Exposure to lead from exhaust fumes has cost the U.S. population a loss of more than 820 million IQ points
According to American scientists, past exposure to lead continues to affect the health and well-being of our contemporaries in ways we do not yet fully understand.
Lead, a heavy metal and toxic chemical element that has cumulative properties and detrimental effects on the body, accumulates in marine sediments and fresh water. In the 20s of the last century Americans were the first to decide to add it (or rather, tetraethyl lead) as an additive to gasoline: before that the fuel had a low octane number, that is, it had a bad effect on the performance and survivability of the engine and its operation.
The toxicity of lead was known, but it was apparently thought at first that the low content would not cause much harm. However, in 1996 the USA and Germany banned the use of this poisonous and carcinogenic organometallic compound in gasoline, and other European countries and Russia - at the beginning of the XXI century.
The world is still reaping the benefits: in developed countries, the historical use of lead in paint, pipes, and gasoline has left water, soil, and homes enriched with this element. As a new study by scientists from Florida State University and Duke University in North Carolina (USA) has shown, lead exposure affects not only the basic systems of the body, weakens immunity, disrupts metabolism, provokes the development of cancer and so on. Among other things, mainly inhaling it with exhaust fumes in the past reduced the IQ of living Americans by a total of 824 million points.
The results of the work published in the journal Proceedings of the National Academy of Sciences. As noted by its authors, from the late 1960s to the early 1980s, the average level of lead in the blood of a resident of the United States was three to five times higher than the reference value today (three and a half micrograms of lead per deciliter of blood - a reason to go to the doctor). That is, millions of current adults, at least in the United States, were exposed to high levels of lead as children. This, according to previous animal studies and epidemiologic data, impairs brain, bone, and cardiovascular development and ultimately affects cognitive ability, fine motor skills, and emotional regulation.
The scientists used United States Census data, statistics on lead exposure from exhaust fumes, and a national survey on the topic conducted by the Centers for Disease Control and Prevention from 1976 to 2016. They estimated the number of Americans as of 2015 who were born no later than 1996 and were exposed to lead at various concentrations before, during and after the leaded gasoline era.
Of the 318 million people, only 131 million had blood levels of the element below five micrograms per deciliter during childhood, the analysis found. Nearly 100 million - 31% of the population - had levels above ten micrograms per deciliter of blood, double the 2015 norm. About ten million people alive in 2015 had 25 micrograms of lead per deciliter of blood (seven times the norm) as children.
"Exposure to lead in early childhood varied considerably by cohort. <...> Its levels were relatively low in people born in the 1940s, increased sharply in middle-aged residents, and declined sharply in younger adults," the researchers said. Thus, the level of lead more than five micrograms per deciliter of blood in childhood found in 90% of Americans born in 1951-1955, 99% of those born in 1956-1960-ies, 97% of people born from 1961 to 1965, and all born in 1971-1975-ies.
By comparison, the same was found in only 6% of children born between 2001 and 2005, 3% of those born in the 2006-2010s, and only 1% of those born between 2011-2015.
"People born between 1951 and 1980 had particularly high levels of the element in their blood during childhood. For example, about 78% and 73% of children born between 1966 to 1970 and 1971 to 1975 had it above 15 micrograms per deciliter of blood," the scientists add. They believe that in 2030, at least 43% of U.S. residents will have blood lead levels above five micrograms per deciliter (in childhood), and 23% will have blood lead levels of ten micrograms per deciliter or higher. The rate will continue to decline over time.
In terms of cognitive decline due to exposure to the toxic element, in 2015, the U.S. population lost 824,097,690 IQ points - about 2.6 points per person.
In addition, more than 7% of Americans born in the 1966-1970s and 1971-1975s (nearly three million children combined) had lead levels above 30 micrograms per deciliter of blood, and their cognitive abilities were below average, often in the range of diagnosable mental retardation (IQ <70).
"We project that the loss of IQ points due to childhood lead exposure will be similar in the future: by 2030, the population's IQ will consequently decline by 709,054,633 points, or 2.03 IQ points per person," the study emphasizes.
It may seem that nothing terrible will happen, but at the individual level, even a relatively minor deficit in cognitive ability can have a major impact on a person's life, health, well-being and professional achievements.
Scientists are confident that pronounced early childhood lead exposure will remain a hallmark of the United States population for the next several decades. In addition, even recent blood levels of this element are abnormal. Indeed, the United Nations Children's Fund estimates that 800 million children in the world today are exposed to lead, largely due to inadequate regulation of businesses in developing countries.