An estimate of the number of people in the US that were impacted by lead exposure in 2015 was recently published in PNAS. Using data from NHANES, estimates based upon leaded gasoline consumption and accepted models of IQ loss, the authors determined elevated lead exposure during childhood, and the impact this has had on IQ.
Their findings indicate that most of the US had elevated blood lead levels during childhood averaging approximately three times the current acceptable reference level of 3.5 ug/dL. Among cohorts born between 1951 to 1980, a BLL greater than 5 ug/dL was nearly ubiquitous (90-100%, depending on the year), with a significant portion having much greater exposure; for example, 78% of those born between 1966-1970 had BLLs greater than 15 ug/dL.
Exposure to lead has had tremendous consequences. These researchers estimate the US lost 824,097,690 million IQ points, or an average of 2.6 points per person, though some cohorts lost more (e.g., the 1971-1975 cohort lost 5.7 points per person). It has previously been reported that childhood lead exposure is inversely linked to cognitive function among adults, as well as socioeconomic status and social mobility.