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After a night of pouring rain and howling winds, when you open your window and take a deep breath of crisp morning air, does it occur to you that the air could contain tiny lead particles?
Unfortunately, the air from the 1960s to 1980s surely contained alarming concentrations of lead. Due to the rampant use of lead in gasoline, pipes, and paints, which leaked lead into airways, water, and soil, the average blood–lead level (BLL) for the general US population was three to five times higher than the level that posed a clinical concern. Because of this, millions of American adults today were exposed to dangerous levels of lead in childhood.
While reading the book What the Eyes Don’t See, which describes the shocking tragedy of the Flint Water Crisis, Sociologist Michael McFarland recalled seeing a graph illustrating how much lead was added to gasoline in the U.S. over time. Previous literature had already established the negative health consequences of heavy metal pollution, such as cardiovascular diseases and loss of cognitive functions. McFarland was startled by the sheer number of people that were exposed to adverse lead levels in childhood. “How are we not talking about this? How is this not taught in the curriculum of population health?” he said.
High blood levels of lead can pose serious consequences to one’s quality of life and society as a whole. Studies have shown that lead can disrupt healthy organ development, negatively impacting a person’s cognitive ability, fine motor skills, and emotional regulation. The researchers of this study estimated that high lead exposures had already cost a total of 824,097,690 million IQ points to be lost among populations in 2015. Significant IQ loss can broadly impact economic development, criminal behavior, social mobility, psychopathology, and more. On an individual level, even small deficits in achieved IQ can impact one’s educational and occupational attainment, health, wealth, and happiness.
To provide a better estimate of the scope of the lead contamination problem, McFarland and his colleagues predicted the blood lead levels of American populations based on data from the U.S. Bureau of Mines, which recorded the yearly consumption of lead-based gasoline from 1933 to 1993. Alarmingly, the researchers found that more than half of Americans had childhood BLL above the threshold that caused clinical concern in 2015, sometimes 3 to 5 times more. The cohort with the highest childhood BLL consisted of middle-aged adults born in the 1950s to 1980s. Levels gradually decreased among the younger and older cohorts. This finding corresponds with the boom in gasoline use in the 60s to 80s, which led to massive lead contamination.
By quantitatively calculating the demographic estimates of lead exposure and cognitive deficits among U.S. populations in this study, the researchers highlighted the scope and importance of lead contamination. This issue, however, did not stay in the past. Although younger populations born after the 1980s experienced much lower lead exposure, their BLLs are still much higher than their pre-industrial counterparts. Therefore, researchers concluded that future research into the impact of lead contamination is critical, for there are still many unknowns for this urgent yet latent public health crisis.