 By the 1950s, lead a dangerous neurotoxin that was once buried deep in the ground far, far away had polluted the entire planet thanks to leaded gasoline. I mean, it's hard to imagine a better way for maximizing population exposure to a poison than to have it emitted by a ubiquitous mobile source to line the surfaces of our neighborhoods with it. Overall, about 5 million metric tons of lead was deposited. A single busy street could receive more than a ton a year, and the lead just built up decade after decade. But at least thanks to regulations starting in the 70s, we stopped spewing so much into the air. And as lead use dropped, so did the levels of lead in our blood, resulting in a 98% reduction in the percentage of young children with elevated blood lead levels. Of course, the term elevated is relative. Prior to 1970, lead toxicity was defined as 60 micrograms per deciliter or higher. But then they dropped the definition to 40, then 30, then 25, then 10, as lead levels previously thought to be safe or inconsequential for children was consistently shown to be risk factors for cognitive and behavioral problems. Currently, elevated is considered more than 5, but under 5, your lead level is considered non-elevated, normal. But what does having a normal lead level mean? Virtually all residents of industrialized countries have bone-led stores that are several orders of magnitude greater than those of our pre-industrial ancestors. If you go to a museum and test the lead levels of ancient skeletons buried a millennia ago, they have a thousand times lower lead level compared to people today, which indicates the probable existence within most Americans of dysfunctions caused by poisoning from chronic excessive overexposure to industrial lead. This is a graphical representation where each dot represents 40 micrograms of lead. The amount of lead in the right figure represents overtly symptomatic lead poisoning, where you might be doubled over in pain, whereas the middle figure is the lead in a typical American citizen and the left figure is how much they found in pre-industrial bodies. See, what the medical and research community has failed to understand is that they've just been looking at these two figures, people with lead poisoning, and those of us down at normal levels, so-called very low levels. But what this new data on what's natural for our species shows is that typical levels of lead in humans are quite definitely not very low at all, but instead constitute grossly excessive thousandfold over exposure levels. The bottom line is that no level of lead exposure appears to be safe, and even the current quote-unquote low levels of exposure in children are associated with neurodevelopmental deficits, including reduced IQ, but hey, it could have been a lot worse if we hadn't started restricting leaded gas. Thanks to falling blood lead levels starting in the 70s, preschoolers born in the 90s were like 2-5 IQ points smarter than kids like me born before 1976. So when we see our kids and grandkids being such whizzes 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 kids are less brain damaged. If that seems like a lot for just a few IQ points, what you have to realize is that even a small shift in average IQ could result in a 50% increase in the number of so-called mentally retarded millions more in need of special education and services. So the removal of lead from gasoline in the United States may be one of the great public health achievements of the 20th century. But it almost did not happen. Tremendous pressure by the lead industry was brought to bear to quite even intimidate researchers and clinicians who dared report on or identify lead as a hazard. Decent scientists and health officials faced enormous opposition, but never lost sight of the mandate to protect public health. In this personal perspective, two of the idealistic young employees at the newly formed EPA who played key roles in the fight recount how naive they were to the ways of Washington. Our youth was used against us, they recall, their inexperience cited as a reason for rejecting their proposals. In retrospect, however, their youth and inexperience may have helped them to succeed in taking on a billion-dollar industry. We were too young to know that regulating lead in gasoline was impossible.