higher than kids like me born before 1976. So, when we see our kids and grandkids being such wizzes at technology that it’s hard to keep up with them, a small part of that may be them not suffering as much lead-induced brain damage as we did. And, what that means for the country is potentially hundreds of billions of dollars of improved productivity because our children are less brain-damaged.

If that seems like a lot for just a few IQ points, as you can see at 4:26 in my video, what you have to realize is that even a small shift in average IQ could result in a 50 percent increase in the number of the “mentally retarded,” millions more in need of special education and services.

So, “removal of lead from gasoline in the United States has been described as one of the great public health achievements of the 20th century, but it almost did not happen.” Indeed, “tremendous pressure by the lead industry itself was brought to bear to quiet, even intimidate, researchers and clinicians who reported on or identified lead as a hazard.” Decent “scientists and health officials faced enormous opposition but never lost sight of the mandate to protect public health.”

Two of the “young, idealistic employees” at the newly formed Environmental Protection Agency, who played key roles in the fight, recount how “naïve [they were] to the ways of Washington”:

“Our youth was also used against us. Our inexperience was cited as a reason for rejecting the lead regulatory proposals….Finally, in retrospect, our youth and inexperience also helped us to succeed in taking on a billion dollar industry. We were too young to know, that regulating lead in gasoline was impossible.”

What about lead exposure after childhood? That’s the topic of my video The Effects of Low-Level Lead Exposure in Adults.

What can we do about lead exposure? See:

If you missed the first three videos in this series, check out:

For the effects of mercury, another heavy metal, see:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

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