It’s been nearly 30 years since leaded gasoline was banned but its pernicious effects live on. Exposure to car exhaust from leaded gasoline has collectively stolen 824 million IQ points from some 170 million Americans.

That’s the recent finding by psychology researchers at Duke and Florida State universities, who calculated the cumulative effects of lead exposure nationwide.

Once in the bloodstream, lead can find its way into the brain by crossing the blood-brain barrier. From there, it can erode brain cells. And even a little lead can cause a lot of problems: Health experts say there is no safe level of lead exposure.

Using publicly available data on leaded-gas use and childhood blood-lead levels, the researchers determined the lifelong burden of lead exposure for every person in America in 2015.

Lead’s assault on collective intelligence surprised even the researchers. Virtually everyone born in the 1960s and 1970s had some level of lead exposure — most of it due to vehicle emissions. Half of the U.S. population — some 170 million people — had clinically concerning levels of lead in their blood as children. The researchers determined that likely resulted in lower IQs and a higher risk of long-term health problems such as higher prevalence of cardiovascular disease and mental illness in adulthood.

Individually, lead exposure led to an average IQ loss of three points per person. For those born in the mid- to late 1960s, the toll may have been six IQ points. For children with the highest levels of lead in their blood, the toll may be more than seven IQ points.

Younger people have no doubt benefitted from elected officials getting the lead out — of gasoline, that is.